Lecture 3

Question 1

state the 4 important elements of Darwin’s theory

Answer 1

1. Evolution occurs primarily at the level of populations - individuals do not evolve
2. Variation is not directed by the environment - individuals do not induce adaptive variation when needed
3. Most fit type depends on the environment and changes from generation to generation
4. ‘Survival of the fitter’ - evolution works with available variation, and will not necessarily achieve perfection

Question 2

State the implications of Darwin’s theory

Answer 2

The concept of a changing universe; a phenomenon with no purpose

Question 3

State the 4 sources of evidence for evolution:

Answer 3

• Geology
• Homology
• Biogeography
• Domestication

Question 4

Lessons from Geology

Answer 4

1. Earth is very old - this allows for an immense amount of time for biological evolution
2. Intermediate forms - evidence for transitional fossils linking features of seemingly dissimilar relatives (eg ungulates and whales, or tetrapods and fish)
3. Fossils in younger strata increasingly resemble modern species in the same region - older strata show increasing differences

Question 5

Give an example of how discoveries of transitional fossils continue today

Answer 5

Tiktaalik roseae, discovered 2006
- has 2 legs and 2 fins
- nickname: fishapod

Question 6

Define homology

Answer 6

Similarity of traits in two or more species that is due to inheritance from a common ancestor

Question 7

Lessons from homology

Answer 7

Vestigial traits provide evidence of the evolutionary past:
- have no function/reduced function in extant organisms
- can only be explained by the presence of functional traits in ancestors, followed by evolutionary degredation

Homologous structures are ubiquitous across organisms:
- fundamental structural similarity reflects common ancestry
- homologous structures have evolved to serve very different functions

Question 8

Define a vestigial structure

Answer 8

• features inherited from an ancestor, but reduced in morphology and function
• are homologous to functional structures in related species

Question 9

Describe vestigial structures in Galapagos flightless cormorants compared to mainland cormorants

Answer 9

Mainland cormorants need to fly as they nest on trees; GF cormorants do not as they nest on rocks by the water. The wings of these two species, albeit varying in use, are homologous structures.

Question 10

what is a vestigial structure in cave-dwelling morphs of Astynax Mexicanus?

Answer 10

they have evolved to lose their eyes as they do not need them

Question 11

vestigial structures in humans

Answer 11

• ear muscles
• appendix
• tailbone
• goosebumps

Question 12

why is the presence of vestigial structures significant?

Answer 12

• organismal features are consistent with modifications of pre-existing structures
• this would not be expected if each organism was individually optimally designed

Question 13

describe homology in genes

Answer 13

• approximately 500 genes are shared across all forms of life
• there is a strong, shared constraint for genes involved in basic cellular function (eg transcription/translation)

Question 14

Lessons from Biogeography

Answer 14

Remote islands biotas:
- have continental affinities
- are dominated by good colonists
- have locally-differentiated species

biogeographically isolated regions:
- have species adapted to niches unusual for their group
- harbor endemic radiations of species that are convergent with radiations elsewhere

Question 15

3 main points of evidence from biogeography

Answer 15

• geographically close organisms resemble each other
• different groups of organisms adapt to similar environments in different parts of the world
• geographically isolated regions have unusual organisms

Question 16

use Australia as an example of a location with an interesting Biogeography

Answer 16

• although a continent, Australia is also an island
• distinct flora and fauna with high endemism and many unique adaptations
• australia has endemic radiations of species that are ecologically convergent with those of other continents

Question 17

what is Australia’s biological uniqueness a result of?

Answer 17

its long history of isolation from other land masses

Question 18

give a summary of evidence from domestication

Answer 18

Heritable variation can be selected on, leading to dramatic changes over generations