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Mechanisms of Evolution > History of Life > Flashcards

Flashcards in History of Life Deck (28)
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1
Q

What were the 3 evolutionary innovations?

A
  1. Origin of life
  2. Origin of eukaryotes
  3. Origin of multicellularity
2
Q

How did life begin on earth?

A

Early earth had a reducing atmosphere with lots of free energy, which allowed for abiotic synthesis of organic molecules - the monomers of biological macromolecules

3
Q

Can non-living molecules be naturally selected?

A

Yes, if they are self-replicating

4
Q

What are the oldest known fossils?

A

Stromatolites. Fossilized mats of bacteria that is 3.5 billion years old

5
Q

When did eukaryotes evolve?

A

First fossils appeared 1.8 billion years ago, but do have molecular evidence from 2.7 billion years old. However, that chemical evidence might be from contamination

6
Q

How does multicellularity differ from just a bunch of cells living together?

A

Multicellularity has true cell specialization

7
Q

What are the advantages of being multicellular?

A
  • Division of labour and cell specialization required to be larger and develop organ systems
  • Evolution of cell adhesion
  • Intracellular bridges to move nutrients and signalling molecules
8
Q

When did multicellularity appear in the fossil record?

A

1.2 billion years ago

9
Q

What are the types of fossils found in Mistaken Point, Newfoundland?

A

Ediacaran fossils. Early animals or multicellular organisms that aren’t true animals from before the Cambrian

10
Q

What do the Ediacaran fossils look like? What happened to them once the Cambrian began?

A

Very flat, hardly anything 3D characteristics unlike Cambrian fossils. There weren’t any direct descendants that survived into the Cambrian, but there might have been branches that came off them and did survive

11
Q

What is the Cambrian explosion?

A

A massive amount of adaptive radiation in the early Cambrian that gave rise to most modern animal phyla

12
Q

How did the Cambrian fossils differ from the Ediacaran fossils?

A

The Cambrian fossils definitely could move in ways that the Ediacaran fossils couldn’t: swimming, burrowing, and climbing. First signs of segmented body plans, exoskeletons, appendages, and true eyes

13
Q

What are living fossils?

A

Organisms that have undergone very little morphological changes over time so that they are in morphological stasis

14
Q

Why do living fossils exist?

A

Stabilizing selection from low competition and relatively isolated and stable habitats. Individuals weren’t pressured to change, so natural selection favoured traits with mean values

15
Q

Do living fossils have low genetic variation?

A

No, no evidence for that. Protein polymorphism isn’t too low either

16
Q

What are the intrinsic causes for the Cambrian explosion?

A
  • Diversification in body plan organization

- Exoskeleton and locomotion established the predator-prey arms race

17
Q

What are the extrinsic causes for the Cambrian explosion?

A
  • The single supercontinent was beginning to break up, which exposed more shallow seas
  • The shallow seas were favourable for photosynthesis
  • Oxygen content increased in the water
  • Increased metabolism in the organisms lead to increased growth
18
Q

What are the genetic causes for the Cambrian explosion?

A

Changes in Hox genes provided developmental flexibility

19
Q

What is contingency?

A

Chance loss of life forms due to unpredictable events like asteroid impacts that natural selection can’t prepare for

20
Q

When did the first land plants appear? What were they like?

A

Colonized land in the late Ordovician or early Silurian. They were liverwort-like plants that were true land plants, but were still highly dependent on water

21
Q

When did the first vascular plants appear?

A

During the Silurian

22
Q

When did terrestrial arthropods appear? What were they like?

A

During the Devonian. They were scorpions, millipedes, centipedes, and wingless insects

23
Q

When did seed plants first appear?

A

Devonian

24
Q

Why did the evolution of the amniotic egg lead to adaptive radiation?

A

It let eggs be completely free from dependence on water, because it provided them with nutrition and be not worry about drying out. This allows amniotes to move further inland and diversify

25
Q

Which group is closely to modern primates?

A

Flying lemurs - Demopterans

26
Q

What are successions?

A

Major changes in dominant taxa

27
Q

What causes evolutionary succession events?

A
  • Competitive advantages of superior life forms
  • Extinction events opening new niches
  • Spread of new adaptations that open new niches
  • Continent joining and fragments
28
Q

How did bivalves replace brachiopods as the dominant taxa?

A

Bivalves weren’t dominant at first, but they had similar food and habitat requirements as brachiopods. Bivalves were better at exploiting their niche, so they replaced brachiopods as the dominant group