Lecture 3-5 Flashcards

Question

When did the Earth cool enough that rocks and oceans began to form?

Answer 1

The end of the Hadean Steam in the atmosphere cooled down and fell as rain on the Earth to create oceans FIrst continents began to form (rocks in early oceans)

Answer 2

Zircon crystals from Western Australia have been dated to 4.4 billion years making it the oldest rocks on earth. - This suggests that within the first 100-200 million years of our planet, there was enough cooling to form a crust. Ratio of O isotopes within this zircon crystal indicates that it likely formed in a cool, wet process at the Earth's surface - This suggests that parts of Earth may have been covered with liquid water

Answer 3

Archean -- meaning "beginning, origin" Liquid water was prevalent Emergence of life on Earth (first evidence) Onset of plate tectonics

Answer 4

All of the crust on Earth moves around like floating slabs of rock (about 96km thick) on top of hot, mushy rock in the mantle, the hotter part of the Earth between us and the Earth's iron core. The Earth is chewing itself up, melting itself down, and making itself anew (a way that the Earth recycles itself) Made up of rigid cool lithosphere (the rocky crust of the ocean floor and continents, down to the upper mantel)

Answer 5

Alfred Wegener in 1915 Idea that the Earth's continents have moved over geologic time relative to each other, thus apearing to have "drifted" across the ocean bed Explained why look-alike animal and plant fossils, and rock formations, are found on different continents (fossil evidence)

Answer 6

The species evolved independently on separate continents contradicting Darwin's theory of evolution They swam to the other continents in breeding pairs to establish a second pop.

Answer 7

Rocks of the same age across the ocean

Answer 8

Plate tectonic theory

Answer 9

Core - rich in iron - solid inner core - liquid outer core (source of Earth's magnetic field) Mantle: very hot rocks - rich in silicon and oxygen (SiO2) - becomes hot enough to become ductile and weak, behaves "plastically" Crust: cooler, stiffer rocks - rich in silicon and oxygen (SiO2)

Answer 10

Oceanic crust: - thin (7 km) - dense (sinks under continental crust) --> nk - young Continental Crust - thick (10-70 km) - buoyant: less dense than oceanic crust - mostly old Density differences due to chemical differences; when it interacts with continental crust it tends to sink - Continental crust has more aluminum, silicon, less magnesium, iron - Oceanic crust has more magnesium, iron, less aluminum and silicon

Answer 11

Earth's crust is divided into 12 major plates which move in various directions Plate motion causes them to collid, pull apart or scrape against each other Each type of interaction cuases a characteristic set of Earth structures or tectonic features (e.g. volcanoes, mountains, ocean trenches) The word tectonic refers to the deformaiton of the crust as a consequences of plate interaction

Answer 12

Stiff tectonic plates are carried along the top of the mantles as if they were on giant conveyor belts Convections causes the movement

Answer 13

Zones of contact between plates. They do not correspond to those of the continents.

Answer 14

Divergent: moving away from one another Convergent: moving toward one another Transform: moving up against one another

Answer 15

The space created can be filled with new crustl material sourced from molten magma that forms below (the magma comes up in space created by divergent boundaries) Divergent boundaries form within continents to produce rifts in continental crust. When the rift opens wide enough, it will form the thin rocky floor of a new ocean. Some rifts failed to open, and created long-lasting valleys where major rivers run Iceland being slowly torn apart is an example of continental rifting

Answer 16

Underwater mountain systems Most active divergent plate boundaries are between oceanic plates. As plates move apart, small amounts of magma rise to the seafloor and add new crust (seafloor spreading -- ocean is growing wider)

Answer 17

Near the continents The age of seafloor increases relative to oceanic rifts

Answer 18

Also known as hydrothermal vents, they are sea-floor hot springs. Molten hot magma heats up the water and pushes it up through the vent. Entirely different ecosystem of organisms that we never knew about. We discovered organisms at these vents get their energy from the vent itself and not from sunlight (chemotrophs) --> beginning of life on the planet?

Answer 19

Refer to plates colliding. Typically the denser plate is subducted underneath the less dense plate. The plate being forced under is eventually melted and destroyed. 3 types of convergent boundaries: - continent-continent collision - continent-oceanic collision - ocean-ocean collision

Answer 20

Continental crust meets continental crust Both continental crusts are too buoyant (light) to subduct so a continent-continent collision occurs, creating especially large mountain ranges

Answer 21

Continental crust meets oceanic crust The denser oceanic plate is subducted, often forming a mountain range on the continent

Answer 22

Occur when one of both of the tectonic plates are composed of oceanic crust. Leads to oceanic crust being recycled.

Answer 23

Ocean crust meets oceanic crust Two oceanic plates collid; one oceanic plate is eventually subducted under the other Formation of really deep trenches such as the Mariana Trench which is 11 km deep

Answer 24

Plates slide past one another As plates rub against each other, huge stresses are set up that can cause portions of the rock to break, resulting in earthquakes. Places where these breaks occur are called faults Lithosphere is neither created nor destroyed

Answer 25

Plate motions are on the order of a few centimeters per year Along their edges, most paltes either converge of diverge

Answer 26

Plate tectonic movements affect geography (create mountains, give birth to new oceans, produce volcanoes that spew gases into the atmosphere), they could in turn affect food supply, climate, and the diversity of life Mountain ranges form a physical barrier that allows isolation of gene pools Ex. When the Grand Canyon formed, squirrels and other small mammls that had once been part of a single pop. could no longer contact and reproduce with each other across this new geographic barrier

Answer 27

Supercontinent that assembled from earlier continents approximately 335 million years ago, and it began to break apart about 175 million years ago.

Answer 28

Plate tectonics has been one of the main driving forces promoting the biodiversity of organisms Terrestrial organisms were able to migrate across all the continents and were only limited by their biotic potential. As Pangeo began to separate, it created physical barriers such as seas Species were separated and became exposed to different physical (i.e. climate) and biotic (i.e. changes in predators) conditions, each species adapts differently and eventually forms new species on the newly separated continents New habitats were created due to a change in biotic and abiotic factors such as climate (temp. and moisture)

Answer 29

The breakdown of minerals in rocks at or near the Earth's surface -- releasing nutrients Weathering is caused by chemical and physical interactions with air, water and living organisms Nutrients in the oceans ultimately come from weathering and erosion of rocks on the continents When weathering and erosion rates increase for extended periods, more nutrients are supplied to the oceans

Answer 30

When tectonic plates collide, mountains are pushed upwards and erosion causes an increase in nutrients in the oceans

Answer 31

Plate tectonics helps regulate the planet's temperature, recycles nutrients and many other important functions. Of all planets, Earth is the only one known to have plate tectonics. It is also the only one known to harbour life. Some research argues that plate tectonics might be necessary for the evolution of advanced species. Dry land on continents is necessary for species to evolved the limbs/hands that allow them to grasp/manipulate objects, and that a planet with oceans, continents and palte tectonics maximizes opportunities for speciation and natural selection

Answer 32

Consumes and produces energy Reproduces Non-motile Considered life

Answer 33

Collect sediment cores that are meters to kms below the seafloor Deep sea sediments contain lots of single-celled organisms (mostly bacteria) - dormant for years - lifespan can be very different from life on the surface (average cell may divide once in 1000 years)

Answer 34

Virus that infects and replicates within bacteria Has DNA or RNA (contains building blocks of life) Needs host to reproduce Cannot make their own energy Debate whether considered life or not since they cannot reproduce without a living host

Answer 35

No single accepted definition NASA def: Life is a self-sustaining chemical system capable of undergoing Darwinian evolution (according to NASA, viruses would then be considered life)

Answer 36

Maintain internal homeostasis: must have a mechanism to maintain its internal envr separately and independently of its exterior envr. - membranes Respond to external stimuli: must respond to its envr. - Movement or chemistry Consume and produce energy: must be able to process energy - electrochemical gradients Reproduce and have a form of heredity: must have a way of passing on info between generations and individuals - DNA and RNA

Answer 37

The inside of a living thing is different than the external environment (distinct thermal and chemical makeup). Cell must be able to maintain this interior in the face of changing external condition. Organisms regulate their internal envr. to maintain the relatively narrow range of conditions needed for cell function (internal temp., pH, concentration of proteins and solutes)

Answer 38

Cell membrane barriers that protects cell Transport across membranes allow cell to bring things in or push things out in a controlled way (maintains concentrations of ions)

Answer 39

External stimuli: a change in the environment. Responses can be physical (ex. movement) or chemical (ex. hormones) Everything from complext multicellular organisms to single cells respond to external stimuli - single-celled organisms may migrate toward a source of nutrient or away from a noxious chemical

Answer 40

Living things must use energy and consume nutrients to carry out the chemical reactions that sustain life (e.g. replicating or repairing DNA< synthesizing new proteins) - Metabolism

Answer 41

The sum total of the biochemical reactions occuring in an organism

Answer 42

Heterotrophs (breaking down organic carbon compounds) --> humans, animals Autotrophs (light/chemical reactions) --> algae, plants, certain microbes

Answer 43

Cellular energy currency for all cells --> all life on Earth uses ATP Energy is moved around the cell as adenosine triphosphate (ATP) Protons accumulate on one side of a membrane establishing an electrochemical potential energy gradient (like water in a dam) Movement of the ions back across the membrane is used to do work (generates energy in the form of ATP through these membranes) - proton gradient from high (in) to low (out)

Answer 44

All life must have a mechanism for reproduction Reproduction is the process by which living things give rise to offspring and transmit hereditary info

Answer 45

Asexual: single organism creates clone of itself. Most species on the planet reproduce asexually (including all bacteria, archaea, many plants and even some animals) --> much more common than sexual reproduction Sexual: cells from new parents unite to form first cell of new organism. Offspring is different from parent

Answer 46

Living things are able to pass on their traits through genes (a sequences of DNA or RNA) that are passed from parent to offspring each generation

Answer 47

A complex code made up of nucleotides Allows for incredible flexibility in the info recorded

Answer 48

During the Archean, from at least 3.5 billion years ago

Answer 49

Chemical building blocks: O, H, C, N, S, P Energy source: UV light from sun, electrical energy from lightning, and chemical energy

Answer 50

Carbohydrates Lipids Proteins Nucleic acids

Answer 51

A large biological molecule made up of smaller subunits or monomers

Answer 52

Proteins - Amino acids Lipids - Fatty acids - Sugar residues --> glycerol Carbohydrates - Sugar residues --> mono-saccharides DNA or RNA - Sugar residues --> monosaccharides --> nucleotides - nucleobases --> nucleotides

Answer 53

The "last universal common ancestor": suggests that all current life evolved from a single common ancestor Does not necessarily mean that life only evolved once on Earth - Other forms of life could have gone extinct very early in evolutionary history and left no record in modern-day life for us to find Evidence: all extant life has: - carbon based - similar enzymes with similar gene recipes - enzymes for most basic biological functions are the same across very different species - passes heredity info through DNA or RNA - Amino acids and nucleic acids are found in two different configurations (left handed and right handed --> same compound they are mirror images) -->all extant life has ONLY left-handed amino acids and right handed nucleic acids

Answer 54

Based heavily on the idea that the early earth environment consisted of high concentrations of compounds and elements known to be abundant in life (C, H, water vapour, ammonia)

Answer 55

1) Early Earth had a chemically reducing atmosphere - very low levels of gaseous oxygen - high levels of reducing gases (e.g. carbon monoxide) - oxygen was found on earth, but almost all bound in minerals. Essentially inert and unavailable 2) This atmosphere, exposed to energy in various forms produced simple organic compounds (monomers) - energy may have come from lightning or the sun (UV) 3) These compounds accumulated in a "soup", which may have been concentrated at various locations (shorelines, oceanic vents, etc.) 4) Concentration led to the eventual formation of complex organic compounds (polymers) - life eventually arose from these complex polymers - early cells then broke down these organic molecules to generate ATP --> heterotrophy

Answer 56

Experimental support to the primodial soup theory Test for production of monomers under early primitive Earth conditions Results: - Found that 25 different amino acids had been produced (the basic building blocks of proteins) Conclusion: if free oxygen is present, no organic compounds are formed - Assumes that amino acids formed first and would eventually connect somehow to form proteins

Answer 57

No mechanism for the generation of complex polymers from simple monomers No mechanism for the evolution of cells from monomers and polymers Need sustained energy for life to develop (not one time "spark")

Answer 58

RNA formed first Proliferation of RNA eventually lead to DNA and protein formation RNA can store replication info (like DNA), can replicate itself, can act as an enzyme --> ribozyme, could have provided heredity and catalyzed reactions before the evolution of DNA and proteins Does not necessarily preculde the primordial soup theory (theories are not mutually exclusive) - organic molecules were the precursors to nucleotides

Answer 59

Experimental: Nucleic acid precursors and nucleotides have been produced in the lab from simple compounds common on early earth (hydrogen cyanide, hydrogen sulfide) and UV light Observational: Some viruses contain RNA only. Viruses generally considered to be ancient form of life

Answer 60

How does a combination of DNA, RNA and proteins lead to cell formation How are membranes produced? Attemps to create self-replicating RNA under plausible early-Earth conditions have failed - RNA is not very stable in water Does not make sense since viruses need a cell to infect

Answer 61

First theory to seriously challenge the primordial soup theory Involves the generation of electrochemical gradients and metal-containing enzymes as the first precursors to life - allowed for the generation of chemical energy Once energy could be reliably generated - organic monomers and polymers would be formed naturally - RNA, DNA, and proteins would follow - Eventually all would combine behind a membrane which could safely leave the vent, colonize the rest of the ocean and eventually the planet

Answer 62

Small cracks on the seafloor from which geothermally heated water issues Called black of white smokers Found in the mid-ocean ridges where seafloor is spreading (magma reaches the ocean) - at divergent plate boundaries The deep sea hydrothermal vents have very unique chemistry - alkaline water from vents meets slightly acidic oceanic water (OH- and H+) --> creates a natural proton gradient (creation of energy ATP)

Answer 63

Porous geological structures produced by chemical reactions between solild rock and water Hot hydrothermal fluids mix with near-freezing seawater. These minerals solidify as they cool, forming chimney-like structures (chimneys are very porous) Chimney structures can be porous and act as a primitive semi-permeable membrane - Worked well enough to create different proton concentrations in different locations - energy would be generated when a proton went with the gradient

Answer 64

Experimental: articial hydrothermal vents have generated proton gradients under laboratory conditions Observational: many of the oldest enzymes contain iron or sulfur in their complexes. Reconstruction of proteins from ancestral bacteria show high heat stability (i.e. they evolved in a warm/hot place)

Answer 65

No clear mechanism yet for how biomolecules eventually developed

Answer 66

Perhaps, meteorites such as Tagish Lake Meteorite have been shown to contain an abundance of organic materials including amino acids. Another example is Murchison that has been estimated to be nearly 4.95 billions years old. It contained organic compounds including amino acids as well as purine and pyrimidine compounds. Both purines and pyrimidines are needed to form RNA and DNA

Answer 67

Life is actually everywhere in the universe Microbes which can survive the effects of space can become trapped in debris ejected into space after collisions between planets and small Solar System bodies that harbor life.

Answer 68

1) that organic molecules originated in space 2) that life originated from these molecules extraterrestrially 3) that this extraterrestrial life was transported to Earth - this is improbable --> temperatures surviving in outer space and entering our orbit does not make very much sense since it is too hot for microbes to survive

Answer 69

THere was a reducing atmosphere of methane, ammonia, and other gases which would be toxic to most life on our planet today. No free oxygen (O2) was present No ozone O3 layer to shilef Earth from UV radiation, and other solar and cosmic radiation High rates of metero bombardment

Answer 70

A sign of life (proof that life was present) Any substance--such as an element, isotope, or molecule--that provides evidence of life.

Answer 71

Fossils Chemical fossils Isotopic signatures

Answer 72

Remains or traces of ancient life that have been preserved by natural processes Can include anything ranging from sea shells, imprints of microbes, to large skeletons In the context of early life, it was an imprint of a microbe (cells)

Answer 73

Molecular biological markers (biomarkers) are natural products that can be traced to a particular biological origin The most effective biomarkers are compounds with specific biological sources, whose structures can be preserved through geologic time Lipids are the most stable macromolecules and are an example of chemical fossils. They are preserved in sedimentary rocks and can offer insights into Earth's history (different organisms make different lipids --> can trace them back in time)

Answer 74

Unstable isotopes can tell us about the age of a compound Stable isotopes tell us about the source (e.g. biotic or abiotic) - how molecule was made

Answer 75

By measuring the amount of the ratio of carbon-12 to carbon-13 Different processes have different stable carbon isotopic signatures Stable carbon isotopic signatures will reflect unique biological processes - organic compounds can have unique isotopic signatures

Answer 76

Banded Isua rocks are the oldest known metamorphosed sediments These rocks have graphite in them - graphite = pure carbon - graphite is not a biosignrature, but it can form by cooking organic matter - graphite can keep most of the original stable carbon isotopes Isotopic signatures suggested that this carbon originated possibly photoautotrophic microorganisms - Hypothesis was that microbes using sunlight to make their own carbon. Carbon was consistent with some photosynthetic process rather than abiotic production (HOWEVER, this was disproved)

Answer 77

Apex Chert is part of the Pilbara Craton: an old and stable part of the continental lithosphere One of the few places on the planet where geological evidence of early Earth has been preserved, largely because it has not been subjected to geological processes that would have altered it, like burial and extreme heating due to tectonic activity Theory: evidence of life because it looked like certain bacteria. This was argued that this could also look like minerals. The microbe theory was proved to be right Isotopic signature showed that they were consistent looking. Stable carbon isotopic compositions confirmed that microscopic fossils discovered in a nearly 3.5 Ga rock from Apex Chert are the earliest direct evidence of life on Earth

Answer 78

Stromatolites are the least controversial evidence of early life Stromatolites are rocklike structures made up of layers of bacteria and sediment, found in shorelines Found throughout Archean rocks and become more common later in the Archean.

Answer 79

Created through the trapping, binding and cementation of grains of sediment by microbial mats (i.e. biofilms) Mucus secreted by the bacteria collects grains of sediment, and these grains and cells become stuck together with calcium carbonate also from the bacteria (grow over long timescales) In modern environments, stromatolites are found in coastal regions or areas submerged in water

Answer 80

From 3.5 Ga ago from the Warrawoona Group (Western Australia)

Answer 81

They are usually found in hypersaline lakes and marine environments where the extreme salt level prevents animals such as snails from grazing on them. Modern stromatolites' size in non-hypersaline environments tend to be smaller since snails graze on them

Answer 82

Cyanobacteria: - autotroph (makes its own food) - photosynthetic (obtain energy through photosynthesis) - found in almost every terrestrial and aquatic habitat (oceans, lakes, ponds, rivers, etc.)

Answer 83

Can be composed of diatoms, cyanobacteria, purple sulfur bacteria, sulfate- reducing bacteria Microbial mats can contain more than just autotrophs There are lots of other microorganisms that live in and on them For example, cyanobacteria excretes glucose that can be a food source for other heterotrophic microbes --> first microscale ecosystem Stromatolites were actually micro-scale ecosystems

Answer 84

Photosynthesis without the production of oxygen Does not use water as an electron donor, but rather can use a variety of substrates including sulfide, iron, and hydrogen CO2 + 2H2A + light energy --> Ch2O + 2A + H2O

Answer 85

Purple sulfur bacteria Green sulfur bacteria Purple nonsulfur bacteria We think that the dominant microbes during the Archean were anoxygenic microbes due to sulfur

Answer 86

Sulfate reducing microbes - heterotrophs - live in anaerobic environments (low or no O2) - Use sulfate as an electron acceptor instead of oxygen

Answer 87

Also called the oxygen catastrophe, oxygen crisis, oxidation resolution The bioloigcally induced appearance of dioxygen (O2) in teh Earth's atmosphere through the activity of oxygenic phototrophic microorganisms (cyanobacteria) In other words, cyanobacteria oxidized the planet --> induced detectable O2 into the atmosphere

Answer 88

Not entirely sure There are many sinks for oxygen - O2 being produced is balanced by sinks and respiration - Microorganisms learned to use O2 expansion of aerobic microorganisms - banded iron formations and red beds as O2 sinks

Answer 89

Require oxygen as electron acceptor Oxygenic photosynthesis : CO2 + H2O --> glucose + oxygen Heterotrophic respiration is the contrary, and produces ATP as well

Answer 90

Alternating layers of iron-rich material (commonly magnetite) and silica (chert). Each layer is relatively thin, varying in thickness from a mm or so up to several cm

Answer 91

Around the time of the Great Oxidation Event BIFs are abundant in Proterozoic rocks ranging in age from 1.8-2.5 billion years old Appear on all continents Huge deposits, km thick and 1000s of km^2 wide Most common rock mined for iron

Answer 92

BIFs are thought to have formed through the caputre of O (released by photosynthetic processes) by iron dissolved in ancient ocean water - sedimentation of biomass and iron minerals - free iron in ocean consumed oxygen Once nearly all the free iron was consumed in seawater, oxygen could gradually accumulate in the atmosphere, allowing an ozone layer to form

Answer 93

The banded structure is thought to occur from fluctuating densities (or blooms) of cyanobacteria in the ocean The periodic process might have been due to seasonal fluctuations or storm surges or factors that we don't know about Layers of iron and sediment

Answer 94

Red beds form when iron is weathered out of rock in the presence of oxygen Red in colour due to the presence of ferric oxides (iron and oxygn interact to form ferric oxides) Earliest confirmed redbeds are thought to have formed about 2.2 Ga ago. For several million years BIFs and red beds overlap indicating the presence of low levels of atmospheric oxygen.

Answer 95

Once production exceeded consumption/sinks, O2 could accumulate in the atmosphere By 2 Ga, O2 levels began to build up in the atmosphere The presence of O2 had a profound impact on life on Earth - O2 is toxic to organisms that don't have protective mechanisms; many died as O2 levels built up - many anaerobic organisms survive (even today) only in environments with little to no O - some organisms developed means to use O2 in respiration to extract more energy from foods (aerobic respiration) The formation of the ozone layer (O3) soon after oxygenation of the atmosphere provided protection from UV radiation and allowed life to expand to regions at and near the Earth's surface

Answer 96

Towards the end of the Great Oxygenation Event: diverse microfossils of bacteria become more common in sedimentary rock Their sizes (<10 micrometers) suggest that most were prokaryotes --> simple single-celled organisms (probably needed very little O)

Answer 97

Have a membrane bound organielles (prokaryotes do not) - Eukaryote cells are more large and complex compared to prokaryote cells DNA within membrane-bound nucleus; linear chromosomes Cytoskeleton: protein filaments in cell membrane provide structural framework Complex organelles: some organelles (mitochondria and chloroplasts) contain their own DNA and replicate independently

Answer 98

Prokaryote only: nucleotid, circular DNA Both: Cells, cell membrane, ribosomes Eukaryote only: nucleus, organelles, linear DNA

Answer 99

1.9 Ga in Gunflint Chert, North America Sequences of rocks that are exposed in Minnesota and Ontario

Answer 100

No clear answer, could be because of eukaryotes' need for oxygen The use of O as an electron acceptor provides substantially more energy to a cell (way more ATP generated, eukaryotes have higher cellular needs?)

Lecture 3-5 Flashcards

(124 cards)