0. CORE (Volume Zero) Flashcards

Question

monotypic

Answer 1

monotypic genus including a single representative —used especially of a genus with only one species.

Answer 2

rln is a nerve in all vertebrates that unnecessarily loops around the aorta which illustrates the inefficiency & randomness of evolution

Answer 3

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Answer 4

All of the shark’s ancestors lived in the sea. The dolphin’s ancestors left the sea, evolved into mammals, then returned to the sea. The evolution of dolphins, or Delphinus, is believed to have started with the Pakiectus, a four legged, land walking mammal. The Pakiectus dates back to approximately 50 million years ago. Throughout the centuries, these animals have gone through drastic changes to become the modern day dolphin.

Answer 5

Like all other cetaceans, Pakicetus had a thickened skull bone known as the auditory bulla, which was specialized for underwater hearing. Cetaceans also all categorically exhibit a large mandibular foramen within the lower jaw, which holds a fat pack and extends towards the ear, both of which are also associated with underwater hearing. "Pakicetus is the only cetacean in which the mandibular foramen is small, as is the case in all terrestrial animals. It thus lacked the fat pad, and sounds reached its eardrum following the external auditory meatus as in terrestrial mammals. Thus the hearing mechanism of Pakicetus is the only known intermediate between that of land mammals and aquatic cetaceans."

Answer 6

For example, for many years elephants were classified into 2 species: African elephants and Asian elephants. In 2010, DNA tests on African elephants revealed that there are actually 2 species of African elephant: African bush elephants and African forest elephants. This means that there are now 3 species of elephant in total!

Answer 7

the class Artiodactyla (herbivorous mammals such as pigs, deer, hippos and cattle).

Answer 8

The grey wolf is in the domain Eukarya along with plants and fungi.

Answer 9

There are only three domains: Eukarya, Bacteria and Archaea.

Answer 10

Groups of single-celled microorganisms? Archaea and bacteria, Although they resemble one another, there are several biochemical differences between archaea and bacteria.

Answer 11

the domain that contains fungi, plants, animals and protists. Eukarya, In fact, any organism whose cells have a nucleus is a Eukaryote.

Answer 12

Loosely speaking, members with the same overall body plan have the same? phylum. For example, members of the animal phylum Chordata (chordates) all have a notochord – a flexible central rod.

Answer 13

There are actually additional ranks between the main taxonomic ranks. Under phylum is a rank called subphylum.

Answer 14

The five characteristic features of chordates present during some time of their life cycles are a notochord, a dorsal hollow tubular nerve cord, pharyngeal slits, endostyle/thyroid gland, and a post-anal tail.

Answer 15

The grey wolf is in the phylum: and the subphylum: Chordata, and Vertebrata, along with all animals with backbones, such as birds and amphibians.

Answer 16

group of animals that have backbones. The subphylum Vertebrata. Members of this group are known as vertebrates. (‘Invertebrates’ is a term used to describe all animals outside of this group.)

Answer 17

have hair and are warm blooded? The animals in a Class such as Mammalia (mammals) all share certain characteristics. For example, all mammals have hair and are warm blooded? (yes, even whales and dolphins have hair, although it’s sometimes only present on very young animals).

Answer 18

Other examples of animal classes include: Arachnida (spiders & scorpions, etc.), Insecta (insects), Aves (birds) and Reptilia (snakes and lizards, etc.)

Answer 19

Gray wolf, tiger and walrus: all are members of the order Carnivora

Answer 20

the class Mammalia (mammals) also contains orders such as: Proboscidea (elephants), Sirenia (dugongs, manatees, and sea cows), Primates (apes and monkeys) and Rodentia (mice, rats and beavers, etc.)

Answer 21

Gray wolf, fennec fox and red fox. All are in the family Canidae, which includes dogs, foxes and jackals.

Answer 22

Examples of animal families include Hominidae (great ape family), Corvidae (crow family) and Delphinidae (oceanic dolphin family).

Answer 23

The grey wolf is in the genus Canis with coyotes and jackals

Answer 24

There are around 37 subspecies of grey wolf. They include the dingo and (believe it or not) the domestic dog.

Answer 25

Although subspecies are essentially the same type of animal, there may be slight differences between them, and they usually live in different areas. Subspecies of the same species are able to breed and create fertile offspring.

Answer 26

A rainforest is a forest that grows in an area with a high rainfall. Most rainforests receive over 2,000 mm (80 in.) of rain every year.

Answer 27

Running parallel above and below the Equator are two more imaginary lines: the Tropic of Cancer and the Tropic of Capricorn respectively. The world’s tropical regions are located within these two lines.

Answer 28

In tropical regions, the sun is directly overhead at least once during the year.

Answer 29

What percentage of earth species live in rainforests? As much as 50 percent of all the Earth’s species live in tropical rainforests.

Answer 30

The ‘typical’ tropical rainforest is known as a **lowland tropical rainforest.** Here the temperature is high, rain falls for much of the year, and the atmosphere is humid. **Montane rainforests** are found at higher altitudes. They are cooler, and are often covered in mist. For this reason, they are often known as ‘cloud forests’. Trees in montane rain forests are often shorter than those in lowland rainforests. **Mangrove rainforests** grow in coastal regions where the land is often continuously submerged in salty water. Flooded forests occur where the land is often flooded by freshwater, and monsoon forests have high seasonal rainfall interspersed with dry spells.

Answer 31

Are all rainforests tropical? Not all rainforests are tropical rainforests. Rainforests do grow outside of the Tropics, in both the Southern and Northern Hemispheres. The climate away from the tropics is generally cooler, and these forests are known as temperate rainforests.

Answer 32

Soils that have formed where there is a lot of activity from volcanos Are called Andisols, often have special chemical properties. They are often very rich in nutrients and hold water well because of their volcanic ash content. They are often very young, and acidic depending on which type of volcano they come from. Volcanic soils around the equator can be very well weathered, and can lose some of their nutrients unless there is another eruption. These materials can be very dark in color.

Answer 33

Tamborine Mountain is home to 10 different types of forest including subtropical rainforest, wet eucalypt forest and open eucalypt forest. Incredibly, these forests contain more than 900 different species of plants representing 65 per cent of all the plant species found in the ‘mega-diverse’ Gold Coast area.

Answer 34

Ironbark is a common name of a number of species in three taxonomic groups within the genus Eucalyptus that have dark, deeply furrowed bark.[1] Instead of being shed annually as in many of the other species of Eucalyptus, the dead bark accumulates on the trees, forming the fissures. It becomes rough after drying out and becomes impregnated with kino (red gum), a dark red tree sap exuded by the tree.[2] The tree is so named for the apparent resemblance of its bark to iron slag. The bark is resistant to fire and heat and protects the living tissue within the trunk and branches from fire.

Answer 35

Red Bloodwood Corymbia gummifera, commonly known as red bloodwood,[2] is a species of tree, rarely a mallee, that is endemic to eastern Australia. It has rough, tessellated bark on the trunk and branches, lance-shaped adult leaves, flower buds in groups of seven, creamy white flowers and urn-shaped fruit.

Answer 36

all living things evolved from one common ancestor 3.5 billions years ago

Answer 37

a single species group is called a monospecific taxon

Answer 38

monospecific taxons include homo sapiens , welwitschia mirabilis, amborella trichopoda, sphenodon punctatus, orycteropus afer, limnognathia maerski,

Answer 39

for hundreds of millions of years welwitschia like plants were abundant as well as other non flowering groups. but then about 125 million years ago in the cretaceous period flowering plants emerged

Answer 40

the most basal living angiosperm amborella trichopoda can help botanists understand the sudden and impressive evolutionary success of angiosperms. the amborella mitochondrial genome contains 4 almost complete genomes from other plants & a total of 6 genome equivalents of foreign dna, the transferred genes come from all manner of photosynthetic species including algae, mosses, & other angiosperms.

Answer 41

soul surviving member of a separate reptilian order sphenodon punctatus is a tuatara that diverged from the ancestor of true reptiles ~250 mya. its skull is different to the regular squamates (lizards snakes) and is more similar to plesiosaurs & ichthyosaurs. also have a parietal eye

Answer 42

ardvarks only mammal alone in its order. orycteropus afer. all we know is that the ardvarks line appears to be an early offshoot of a very ancient group of ungulates (hooved) which is at least 20 mya

Answer 43

where separate animals evolve the same trait convergent evolution

Answer 44

one of the smallest living things thats also maybe alone in its phylum limnognathia maerski. some classifiers say its in its own class or subphylum instead. these havent been discovered for long so are still being explored. found in arctic lakes and subantarctic waters. not known why they have been found on opposite sides of the planet. all individuals found so far have been female. this may he because the males are even tinier. these animals are only 80 - 150 micrometers long. they may display sequential hermaphroditism which would explain the lack of male discoveries, or they are just parthenogenic.

Answer 45

animals that are born male and switch to female as they grow larger sequential hermaphroditism

Answer 46

parthonogenic

Answer 47

fast changing environmental conditions can include human encroachment, invasive species, climate change, habitat loss or fragmentation, exposure to novel biotic or abiotic stressors

Answer 48

some species can rapidly adapt to fast changing environmental conditions such as cliff swallows, sport fish, mosquitos, turtle headed sea snakes, ocean microbes, ediths checkerspot butterflies, elephant tusks,

Answer 49

biologists call high speed adaptation evolutionary rescue. some species can use this to respond to high intensity existential turmoil

Answer 50

cliff swallows evolution build nests on cliffs usually but most have quickly adapted to nest under bridge supports instead which means theres usually alot of cliff swallows around roads. they have also adapted to the threat of cars very rapidly, since the 1980's the number of road killed swallows has declined even though there are increasing amounts of birds and cars. this is because swallows that evolved next to roads developed shorter wings. it has been found that road killed cliff swallows tend to have longer wings at 5% longer on average. longer wings are better for air speed and gliding but shorter wings allow more maneuverability. the change in wing length happened in less than three decades! shorter wings are even helping them survive climate change, in 1996 a large fraction of a population of swallows died from starvation after a cold snap killed most of their insect chow, but the shorter wing swallows survived since they were able to catch their food more efficiently.

Answer 51

sport fish evolution due to overfishing species like salmon, cod, and herring have all evolved quickly to avoid extinction so now they are living fast and dieing young. since fishing targets larger specimens many species evolved to be smaller overall or are becoming sexually mature at a younger age and sometimes both. in some populations the change is really dramatic in that the average adult fish is 20% smaller than the species used to be and lives only 75% as long. this happens very quickly for example when they were over harvested in the 1920's the chinook salmon took only 30 to 40 years to get roughly 25% smaller

Answer 52

mosquitos evolution when the london underground was built in 1863 the workers inadvertently created a tidy isolated habitat for mosquitos. standing water would collect in the tunnels which served as perfect breeding grounds. humans discovered this in world war 2 when civilians used the tunnels as overnight bomb shelters. what was strange is that the mosquitos in the underground were biting humans at all since they are a subspecies known as culex pipiens that usually feed on avians above ground. so in the 8 decades it spent apart from its kin it switched to preferring the blood of mammals (rats). also unlike the above ground version, the london underground mosquito doesnt hibernate in the winter and the females dont need blood in order to lay their eggs. in fact the two types are now so genetically distinct that they cannot reproduce. so now its technically a new species, not just a subspecies. it only took a few hundred generations for this new species to evolve

Answer 53

turtle headed sea snake evolution ocean pollution has been dramatic but this species has evolved to adapt to chemical pollutants. around 17 years ago researchers noticed that the turtle headed sea snakes living in the noumea lagoon in new caledonia were mostly black instead. they get that color from the pigment melanin, and it just so happens that it doesnt just give color but also makes it very good at binding to heavy metals like zinc, lead or arsenic that can accumulate in animals tissues. scientist actually collected shed skins from new caledonia snakes and found higher levels of zinc, nickel and lead

Answer 54

adapting to chemical pollutants industrial melanism, in other words they are getting darker. they get that color from the pigment melanin, and it just so happens that it doesnt just give color but also makes it very good at binding to heavy metals like zinc, lead or arsenic that can accumulate in animals tissue

Answer 55

ocean microbes plastic theory the north pacific garbage patch alone contains about 79000 tons of plastic in an area about the same size as alaska. this is massive but apparantely not as massive as it should be, scientists say they are only finding a hundredth of the plastic there should be and the garbage patches dont appear to be getting any bigger. some believe this is due to the rise of microbes that eat plastic. the mere presence of the trash could be acting as a strong selective pressure driving the evolution of molecular pathways for chopping up plastic. this has been found in other species, considering the type of plastic garbage they eat has only been around for 70 years they evolved very quickly. the account of the ocean patches though could also be explained by declaring that perhaps these plastics dont last as long as we thought

Answer 56

ediths checkerspot butterfly evolution on a cattle ranch in nevada a population of ediths deviated from their kin. in their natural habitat these butterflies lay their eggs on blue eyed mary plants which is a native species of wildflower. but on the cattle ranch the farmers introduced an invasive species called english plantain and it turned out the eggs laid on the plantains fared better than their native medium since they live longer, they quickly evolved to prefer this new host plant and things went well until the cattle moved away and grasses that shaded the plantains grew abundant so the catterpillars living on them didnt get the warm sunlight they were used to. the poor butterflies simply werent able to switch back to the wildflowers quick enough so went extinct in a couple of years.

Answer 57

even rapidly evolving species only adapt at a rate of every 10 to 100 generations

Answer 58

evolutionary escape ability is mostly seen in species that breed young and have lots of offspring. the exception is the case of tuskless elephants, they only seemed to evolve quicker because they already had a 2 in 4 rate of mutation that causes tusklessness

Answer 59

human anatomy and behaviour evolution hasnt changed much in the last 65'000 years

Answer 60

evolution is defined as changes in the frequency of certain gene variants in a population over time; the genes that control those traits

Answer 61

gene variants except in specific cases humans have the same number of chromosomes and the same basic set of genes, but the exact sequence of our dna varies from person to person, thats what we mean when we refer to variants.

Answer 62

different variants of a gene are referred to as alleles of that gene, those alleles create the variation that makes us different from one another. if an individual with those alleles survives to reproduce those alleles get past on to the next generation causing their frequency to increase over time.

Answer 63

since evolution is defined in the change of gene frequencies one way to tell if a population has adapted to harsh conditions is to look for an increase in the frequency of those alleles that help you deal with these conditions

Answer 64

the LD50 is the dose of a substance required to kill 50% of a test population. is measured in a ratio of milligrams of toxin to kilograms of body weight.

Answer 65

clostridium botulinim LD50 one nanogram. a billionth of a gram per kilogram. enough to fill a grain of sand could kill 9600 people.

Answer 66

cyanide in apple seeds they contain a chemical that produces cyanide when it comes into contact with digestive enzymes.

Answer 67

color of the sun the real color of the sun is completely white, from earth surface blue and violet are scattered by the atmosphere which leaves over a yellow/ orange color. the sun is about 5800 kelvin and the radiation is in the visible range. this is exactly why this is our visible range because we evolved with the sun.

Answer 68

color of temperature heating metal causes it to glow different colors as it releases thermal energy as electromagnetic radiation. the emitted black body radiation is a mix of certain wavelengths whose lengths depend on the temperature. when things get really hot they can emit into the ultraviolet (above visible spectrum). the human body emits radiation in the infrared.

Answer 69

fires color the different colors in fire are due to how things glow due to black body radiation. its hotter where it glows blue and where its cooler glows yellow/orange. you can often see at the base of a flame an absence of fire, thats where vaporised wax is coming off of the wick but hasent started to burn yet. not all the carbon in the candle gets converted to co2 so leftover carbon particles come together to form tiny amounts of soot which heat up and glow orange and yellow, this glowing soot is where most of the flames light comes from.

Answer 70

fire inside the flame there can be hundreds of chemical reactions taking place. the oxygen in the air and the carbon and hydrogen in the candle dont do anything on there own, it takes a little external heat to get things started. solid fuel is vaporised by the heat and ripped into smaller chunks (pyrolysis). you cant have a flame without pyrolysis. right where the flame starts the hydrocarbons and oxygen molecules slam into each other and their atoms begin to rearrange. sometimes electrons in those atoms get into an excited state and when they settle back down again it gives off light which is why the bottom of the flame glows blue. at the end of the flame the unconverted carbon soot is all burned away and we are left with only carbon dioxide and water floating off into the air.

Answer 71

fires shape gravity pulls cool denser air down and makes hot air rise and this buoyancy is what gives flames their shape. but if you light a flame in zero g it will look very different. all the chemical and quantum reactions that make a flame glow can only happen where it meets the air, so even though they look like solid cones flames are actually hollow. as long as theirs fuel and oxygen a flame will burn.

Answer 72

why does a flame be a flame? its not the molecular ripping apart that causes the heat, its the formation of new molecules and bonds that creates heat, and that heat drives the chain reaction forward like a cascade

Answer 73

plasma vs fire plasma is the fourth state of matter in which atoms are stripped of their electrons. like fire and unlike the other kinds of matter, plasmas dont exist in a solid state on earth. they only form when gas is exposed to an electric field or super heated to temperatures of thousands or tens of thousands degrees. by contrast fuels like wood and paper burn at temps of few hundred degrees, far below the threshold of whats considered a plasma. also plasma is a state of matter whereas fire is not matter at all, its merely our sensory experience of a chemical reaction called combustion. in a way fire is like the leaves changing color in fall, the smell of fruit as it ripens, or a fireflies blinking light. all of these are sensory clues that a chemical reaction is taking place. whats profound about fire is it engages many of our senses all at the same time

Answer 74

Cacti use a different form of photosynthesis Known as CAM which uses way less water. Cam plants gather co2 through pores at night and store it in the form of organic acids. Then they can close those pores during the day to minimize water loss, using the stored carbon to get on with the light dependant parts of photosynthesis.

Answer 75

Moss and moisture Moss is a non vascular plant and thus does not have the necessary plumbing to transport water inside of them so they need all the moisture they can get.

Answer 76

Some parasites can live inside Cells.

Answer 77

Plasmodium (malaria), rickettsia (rocky mountain spotted fever, typhis) Legionella pneumophilia (legionaires disease & pontiac fever) Chlamydia Microsporidia

Answer 78

Microsporidia An entire phylum of single celled organisms. Parasites with tiny spores they use to invade cells. But they arent bacteria, current research suggests they are either a type of fungus or something closelyrelated to it. Most ofthe infected dont show any symptoms, tends to impact those with compromised immune systems.

Answer 79

Polypodium These parasites arent bacterial or single celled, they may be more related to jellyfish.

Answer 80

barnum effect psychological tendency to relate to broad statements

Answer 81

The Aurora A natural light display particularly in high latitude regions that is caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermoshere)

Answer 82

Its complicated as clocks tick slower towards the centre of the earth and motion also changes time.

Answer 83

El Nino Spanish for "the Nino" A few centuries ago fishermen in peru noticed every so often the water in the eastern pacific would get warmer. It didnt happen every year, but when it did, it always happened close to xmas, so they named this phenomena forthe "christ child" or El Nino. To understand how El nino works, think of the pacific ocean like a giant bathtub. Thanks to earths rotation and the Coriolis effect, winds near the equator usually blow east to west, and just like when you blow across a cup of tea, that wind actually pushes the water, so much so that sea level in Indonesia is usually a half metre higher than in peru. As that water near the surface, warmed by the sun, is forced west, it causes deep, cold water to rise in the east to replace it. If those east-west winds blow harder, warm water is pushed way west and the eastern pacific gets even colder. This is called La Nina. But if those east west winds weaken, theres less cold upwelling, and that huge mass of warm water ends up sitting just off the coast of south america, thats El Nino. Elnino can hold a ton of energy, the 1997 El nino moved 35 million million billion joules of energy into the eastern pacific, as much as 160'000 Tsar bombas, 100 times the energy used by everyone on earth in a year, 1/14th as much as the meteor that killed the dinos. This is alot of energy, and when it gets transferred to the atmosphere, where weather happens, it can have effects that reach around the world. The elnino during the northern hemisphere winter of 1997 & 1998 was the strongest ever on record. Rain and mudslides in california and peru caused disasters. Kenyas annual rainfall was 40 inches above normal. And on the other side of the pacific indonesia had massive droughts, temps in mongolia hit 42c. And while elnino usually means a quieter atlantic hurricane season, it can mean more and stronger storms in the pacific. In 1997 hurricane pauline dumped 27 inches of rain on western mexico in a single day. With so much money and life at stake, it would be nice to be able to predict el ninos in advance. Will california finally get rain, will the northeast get less snow? We just dont know. An elnino event can show up anywhere from every 2 - 7 years, or sometimes not at all. Its less of a cycle and more of a periodic-sometimes-quasicycle.

Answer 84

Why weather predictions are so difficult Truth is, for systems like elnino, prediction isnt just hard, it might be near impossible. One day in 1961 meteorologist edward lorenz was running some mathematical weather simulations on his computer. He needed to repeat one he had done earlier, so he re-entered his variables by hand and pressed start. Only when he looked at the results, they were completely different than the first time. He was baffled, he checled his work and realised he had accidentally rounded one of his variables. Instead of 0.506127, he had left off the last three decimal places (0.506). This tiny difference, just a few ten-thousandths of a unit, had completely changed the result. This accident gave birth to chaos theory. Lorenz had stumbled across the answer for why no matter how advanced our computers or models may get, we can never accurately predict the weather more than a few days out. In any system, the tiniest change in initial conditions could lead to completely different outcomes, and the farther out you try to look, the more those tiny uncertainties are amplified. It was this realization that lead lorenz to ask his now famous question of the butterfly effect. Our atmosphere is about as complex as things can get, an enormous fluid made of countless individual particles, each of them depending upon variables such as sunshine, temperature, wind, atmospheric pressure, humidity. All of those particles obey the laws of physics though, and we have equations to describe those laws, and huge powerful computers to put it all together. The thing is, even if we are able to measure what every particle in the atmosphere doing at any moment, for every measurement there is that tiniest built in uncertainty. And lorenz chaos theory tells us that this uncertainty, once we go out a few days, even a week, is amplified into no more than a lucky guess. Uncertainty is simply built into the universe.

Answer 85

The scientific method "evolution is just a theory." I understand your frustration, we're all searching for ultimate truth. And complex challenging concepts dont always fit nice and neatly in our brains. But what is truth? Are there different levels of truth? Are some truthier than others? We dont know, but we do know this: science is the absolute best tool we have for understanding how the universe works and what it hides. Theory like hypothesis, fact, and law are words in a language toolkit and mean different things. "Facts" are just observations about the world around us. That "jemma is a magnet for roaming flocks of fiendy felines!" And we often develop explanations for those observations such as, "cats love fish, so they must be trying to flock & feast on jems filthy fishy jayjay." Congrats, you just developed a hypothesis. But a hypothesis isnt something you prove, it is something you test. So, a smell test is in order. Is it stank like carp carrion? Yes! Hypothesis confirmed. We often come up with multiple hypotheses to explain an observation, we just eliminate the ones that are wrong, whats left over is not a theory or a law or an "ultimate truth", its just a possible explanation for something, one that can lead us to new hypotheses, which may agree or disagree with the original one. When enough hypotheses have been verified, we can pile all these together and turn these into something greater: a Theory. A Theory is the way we know something works, based on the evidence we've collected so far. Based on all the hypotheses we successfully put to the test. The best thing about a theory is that we can use it to make predictions, and not just about the way things are, but how they will be. This cycle, taking facts and observations, thinking up possible explanations, testing those explanations and then making predictions based upon them, thats what this whole science thing is about. Being a theory isnt a bad thing, it means that idea got the gold star saying "countless experiments have shown that this is sufficient to explain all the observations that it encompasses". Consider gravity. In science a Law is a detailed description, usually with math, of how something happens, like the movement of gas molecules related to temperature, or how mass and energy are always conserved. But a law doesnt tell us why it happens. Gravity as it turns out is both a Law and a Theory. Newtons law of universal gravitation describes precisely how two objects will attract each other based on their masses and the distance between them, and gives us a nice formula we can use to figure it out. Textbook "law". But newtons equation doesnt describe what is happening or why. To do that, we need a theory of gravity. Fact: if i drop this object it falls. Law: i can mathematically describe how fast that object and earth accelerate towards one another based on their masses and distance. But why? Hypothesis: there is a force pulling on the object, or maybe theres something about the way the universe is structured that makes massive things fall toward one another, or maybe its magnetism. Eliminate the bad ones and we are left with a theory. Thanks to Einstein we've got a theory of gravity, called General Relativity. But once scientists stumbled upon quantum mechanics, they began to realise that Einsteins relativity didnt account for what was happening on the very smallest gravitational scales in the universe. Its still great at describing the universe at the scale that we interact with it on, but even the theory of graviry is incompletw. Does that mean we throw it out because it cant explain everything? All of these elements fit together to make the scientific machine. We're constantly adding and taking away parts, but it keeps on running just fine.

Answer 86

Protection of medical volunteers Laws put in place in the 1970's called the Belmont Report. Three key ethical principles to guide all human research. The first point is called Respect for persons which encompasses informed consent. The second is Beneficence, means the researchers should try not to have any negative impact on the subject. Final point is Justice, eliminating exploitation.

Answer 87

Where did life come from? In 1952 a scientist named Stanley Miller first cooked up primordial soup. Millers experiment took some simple chemicals, like those found on early earth (methane, ammonia, hydrogen) , bubbled them up through a tube, zapped them with electricity, and after a few days floating in this soup he found amino acids - the building blocks of proteins, and one of the essential ingredients for life. This idea - that lifes origins could be found in a puddle of chemicals - is an old one. In the 1920s, two different scientists theorized about life arising from what they called a "prebiotic soup". And this soupy speculation even goes back to Darwin, who in 1871 wondered if life may have formed from chemicals "in some warm little puddle". What made millers experiment so special was it gave us proof: regular non life stuff could become cool life stuff super easily. But everything living we see today, even the most basic bacteria, is so complex, built of such intricate machinery, its impossible to imagine they just popped out of some soup. Thats because they didnt. We're gonna go on a journey in search of the origins of life. But the question shouldnt be how but moreso when. Life couldnt exist before earth existed, and it formed around 4.4544 Bya at the dawn of the Hadean Eon. Soon after that 4.52 - 4.42 bya, another planet collided with the young earth, melted the entire crust, and created the moon in the process. After the crust cooled, there was even some liquid water, at least for a little while. Because for the next couple hundred million years, earth was showered with hundreds of massive space rocks. The oceans boiled away, the crust melted again, and earth was basically no place for life. Until things settled down about 4 mya, at the dawn of the Archean Eon. This is the earliest possible time that life could have started on earth, the beginning of what we call the Habitability Boundary (4.6 - 3.9 Bya). And fossil and chemical evidence tell us that early microbes existed by 3.7 bya, whats known as the Biosignature Boundary (3.7 - 2.2 Bya), at some moment in this boundary, non life became life: we call this Abiogenesis. We cant look back to find that exact moment,but if we could, what would we look for? This brings us to the next big question, what is life? You would think biology would have a good definition for life, the thing that it studies. But this is much harder than it sounds. In one chapter of biologist JBS Haldanes 1949 book What Is Life? He literally writes "I am not going to answer this question". I think we might be asking the wrong question, because life isnt a thing that things have, life is what living things do. In school many people learn a checklist for the characteristics a thing must have in order to be considered life "MRS GREN" being the acronym for Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition. But this list came from looking at life as we know it today. Life at the very beginning was probably much simpler. A physicist Erwin Scrodinger, looked at all these things that life does and saw something only a physicist would see: according to the second law of thermodynamics the universe works to maximise entropy, in other words energy and matter are slowly inching towards perfect equilibrium, everywhere. But inside living cells theres a huge amount of order and complexity. In 1944 Schrodinger defined life as a struggle against entropy - the persistent resistance of decay, the preservation of dis-equilibrium. Since then we've learned a lot more about entropy, and it may be that the rise of complexity is as inevitable as its decay. Life creates these little closed systems where it works to keep things nice and ordered. But this definition still leaves out one important thing: living things evolve. Inside the very first living thing must have been molecules - chains of atoms - that carried information - instructions for building things or codes for doing stuff. Thses molecules must have copied and made more of themselves, some a little different than the others. And a few of those codes and instructions must have been better at doing whatever they did, so they made even more of themselves. What we're describing is evolution by natural selection, darwins famous idea, and for life to move forward, it must have been there from the beginning. Life is a product of evolution. With all this in mind, maybe we're finally able to come up with a better definition: life began the moment that molecules of information started to reproduce and evolve by natural selection. Now that we have a definition we can make some rules for what something has to do to be alive. 1) A living thing must work to avoid decay and disorder. 2) To do that, a living thing has to create a closed system. 3) They have some molecule that can carry information. 4) This information must evolve by natural selection. But rules are one thing, the ultimate question is how this would actually happen? Lets take these rules one by one. What would it require for these things to arise? And most importantly, how likely are each of these steps based on what we know from science. Today no matter where we look in the tree of life, most cell machinery is made of protein - chains of folded amino acids. When modern cells make proteins, they copy genes from DNA into RNA and then use that RNA as a blueprint for making the proteins through Replication, Transcription, and Translation. We call this universal pathway the Central Dogma Of Biology, because it sounds really cool, and because its something that all life shares. But theres a paradox hidden in here, a puzzle. Like a chicken egg problem. DNA needs protein to make more of itself. And cells need DNA and their instructions it holds to make proteins. So which came first? We can solve this paradox in a pretty simple way, just get rid of DNA and protein in the earliest days of life, and let RNA do everything. RNA is the molecular cousin of DNA. It contains the same four letter alphabet code as DNA (GTAC), only T is replaced by a similar molecule U (GUAC). And instead of two strings in a helix, RNA is usually found in just one string. RNA is special, because in addition to carrying information in that 4-letter code, it can fold up into interesting shapes and actually do stuff. The same way that protein enzymes can do all kinds of chemical reactions, RNA enzymes - called Ribozymes - can work lifes machinery too. Its now thought that life began in an RNA world. Before DNA became a more permanent form of storage, different RNA chains could have carried information and been the machines for all lifes important chemistry. Unfortunately the RNA only world went extinct more than 3 bya, but we can make these RNA enzymes today. Scientists have constructed Ribozymes that can copy themselves, just like DNA gets copied. And these copies occasionally have errors or changes, so RNA can evolve too. If you need more proof you can find it right inside your cells. The Ribosome, the massive structure that stitches amino acids into protein, is mostly RNA. We also find Nucleotides, the single molecular units of RNA, inside a bunch of other molecules our cells need for metabolism. This all makes sense only if the earliest days of living chemistry were dominated by RNA. And it solves our chicken egg problem. The RNA world takes care of two of our four rules: A molecule that can carry information (3), and that can evolve (4). To find answers for the other two, we need to ask one more question: Where did life begin? Theres been alot of theories about where life came from, but they boil down to these: Either life arose on earth, or life arose somewhere else and was brought here. Its well known that space is full of the chemical building blocks of life, from amino acids to DNA and RNA letters... buried inside meteorites like the one that fell on Australia in 1969. It shows the chemistry that makes biological molecules can happen pretty much anywhere. But the idea that life was delivered to earth on space rocks, which goes by the awesome name Panspermia, theres just no proof that it ever happened, and it doesnt really explain the origin of life anyway. It just moves it somewhere else. We know that early earth had plenty of chemical ingredients, but the problem with the old idea of primordial soup is that soup cant do anything on its own - those chemicals cant react without outside energy. We get a hint of where this primordial energy came from by looking again at our own cells. Instead of lightning or heat energy, our cells pile up a bunch of hydrogen ions (protons) on one side of a wall, let em flow downhill, and use this like a water wheel to push on cellular machinery (and make things like ATP in the Mitochondria). We burn food to keep our hydrogen pump going, but the first life forms wouldnt have been able to do this, because tacos hadnt been invented yet. Instead they would have needed some natural source, and they could have found it at the bottom of the ocean. Deep sea Hydrotheermal Vents are covered in microscopic little pockets, which could have served as molds for the first cells. Molecules with one oily water-hating end (hydrophobic) and one water-loving end (hydrophilic) have a neat habit of forming bubbles and sheets on their own, and there were plenty of these in the chemical soup near deep sea vents, ready to give rise to the first cell membranes. These vents also create natural streams of hydrogen ions near those little pockets in the rock. Imagine an early life form sitting there, wrapped in its little membrane bubble, with a free source of energy flowing by, powering all the work it takes to create ordered life and resist entropy. But this would have been the absolute simplest form that life could take. For this life form to become life that looks likfe what we know today, a lot more stuff had to happen: it had to switch from storing its genetic information in RNA and start using DNA. Instead of using RNA and Ribozymes to run all its cellular machinery, it had to start stitching amino acids into proteins. This opened up new possibilites for making and storing energy that let early life become free living and more complex. One of these complex life forms is the ancestor of everything alive today, the last universal common ancestor, or LUCA.

Answer 88

what was the ancestor of everything? The more fossils we can find and study, the more branches and twigs we can add to the tree of life - that web of relationships that connects all oranisms, living and extinct. But fossils can only get us so far. As any astrophysicist will tell you, the story goes back way farther than any fossil. The story of life actually begins with the beginning of everything. In the aftermath of the big bang the universe was an energetic, structureless mess. But that mess pulled itself together into atoms, stars, galaxies, planets, and finally into life. How did these little eddies of order form in a universe otherwise prone to increasing disorder and chaos. The search for our origins goes back to a single common ancestor, one that remains shrouded in mystery. If you trace all the branches on the tree of life backward, you realize they all come from the same trunk. That initial point before anything branches, in a single species. Darwin theorized that such a thing must have lived, he called it "a primordial form into which life was first breathed". Today we call it LUCA. Luca isnt the first to have lived, instead its the common ancestor of everything thats alive today. Even though Darwin suggested that there was a universal common ancestor, we couldn't even guess what it might have been until we started to master genomics, the science of mapping and studying the genetics of all living things. Today we know that all life uses the same molecules of RNA, DNA and Protein. And the genetic code thats responsible for making that stuff is basically universal, from bacteria to humans. Thats one of the best arguments to support the notion that everything came from the same place. Its also why most of the research thats gone into learning what LUCA was has involved comparing genomes of all kinds of living things, to see what else they have in common. One of the first to take this approach was American biologist Carl Woese, in 19 77 he discovered the existence of organisms that would make up a whole new domain of life, and a key to the search for LUCA. He discovered Archea. Archea are a group of Prokaryotes - simple single celled organisms that are vaguely similar to bacteria. But they turned out to be so diverse and different from any other living thing, that Woese proposed a new tree of life - one that divided life into three domains: Archea, Bacteria, and Eukaryotes. And, he said, where those three main branches converged, there was LUCA. But he saw the three domains arising NOT from a single cell, but from a chaotic environment more than 4 bya, when cells didnt quite exist yet. In this scenario he proposed there were extremely simple things that were even more basic than cells. He called them Progenotes and envisioned them as tiny scraps of genetic information, surrounded by a membrane. These Progenotes wouldn't have been complex enough to create true offspring, they might have been able to copy their genetic material, but not accurately. So instead, they may have just floated about at random, constantly swapping little snippets of genetic code among themselves. Sometimes that genetic info might have worked well for a progenote, and could be copied. Other times not. But out of this basically random transfer of information, Woese thought, some of the key elements of life could have arisen. For instance the genetic code that makes up genes as we know them could have come about pretty early. But that information might have been stored in RNA, not DNA as it is today. Now RNA, in addition to storing information, can do stuff - biochemical reactions - like we see in the Ribosome, where RNA is used to not only code for, but also build, proteins. Early on, RNA machines like the ribosome would have evolved alongside genetics version 0.1. So its likely the first life arose and evolved in this so-called RNA world, and only began storing genetic information in DNA later on. So instead of being a specific organism, or even a group of things, Woese thought that Luca was the whole process by which Progenotes acquired the genes to make these essential molecules. And from them would have come three lineages that evolved into modern bacteria, archea, and us eukaryotes. Now Woeses view of Luca hasnt been abandoned, but many scientists have moved away from it. Thats partly because, when Woese was publishing these ideas, genetic sequencing was just coming of age. Back then only a handful of genomes had been sequenced. And now we've mapped thousands of living things. And that means we can try looking for Luca in new ways - like, by lining up genomes from across all of the domains of life and comparing them to see what they have in common. If a gene appears in basically every living thing - so its considered universal - then it must have come from Luca, or so the thinking goes. So, many researchers who study Luca are trying to reconstruct its genome. One way they do that is by finding what they call the Minimal Genome - the smallest amount of genes that a cell can have and still survive. Since these most basic, essential genes are thought to have come from Luca, if we could identify them, that could tell us how Luca looked and lived. This work has been spearheaded mainly by researchers in Maryland who have studied the genomes of bacteria like Haemophilus and Mycoplasma. And based on what those microorganisms had in common, the team proposed back in 2003 that Luca probably had 5 or 6 hundred genes. Those genes would have provided for a simple metabolism and a genome based on RNA - but not for making and copying DNA. Now, as genomes go, that is tiny. A few modern organisms do have about 500 genes, but they are parasites that steal what they need from their hosts instead of using genes to make stuff. Meanwhile the bacterium E. coli has around 5 thousand genes, and we humans get about 25'000. Could Luca survive on its own with so few genes? Well another study done in 2006 found that Luca would likely have had more like 1000 genes, maybe around 15 or 1600. According to this slightly more recent take, our common ancestor might have been a little more complex and may have seemed more familiar - to microbiologists at least. That means a genome based on DNA, ribosomes to translate the genetic code, and a metabolism that could break down sugar for energy. So the basics of biochemistry as we know it. A lot of this minimal genome research took place at the turn of the millennium - around the same time Woese was thinking about Luca. But in the last 20 years, the genetic revolution has redrawn the tree of life. Recently many scientists have begun to argue that the tree of life should have two main branches, with bacteria on one branch, and archaea plus all of the eukaryotes on the other. Thats because the more we learn about genomics, the more it seems that all modern eukaryotes are genetically more similar to Archaea than to bacteria. In fact many researchers now belive that archaea are our ancestors. So of course, this has enormous implications for what Luca was, too. In this case, Luca would sit below where those two main branches separate , before eukaryotes even formed. And based on this new line of thinking, a surprisingly complete picture of Luca was published in 2016, in the journal Nature Microbiology. Here, evolutionary biologists based in Germany compared the genomes of more than 130 Archaea and over 1800 bacteria in an attempt to reconstruct Luca's genome. Keep in mind here, in the two branch model, archaea and bacteria are the most distantly related forms of life omn earth. So if you can find any gene in both archaea and bacteria, then there are two possibilities: either the two groups traded genes at some point, which prokaryotes sometimes do, or they both inherited that gene from Luca. The researchers looked for genes that appear in two different groups of Archaea, and two different groups of bacteria, reasoning that if a gene shows up in all four of those places, it must go back pretty far. Now this is different from the minimal genome approach, because it tries to identify the oldest genes, not the ones that everyone has. And the genes that were recovered in this research suggest that Luca lived in hydrothermal vents. How did they know? Well for one thing, they recovered a set of genes that we know are used by extremely ancient groups of archaea and bacteria that live in oxygen-free environments, where they metabolize hydrogen gas and carbon dioxide into methane. Hydrogen gas is hard to find on earth, but it can come from deep sea vents; so thats one clue. Other genes they found use metals like iron, nickel, and molybdenum in order to function. And these are all found in the same kind of environment as hydrothermal vents. Scalding hot vents full of metals and sulfur might seem pretty hostile, but our earliest ancestor might have called these places home. Now, how could that be? Like, we dont metabolize hydrogen and CO2 to methane. And neither do most organisms we know. So how could the ancestor of everything have been so different from us? Well its at least possible, because genes are often lost over time. As creatures evolve and adapt to new environments, lots of old genes arent always needed. Thats basically why cats have genes to make fur, and not scales. So by the same token, long after molecular oxygen became available on earth, about 2.5 bya, many of Lucas descendants were able to lose the genes for metabolizing hydrogen and CO2 and still live comfortably. This is only one possible picture of Luca. Both the Progenote model and the Minimal Genome idea have proven useful to guide our thinking, but they probably dont represent the true Luca. And not everyone agrees that Luca lived in vents either, theres plenty more research to be done.

Answer 89

the physics of life Our universe is prone to increasing disorder and chaos. So how did it generate the extreme complexity we see in life? Actually, the laws of physics themselves may demand it. How did life begin? We can seek the answer in the chemistry of the early earth or in the biology of the first cell. But we all know that chemistry and biology are just applied physics. So can we approach the question of the origin and the very nature of life from the point of view of physics? We can sure try. To understand life, we need to understand entropy. The universe tends toward disorder, decay, and equilibrium. A hot cup of coffee will tend towards the same temperature as the room, and the hot, dense early universe will expand. Stars always burn out, black holes evaporate. The particles that make up any system all have some degree of random motion. That random motion tends to drive the system towards the most common arrangement of particles. Such a random disordered, unspecial arrangement is a high entropy state. Interesting arrangements, like thermal energy being concentrated in your cup of coffee or all the matter in the observable universe being crunched into an infinitely dense point are low entropy. Theyre highly specific configurations that almost never happen by chance. So entropy is sort of a measure of the boringness of a system, the commoness of the arrangement of particles. The second law of thermodynamics tells us that a closed system will only increase in entropy. The universe will only get more boring. But theres one type of system that seems to resist the second law of thermodynamics and maintain low entropy. That system is life. It has a very low internal entropy because its structure is extremely specific and non-random. The molecular machinery of even a single cell defies belief. Cells are complex. Inside just a single one of your cells, you have 6 billion base pairs of DNA, storing hundreds of megabytes of data. Intricate molecular machinery made of RNA and protein unpacks, transcribes, cuts and splices, and processes that dat to build and control an entire factory of protein molecular machines, which in turn, power the entire biological process that is you. Not only is life stunningly complex, but that complexity increases over extremely long time scales, in fact, over eons. When we look at the fossil record we see evidence of evolution carved in stone. When we trace the development of fossils over the nearly 4 billion years of life on earth, we see clear as day the steady trend toward greater complexity, from the first single celled orgnisms to simple ocean invertebrates to an explosion of complex animal life, and finally, to us. Naively, this preservation and increase in order appears to contradict the second law of thermodynamics - entropy appears to either stay constant or decrease. The earths biosphere, at least, becomes less boring over time. But lets be clear, there is no violation of the second law. The seocnd law tells us that closed systems must increase in entropy. So a systems unable to exchange energy with the outside environment. But living organisms and indeed the earths biosphere are not closed. Both recieve energy from outside. Ultimately that source of energy is the sun. Its light warms the atmosphere in the oceans and it powers photosynthesis at the bottom of the food chain, driving a complex chain of nutrient synhtesis that ends with whatever you had for dinner last night. On the other hand, the system of the earth plus the sun in increasing in entropy. Life acts to reduce its own internal entropy by increasing the entropy of its surroundings. This was first pointed out by Ludwig Boltzmann, who described life as a struggle for entropy, well, more accurately, against entropy or for negative entropy. Erwin Schrodinger in his 1944 book What is Life, describes life as a process feeding on negative entropy. Life absorbs order and it ejects disorder into its surroundings. The type of order that life feeds on can be thought of as free energy. By free energy, i mean the special out-of-equilibrium energy sources like a cup of coffee or the sun. Another way to say this is that life feeds on energy gradients. When two systems with very different energy densities come into contact, energy must flow. Life feeds on that flow. In fact, the importance of energy gradients to life can help us understand the actual origin of life and its precursors. The origin of life on earth isnt known. We think it started with a self replicating molecule similar to RNA. Following that synthesis, evolution took hold, and the first protocell and then first true living cell pulled itself together. But where on earth did all this happen? There are a few hypotheses. Perhaps it was in tidal pools or around deep sea hyrdothermal vents or even on the undersurface of earths ice caps. These environments share a critical property. They sit at persistent energy gradients. The water of tidal pools is both cooled by the earth and the ocean and warmed by the sun. Around deep sea vents, the searing gases from earths hot interior meet the frigid water of the ocean depths. Beneath the thick ice caps, theres the transition between the solid and liquid phases of water. These are places struggling to return to equilibrium. These systems are doing their best to obey the second law by redistributing their energy as evenly and randomly as they can. Heat energy flows from hot to cold, seeking a uniform temperature, but energy is also dispersed into every form it can take consistent with the laws of physics. Some of that energy gets distributed into chemical bonds as simple molecules form via every chemical reaction thats possible given the available raw materials. As those molecules form, new channels open up for distributing energy into the chemical bonds of increasingly complex molecules. Normally this local rise in complexity would all cease when the system reaches thermal equilibrium, energy is perfectly evenly distributed and new molecules break apart exactly as often as theyre formed. But when our energy source is flowing into a much larger reservoir, the ocean for example, then equilibrium is nerver reached. Complexity can increase indefinitely as a byproduct of the system striving to redistribute the endless gradient in energy. And at some point natural selection takes over. Molecules self-catalyze, they help drive the very reactions that create more of the same. Molecules better at that process become more abundant, and at some point they become true self replicators, and eventually they become life. But even life and self replication might be a very natural part of the same thermodynamic drive to dissipate energy. I mean think about it. Living things are incredible heat dissipation, entropy maximizing machines. The most random possible form for energy is thermal radiation, and the lower the energy of its component photons, the higher the entropy. A plant absorbs the concentrated ultraviolet light from the sun and reprocesses it into a much higher entropy infrared heat glow with gradients in its concentration. Animals consume high energy desnity packets of matter called food and convert it to lower energy density waste as well as that same infrared heat glow. Life is great at disspating energy, and more generally, it may be that self replicating systems are the best possible energy dissipators of all. This is a new idea poposed by MIT biophysicist Jeremy England, who puts the thermodynamics of life on more solid theoretical grounds. Hes demonstrated mathematically that self-replicating molecules and simple single cell life are extremely good at shedding heat in the act of reproduction. Self replication randomizes the environment, even if each new replicator is highly ordered. And its not just life that does this. Consider a perfectly streamlined or laminar flow of some fluid. This organised flow is disrupted by introducing turbulence. The laminar flow has a lower entropy than the turbulent flow because there are fewer ways to rearrange the particles in the former while preserving its global properties. But, watch the transition from laminar to turbulent. While the global structure is disrupted, substructure develops. Waves and vortices have their own complex and regular structures, but they ultimately serve to dissipate the flow. Any given eddy taken separately has a lower internal entropy than its chaotic surroundings, but the source of that local incidence of low entropy is the streamline flow that it formed in. And those turbulent eddies ultimately serve to increase the entropy of the greater flow. So, given a much larger source of order, the global process of dissipating of that order results in eddies of low entropy. Life appears to be just such an eddy. In the case of life, the original source of extreme low entropy is the Big Bang itself. In the process of redistributing energy into the most random possible state, little eddies of order, like galaxies, stars, planets, organisms, and cells naturally emerge. These blips in order are actually serving the second law, helping the universe disperse its early extreme low entropy state. So it essentially makes us little eddies of order, a momentary fluctuation of interesting but ultimately, in service of the spread of disorder and dullness, an agent in the inexorable trend to maximise the entropy of spacetime.

Answer 90

Why is there land? Its possible that land didnt always exist. And technically speaking, it doesnt have to. If you were to just smooth out the earths crust, the oceans contain enough water to cover the planet in a sea more than two kilometres deep. So, why does land exist? Why is it so varied with all those mountains and valleys and flat plains? And, Could anything ever get rid of land on earth? To answer these questions we need to travel back more than 4 billion years. Billions of years ago, earth started as a cloud of dust and grains left over from the suns formation. Then, over time, those pieces slowly balled together into proto-earth. That ball was made of all kinds of elements. And as it aged, the denser ones, like iron, sank towards the center of the ball to become the earths core, while lighter ones stayed towards the outside. Eventually the planet separated into the layers we know today: the inner and outer core, the gooey mantle, and the crust. These days there are two kinds of crust - continental and oceanic - and theyre made of different ingredients. Oceanic crust tends to be mostly a type of rock called Basalt and contains more heavy compounds. Continental crust which generally makes up land, tends to be mostly Granite and contains more relatively light compounds. But the composition of the early crust and how it changed in earths first billion years or so is pretty hard to pin down. Like a lot of earths early history, most of the material has been recycled and destroyed by now. So there are alot of interpretations. But mostly, models seem to start with a crust that would more resemble oceanic crust today, with continental crust slowly growing over time. The exact date when the first continental crust appeared is one of the big questions in geoscience. Some models say it started growing almost immediately, others say it didnt really get going until about 3.6 bya. But theres something potentially really interesting hidden in there. Because depending on which of these models is right, early earth might have been a water world. We think the oceans had to have existed by around 3.8 bya. Thats based on evidence like ancient pillow lavas dated around that time, which only form when lava flows into water. So if continental crust hadnt formed by then, there would have been a point in time at which the earth was, indeed, an ocean world - where land did not exist. As for why continental crusts started forming, there are a couple of ideas. One of the most well-studied relies on the movement of tectonic plates, the big slabs that make up earths crust. And it goes like this, at some point, the idea says, the crust started to form into these giant plates, possibly thanks to massive magma plumes from deep within the earth. And as the plates started pushing against each other, some of them began sliding down towards the mantle in a process called Subduction. And as that happened, the increased heat near and in the mantle began to heat the rock. But since rock isnt completely homogenous, its not like it all melted at once. Instead, different chemicals started to liquify at different rates, and the rock separated in a process known as Partial Melting - with some areas being denser, and others less dense. Over time, this process repeated, and we ended up with new oceanic crust and the first continental crust material. That material was brought up through volcanic eruptions, which then built up into small volcanic islands above the ocean. The very first land! And as more volcanoes erupted and material got scraped off subducting plates, these islands would have grown over time into larger continents. Studying the beginning of the eartsh history is hard, so not all scientists agree that subduction was necessary to build the first continents. Like in 2012, one group proposed something a little more... oozey. They got this idea while looking at rocks from the Isua Greenstone Belt in Greenland, which are more than 3.5 byo. They compared the amount of trace elements found in those rocks to amounts we'd expect to see if they had formed by subduction, and they concluded that this ancient crust may not have needed to get all the way down into the mantle via subduction to melt and reform. Instead it might have kind of oozed up as rocks melted higher up in the crust. So no subduction needed. No matter how this occured, though, eventually the earth did get its first continent. Based on various pieces of evidence, researchers have proposed that this continent, which they call Vaalbara, was made of rocks that are today found in Southern Africa and Australia. While others favor Ur, a land mass made up of what would today be parts of India, Madagascar, and Australia. In any case, land happened, and so far as we can tell, earth has had it ever since. Since the time of Ur and Vaalbara, plate tectonics and other forces have kept continents above water and made them even craggier. These days, new continental crust is still being formed and destroyed at subduction zones. And plate collisions have also pushed up mountains, like in the himalayas, making the earth even less smooth. Meanwhile erosion and other processes have also played a part, with wind and rain carving canyons, arches, and other amazing landscapes. So, no matter how it got here, the land hasnt been unchanging and still. Its continually shaped, changed, and even sometimes destroyed or completely hidden by forces of nature. And that makes you wonder, if all these forces are still at play, reshaping the lanscape all the time... Could these forces ever make land disappear? The good news is, continental crust is usually fairly stable. Its mostly the oceanic stuff that subducts and is recycled when plates collide. And today, the earth has reached more or less equilibrium between the amount of crust made and the amount of crust lost. But some models have suggested that the amount of continental crust has actually decreased from some ancient peak. A 2016 paper suggested that when India hit Asia, a substantial portion of the continental crust (50%) ended up being forced down into the mantle. So it is possible to destroy continental crust on a large scale. But even then, land will probably never disappear entirely. We also have plate tectonics working to push parts of the ground higher and higher above sea level all the time - so even if some sort of catastrophic flooding happened, that wouldnt be the end of dry land. Even if plate tectonics stopped all together - which is very unlikely, since plate tectonics is powered by heat from the earths core, and thats not cooling down anytime soon - earth still wouldnt become perfectly spherical. Researchers at caltech noted that while erosion might wear the mountains down into hills, there would still be other processes. Things like meteroite impacts could still happen, which could create large dents in earths surface - little rings of land that could stick above water. Volcanoes would still exist too - because altho many are powered by magma from those all important subduction zones, they can also exist far away from the plate edges, like the hotspot under hawaii. In those places you dont need a subduction zone. Instead, magma plumes in the mantle are hot enough to melt their way up through the crust. In fact, while earth is the only planet with active tectonic plates, volcanoes like this have created land on other worlds, too. Like even tho its dry now, mars used to have a huge ocean. But it still had dry land - in part thanks to things like Olympus Mons, its gigantic now extinct volcano. So even if earth was a water world billions of years ago, the odss of that happening again are pretty slim.

Answer 91

Algorithms from nature Nearest Neighbours: When you think about algorithms you probably think of google searches or youtube recomendations. An Algortihm is basically any recipe of calculations that a computer can follow to produce a specific kind of information. Algorithms arent just for computers. They show up all through nature, too, in places like your immune system and in schools of fish. And just as engineers borrow ideas from natures physical designs, some computer scientists look for inspiration in natures algorithms. Technology has improved thanks to algorithms we swipe from nature. Nearest Neighbours: Say youre looking for the perfect fuzzy animal photo to send as a virtual hug to your friend. An image search pulls up some cuddling kittens that are almost right, if only you could find a slightly more zoomed out version... What you want in this situation is something called nearest neighbours search - an algorithm that can quickly search a big database to find the items most similar to the one you specify. That gets harder as the database gets bigger; and on the internet, there are way too many images for the search engine to compare every single one. So how do search engines pull of that feature that gives you "visually similar images?" One technique is called Locality-Sensitive Hashing. This is a type of algorithm that digests each image into a short digital fingerprint called a hash, with similar hashes for similar inputs. For example, if your inputs were essays, a decent hash might be the first letters of the first twenty sentences. So if one essay was copied from another, their hashes would likely be very close. This method makes it easy to find similar inputs. Instead of comparing your kittens to every other image on the internet, google can organize images by their hashes and just pull out the similar ones. The catch is that locality sensitive hashing can still be kind of slow, and sometimes innacurate. That is where fly brains come to the rescue. See, a fly can smell, bit it doesnt differentiate every subtle variation of odor; it groups odors into categories so it can learn that, for instance, cheese smells often lead to fruit, but book smells dont. In 2017 a team of computer scientists and biologists realized that fly brains group odors using a form of locality-sensitive hashing. Except, in the flys version, the brain boils a smell down to a few numbers by first expanding the smell data into a much larger collection of numbers. Only then does it select a few of those numbers as the hash. Its sort of like expanding an essay by replacing each character with a random 10-character code, producing a string of gibberish ten times as long. Then you could find the hundred gibberish words that appear most frequently, take the first letter, and use that as the essays hash. As strange as that strategy sounds, it turns out to work really well. All the extra gibberish gives the algorithm more oppurtunities to find patterns that jump out strongly for one cluster of inputs but are conspicuously absent for others. When the computer scientists built their own fly based hashing algorithm, it was up to twice as accurate than traditional methods - and also twenty times faster.

Answer 92

Algorithms from nature Object Recognition Computer vision is everywhere. Self driving cars, MRI tech, facial recognition, they all use it. Most of these systems need to do some form of object recognition - meaning they need to identify the contents of an image. For decades, scientists used handcrafted algorithms to extract image features like edges and contiguous shapes. Then, they could build other algorithms that used those features to guess what was in each part of an image. But all these hand tuned algorithms tend to be fragile. Its up to the cleverness of engineers to design the right kinds of analysis and tweak the parameters just so. Now, engineers are pretty clever, but there only so much subtlety and detail they can code up. In the background though, a different approach was taking shape: convolutional neural networks (CNN's). In AI most kinds of neural networks are based on nature only in a crude way. Theyre called neural networks because they kind of work like neurons. But Convolutional Neural Networks are based on nobel prize winning research on cat brains. Back in the 1950's, a pair of neuroscientists discovered that some neurons in a cats visual cortex, called simple cells, would respond only to simple visual elements - like a line in a specific place at a specific orientation. Those simple cells pass information to so called complex cells, which aggregate the information across a wider area. In other words these rezearchers discovered a hierarchy in the brains visual processing: Earlier layers detect basic features at different locations, then later layers add all that together to detect more complex patterns. That structure directly inspired the first convolutional neural networks. In the first layer of a CNN, each simulated neuron looks only at one small patch of the image and checks how well that matches a simple template, like a spot of blue or an edge between light and dark. The neuron gives the patch a score depending on how well that patch matches the neurons template. Then the next level looks at all the scores for edges and spots in a slightly bigger patch and matches them against a more complex template, and so on up the hierarchy until youre looking for cat paws and bicycle wheels. A CNN learns these templates automatically from data, saving engineers from manually specifying what to look for. Today, CNNs totally dominate computer vision. And although they now have bells and whistles that have nothing to do with the brain, the visual hierarchy is still baked in.

Answer 93

Algorithms in nature Immune Systems Companies really hate getting hacked, there are lawsuits and bad press, and its pretty inconvenient for them and the people who rely on them. So if a companys network starts getting hammered with unusual traffic, it might be a good idea to lock things down. But detecting what counts as unusual traffic isnt always easy. Its an example of whats called anomaly detection, or scanning for atypical data, which can be tricky. See, you cant just lay out rules for what normal traffic looks like. For one thing, what is normal is always changing. And anyway, hard rules would be too rigid: you wouldnt want a red alert before every holiday just because a bunch of employees traveled early and logged in from home. It might be tempting to try supervised machine learning, where you show an algorithm lots of good and bad examples, and it figures out how to tell them apart. With anomaly detection, you often dont have many examples of the bad stuff youre trying to catch. Most of what a company has, of course, is logs of normal network traffic. So how can it learn what abnormal traffic looks like? One particularly cool solution is based on our bodies. Because you know whats really good at detecting a few bad guys in a sea o f things that belong? Our immune system. To recognize and kill off invaders, your immune system uses cells called lymphocytes, which have little receptors that detect foreign proteins. But your body actually produces a huge variety of lymphocytes, with receptors that detect pretty much any random protein snippet - including bits of proteins that are supposed to be around. You dont want to attack those, so before your body releases its lymphocytes, your thymus gland sleectively kills of the ones that would detect familiar proteins. As a result, the only lymphocytes that survive are the ones that detect foreign proteins. This is called negative selection, and anomaly-detection algorithms can use a similar concept to spot unusual traffic. They can generate detectors for random sequences of traffic data, then delete any detectors that go off on normal traffic logs. The ones that remain, thus, respond only to abnormal patterns.

Answer 94

Algorithms in nature Decentralize In lots of situations, having multiple computers coordinate to divide up a task is crucial - for example, to carry out a robotic search and rescue mission, or to index the entire internet. When you have just a few computers in a network, its easy to have one central command computer coordinate them all. But if youre coordinating hundreds of thousands of machines, or the machines are cut off from one another, controlling them with one central computer becomes impractical. So all those machines need a process that they all follow independently that somehow gets the job done efficiently and without horrible mistakes. Little machines... acting independently... getting big projects done sounds kind of like an insect colony. As it happens, theres a whole niche of what are called swarm intelligence algorithms that tackle problems like this, and many are based on insect behaviour. For example, there are construction robots that collaborate by imitating termites. We still dont know exactly how termites build their massive mounds. But we do know that each worker can only see its local environment - whats been built right there and where surrounding workers are. That means the only way for the termites to coordinate is by leaving indirect signals for each other in their shared environment. Like, when one termite does a bit of construction work, it leaves the soil arranged as some kind of cue to other termites about what needs to be done next. This indirect coordination strategy is called stigmergy. Inspired by termite stigmergy, a system of robots called termes allows a fleet of little robots to build arbitrary structures with no central coordination. Just by sensing whats been built and following some basic traffic rules, each robot figures out what to do next to get closer to the target structure. The hope is for similar robots to one day build complex structures even in hostile environments like warzones or on mars, without depending on a centralized controller.

Answer 95

Nature inspired algorithms can get a bit out of hand. People have designed algorithms based on wolf pack behaviour, virus evolution, lightning paths, and so on. Nature inspired computing has been criticised for encouraging cute metaphors that dont add insight or are unnecessaril complicated. But sometimes natural phenomena really can make for great inspiration. Nature can be quite the computer scientist.

Answer 96

volcanic nurseries If you were to imagine the perfect place to build a nursey, and active volcano probably wouldnt be the first choice. But it turns out that lots of animals use the heat from volcanoes to incubate their unborn babies. All developing embryos benefit from a bit of heat. Heat is just molecules moving around faster, and that means, it speeds up all sorts of chemical reactions - including the ones inside of eggs that transform yolk compounds into baby animals. So eggs in cold environments can take a very long time to incubate. For instance, the eggs of some skates - a kind of fish related to stingrays - can take 4+ years to hatch. Thats because they live in the deep ocean, where the water temp is similar to the milk in the fridge. But deep dwelling pacific white skates have figured out a way to fast track their youngs growth. They tuck their egg cases into the rocks of a kind of undersea volcano called a hydrothermal vent. In fact when this was first observed in 2015, the researchers noted that the egg cases were mostly placed within 20 meters of an active vent chimney, where hotter than boiling water is shooting out of the seafloor. And thyre not the only ones taking advantage of these deep ocean hot spots. In 2018, Nautilus Live stumbled upon over a thousand otherwise-solitary deep sea octopuses grouped together at a hyrdothermal vent. They were all tucked weirdly into the rocks with their arms flipped backwards, protecting their eggs. And deep sea animals arent the only ones getting in on volcanic nurseries. For creatures like us that maintain a pretty constant body temp regardless of their environment, it seems to be even more critical to keep embryos warm while they develop. In some species eggs wont develop at all unless theyre kept close to their parents body temperature. Thats because embryos lack the ability to regulate their own temperature. Most mammals have solved this problem by incubating their embryos sinside their bodies, which are body temperature, whereas birds generally sit on their eggs to keep them warm. But not the Maleo. Its a stocky chicken sized bird found on two of the islands in Indonesia, and it uses volcanically heated soils to incubate its enormous eggs. A mated pair will "test" soils with their temperature-sensitive mouths until they find a spot thats a toasty 33c. Then, they dig a hole for one egg - which is five times the size of a chickens egg. When thats laid, theyll cover it up and leave it to incubate - and hatch - all on its own. No need to stay by the nest if youve got volcanic soils to keep everything perfectly toasty. Its even thought that massive Sauropods - long necks - used similar hydrothermally-active nesting grounds. Places like the hot springs of yellowstone. Paleontologists think thats because, with eggs and embryos that big, these animals may have especially benefited from speeding up development with a little extra warmth. Now of course, you will be unsurprised to hear that there are risks to this. The trick is getting close, but not too close, to the heat source. Most enzymes have a limit to how much heat they can tolerate. So if you heat an egg up too much it wont develop normally, or at all. Thankfully volcanoes are fairly well behaved on biological time scales anyway.

Answer 97

formation of new species by speciation Why are the animals in australia so unique? The kangaroo, koala, and platypus will be extrapolated in how they formed through Speciation. Speciation is the formation of a new and distinct species in the course of evolution. When the continents were all joined together as Pangea over several hundred million years these continents slowly drifted apart from each other, when australia finally separated from the other continents, its animals and plants were cutoff from those on other land masses. This isolation is the first step in the formation of new species. It splits the species into two different gene pools as the animals and plant groups on australia drifted away from their relations, they became isolated from other populations of their species. Each gene pool was now exposed to different conditions, like climate, food, and competition. This si the second step in speciation. Some animals and plants that were not well adapted to the new conditions died. Whereas those who adapted survived. To the process of natural selection, the gene pool changed and organisms became more and more different from those left behind. This is the third step in speciation. Eventually these differences became so great that isolated populations are no longer able to interbreed and a new species is formed. This si the final step in speciation. There are many other examples, the lemurs and baobab trees in madagascar that became isolated from continental Africa, or the famous giant turtles and unique flightless cormorants of the galapagos islands of south america. Their ancestors arrived either by flight, swimming or on natural rafts from the nearest mainland. Some of the species presented here are highly specialized.

Answer 98

Evolution is the development of life on earth. This is a process that began billions of years ago and is still continuing to this day. Evolution tells us how it was possible for the enormous diversity of life to develop. It shows us how primitive Protozoa could become the millions of different species that we see today. Evolution then, is the answer to the question that we all have asked on seeing a Daschund and a great dane together: how is it possible for ancestors to have descendants that look so very different to them? In answering this question, we want to focus on animals, excluding other forms of life such as fungi and plants. The first question to ask is therefor: how can one animal develop into a whole new species of animal? But first, what exactly is a species? A species is a community of animals that is capable of producing offspring with one another, with those offspring also being capable of reproducing in turn. To understand this answer better, we need to take a closer look at the following points: Uniqueness. The uniquesness of living creatures, guaranteed through the excess production of offspring and heredity, and as a second key point: Selection. Uniqueness: Every creature that exists is unique, and this is essential for evolution. The members of a species may strongly resemble each other in appearance; however, they all have slightly different traits and characteristics. They may be a bit bigger, fatter, stronger, or bolder than their fellow animals. So what is the reason for these differences? Lets take a closer look at a creature. Every creature is made up of cells. These cells have a nucleus. The nucleus contains the chromosomes, and the chromosomes hold the DNA. DNA consists of different genes, and its these genes that are lifes information carriers. They contain instructions and orders for the cells, and determine the characteristics and traits that living creatures have, and its precisely this DNA that is unique to every creature. Its slightly different from to individual to individual, which is why each has slightly different characteristics. But how is the enormous range of DNA created? One key factor is the Excess Production of offspring. In nature we can observe that creatures generally produce far more offspring than is necessary for the survival of their species, with many offspring dying an early death as a result. Often there are even more offspring than the environment can support. This is one factor in increasing diversity within a species. The more offspring that are produced, the more little differences occur, and this is what nature wants: as many little differences as possible. The second major cause of the uniqueness of individuals occurs in heredity itself. Heredity means the passing on of DNA to offspring. Two very interesting factors come into play in this process: recombination and mutation. Recombination is the random mixing of the DNA of two creatures. When two creatures fall in love and mate, they recombine their genes twice. The first time they do this separately when they generate the gametes - that is, sperm and egg cells. The gametes take half of the genes and shuffle them. The second recombination occurs when a male inseminates a female. The parents each provide 50% of their DNA, in other words, 50% of their unique traits and characteristics. These are then recombined or mixed, and the result is new offspring. These offspring have a random mix of DNA, and therefor the traits and characteristics of their parents. This increases the diversity and differences within a species even further, but mutations are also important for evo. Mutations: Mutations are random changes in DNA. These can also be described as copying errors within the DNA, triggered by toxins or other chemical substances, or by radiation. A mutation exists when part of the DNA is altered. These changes are often negative, and may result in illness such as cancer. However, they may also have neutral or positive effects, such as the blue eye color in humans, which is one such random mutation. In all cases, a mutation has to affect a gamete, that is a sperm or egg cell, because only the DNA in the gametes is passed on to the offspring. This is also the reason why we protect our sexual organs during xrays, whilst other parts of the body are not at risk. In summary then, in the Heredity process, creatures pass on their characteristics to their offspring in the form of DNA. Recombination and mutation change the DNA so that each child looks different to its siblings, and recieves a random mix of the characteristics of its parents. The key word here is Random. All of these processes are based on chance. Random recombination and mutations result in individuals with random mixes of traits and characteristics, which in turn mix these randomly, and pass them on. But how can so much be down to chance, when all living creatures are so perfectly adapted to their environment, for example, the stick insect, the hummingbird, and the frogfish? The answer is provided by the second key point: selection. Selection: Each individual is subjected to a process of natural selection. As we have learned, each individual is somewhat different to its fellows, and there is extensive variation within a species. Environmental influences have an effect on living creatures. These so called selection factors include: predation, parasites, animals of the same species, toxins, changes in habitat, or the climate. Selection is a process that each individual is subjected to. Every creature has a unique mix of traits and characteristics. This mix helps them survive in their environment, or not, as the case may be. Anyone with an unsuitable mix will be selected from the environment. Those with the right mix survive, and can pass on their enhanced traits and characteristics. This is why diversity is so important. This is why creatures make so much effort to produce offspring that are as different as possible. They increase the liklihood that at least one of their offspring passes natures selection process. Maximizing survival chances. A good example of this can be seen in a group of finches living on a remote island. They are some of the most famous animals in the world of science, and are known as Darwin finches after their discoverer.

Answer 99

Story of the finches A few hundred years ago, a small group of finches was blown onto the galapagos islands in the middle of the pacific, probably by a big storm. The finches found themselves in an environment that was completely new to them, a real finch paradise: an abundance of food and no predators. They reproduced rapidly and numerously. The islands were soon heaving with finches. This meant that food supplies became increasingly scarce. The finch paradise was threatened with famine, and finch friends became competitors. This is when selection intervened. Their individuality and small differences, in this case their slightly different beaks, meant that some of the birds were able to avoid competing with their fellow finches. The beaks of some of them were more suitable for digging for worms. Others were able to use their beaks better for cracking seeds. The finches consequently sort out ecological niches. In these niches, they were safe from excessive competition. They soon began to mate primarily with other finches that used the same niche. Over the course of many generations, these characteristics were enhanced, enabling the finches to exploit their niches successfully. The differences between the worm diggers and the seed crackers became so large that they were no longer able to mate with one another. Different species emerged as a result. Today, there are 14 different species of finch living on the galapagos islands, all of which are descended from the same group of stranded finches. This is how new species are created by evolution: through the interaction of unique individuals, the excess production of offsrping, recombination and mutation in heredity, and finally through selection. Why is this so important? It tells us where the variety of life comes from, and why living creatures are so perfectly adapted to their habitats. But it also affects us personally. Every person is the result of 3.5 billion years of evolution, and that includes you. Our ancestors fought and adapted in order to survive. This survival was an extremely uncertain thing. If we consider the fact that 99% of all the species that have ever lived are extinct, then you can feel pretty lucky to be alive.

Answer 100

evolution misconceptions Sometimes the way we use words in conversation is different from the way scientists use them in a formal setting. Evolution as a subject is especially vulnerable to these kinds of misunderstandings. Like you may have heard someone dismiss it as just a theory. But in science theres nothing "only" about theories. So here are the most common misconceptions about evolution - and why they are so wrong. Youre probably familiar with the basics of evolution: its a change in the genetic makeup of a population of organisms. Different organisms have different genetic mutations, which create the variation that leads to evolution. If an organism dies without leaving offspring, its genetic material is gone from the population, so the gene pool has changed. If another organism has lots of offspring, its genes are overrepresented in the next generation which is also a change in the gene pool. Natural selection can cause those kinds of changes, but so can other factors, including random chance. One of the most common misconceptions about evolution is that it is "just a theory". And its true, evolution is a theory, but in the dictionary of science "theory" means alot more than it does in everyday conversation. Often when someone - like when I say Ive got a theory, it means that ive got a hunch or ive gotta guess. But when scientists talk about theories, thats not what they mean. In science, a hypothesis is a prediction of what might happen based on available evidence. And a theory is a whole collection of hypotheses. Theories fit all the facts. They are a sort of framework of thought we use to make further predictions. A stronge scientific theory can expand to fit new evidence; it can accomodate things that arent necessarily even known yet. For example Darwin knew practically nothing about genetics. He understood the variation among individual organisms could be inherited, but he didnt know how. Even so, as knowledge of genetics grew in the late 19th and 20th centuries, that knowledge slotted neatly into our understanding of evolution. So yes, evolution is a theory. Its a rigorous framework of testable predictions that accounts for all known evidence, and can account for more evidence that we dont even have yet. Speaking of darwin another common misconception is that he invented the theory of evolution. It is true that in its current form, evolution traces its academic roots to darwins book on the origin of species. But its totally unfair to say he came uo with the whole idea. Darwin didnt invent evolution. Lots of people before him had noticed that groups of organisms can change over time, and many scholars proposed their own theories of evolution before darwin. One of the best known is Jean Baptiste Lamarck, whose work darwin knew about and referenced. Lamarck got the "what" of evolution right, but he got the "how" wrong. The "what", that species were changing gradually over time, was totally true. As for the "how" though, he thought organisms could pass on characteristics acquired during their lifetimes, which doesnt quite gel with our understanding of genetics. We do now know that a parents environment can have effects on its offspring through epigenetics, but those changes dont seem to stick around in the genome and drive evolution the way Lamarck was imagining. So, Darwins contribution wasnt the idea of evolution. It was the mechanism, the "how". It was natural selection. He even borrowed the phrase "struggle for existence" from an economic thinker, Thomas Malthus. By that, both of them meant that populations grow faster than the resources that support them, which leads to competition for limited food, space, and other needs. Darwin also knew that not every individual is the same. Some individuals might be taller, or faster, or have stronger teeth. Those variations give them an edge when they compete for resources, and can also be passed down to offspring. Organisms with more advantageous variations (genetic traits) tend to have more successful offspring, so those variations show up more and more in later generations. Even the idea of natural selection wasnt totally original to darwin. An 8th century Arab scholar called Al-Jahiz made similar observations about competition and predation. Al-Jahiz still credited a creator with the ultimate origin of species, whereas darwins framing called for only mechanisms that can be observed in the natural world. So it wasnt like he was just ripping off that other guy. But the evidence has been there for a long time for people other than darwin to observe and think about. Scholarship never originates with just one person. But darwin developed the foundation of the theory of evolution that we know today, and popularized it among other scientists.

Answer 101

The missing link There are more specific mythcons about evolution, too - like the idea that theres a missing link between humans and apes out there that we just havent discovered yet. Basically people figure that apes are a lower or more primitive form of life, so there must be a link thats somewhere in between more primitive apes and humans. But thats not quite how evolution works, because there is no single, unbroken chain between our ancestors and us. Evolution is about diversification, not linear progression. Far in the distant past, we humans share an ancestor with apes. Some of the offspring of that ancestor developed an interest in walking upright, banging rocks together, and eventually barbershop music. Others stuck with foraging for fruit and grooming insects off of each other. But for a while, those two populations werent all that different - they could still interbreed and swap genetic material. For example, modern humans once interbred with other species of hominids - the neandertals and the denisovans. You can still find their dna in humans alive today. We know that neandertals and denisovans arent our direct ancestors, but we also know they branched off from our common ancestor and continued to trade genes with us for a while. Evolution tinkers around with organisms, but it makes branching trees, not long chains. So, there is no need for a missing link because theres no one chain. Its more of a bush.

Answer 102

survival of the fittest Its another thing thats often associated with darwins thinking, but it wasnt original to him either. It was coined by sociologist Herbert Spencer. This phrase is considered unfortunate by many evolutionary biologists because of how easily it lends itself to misunderstanding. It conjures up an image of the most ruthless, cutthroat, strongest organisms trampling over their peers to like "win" evolution. But "fittest" doesnt necessarily mean strongest. If it did, youd expect the most successful dinosaurs alive today to be like the t-rex. But instead its chickens. Fitness is another one of those words whose rigorous scientific definition is different from its everyday one. In evolutionary biology, fitness refers to: an organisms capacity to thrive in its environment well enough to have offspring. And that can mean very different things in different contexts. In some environments a plant with nice broad green leaves is probably able to harvest more sunlight than its competitors, making it more fit and better able to reproduce. Whereas if you had broad green leaves, then you should probably get that looked at. In other words, there isnt any one adaptation thats a magic bullet, and there isnt one ultimate form for an organism. Something incredibly beneficial for one scenario could be detrimental to another.

Answer 103

evolutionary change is always good We defined evolution as a genetic change in a poulation, and sometimes that happens for literally no reason. Genetic mutations can be helpful or harmful, but sometimes theyre just tradeoffs that are sorta good and sorta bad. And a whole bunch of the time, they dont make any difference at all. Thats because alot of our dna doesnt do much. And even the important regions usually have a little flexibility. So, sometimes a mutation doesnt do anything except sit there, being a little different than it was before. The laws of statistics have a kind of surprising effect on these neutral mutations - they contribute to a type of evolutionary changed called genetic drift. Among all the organisms in the population, there might be ten different versions of the same gene that do the same thing. But since these trivial mutations dont affect an organisms ability to preproduce, natural selection doesnt control whether a mutation is passed on. Every time a parent reproduces, its just random chance which version of the gene gets passed on. So you might think that eventually, youd just end up with more and more neutral variants of the gene within the population. But because statistics are kind of strange, thats not what happens. Instead, over a long time and many generations, only one neutral variant of a gene will stick around. All the others vanish because of pure chance. Genetic drift doesnt have as much of an effect on larger populations, because theres more room for the effects of random chance to equal out. But in smaller populations, it can lead to pretty significant genetic changes, just by chance. So the idea that evolution is always beneficial is just another mythcon.

Answer 104

unlikely ecosystems Redwood Canopies: Along the west coast of the US trees called coast redwoods grow taller than any other tree in the world; sometimes reaching up to 37 stories high. It took til the late 1990s before people began exploring these redwood canopies, But when people finally got up there, they found way more than they expected. In fact, redwood trees were so large, and extended so far from the ground, that their canopies had become ecosystems of their own. Scientists essentially found a forest growing on top of a forest, completely hidden from sight on the ground. Up in the canopy, single trees split into multiple trunks. In one study researchers counted 137 trunks growing out of a single tree. These arent like little scrawny trunks either. The trunks could be a meter wide. So you probably couldnt tell apart from trees on the forest floor, except that theyre 50 meters or more up in the air. These werent just redwoods, either. Trees of all different species, like Sitka spruce and Douglas fir, grew off of the redwoods branches. Researchers even found a californian bay laurel tree with its roots some 98 meters above ground. And these trees can grow here because there is actually soil to grow in. Canopy branches grow really wide, sometimes two meters across, and they can get covered in ferns. Over time these fern mats trap dead branches, broken trunks, and other debris, building up a layer of soil and organic material, a lot like whats on the forest floor. And like the forest floor, that soil is full of critters, like snails, and earthworms, and even moisture loving salamanders. What are they even doing all the way up there? Now that scientists actually know whats going on up there, they can work on protecting these systems and all of the diversity that they support. For instance, they now know that its not enough to protect young redwood forests, since they dont have these complex canopies that these old growth forests have. But dwindling numbers of redwood have isolated some of these canopy ecosystems, so scientists have begun looking at ways to speed up canopy growth in younger trees to help keep this incredible ecosystem alive.

Answer 105

unlikely ecosystems Whale falls There are lots of incredible ocean ecosystems, but the ocean floor is home to one especially unique one: whale carcasses. You might think of whales washing up to the shore when they die, but most of the time, dead whales actually sink, dropping all the way to the bottom of the ocean floor. These are called whale falls, and these dead bodies become incredible hotspots for underwater life. We've actually found very few of these in nature because the ocean is so massive and so deep that its pretty hard to look for things on the bottom. Like in 2013 scientists discovered a whale fall more than 4000 meters deep in the atlantic ocean. And that was only the seventh natural whale fall theyd ever studied in detail. So other times, scientists have intentionally dropped carcasses into the ocean in order to better understand the ecosystems that develop around them. And whats amazing about whale falls is that they create an ecosystem in a place where, otherwise, not much can survive. There arent many nutrients at the bottom of the ocean floor, but when a whale dies, literal tons of food arrive all at once. And that attracts a huge diversity of creatures. Scientists have spotted animals like deep sea octopuses, crabs, snails, limpets, and even bone eating worms. Theyve even seen animals that they have never recorded anywhere else. On one whale carcass, the majority of the 41 species researchers identified were totally new to scientists. These are exciting places to study marine life because we actually dont know alot about what goes on undersea. I mean, only about ten percent of the ocean has even been mapped so far. So whale falls are kind of like a microcosm of life in the deep sea, and they give scientists a rare chance to discover and learn about the species that thrive there.

Answer 106

unlikely ecosystems hydrothermal vents Fissures in the ocean crust where blistering hot water full of minerals bubbles out of earths crust. And as unfriendly a place as it seems, lots of life has evolved to survive here. Since theres no sunlight that deep in the ocean, photosynthesis is a no go. Luckily, these vents release a slurry of chemical compounds including sulfide, hydrogen, and methane which these organisms can use in a process called chemosynthesis. Basically instead of using energy from the sun to convert carbon from the environment into organic compounds, organisms at these vents create organic compounds using energy from chemical reactions. Which is ingenius. But its not just extreme microbial life living it up at these vents; their energy gets transferred up the food chain. Even though temps can reach more than 350c, yes, that more than 3 times the boiling point of water, because the pressure is so great that it doesnt boil, the structures that form at these vents host creatures like giant tube worms, mussels, clams, crabs, and shrimp. And now scientists are realizing that ecosystems at hydrothermal vents may actually have a really wide influence on the rest of the planet. These organisms consume the vast majority of the methane from these vents, preventing this powerful greenhouse gas from being released into the atmosphere, which would have an enormous effect on the earths climate. These vents also release iron, which helps fuel the growth of phytoplankton, small organisms that play a massive role in capturing carbon in the ocean. Aside from that, these hydrothermal vents might also help us understand some of our planets earliest life, since they have existed ever since liquid water first accumulated on earth. In fact, scientists have found traces of organisms from almost 4.3 bya that lived at hydrothermal vents in the ancient seafloor. So bu studying the inhabitants of modern vents, we might gain insight into the earths earliest microbial communities.

Answer 107

unlikely ecosystems icebergs You might not think a giant hunk of ice floating through frigid waters is a great place to live, but for many creatures, an iceberg is a floating oasis. As icebergs float through water, even really icy water, they are always melting, at least a little bit, creating a pool of freshwater that surrounds the iceberg. And as they melt, they release the dust and minerals that were frozen up in the iceberg, which are a good source of iron. The iron in that meltwater helps fuel photosynthesis, which stimulates the growth of phytoplankton around the icebergs, including some species of phytoplankton that normally live in freshwate. And even though icebergs are relatively small, they can have a pretty wide-reaching effect on the region around them. Thats because it can take over a year for a big iceberg to completely melt, so it can cover a lot of ground in that time and spread its minerals far and wide. In a study of giant icebergs between 2003 and 2013, researchers found a significant boost in chlorophyll production in the 500km surrounding the iceberg. And sometimes as much as 1000km away. These phytoplankton communities attract all sorts of other organisms to the area around the iceberg, including fish, krill, jellyfish, and seabirds. Not only do they form the basis of this floating ecosystem, but phytoplankton also absorb carbon in the ocean. So understanding how icebergs are connected with these organisms can help us understand and predict the ways that climate change will affect our oceans, as more icebergs break off and enter the open sea.

Answer 108

unlikely ecosystems chernobyl exclusion area Although there are many extreme environments in nature, not all ecosystems have natural origins. And one of the most unusual ecosystems on earth is the result of a human caused catastrophe back in 1986. That year, an explosion at the chernobyl nuclear power plant released huge amounts of radioactive material across 200 thousand square kilometers in europe. It was one of the worst environmental disasters in human history, and humans have been evacuated from the 4'000 square kilometers around the power plant for more than 30 years. This is called the Chernobyl Exclusion Zone, and it is still unsafe for humans to live there. Still, as deadly as the region is, some species actually seem to be thriving inside it. Things havent gone exactly back to normal. Even this long after the disaster mutation rates in animals and plants are really high. Research has also shown that radiation exposure has shrunken the brains of some birds and caused a rise in tumors, fertility issues, and other abnormalities. Parasites may also be using these weaknesses to find new ways to attack their hosts. In general, all the major animal groups studied within the exclusion zone have declined, including bees, grasshoppers, birds, spiders, and mammals. But in spite of all that, some animals are doing better than youd think. Some species of birds seem to have responded to high radiation levels by producing higher levels of antioxidants, which help reduce the damage to their dna. Weirdly enough the birds ability to adapt seems to be tied to their pigmentation; flashier looking birds seem less able to produce antioxidants to protect themselves from the radiation. But its not just dull birds and parasites that are able to survive under these conditions. Some mammal species are actually more abundant inside the exclusion zone than they are outside. Scavengers, like wolves and eurasian otters, seem to be diverse and thriving. And as bizarre as that might sound, the explanation is likely pretty simple: for some organisms, a radioactive ecosystem is better for survival than one that has humans in it, thanks to the stress we put on environments. Even though these radioactive or far flung ecosystems might not seem especially homey to us, they go to show that life can make a home out of just about anything.

Answer 109

Why do our bones make our blood? The marrow in our bones does so much for us. In addition to storing fats and making sure our bones stay healthy and strong, its responsible for pumping out hundreds of billions of blood cells every day. Its also weird when you compare us to other animals. While birds are very similar, fish make blood cells in their kidneys. And in frogs, production tends to start in the liver or kidneys, then move to the bones as the cells grow up. Plus, when you think about it, since blood connectsto everything in your body, blood cells could come from anywhere. Which makes you wonder why our lineage settled on bones. Though the answer is not 100% certain, scientists have a strong idea: its because the space inside our bones is dark. No one fully understands why blood is made in different, but the areas do seem to have something in common: they protect blood-generating cells from damage. Of special concern are the hematopoietic stem cells, which produce every type of blood cell, as well as hematopoietic progenitor cells, which are similar but cant renew themselves quite like stem cells can. Damage to these blood-making cells can create mutations in their genomes. And mutations can kill the cells or lead to functional issues in the blood cells they generate. Luckily, the right conditions can help limit mutations. And thats where bones come in, probably because one of the things that causes mutations is sunlight! Now this idea isnt exactly new. Over 40 years ago, a researcher hypothesized that blood production migrated into bones because vertebrates migrated onto land. See, the suns rays get scattered by water, so the light is more diffuse under the water. On land, light is more direct, so animals would be more vulnerable to UV damage. The only problem was, there wasn't much to back this hypothesis up. Then, in a 2018 Nature paper, researchers published evidence that the blood-producing cells of fish also seek sun protection. The researchers were examining zebrafish when they discovered little umbrellas of melanocytes covering their kidneys. Melanocytes are pigment-producing cells, and in these fish, they form an opaque layer over the kidneys, the home of their hematopoietic stem and progenitor cells. Now, that alone doesnt prove the goal is sun protection, so the research team engineered fish that couldnt make the umbrellas to see what would happen. Lo and behold, the blood-making cells in those fish ended up with much more UV damage. These shade-making parasols were found in a number of other fish species, from catfish to lungfish to lampreys. And the researchers noted similar pigmentation patterns occur in the livers and kidneys of different species of tadpoles, wherever the animals produce their blood. Thing is, once tadpoles grow legs, blood production moves into their bones, which presumably readies them for a bright future on land. And that's basically what experts now think happened long ago in the first land vertebrates. And some of them, their blood making cells wandered a bit - something these cells do from time to time, until they happened to find themselves inside a bone. And if that meant their blood stayed healthier for longer, it could have given them just enough of an edge to help them win out, leading to an entire lineage of animals with blood factories in their bones.

Answer 110

foxes might use magnetic fields to hunt You might be familiar with the cute pouncing technique many foxes use to hunt mice and voles. They jump high into the air and come down nearly directly on top of their prey, even if that prey is hidden from sight in snow or grassy underbrush. This is a tricky hunting technique to master, because a fox needs to know exactly where their prey is so they can successfully line up their attack and close the distance with that jump. Scientists know theyre using their big ears to help zero in on their target. But some think theyre also using another sense - that the foxes are actually hunting using magnetic fields. And no, it isnt like theyve got a built in metal detector for mice. Rather, they may be sensing the earths magnetic field. In fact, foxes might be the first animal we know of to use magnetoreception to gauge the distance to their prey - and this sense may be crucial to their pouncing success. In a 2011 study of red foxes in europe, researchers noticed that when their prey was hidden by vegetation, a whopping 74% of successful hunting pounces occured when the fox was pointed in a northeasterly direction. They combed through their data, looking for other factors that might bias the direction of attack, like the wind, or sunny versus cloudy conditions. After ruling all that out, they proposed that the foxes were using magnetoreception to orient themselves roughly toward magnetic north. While they werent sure how, they did make a suggestion for why doing so would be helpful to the fox. You see, as a fox approaches its prey, it will use its other senses to gauge where its target is. If they cant see their prey, they listen for it. But the fox wants to know exactly where that hidden morsel is in order to jump the right distance to neatly close the gap. The researchers in this study proposed that the fox is searching for where its other sensory cues line up with the angle of the earths magnetic field. That would result in a sort of overlay targeting system. The angle of the magnetic field is fixed, meaning the fox could basically be using this stable reference point to line up where it thinks its prey is. Once it matches that angle, the fox knows the distance to its prey, and can employ the exact same pounce successfully, nearly every time. Its almost like it has its own biological heads-up display - basically something in its visual field pinging when its at the right distance. So no matter when or where or what a fox is hunting, it pays to have learned just one move to come down right on top of dinner. Now, magnetoreception is actually thought to be fairly common. Many animals, especially migratory birds, are believed to use the sense for long-distance navigation, using it to find the right direction to travel. But this would make foxes the only animal thought to use magnetoreception to sense distance. Scientists have long puzzled over the exact method as to how magnetic fields are sensed. Research in birds and fruit flies suggests that a chemical reaction in light-sensitive proteins could be the key. These proteins are collectively called cryptochromes. And foxes have them in their eyes, just like birds and some other magneto-sensing species. So if these proteins are found in the eyes, and are sensitive to light, what does that have to do with sensing magnetic fields? We're not totally sure, but there is some evidence for how it might work. When a photon of blue light hits a cryptochrome, the cryptochrome transfers an electron to a partner molecule. This new arrangement leaves each partner with an uneven number of electrons. One has an extra electron, and one has one fewer. And every electron has a property called spin, which can either be up or down. In the case of our unbalanced pair, one of those electrons has an up-sign and the other has a down spin at the time of the transfer - but then they flip back and forth and even wobble. Now, this electron transfer reaction is reversible, meaning it can go back the other way. But only when the electron spins are opposite. But because magnetic fields influence the rates of the electrons flipping between up and down spin, and the wobble in that spin, a magnetic field could change the rates and products of the chemical reactions, too. At least, this is how it works in theory. We know migratory bird eyes contain cryptochromes, and that their ability to navigate with magnetic fields may require the presence of light. Foxes, and some other mammals, also have cryptochromes in their retinas. And theyre our strongest candidate for the job of biochemical magnetoreceptor. But we still need to show experimentally that cryptochromes form enough of these electron pairs to signal in some way that this way is north and this way isnt. And in fact, even if cryptochromes are sensitive to magnetic fields at a biologically relevant level, we dont know how that signal would get passed along to the animals brain - so we can't be sure it actually senses anything. So while the chemistry and math seem to check out, scientists are still working on the biological details of foxes hunting magneto-vision.

Answer 111

Radiation (idtimwytim) Radiation: causing horrible things like cancer and warmth and food and cell phones and sunsets since the beginining of time. Its when energetic particles or waves move through space and its pretty much the best thing ever. Radiation includes: Visible light which is always bouncing off of stuff and then hitting our retinas allowing us to not stub our toes and generally enjoy the splendor of the world, Its also what plants convert into the food we eat. Infrared radiation is the stuff that actually warms the earth so its the reason that we are not all freezing to death right now. Microwaves, which not only heat up our hot pockets, but also transmit our cellphone calls. A huge amount of studies into whether this microwaves cause cancer indicates that they probably do not and the world health organization classifies them in the "needs more study" category, along with coffee and pickled vegetables. Radio waves, which carry radio signals, also 3G and wifi and all that good stuff. And then we have the extremely low and very low frequency waves which arent super useful but dont hurt anybody either. Unlike all of the above examples, some kinds of radiation can transfer their energy into atoms and ionize them, removing electros, which is where the problems begin. When most people think of radiation what they are really thinking of is this radiation, which is ionizing radiation. Including Xrays, that can ionize atoms, but its generally worth it to take a peak at your broken bones. Ultraviolet radiation, which is mostly non-ionizing, but can excite atoms enough to cause some unwanted reactions like in our skin, which is why we put on UV protection in our sun block. Gamma rays, which are pretty much the worst kinds of all the radiations because they can travel through pretty much any material and then ionize an atom right out of your DNA, leading to some serious problems. And thus far we've only been talking about waves, but as mentioned, radiation is energetic waves or particles, so there are some forms of radiation that are actually particles with mass. These kinds of radiation are only caused by nuclear reactions. An alpha particle is a flying bit of an atomic nucleus. Two protons and two neutrons stuck together. Theyre so big and slow they dont generally cause much damage unless you ingest something thats emitting them. Beta particles are energetic electrons that are more ionising than alpha particles, less ionising than gamma rays, so they cause serious damage as well. So now we know that radiation isnt just a bad dude, hes a misunderstood dude.

Answer 112

How radiation changes our DNA Radiation, its everywhere. Radiation on its own isnt necessarily harmful. The term is super broad, gamma rays shooting out of stars is radiation, heat coming off the pavement is, and the radio waves, even visible light. What does ionizing radiation such as gamma, ultraviolet, and xrays do when it hits your body? In 1927 in the journal science, hermann muller published a paper showing the ionizing radiation of xrays damaged the genes of fruit flies. Which he won a nobel for. Ionizing radiation is a high energy radiation, its got a lot of energy in it. When this high energy particle or wave hits an atom, the atom absorbs the energy; causing the weakest electron to pop off. This creates a charged atom called an ion. Do that enough and all that high energy can cause chemical changes in our tissue. If ionizing radiation affects too many cells at once, or we absorb a bunch over time - thats when we risk sickness, radiation poisoning, or eventually cancer. That happens when the radiation changes how things fit together. It might knock off bits of our DNA, mess with its structure, or at worst break one or both strands of the dna double helix. That alone isnt damaging, but sometimes, the body makes mistakes when repairing that damage - causing wide spread issues. But chances are, youll never have to worry too much about how much radiation youre being exposed to. Radiation dosage is measured in sieverts. 1 sievert in a short time can cause radiation sickness and 10 can kill. But because we'd never really encounter a full sievert, scientists usually talk in millisieverts. Every years, just living on earth exposes us to 2.4 mSv in natural background radiation, and its fine. A chest xray for example, is 6.8 mSv, so while one xray wont hurt you, a bunch throughout your life can damage your tissues enough to cause health problems. If that werent complicated enough, there are different types of ionizing radiation. Alpha, beta, gamma, and xrays; listed in increasing energy levels. Alpha radiation is the slow big fella, it cant really penetrate your body, but its essentially a handful of protons and neutrons. Beta is basically a tiny fast moving electron; it can penetrate your body, but not some denser materials like aluminum. Gamma radiation is fast moving pure energy. Its so small it can pass between your cells, but if it hits your DNA itll mess you up. In fact, gamma is so high energy it can pass through you, aluminum and even concrete walls - though not lead since its too dense. Xrays are like gamma rays, but lower energy. In the end you probably dont have to worry a lot about ionizing radiation. UV rays can damage dna over time, so wear sunscreen. Xrays are highly regulated, and hopefully you havent spent too much time near unbridled nuclear reactions, or exposed yourself to cosmic rays. Most radiation is just regular non-ionizing stuff. We even absorb ionizing radiation from food like bananas.

Answer 113

the science of hypnosis researchers estimate that around 10 to 15% of people are highly hypnotizable, another 20% are resistant to hypnosis. And the rest of us fall somewhere between. One study found evidence that suggestibility might have to do with slight variations in brain anatomy. These researchers used magnetic resonance imaging and found that the subjects who were more easily hypnotized has a significantly larger rostrum than those who werent. The rostrum is the region in the brain involved in attention. Other scientists wanted to look at the brainwave patterns of hypnotized people. Basically, your brain depends on electrochemical energy to work because thats how your neurons communicate with each other. Using an electro-enchephalogram, researchers can monitor the electrical activity of your brain and see different patterns of brainwaves. In this study, the researchers found that hypnosis, especially in highly hypnotizable people, leads to an increase in theta waves, which are linked to attention and visualization. Like when doing mental math of daydreaming. So MRIs and EEGs seem to show that hypnosis can affect how our brains pay attention to things, which supports the idea that it is a state of focused relaxation. But how does that focused relaxation let hypnotists make suggestions and influence what their clients think or do. Well, it has to do with a concept called Top-Down Processing. Our brains recieve a lot of sensory information from the world around us. But we do a lot of processing and interpretation to figure out whats going on. The idea of top-down processing says that what you expect from memories and assumptions, the top level of information, can have a big impact on what you percieve with your senses, the bottom level of information. Cognitive scientists have known this for a long time. And there are lots of different experiments that show this effect. For example, a group of researchers had people drink wine that they thought was expensive and wine they thought was cheap. They were actually the same wine, but the people said they enjoyed the expensive ones more probably because they expected it to taste better. Not only that, but a pleasure processing part of their brains became more active when they drank the expensive wine as well. Top-down processing also explains the placebo effect. If a doctor gives you a pill and says it'll make you feel better, youre probably gonna say that it does even if the pill was actually just sugar. Basically, this means that because a hypnotized person is more open to suggestions, their expectations can be tweaked, which can also change the way they percieve the world. And theres scientific evidence that hypnosis can affect perception like this. Take the Stroop test, where you look at a bunch of words describing colors like red, green, blue. But instead of reading the printed word, you have to say the color of ink the word is printed in. So if the word yellow is printed in blue, for example, you have to say blue. Its pretty hard to do because of the conflict in the task. Your brain is processing the word and the color of the word at the same time. So, a team of neuroscientists decided to use the Troop test to see if hypnosis could affect how people percieved the words and their colors using a functional MRI scanner to monitor their brain activity. The researchers used relaxation techniques that hypnotize a mix of people who are highly hypnotizable, and less hypnotizable. Then the subjects were given a very specific suggestion. The words they would see in the fMRI scanner were gibberish, and they had to identify the color shown as quickly as possible. A couple of days after the hypnosis session, the subjects took the stroop test while having their brain scanned. And highly hypotizable people, who were probably more receptive to the suggestion, were faster and more accurate at picking the color of the words. Even more amazingly, there were measurable differences in their brain activity. Specifically, a brain region responsible for decoding written words didn't become activated. So their brains didn't seem to be recognizing the words as words. At the same time, their brains didn't seem to register any conflict in the task, unlike the brains of participants who were resistant to hypnosis. So it seems like hypnotic suggestion did change the subjects expectations so they percieved gibberish instead of words and could focus on the colors. A different study by neuroscientists even found that hypnosis could block memories. The subjects watched a 45 minute film and came back a week later to be hypnotized. They were given a suggestion to forget the film when they heard a certain cue, and could have their memory restored with another cue. Then the participants entered an fMRI scanner, and were given the forgetting cue. After that they were given a test and couldnt remember the details of the movie even though they could remember details of the room they watched it in. Plus, certain memory related regions of their brains werent as active as those of a control group who hadnt been hypnotized. So, like you can theoretically be hypnotized to forget a movie so you could watch it again. This is known as Post-Hypnotic Amnesia, and is actually used for models researching functional amnesia. Like the kind caused by traumatic brain injury.

Answer 114

Organic (idtymwytim) When I hear "organic" I don't think groceries, I think chemistry. And in the world of chemistry you often hear it said that an organic compound is anything with carbon in it and organic chemistry is the study of carbon compounds. But theres no actual single definition of what organic means in chemistry. And scientists have been arguing about it for a long time. It usually comes down to whether the stuff youre talking about is organic enough. The confusion has its roots hundreds of years ago. Until the 1820s no one had any idea what chemical compounds made life possible or how they differed from the stuff that was obviously not alive. The substances found in animals and plants were all simply thought of being the product of some vital force, some ineffable power that just made things alive. These substances were called organic or organical because they came from organized living beings. By extension, everything found in objects with no vital force was considered inorganic. So what changed all this? Man-made pea. In 1828 german chemist friedrich verner was experimenting with inorganic substances when he combined two of them, aluminum salt and cyanic acid and accidentally created urea, the main ingredient in urine. Because urea was only known to come from living things it was considered organic, so suddenly the whole idea of what was organic and what wasnt was up in the air, and it still is! Since then though we have come to some important realizations like we've learned that many compounds that are unique to living things contain carbon. Carbon is the neediest of all elements, always demanding other atoms electrons, this neediness means that carbon can bond with up to four atoms at a time which makes for long strong complex molecules like amino acids, sugars, lipids; the stuff of life. But still just because something has carbon doesnt mean that its alive. Diamonds for instance, or coal. So since the days of early years, chemists have managed to if not define what is organic, at least rule out a few things that arent. The funny thing is the distinction usually comes down to is it found in living things or not. Carbides for instance are typically considered inorganic because theyre made of carbon bonded to an element with a less negative charge, usually heavy metals. Tungsten carbide for instance is a super strong carbide used in making machine tools. Carbonates likewise are compounds that contain the carbonate ion, carbonated water has this in abundance, as do minerals like limestone and dolomite; these are all considered inorganic, but when the ion reacts with other larger compounds that also contain carbon it can form complex molecules like esters which are important in biology and are called organic carbonates. Confused yet? Well how about this, oxides of carbon are also inorganic like carbon dioxide which we are exhaling right now, even though its coming out of our body its not considered to be an organic compound, why? It all depends on who you ask and what their chemical argument is. Some say that a carbon compound has to be big and complex which co2 isn't. Others argue that organic compounds require a covalent bond, thats where two atoms share an electron between carbon and another element, but thats what co2 has and no one likes to call that organic. Still others say that organic compounds have to contain carbon bonded with hydrogen. But then that would exclude things like urea which started this whole debate in the first place. Also it would include gasoline. In the end deciding whats organic is kind of like deciding which baby food healthiest. Everyone has a different opinion.

Answer 115

Flavour science There is much more to a pumpkin spice latte that meets the eye, or rather, meets the tongue. Say you take a big swig, it hits your tongue, and flows over your papillae, the little bumps where your taste buds live. Within each taste bud, special receptor cells bind with the compounds in the drink and send taste information to your brain. Meanwhile, the scent of the latte travels up your nose, where more receptor cells - this time for smell - tell your brain which chemicals they detect. Those signals, plus other information like the color and texture of your drink, combine to form what your brain interprets as the taste of pumpkin pie in delicious liquid form. But, you haven't actually consumed any of the spices youd normally associate with pumpkin spice flavor, like cinnamon, nutmeg, and cloves. Your brain thinks you have, because the drink contained compounds specially designed to trick your brain. Thats the science of synthetic flavoring, and its involved in practically every processed food. At some point in your life youve eaten something with "natural flavors" or "artificial flavors" listed as ingredients. That means that the food has some added compounds to give it a specific taste. The science involved can be incredibly complex - and flavorists, the scientists who work with flavor, often have to study for five years or more to get certified by the society of flavor chemists. And thats after getting a bachelors degree in biology, chemistry, or food science and usually a masters too. But this area of speciality has allowed the food industry to become what it is today - where you can make practically anything you want, have it taste like anything you want, and do it all cheap. Whenever you eat anything - from a fast food cheeseburger to an apple - whatever youre tasting, your brain is picking it up from the chemicals in your food. Literally everything in the universe is made of chemicals. Thing is, its often hard to tell what theyve actually included under the vague heading of natural or artificial flavoring, because the ingredients that make up different tastes are mostly kept secret, closely guarded by the companies that manufacture them. But, at least in the united states, every chemical in a flavoring has to be on the FDAs list of compounds it calls Generally Recognized As Safe, or else shown to be safe by whatever company is using it. For a compound to be considered a natural flavor, it has to start out as part of certain living things, like tree bark, meat, or yeast. But not all living things make the cut - something that comes from bacteria, for instance, wouldn't be considered a natural flavor. According ton the FDA, artificial flavors are compounds that arent made from the living things on their list. Which means artificial flavors are just... every flavor that isnt a natural flavor. Isoamyl Acetate, for example, is what youd probably recognize as banana flavor. Its in actual bananas, so if you extracted some from a banana, that would make it a natural flavor. Or you could just mix amyl alcohol with sulfuric acid and vinegar, and youd wind up with the artificial version of the very same flavor. Either way, its the same compound giving your candy that banana taste - but since they were made in different ways, they fall into different categories. Take vanillin, for instance, the compound that gives vanilla its taste and smell, and one of the first flavors ever to be made in the lab. Natural vanilla, which comes from the vanilla bean, contains hundreds of chemicals, but the only really important one for taste and smell is an aldehyde called vanillin. Vanillins structure makes it an excellent chemical to use as a flavor, because its oxygen atoms help it dissolve in water. Plus, aldehydes usually have strong smells, and vanillin also contains a ring of six carbon atoms, known as a benzene ring, that tends to make chemicals even smellier. Back in 1874, a group of german scientists figured out what vanillin looked like and started making it out of a chemical in pine bark called coniferin that smells and tastes like cloves. Over the years, vanillin has been made in lots of different ways, like from apple seeds. But these days it mostly comes from reactions with compounds that start out as petroleum. Vanilla extract from the bean is much harder and expensive to produce, and only makes up about one five hundredth of the vanilla used worldwide every year. If that were the only way to get it, the world would have a lot less vanilla-flavored stuff. Synthetic vanillin on the other hand is way cheaper, and can mostly keep up with the demand - about 10'000 metric tons of it is produced each year. Vanillin has non flavor uses too, like in reactions used to make certain medicines, or in perfumes. But about three quarters of the artificial vanilla produced in the world is used just for ice cream and as a flavoring for chocolate. Another old timey artificial flavor is grape, in the form of a compound known as methyl anthranilate. As far back as the late 1800s, methyl anthranilate was identified as an important part of the scent of orange blossoms, and was used in perfumes. And scientists already knew how to make it - one way involved combining methyl alcohol with anthranilic acid, a type of acid with one of those smelly benzene rings. By the early twentieth century, the chemicals popularity made it easy for food chemists to get their hands on it. Thats when they realized that it kind of smelled - and tasted like grapes. Which makes sense, because methyl anthranilate actually is in some grapes. Its mainly found in just one kind of grape - concord grapes, a variety thats specific to north america and today is typically used in grape juice. Even though people eat many other varieties of table grapes, methyl anthranilate has still come to mean "grape" flavor to a lot of us, especially in the US. Thats why grape flavored foods dont really taste that much like the grapes that most of us buy in the store. Food scientists have an official term for the unique, concord-y flavor imparted by methyl anthranilate. They call it foxiness. There must be no better way to describe it. Not all flavors have to be as specific as vanilla or grape. Just like it you wanted your food to be saltier, youd add salt, if you wanted to give your food a kick of umami, youd add monosodium glutamate. Lots of glutamates show up naturally in things we eat. Theyre amino acids, and you'll find them in most protein-rick foods, from meat to milk. Monosodium glutamate is the synthesized version, and its usually made by fermenting bacteria so they excrete it. Its often added to food to make it taste more meaty, and its usually the secret to making a veggie burger taste even the tiniest bit like meat. A lot of people claim that MSG gives them headaches, or that theyre sensitive to it in some way. And MSG is closely related to glutamic acid, an amino acid that acts as a neurotransmitter in lots of animals, including humans. So researchers figured there could be a connection, and kept doing studies to try and learn more about these reactions, but they came up empty. Some studies have shown that when mice are injected with very high amounts of MSG, they die. But scientists have reason to believe that humans and mice handle glutamates differently - and besides, anything can become toxic when you put enough of it in your body, even water. Studies that try to directly measure reactions to msg have had trouble finding anything reliable. In 2000, researchers tested 103 people who said they were sensitive to the compound. Some people did experience symptoms, but not consistently. Instead, researchers think that people might be sensitive to other ingredients in foods that happen to contain msg - a condition thats been named Chinese Restaurant Syndrome. So your veggie burgers are probably fine. The flavors we've talked about so far turn out to be relatively simple to synthesize: one molecule and youve got it. But other tastes are a lot more complicated - you need more than one compound to capture the nuances of pizza, for instance. Or the experience of eating pumpkin pie. Thats why flavorists develop flavor packs, tailored combinations of compounds that food companies can use to make foods taste like whatever they want. Designing a flavor pack goes beyond just combining all the right flavors - scientists have to consider things like whether one taste will dominate the others, or if the compounds will be used in a food, like bread, where theyll need to be protected from heat during cooking. Usually pumpkin spice lattes arent actually meant to taste like pumpkin - theyre just supposed to taste like the spices you might find in a pumpkin pie. So the flavorists are going for hints of things like cinnamon, cloves, ginger, and nutmeg. But if you actually put those spices in your latte, youd probably find that it tasted more like chai tea, and not reall like pumpkin spice at all. Thats because when you eat a pumpkin pie, the spices have gone through the oven, changing their chemistry. The pumpkin spice flavor pack accounts for those changes, using synthetic compounds that highlight the strongest notes of pumpkin spice flavors - once the pies out of the oven.

Answer 116

what is impossible in evolution? Why don't we see certain traits in nature? If evolution is so innovative, if its powerful enough to create this and that extraordinary lifeform then why cant humans grow wings and take to the sky? Or why don't fish have propellers? Why are there no 5-legged cats or giraffe-sized chickens? Why do no animals have wheels? This is going to be about the limits of evolutionary creativity and why certain traits are impossible to evolve. Theres a myth in evolution that nature is infinitely creative. It isn't. Probably. By considering the reasons why certain things cant evolve we can learn a lot about how evolution actually works. The "wheeled animal" question is a canonical case study when it comes to impossible things in evolution, or "forbidden phenotypes". And remember, a phenotype is the observable physical properties of an organism. There are organisms that roll up their entire bodies to enable wheel-like rolling movement, like pangolins, spiders, tumbleweeds, and roly polies. Or maybe we could envision an animal rolling around like the mulefa, a fictional species in the fantasy series dark materials, which hooks its feet into round seed pods and uses them as wheels. But acting like a wheel or using a found object as a wheel is not the same as having wheels as body parts. This is fucking obvious shit... But there are other less obvious reasons animals dont have wheels. To a bronze age foot soldier, the most terrifying sight imaginable would've been enemy chariots rolling onto the battlefield. Manned by a driver and either an archer or javelin thrower, the ability of these horse drawn wheeled vehicles to move quickly across the field of battle made the chariot the dominant shock and awe weapon of its time from mesopotamia to the mediterranean. But by the 6th century AD, the chariot, along with almost every other wheeled form of transportation, had basically disappeared between north america to central asia. How could such a seemingly dominant technology vanish? Because wheels had been replaced by camels. This happened for several reasons: the roads originally laid down across the roman empire had deteriorated. The skill and craftsmanship required to make efficient wagons and carts had been slowly forgotten. But most simply, in this particular region camels were just better and more efficient than wheels when it came to carrying stuff. The camel can travel further with less food and water than a horse or ox. They can cross rivers and rough terrain easier than a wheeled cart, and where a wagon requires a person to tend every two animals or so, half a dozen fully loaded camels could be managed by one person. Likewise, europeans were stunned to find no wheeled vehicles used by the aztecs, incas, and other american indigenous cultures, even in places where llamas were used as pack animals. Archeological discoveries show us early american cultutres definitely invented wheels of their own, but beyond water wheels for milling, or toys, they didn't find wheels all that useful or necessary for their particular terrain and environment. And this is how chariots and camels and creepy wizard of oz sequels relate to evolution: biological or cultural adaptations depend on the environment in which they arise. The best solution to a probelm depends on the problem. While propellers and spinning blades are an optimal way to move human-made craft through the water, the fins of fish are actually more efficient at providing propulsion in most cases. So, theres no fish with propellers, and because we havent been able to match evolutions aquatic creativity, we dont have boats powered by big tail fins. Likewise the wheel as a technology isnt intrinsically better or more advanced than other ways of moving. The wheel only dominated in certain environments, under certain conditions. And even if animals were capable of growing wheels as body parts, in most environments and terrains they would probably work worse than feet or hooves. Which brings us to a different kind of terrain altogether, the fitness landscape. In biology, fitness is essentially a score that prepresents a traits ability to survive and reproduce. The wings of birds, bats and even pterosaurs are all modified structures of the arm, hand, and fingers. They are an example of convergent evolution. You have to go pretty far back to find the common ancestor between these winged creatures, but the wings of birds, bats, and pterosaurs are all descended from an arm that is built essentially the same as yours or mine. One bone up here, two bones here, lots of little bones here and long bones here. So theoretically, humans could evolve wings, right? Actually no. When a trait evolves, every stage of its evolution pretty much has to provide an advantage, or at least not be harmful. Even if the final trait, like humans flying with wings, would be super cool and give us lots of new advantages, we would have to be able to get from this to wings in a way that every step is beneficial. You can't evolve anything that reduces your fitness. A fitness landscape is a way to look at a lot of different variations and how they score versus one another. Each square represents a variation or genetic possibility. The closer the squares, the more similar two variations are, and the further the squares, the more different they are. The fitness of each genetic possibility is represented by its height on the landscape. Heres the problem. You can only ever move uphill, toward higher fitness. There may be a highest peak, with the best trait on your landscape but you cant get there because youd have to travel down into a valley first. Evolution is walking around this landscape blind, it doesn't plan or have foresight, so organisms often get stuck on top of these little hills, called local optima. Theyre as good as they can be without getting worse. The human eye is a perfect example of a local optimum. If the optic nerve and the eyes blood vessels ran behind the eye instead of through it, we wouldn't have a blind spot in our vision. This is how octopus eyes are built and its a much better way to make an eye. But we can't jump all the way to that higher fitness peak, or travel through a valley where we'd make our eyes worse in the meantime. Likewise, if we wanted to have wings like birds, each stage of our evolution from arms to wings would have to provide a benefit. When the first birds were evolving from raptor like dinosaurs, they already had feathers for attracting mates. So they could use them to glide like flying squirrels - that a fitness advantage. And each tweak and variation would help them glide farther - more fitness improvements - all the way up to powered flight at the top of a fitness hill. For humans, variations in our hands or arms that gave us a small amount of gliding ability wouldnt really improve our fitness right away. But having dumb wing hands would have a lot of costs when it came to things like using tools. So even if being able to truly fly would be a huge improvement overall, those intermediate steps cant evolve if they mean moving down the fitness hill. And this is why zebras dont have laser turrets for fighting lions. This would clearly be a benefit, but they can't because the intermediate steps of evolution have to be helpful or at least not harmful. A laser turret is only useful when it is complete. The intermediate functionless laser organ would just be hogging vital nutrients, a fitness loss. And sure, projectile weapons have evolved in other animals. Like archerfish that hunt by spitting water, or antlions that use sand as a projectile weapon. But if you're prey, running away might just work well enough, so youre stuck at a local optimum without laser turrets.Evolution works like trying to make improvements to an engine while the car is in the middle of a race, you cant break your engine in order to make it work better. Of course, Im not willing to give up my dream of flying so easily. Maybe theres another way humans could grow wings. Why cant we just grow a new set of limbs? You can imagine the strategy working for some bugs like millipedes. Entire body segments could be duplicated thanks to mutations in genes controlling how the body develops, and proof: youve got a new pair of legs to add to your 48 other pairs. The mutations in a class of body-patterning genes called Hox genes that have been linked to misshapen feet, hands, skulls, and even extra fingers or toes. In very rare cases humans are even born with extra limbs, like the babies who were born with three arms. But almost always, these duplicated limbs dont function, because the new limb also needs bones, joints, its own muscles and nerves, and each of those duplications would require countless other mutations in other genes. Which is beyond unlikely. Evolving wheels instead of feet, or finding a fish with a propeller, or modifying our hands into wings like a bat, is difficult enough to be impossible. But at the end of the day there also has to be a need to evolve - you dont just get something because its cool. The trabant had a 25 horse power two-stroke engine closer to what's in a lawnmower than a car, a plastic body, no fuel door, no rear seatbelts, not even a turn signal indicator. Although their design changed little from the late 1950s through 1990, when production ceased, more than 3 million were sold. Thats because this was one of the only automobiles available in communist east germany. Before the fall of the berlin wall in 1989, east germany was a closed economy, meaning there was no competition from other car manufacturers and no pressure to improve this vehicle. For natural selection to happen an organism has to run into some challenge that impacts its survival, what we call a selection pressure. The east german lawnmower sedan never had selection pressure from other automobiles forcing it to improve, so it continued to sell well despite being very bad. Until humans experience a selection pressure for gliding, we wont start to evolve adaptations that lead towards flight. And sometimes selection pressures can be so sudden or different, that there is no adaptation for evolution to even act on. The dodo had no adaptations for defending itself, because it never encountered humans or other predators, and they became extinct. But beyond all these principles of evolutionary biology, one of the biggest limitations we face is physics. The reason we dont see gigantic land animals like mr longneck here anymore is because of two pesky bits of physics. One, gravity. Two, the square cube law. As an organism gets bigger, its volume increases much faster than its surface area. So as something grows and gets more volume, any process that depends on the amount of surface that you have will become less efficient unless you change your shape to make more surface shape to make more surface. This is the reason big complex organisms like us are multicellular instead of 6 foot tall single celled amoeba blobs. That wouldnt provide enough surface area to exchange nutrients and waste and make energy for all of our big blobby volume. So instead, our bodies are made of 37 trillion cells, give or take. Its the only way to have enough surface area for all that we are. Gravity and the square cube law combined is why here on earth its unlikely we'd ever get land animals weighing more than 100 tons. Its also the reason if youre ever given the choice of fighting one horse-sized duck or 100 duck sized horses, you should pick the fight versus the duck because duck legs would snap like toothpicks under the weight. And the limitations of physics are not just something animals have to worry about. Calculations of how gravity affects the flow of water in trees estimate the maximum height a tree could ever reach on earth is 130 meters. And sure enough, the tallest tree we know of (Hyperion tree) is just under 116 meters tall. However, a diffrent physical environment comes with different physical restrictions. Blue whales, the largest animals to ever live on earth, weigh up to 173 tons because the buoyancy provided by their watery environment counteracts the gravity. Therefor on different planest with lower gravity or different atmospheric composition, we might be able to see bigger animals. For instance, 300 mya the concentration of oxygen in earths atmosphere was much higher than it is today (reaching as high as 30%). And insects which dont have lungs and circulatory systems - they breathe by gases just diffusing into their bodies - were able to grow much larger than insects today. Dragonflies the size of birds? Nope, thanks. For all of natures creativity, a few empty spots remain on the tree of life where branches seemingly cant grow. What we call impossible phenotypes, that as far as we know have never arisen in the history of earth. Like freshwater coral reefs, or birds that give birth to live young, or plant eating snakes. There are thousands of species of snakes, youd think one would take advantage of the food source that all other snakes are ignoring and go vegetarian. Snakes closest relatives, lizards, many of which do eat plants. I mean, making the switch from a meat eating to plant diet worked for pandas. But maybe theres something about how a snake is built that prevents it from getting enough energy from plants. Of course, maybe we also just dont know yet. For a long time it was believed that all spiders were carnivorous, until we found one that eats plants (bagheera kiplingi). Its difficult to say things are totally impossible. Given more time, evolution may well produce some of the things we've talked about. Imagine if alien evolutionary biologists studied life on earth 450 mya. Flowering plants, flying insects, animals able to walk and breathe on land - these may have seemed like impossible phenotypes back then, but all of them happened. So while there are limits to what evolution can do in single lineages, like humans growing wings or animals with wheels, we dont really know where the boundaries of evolution are as a whole. Like what about animals with an odd number of limbs? Not an animal that lost a limb, or a 5 limbed animal like a starfish - radial symmetry removes many of the limitations that would prevent odd numbers of limbs. I mean a three limbed animal like a dolphin. Think about it, how many legs does a dolphin or whale have? Their fins have two lobes, and their prehistoric ancestors walked on all fours, but for all intents and purposes couldnt we consider a dolphin an animal that evolved to move with three limbs. Does that mean kangaroos and their powerful tails, or monkeys with prehensile tails are, functionally speaking, 5 limbed animals? Are snakes single limbed animals? In these cases, although they are rare, there was an evolutionary path that allowed an odd number of limbs or limb-like appendages to arise from even-numbered ancestors... thats a pretty remarkable leap. For all the rules and impossibilities weve talked about, the things evolution has been able to mold and create are pretty impressive. Instead of looking at what nature hasnt built, maybe we should marvel at all that has been.

Answer 117

Essential Aminos Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine

Answer 118

Non Essential Aminos Alanine Asparagine Aspartic Acid Cysteine Glutamic Acid Glutamine Glycine Proline Serine Tyrosine Arginine

Answer 119

Why are we alive? Energy & ATP. At this very second, you are on a narrow ledge between life and death. You probably dont feel it, but theres an incredible amount of activity going on inside you, and this activity can never stop. Picture yourself as a slinky falling down an escalator moving upwards. The falling part represents the self replicating processes of your cells. The escalator represents the laws of physics driving you forwards. To be alive is to be in motion but never arriving anywhere. If you reach the top of the escalator, theres no more falling possible, and you are dead forever. Somewhat unsettingly, the universe wants you to reach the top. How do you avoid that, and why are we alive? All life is based on the cell. A cell is a piece of the dead universe that separated itself from the rest so it could do its own thing for a while. When this separation breaks down, it dies and joins the rest of the dead universe again. Unfortunately, the universe would like for life to be done with doing its own thing. For some reason, its not a fan of exciting things, but tries to be as boring as possible. We call this principle entropy, and its a fundamental rule of our universe. Living things are inherently exciting. A cell is filled up with millions of proteins and millions more simpler molecules like water. Thousands of complex, self replicating processes are happening up to hundreds of thousands of times every second. To stay alive and exciting, it has to constantly work to keep itself from achieving entropy and becoming boring and dead. The cell has to maintain a separation from the rest of the universe. It's doing this, for example, by keeping the concentration of certain molecules different on the inside and the outside by actively pumping out excess molecules. To do stuff like this, a cell needs energy. Energy is the ability of things in the universe to do work; to move or manipulate a thing; to create change. This ability cannot be created or destroyed. The set amount of energy in the universe will never change. We dont know why, it just is that way. So, billions of years ago, one of the most crucial challenges for the first living beings was to get usable energy. We dont know a lot about the first cells, except that they got their energy from simple chemical reactions. And they found the ultimate energy transfer system: the energetic building block of life. The molecule Adenosine Triphosphate (ATP). Its structure makes it uniquely good at accepting and releasing energy. When a cell needs energy, for example, to pump out molecules or to repair a broken micro machine, it can break down ATP, and use the chemical energy to do work and create change. This is why living beings are able to do stuff. We don't know when or how exactly the first ATP molecule was made on earth. But every living thing we know uses ATP, or something very similar, to keep its internal machinery running. Its crucial for almost every process. Plants, fungi, bacteria, and animals need to survive. Without ATP, no life on earth. Possibly anywhere. While breaking down chemicals for energy is nice and all, early life did miss out on the greatest avaialable source of energy: the sun. The sun merges atoms and radiates photons away that carry energy into the solar system. But this energy is raw and indigestible. It needs to be refined. After hundreds of millions of years of evolution, finally, a cell figured out how to eat the sun. It absorbed radiation and converted much of it into neat little chemical packages that it could use to stay alive: photosynthesis. You take photons that are wobbly with electromagnetic energy, and use a part of this energy to merge and combine different molecules together. The electromagnetic energy is converted into chemical energy stored in the ATP molecule. This process became even better, as some cells learned to create better chemical packages: glucose (sugar). Easy to break down, high in energy, and pretty tasty. This is so convenient, that some cells decided that instead of doing all that pesky photosynthesis work themselves, they would just swallow other cells that did, and take their glucose and ATP. This is widely considered on of the biggest anime betrayals in evolutionary history. And so things went on. Photosynthesizing cells could mostly harness energy at their surfaces, which limited their maximum energy production, which limited their evolutionary avenues somewhat. So, time passed. Some cells made sugar, others ate them. Evolution did its thing, but overall things stayed pretty much the same for hundreds of millions of years. Until, one day, a cell ate another, and did not kill it. Instead, they became one cell. Nothing had changed that day, but earth would be different forever. This cell became the ancestor of all animals on this planet. The merging of two living beings is so important, because when those two cells became one, they became way more powerful. The formerly independent cell in the inside, could stop trying to survive. It could concentrate on one thing: make ATP. It became the powerhouse of the cell: the first mitochondria. The host cells job became to ensure survival in the dangerous world, and provide the mitochondria with food. Mitochondria basically reverse photosynthesis, in a similarly complex process. They take sugar molecules that we got from eating other living things, combust them with oxygen and precursor molecules, to make new, energy rich ATP molecules. This process works like a tiny furnace and spits out waste products like co2, water, and a little bit of kinetic energy that you experience as body heat. This first division of labor, meant the new cell had way more energy available than any cell before, which meant more possibilities for evolution to enable more complex cells. At some point, these cells began to form small groups or communities, which lead to multicellular life, and finally, to you. Today, you are a pile of trillions of cells, each filled with dozens, if not hundreds of little machines that provides you with usable energy to stay alive. If this process is interupted, even for a few minutes, you die. But if life is so fragile, wouldnt it be a good idea to store ATP, like we store sugar in our fat cells, so we don't die if we stop breathing for a while? If life has solved so many problems to make you live today, whats up with the dying quickly thing? Even simple bacteria like E coli make about 50 times their body weight in ATP for every cell division. Your trillions of cells need a lot of ATP to keep you around. Every day, your body produces and converts about 90 million, billion, billion molecules of ATP: about your own body weight. You need a whole persons worth of ATP just to make it through a single day. Even storing enough ATP to last you a few minutes is basically impossible. An ATP molecule is really good for shifting energy around quickly, but its terrible for storage, since it has only one percent of a glucose molecules energy at three times its mass. So atp is constantly produced and used up fairly quickly. This was the short and simplified story of the molecule that allows you to be different from the dead universe. There is this molecule you need to survive at all times. You need it to keep moving, because even a short break brings your slinky to a stop. And you need to make it yourself. Its like driving a car at full speed while producing fuel in the trunk with junk that you pick up from the side of the road.

Answer 120

Red kidney beans contain relatively high amounts of phytohemagglutinin, and thus are more toxic than most other bean varieties if not pre-soaked and subsequently heated to the boiling point for at least 10 minutes.

Answer 121

Psychedelic therapy Psychedelics activate the Serotonin 5HT2a receptor in the brain. Antidepressants and the atypical anti-psychotics also affect this receptor but in different ways.

Answer 122

Navigation by stars The stars that we see in the sky today are the same ones that guided the ancient egyptians in building their pyramids. And maritime travelers in their travels around the globe. At any time of the year anywhere on earth, the stars appear over the horizon at predictable heights and at measurable distances. For example, Ploaris - what most people know as the North Star is an easy target when youre navigating in the Northern Hemisphere. First thing you want to do is find The Big Dipper. Depending on where you are, and what time of day and year it is, the Big Dipper will be in a different part of the sky: Dipping down for Summer. Upside down for Spring. Rightside up for Fall. Basket pointing upwards for Winter. The Big Dipper is always circling the North Star. The Dipper is just a good recognizable feature. Once youve located the Dipper, look at its bucket. On the front edge of this bucket are two stars, Merak (base) and Dubhe (rim). Draw an imaginary line from Merak, through Dubhe following that line out to the bright star of Polaris: thats the North Star. Now that youve found the North Star, youve also found the Little Dipper which extends out from this point. The reason we use the North Star is because it hardly moves, making it a reliable navigational point. However the North Star isnt much help if youre in the Southern Hemisphere. You have to catch it at the right time and place. So if youre in the South, youre going to need the constellation called the Southern Cross. You have to draw a line through the longest angle of the Cross, connecting the stars from the top-down, all the way to the horizon. Then you find the mid-point between the two "pointer" stars on the other end of the constellation and draw a line from that midpoint to the horizon as well. The area where those two lines intersect is the sweet spot we're looking for and that points South. Now obviously, humans travel in more directions than just North or South. Generally theres about 80 to 82 or so bright stars, which are very easily identifiable because they also exist in the major constellations. In order to get the latitude and longitude of your location, select one of these stars, measure its direction and height above the horizon, and the time it was when you took the measurement. Add a little spherical trigonometry and youve got your exact location. A tool that helps determine these calculations is called a sextant. This device is a two-mirrored, doubly reflective instrument. One mirror keeps an eye on the horizon and the other is adjusted by a 60 degree arc to locate the constellation or celestial body. Depending on where you land, the arm has numerical notches that help the user calculate their location. Apollo astronauts had their vehicles equipped with a sextant that they could use in case they ever lost communication with earth.

0. CORE (Volume Zero) Flashcards

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