History of Life

Question 1

What were the 3 evolutionary innovations?

Answer 1

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

Question 2

How did life begin on earth?

Answer 2

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

Question 3

Can non-living molecules be naturally selected?

Answer 3

Yes, if they are self-replicating

Question 4

What are the oldest known fossils?

Answer 4

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

Question 5

When did eukaryotes evolve?

Answer 5

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

Question 6

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

Answer 6

Multicellularity has true cell specialization

Question 7

What are the advantages of being multicellular?

Answer 7

• 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

Question 8

When did multicellularity appear in the fossil record?

Answer 8

1.2 billion years ago

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

What is the Cambrian explosion?

Answer 11

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

Question 12

How did the Cambrian fossils differ from the Ediacaran fossils?

Answer 12

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

Question 13

What are living fossils?

Answer 13

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

Question 14

Why do living fossils exist?

Answer 14

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

Question 15

Do living fossils have low genetic variation?

Answer 15

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

Question 16

What are the intrinsic causes for the Cambrian explosion?

Answer 16

• Diversification in body plan organization

- Exoskeleton and locomotion established the predator-prey arms race

Question 17

What are the extrinsic causes for the Cambrian explosion?

Answer 17

• 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

Question 18

What are the genetic causes for the Cambrian explosion?

Answer 18

Changes in Hox genes provided developmental flexibility

Question 19

What is contingency?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

When did the first vascular plants appear?

Answer 21

During the Silurian

Question 22

When did terrestrial arthropods appear? What were they like?

Answer 22

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

Question 23

When did seed plants first appear?

Answer 23

Devonian

Question 24

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

Answer 24

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

Question 25

Which group is closely to modern primates?

Answer 25

Flying lemurs - Demopterans

Question 26

What are successions?

Answer 26

Major changes in dominant taxa

Question 27

What causes evolutionary succession events?

Answer 27

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

Question 28

How did bivalves replace brachiopods as the dominant taxa?

Answer 28

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