Chapter 25 Pt II: The History of Life on Earth

Question 1

In which type of rock are fossils typically preserved?

Answer 1

Sedimentary

Question 2

What types of organisms are less likely to be preserved as fossils?

Answer 2

rare, short-lived, without any hard parts

Question 3

What are strata?

Answer 3

layers of sedimentary rock which indicate age

Question 4

How can fossil age be estimated?

Answer 4

location in strata and/or radiometric dating

Question 5

How is radiometric dating done?

Answer 5

by measuring decay of radioactive isotopes

Question 6

What are macroevolutionary changes?

Answer 6

important milestones in the history of life

Question 7

What are the four eons of geologic Earth?

Answer 7

Hadean, Archaean, Proterozoic, Phanerozoic

Question 8

What are the three subdivisions of the Phanerozoic eon?

Answer 8

Paleozoic, Mesozoic, Cenozoic

Question 9

What are the six major milestones of the history of life?

Answer 9

1. First single-cell organisms appear (prokaryotes)
2. Photosynthesis and the oxygen revolution
3. First eukaryotic cells appear
4. Multicellular organisms appear
5. The Cambrian Explosion
6. Colonization of land

Question 10

What are characteristics of the Hadean eon?

Answer 10

Origin of Earth, too volatile for any life

Question 11

What are characteristics of the Archaean eon?

Answer 11

Prokaryotes arise, photosynthesis develops at end of era

Question 12

What are characteristics of the Proterozoic eon?

Answer 12

Eukaryotes arise- first unicellular, then multicellular (including animals)

Question 13

What are characteristics of the Phanerozoic eon?

Answer 13

Several major events regarding animal diversity

Question 14

In what rocks are the earliest prokaryotes reserved as fossils?

Answer 14

stromatolites

Question 15

The first prokaryotes to develop photosynthesis abilities are precursors to the modern day ________.

Answer 15

cyanobacteria

Question 16

Where did oxygen accumulate towards the end of the Archaean eon?

Answer 16

the ocean

Question 17

How can we measure the accumulation of oxygen in the ocean?

Answer 17

by observing bands of iron ore that are created when oxygen reacts with iron in the ocean & precipitates out

Question 18

What separates the Archaean eon from the Proterozoic?

Answer 18

mass extinction caused by the accumulation of oxygen in the atmosphere

Question 19

Why did the accumulation of oxygen in the atmosphere cause a mass extinction?

Answer 19

Many prokaryotes had evolved to be anaerobic to the point where O2 was toxic to them

Question 20

What spurred the emergence of the ability to perform aerobic respiration?

Answer 20

The mass extinction caused by the accumulation of O2 in the atmosphere

Question 21

When did the first eukaryotic cells appear?

Answer 21

~2 billion years ago, during the Proterozoic eon

Question 22

How does the endosymbiont theory explain the origin of eukaryotes?

Answer 22

1. Large prokaryote engulfed smaller prokaryote with intention to eat
2. small one could do respiration so the larger one kept it
3. smaller one is precursor to mitochondrion
4. Later, one of these early eukaryotic cells engulfed another smaller one
5. smaller one could do photosynthesis
6. smaller one is precursor to chloroplast

Question 23

What evidence supports the endosymbiont theory?

Answer 23

Mitochondria and chloroplasts are similar to existing prokaryotes

Question 24

How are mitochondria and chloroplasts similar to existing prokaryotes?

Answer 24

• similar enzymes
• similar self-replication
• have their own circular genome
• have their own ribosomes which are more similar to those of prokaryotes

Question 25

What order of events happened as a result of the evolution of photosynthesis in prokaryotes?

Answer 25

1. O2 accumulation 2. mass extinction due to O2 toxicity 3. evolution of aerobic respiration

Question 26

Why do all eukaryotic cells have mitochondria but not all have chloroplasts according to the endosymbiont theory?

Answer 26

chloroplast precursor was not engulfed by cells until much later than mitochondria precursor

Question 27

When did multicellular eukaryotes arise?

Answer 27

~1.5 billion years ago in Proterozoic eon

Question 28

What marks the transition from the Proterozoic eon to the Phanerozoic?

Answer 28

The Cambrian Explosion

Question 29

What was the Cambrian Explosion?

Answer 29

massive increase in the diversity of animals and introduction of predators

Question 30

When did life begin to transition from water to land?

Answer 30

~500 million years ago in the Phanerozoic eon

Question 31

What were the benefits of transitioning from water to land?

Answer 31

many open niches, no predators

Question 32

What were challenges of transitioning to land?

Answer 32

required special adaptations (i.e. lungs to breath air, changed fertilization methods)

Question 33

Dramatic events that appear in the fossil record include

Answer 33

Mass extinctions & adaptive radiations

Question 34

What is the significance of the Permian Mass Extinction?

Answer 34

claimed 96% of marine animal species and defines boundary between Paleozoic & Mesozoic eras

Question 35

What is thought to have caused the Permian Mass Extinction?

Answer 35

extreme volcanoes that released enough CO2 to incr global temp and acidify oceans

Question 36

What is the significance of the Cretaceous Mass Extinction?

Answer 36

claimed >½ marine species and eliminated land animals like the dinosaurs

Question 37

What is though to have caused the Cretaceous Mass Extinction? What evidence supports this theory?

Answer 37

meteorite that crashed, dust blocked out sun for months; Chicxulub crater off coast of mexico

Question 38

What signifies a mass extinction?

Answer 38

extinction is at rate much higher than the baseline rate of extinction

Question 39

Mass extinctions driven by events that change...

Answer 39

...global conditions

Question 40

Approx. how long does it take for biodiversity to recover after a mass extinction?

Answer 40

5-10 million years

Question 41

What is adaptive radiation?

Answer 41

The rapid evolution of diverse species from a common ancestor

Question 42

List the conditions that can lead to adaptive radiations.

Answer 42

- Mass extinctions - The evolution of new, advantageous traits - Colonization of new habitats

Question 43

What 3 reasons cause adaptive radiation after a mass extinction?

Answer 43

- Reduced predation - Reduced competition - Increased niche availability

Question 44

What are 2 examples of adaptive radiation due to acquisition of a new, advantageous trait?

Answer 44

development of placental gestation in mammals and new reproductive structures (like flowers) in angiosperms

Question 45

What are angiosperms?

Answer 45

flowering plants

Question 46

What is an example of adaptive radiation due to the colonization of a new habitat?

Answer 46

single ancestral plant that arrived on the Hawaiian islands 5 million years ago

Question 47

What is evo-devo?

Answer 47

research at the interface between evolutionary biology and developmental biology

Question 48

What does evo-devo demonstrate?

Answer 48

how slight genetic differences can produce major morphological differences

Question 49

Many evolutionary changes are result of ______.

Answer 49

heterochrony

Question 50

What is heterochrony?

Answer 50

evolutionary change in the rate/timing of developments events

Question 51

Give one example of heterochrony.

Answer 51

slowed growth of leg bones led to reduction & loss of hind limbs in whales

Question 52

What is paedomorphosis?

Answer 52

a condition where reproductive organ development accelerates more than other organs so sexually mature organisms keeps features that were only in juvenile ancestors

Question 53

What do homeotic genes determine?

Answer 53

position of basic features Ex) position of legs