Co-evolution

Question 1

Define co-evolution.

Answer 1

The evolution of reciprocal adaptations of 2 or more species that have prolonged close interactions

Question 2

Co-evolution is expected in…

Answer 2

• mutualism (++)
• parasitism (+-)
• competition (–)

Question 3

Co-evolution is unlikely in…

Answer 3

• commensalism (o+)

- amensalism (-o)

Question 4

Give the 2 types of mimicry.

Answer 4

Mullerian & Batesian.

Question 5

Define Mullerian mimicry.

Answer 5

• likely to exhibit reciprocal evolutionary patterns since both species involved are unpalatable and so have the opportunity to affect the evolution of each other’s colour patterns.
• the more abundant species is usually the model since it is what the selective agent (predator) is cueing on.

Question 6

Define Batesian mimicry.

Answer 6

-may not involve co-evolutionary phenomena as the evolution of colour is asymmetric (one is unpalatable).

Question 7

Define adaptive radiation.

Answer 7

spread of new species of common ancestry into different niches, involving an excess of cladogenesis over extinction

Question 8

Define convergent evolution.

Answer 8

organisms not closely related. Independently evolve similar traits as aa result of having to adapt to similar environments or ecological niches.

Question 9

What does diversification into different niches permit?

Answer 9

The coexistence of multiple species.

Question 10

What are KEIs

Answer 10

Key evolutionary innovations, they drive diversification.

Question 11

Factors that promote adaptive radiation.

Answer 11

INTRINSIC
-metabolic & physiological opportunities eg crassulacean acid metabolism, endosymbiosis, toxins.
-developmental opportunities eg Hox genes and segmentations, wings and flight, dispersal.
-efficient dispersal (some organisms lack the ability to disperse over wide ranges)
EXTRINSIC
-empty habitats
-novel environments
-intensity of selection
-founder effects
-ecological release – occurs when a species expands its niche within its own habitat or into a new habitat where there is little competition for resources, which remain abundant (also release from predators and disease).

Question 12

Example of adaptive radiation.

Answer 12

Lake Malawi, ~400,000 years old (up to 2 million).

Single cichlid species >200,000 years ago has since diversified into approx. 1,000 different species

Question 13

Give the model of vertebrate evolution based on lake Malawi Cichlids Streelman and Danley put forward.

Answer 13

1. Divergence of lineages into different major habitats
2. Morphological specialization leading to trophic differentiation within habitats
3. Sensory communication diversification- sexual selection

Question 14

Give 2 examples of convergent evolution.

Answer 14

• marsupial and placental mammals

- African euphorbias and north American cacti

Question 15

Give an example of molecular convergent evolution.

Answer 15

-Antarctic fish vs Arctic fish
-Antarctic fish produce glycoproteins
-Arctic fish produce unrelated anti-freeze proteins
Independent episodes of molecular evolution occurred, with the same functional results.

Question 16

Evidence of adaptive radiation.

Answer 16

homologous structure.

Question 17

Evidence of convergent evolution.

Answer 17

analogous structure.

Question 18

Limitations of convergent evolution.

Answer 18

• contingency
• functional/physical constraints
• developmental constraints
• genetic constraints

Question 19

How can adaptive radiation be proved?

Answer 19

• a recent shared origin of members of the radiation
• an accordance between diverse genetically based phenotypic traits and their divergent environment
• a benefit of the specific phenotypic trait in the correlated environment
• relatively high rate of lineage splitting
• link between a key evolutionary innovation and rapid diversification

Question 20

Fitness decides the outcome of selection, therefore adaptations are described in terms of

Answer 20

their ability to promote fitness

Question 21

Give examples of fitness.

Answer 21

• viability
• growth
• foraging efficiency
• longevity
• fecundity

Question 22

Give experimental approaches to adaptation.

Answer 22

Manipulate species
-population size
-variation (asexual vs sexual, in-breeding/outbreeding)
-attributes (size, colour)
-modify (biomimetics of a tail or wing)
Manipulate environment
-modify species composition
-exclude or add predators/hosts
-alter physical factors (temp, humidity)

Question 23

Give a way to measure the contribution of an adaptive trait.

Answer 23

modify or inactivate it, then study the consequences for fitness

Question 24

Why are microbes a good model for evolution?

Answer 24

• easily propagated
• rapid generation times
• large population sizes
• easily stored
• environment readily controlled
• asexual or sexual
• single or mixed gentype
• phenotypes are easily detected
• whole genome sequencing
• direct genetic manipulations possible

Question 25

Summarise paper on adaptive radiation in a heterogenous environment

Answer 25

Stated aim: examine role of ecological opportunity and competition in driving genetic diversification. Stated conclusions: - ecological opportunities promote morphological diversification - ecological homogeneity does not promote divergence - mutation and selection alone are sufficient to promote new designs - competition amongst niche variants maintains variation - trade-offs in competitive ability drive adaptive radiation