9.1 The Origins of Life on Earth

Question 1

What had to happen for simple prokaryotes to form?

Answer 1

Earth had to cool enough for liquid water to exist

Question 2

What is Primary Abiogenesis?

Answer 2

life came from non-living matter

Question 3

Primary Abiogenesis

Answer 3

-Oparin & Haldane (1920s)
-Life came from non-living matter
-Life arose spontaneously once organic molecules were made
-Organic molecules (with CHO) can combine to create LIFE!

Question 4

Which organic molecules can combine to create life?

Answer 4

-Carbohydrates
-Lipids
-Proteins
-Nucleic acids(DNA + RNA)

Question 5

What was the Urey Miller experiment?

Answer 5

-Simulated life on early Earth
-Created organic molecules from inorganic molecules
-Mimics ancient earth’s water cycle
-Proves that life came from non-living matter (inorganic molecules)
-Others have replicated this experiment many times

Question 6

What theory does the results of the Urey Miller experiment support?

Answer 6

This results of this experiment support the Theory of Primary Abiogenesis

Question 7

Where did life begin?

Answer 7

-Planet cooled enough for liquid water
-Land surface likely too hot for life to exist there
-Likely started in deep sea hydrothermal vents
-Likely chemoautotrophic
-Likely similar to modern day extremophiles or archaebacteria in deep sea vents

Question 8

Chemoautotroph definition

Answer 8

organisms that obtain their energy from a chemical reaction

Question 9

How can we tell that life existed around 3.5 billion years ago?

Answer 9

fossils

Question 10

Stromatolites

Answer 10

-Earliest known fossils
-Dome shaped accumulations of bacteria
-Built up over very long period of time
-Likely first photosynthetic organisms to exist in the anaerobic environment

Question 11

What are stromatolites comprised of?

Answer 11

a mound built up of layers of cyanobacteria and trapped sediment, found in Precambrian rocks

Question 12

How did oxygen change the world?

Answer 12

-The oldest photosynthetic prokaryotes lived 3.5 billion years ago
-Likely evolved from chemoautotrophs
-As photosynthetic organisms became more common, more oxygen was released into the atmosphere
-when oxygen came out, there was a mass extinction→ species couldn’t adapt to new environ.

Question 13

What are obligate anaerobes, and how did having more oxygen in the atmosphere impact them?

Answer 13

obligate anaerobes- don’t need oxygen → oxygen kills them

-more oxygen in the atmosphere caused mass extinction of obligate anaerobes

Question 14

What did more oxygen in the atmosphere lead to?

Answer 14

-led to adaptation & created aerobic organisms
-cellular respiration then developed

-prokaryotes were now aerobic! (i.e. could function/live in the presence of oxygen

Question 15

What was a crucial step in the development of more complex organisms?

Answer 15

more oxygen in the atmosphere

Question 16

Why were aerobic organisms “selected” by the environment over anaerobic organisms?

Answer 16

evolution selects aerobic organisms bc they were more successful and fit than anaerobic organisms

Question 17

What is the theory used to explain the origin of eukaryotes?

Answer 17

Endosymbiosis Theory:
-Ancestral proto-eukaryote engulfed aerobic prokaryote
-Symbiotic relationship established
-Allowed for creation of mitochondria
-Chloroplast evolved same way

Question 18

What did the ancestral prokaryote look like?

Answer 18

had DNA, cytoplasm and a plasma membrane

Question 19

How did the endoplasmic reticulum evolve?

Answer 19

plasma membrane infolded

Question 20

What did the infolding of the plasma membrane lead to?

Answer 20

-endoplasmic reticulum
-nucleus
-nuclear envelope

cell with nucleus and endomembrane system

Question 21

How did mitochondria evolve?

Answer 21

ancestral prokaryote engulfed aerobic heterotrophic prokaryote
- evolved into a mitochondrion

Question 22

What did the ancestral prokaryote with mitochondria evolve into?

Answer 22

ancestral heterotrophic eukaryote

Question 23

How did chloroplasts evolve?

Answer 23

ancestral prokaryote engulfed photosynthetic prokaryote
-evolved into chloroplast

Question 24

What did the ancestral prokaryote with chloroplasts evolve into?

Answer 24

ancestral photosynthetic eukaryote

Question 25

How did sexual reproduction contribute to evolution over the years?

Answer 25

-Allowed for genetic recombination -Variation allows for evolution -The environment selects those variations that allow individuals to survive & reproduce -Unicellular organisms evolved into multicellular organisms over hundreds of millions of years

Question 26

What is a geologic time scale?

Answer 26

Chart that organizes Earth’s history into blocks of time

Question 27

What are the three eras marked by major fossil record changes?

Answer 27

-Paleozoic (old) -Mesozoic (middle) -Cenozoic (recent)

Question 28

Eras are divided into ____

Answer 28

periods

Question 29

Periods are divided into _______

Answer 29

epochs

Question 30

What are the boundaries between eras and some periods marked by?

Answer 30

widespread extinctions

Question 31

Paleozoic Era events

Answer 31

-Sudden increase in diversity of many animal phyla (Cambrian explosion) -Marine algae abundant; colonization of land by fungi, plants, and animals -Diversification of early vascular plants -Diversification of bony fishes; first tetrapods and insects -Extensive forests of vascular plants; first seed plants; origin of reptiles; amphibians dominant -Diversification of reptiles; origin of most present-day groups of insects; extinction of many marine and terrestrial organisms at end of period

Question 32

periods in the paleozoic era

Answer 32

-cambrian -ordovician -silurian -devonian -carboniferous -permian

Question 33

Mesozoic Era events

Answer 33

-Cone-bearing plants (gymnosperms) dominate landscape; origin and diversification of dinosaurs; origin of mammals -Gymnosperms continue as dominant plants; dinosaurs abundant and diverse -Flowering plants (angiosperms) appear; many groups of organisms, including most dinosaurs, become extinct at end of period

Question 34

Which era and period did many marine and terrestrial organisms go extinct?

Answer 34

Paleozoic (era), Permian (period)

Question 35

Which era and period were dinosaurs abundant and diverse?

Answer 35

Mesozoic (era), Jurassic (period)

Question 36

Which era and period did dinosaurs become extinct?

Answer 36

Mesozoic (era), Cretaceous (period)

Question 37

Cenozoic Era events

Answer 37

-Major diversification of mammals, birds, and pollinating insects -Angiosperm dominance increases; continued diversification of most present-day mammalian orders -Origins of many primate groups, including apes -Continued diversification of mammals and angiosperms; apelike ancestors of humans appear -Origin of genus Homo -Ice ages; humans appear -Historical time

Question 38

periods in the mesozoic era

Answer 38

-triassic -jurassic -cretaceous

Question 39

periods in the cenozoic era

Answer 39

-paleogene -neogene

Question 40

name of the current geological epoch

Answer 40

holocene

Question 41

in which era, period and epoch did apes originate in?

Answer 41

cenozoic; paleogene; oligocene

Question 42

in which era, period and epoch did apelike ancestors of humans appear?

Answer 42

cenozoic; neogene; miocene

Question 43

in which era, period and epoch had the origin of genus Homo?

Answer 43

cenozoic; neogene; pliocene

Question 44

in which era, period and epoch was there an ice age and humans appeared?

Answer 44

cenozoic; neogene; pleistocene

Question 45

what's currently happening in the holocene epoch?

Answer 45

-the climate has seen some warming and cooling, including the Little Ice Age -large mammals have gone extinct -humans have possibly caused the Holocene extinction event and added to global warming

Question 46

Continental Drift and Macroevolution

Answer 46

-Plates shift on hot mantle -Same fossils on South America and Africa—fit like puzzle pieces -Explains why Australia split early--> was isolated: has marsupials -won’t find any marsupials anywhere else bc it’s been isolated for so long

Question 47

Pangea

Answer 47

-250mya; one giant land mass -Reduced shoreline -Drained shallow seas, little marine life and fossils -More competition between organisms in one land mass

Question 48

What did the break up of Pangea allow for?

Answer 48

convergent evolution since it led to the formation of continents

Question 49

Mass extinctions

Answer 49

-Long periods of stability followed by mass extinctions are common in Earth’s history -Allows for adaptive radiation of organisms that survive -(ex. rise of the mammals following extinction of dinosaurs) -Five mass extinctions in Earth’s history

Question 50

What do mass extinctions allow for?

Answer 50

Allows for adaptive radiation of organisms that survive -ex. rise of the mammals following extinction of dinosaurs

Question 51

What may be one cause of the extinction of many land plants and animals in North America?

Answer 51

the cause may be the impact of a meteorite 65 million years ago near the Yucatan Peninsula in Mexico

Question 52

Summarize the Miller-Urey experiment

Answer 52

-an experiment that simulated conditions on early Earth -Miller placed gases in a flask to represent Earth’s ancient atmosphere -used electric sparks to represent lightning as an energy source -the experiment produced a variety of small organic molecules that are essential to life, including amino acids — the building blocks of proteins.

Question 53

Why was this experiment important to the primary abiogenesis theory?

Answer 53

The Miller-Urey experiment provided the first evidence that organic molecules needed for life could be formed from inorganic components

Question 54

Why was the development of membrane-bound organelles beneficial to the cell?

Answer 54

Membrane-bound organelles allowed the cell to carry out more complex chemical reactions in separate compartments

Question 55

Describe the endosymbiotic theory

Answer 55

-According to the endosymbiotic theory, mitochondria evolved from small aerobic prokaryotes that lived inside larger eukaryotic cells. -An ancestral eukaryote may have ingested some of these prokaryotes for food. -Instead of being digested, these prokaryotes continued to live inside the larger eukaryote -aerobic heterotrophic prokaryote evolved into mitochondria -photosynthetic prokaryote evolved into chloroplasts

Question 56

Why is sexual reproduction important for evolution?

Answer 56

-sexual reproduction allows for more genetic variation in the population -variation is the raw material for natural selection -the environment selects those variations that allow individuals to survive and reproduce, and those organisms evolve and increase in population

Question 57

What are the three main geological eras in Earth’s history?

Answer 57

-paleozoic -mesozoic -cenozoic

Question 58

What marks the change of eras in general?

Answer 58

-major change in the forms of life -widespread extinctions

Question 59

What are the distinguishing features of each era?

Answer 59

Paleozoic -increase in diversity of animal phyla -diversification of plants, bony fishes, reptiles -extinction of many marine and terrestrial organisms Mesozoic -dinosaurs -gymnosperms (dominant plants) -flowering plants appear -extinction of dinosaurs Cenozoic -mammals, birds, pollinating insects -primates + apes -apelike ancestors of humans -origin of genus homo -ice ages -*humans appear

Question 60

What biological evidence is there that Pangaea once existed?

Answer 60

-diversity of marsupial mammals in Australia -both marsupial and placental mammals lived in Pangaea -the Australian land mass split off early in the break-up of Pangaea and remained isolated -the few placental mammals that lived there became extinct

Question 61

How did continental drift lead to macroevolution?

Answer 61

-it explains why the plants and animals of Australia are so different from those in the rest of the world. -after Australia became an isolated land mass, the organisms living there would have evolved independently of those living on other continents. -this could lead to speciation continental drift could lead to macroevolution because it can cause the origin of different species, the extinction of species, and the evolution of major new features of living things, such as wings or flowers

Question 62

Which location(s) might contain organisms that resemble the first living creatures on Earth? Explain.

Answer 62

since the first organisms were chemoautotrophs, it would be locations where they could survive -e.g. bottom of the ocean(deep sea vents) or in acidic hot springs

Question 63

Describe the four-stage hypothesis on how life arose on Earth

Answer 63

(1) small organic molecules, such as amino acids, formed from simpler molecules present in the environment (2) these small molecules joined together into larger ones, such as proteins and nucleic acids (3) molecules that could copy themselves provided a basis for the inheritance of molecular information (4) these various organic molecules became packaged within membranes and separated from their surroundings, formed pre-cells

Question 64

What evidence is there that mitochondria and chloroplasts evolved from self-sustaining prokaryotes?

Answer 64

endosymbiotic theory -Bacteria, a prokaryote, has circular DNA, as do mitochondria and chloroplasts -This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote

Question 65

Cyanobacteria are believed to resemble some of the earlier autotrophs that existed on Earth. What cellular features do you think helped species succeed on early Earth? Explain why

Answer 65

chloroplasts (later evolved- energy) mitochondria (energy)

Question 66

Give an example of how the evolution of species changed the atmosphere

Answer 66

The first photosynthetic prokaryotes evolved in the absence of oxygen. Over time, they became common and started to increase the oxygen concentration in the atmosphere

Question 67

How do you think human activity today can affect the composition of gases in the atmosphere?

Answer 67

Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and the rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system

Question 68

The endosymbiotic theory explains how eukaryotic cells may have evolved. Which do you think evolved first: autotrophic eukaryotes or heterotrophic eukaryotes? Explain your reasoning

Answer 68

-heterotrophs because they eat other plants or animals for energy and nutrients -autotrophs could have later evolved

Question 69

How can the mass extinction of one group of organisms, such as the dinosaurs, lead to diversification of other species?

Answer 69

-a lot of competitors and predators of mammals disappeared, meaning that a great deal of the pressure limiting what mammals could do ecologically was removed -less predators, the prey can freely reproduce and increase in population

Question 70

what events occurred in the precambrian era?

Answer 70

-Origin of Earth -Oldest known rocks on Earth’s surface -Oldest fossils of cells (prokaryotes) -Concentration of atmospheric oxygen begins to increase -Oldest fossils of eukaryotic cells -Diverse algae and soft-bodied invertebrate animals

Question 71

Which gas was not present in Earth's atmosphere when the first living cells originated? a) ammonia b) oxygen c) carbon

Answer 71

b) oxygen Even though we think of oxygen as being a vital gas for most forms of life, oxygen in the atmosphere of the early Earth was rare, if it existed at all. Ammonia, carbon dioxide, and hydrogen, carbon monoxide, nitrogen, and water vapour were the primary gases at that time.

Question 72

In which era did the Cambrian explosion, which resulted in a sudden increase in diversity of many animal phyla, occur?

Answer 72

paleozoic

Question 73

What event is most closely associated with the formation of Pangaea near the end of the Paleozoic era, 250 million years ago?

Answer 73

permian extinction

Question 74

At the end of the Cretaceous period, about 65 million years ago, many species became extinct including all the dinosaurs. Many environmental changes occurred during that time, but which event most likely dealt the final blow to the dinosaurs?

Answer 74

meteor strike

Question 75

The oldest known insect resembled this springtail. It likely fed on the tips of sporophytes and may have had wings. To which period did this ancient insect belong?

Answer 75

devonian