Phenotypic Plasticity 2

Question 1

2 mechanisms for phenotypic plasticity

Answer 1

1. Darwinian evolution by natural selection on genetic variation
2. Phenotypic plasticity through environmental influence on individual development

Question 2

Baldwin effect

Answer 2

Environmentally induced non-heritable variation (such as phenotypic plasticity) becomes established in population, and then is later genetically ‘accommodated’ so environmental stimulus no longer required

Question 3

adaptive plasticity

Answer 3

Results in a reaction norm that is in the same direction as the optimal value favoured by selection in the new environment

Question 4

non-adaptive plasticity

Answer 4

Results in a reaction norm that is in the opposite direction to the optimal value favoured by selection in the new environment

Question 5

new/ abrupt change in environment

Answer 5

1. New = change in the current environment, or invasion of a new habitat
2. Abrupt change, usually results in extinction, or strong directional selection

Question 6

canalisation

Answer 6

The reduced sensitivity of a phenotype to changes or perturbations in the underlying genetic and non-genetic factors that determine its expression

Question 7

Kokanee vs Sockeye Salmon

Answer 7

Sockeye salmon live in the ocean and spawn in freshwater

Kokanee salmon are the non-migratory form of the sockeye salmon, and live their whole life in freshwater. They are related to the local population of sockeye salmon, not to other Kokanee populations. They are redder than Sockeye salmon.

Question 8

Cryptic variation revealed under stress in Kokanee and Sockeye salmon

Answer 8

• There are fewer nutrients in freshwater than seawater
• Kokanee salmon are redder, which indicates their superior ability to obtain nutrients – they are 3 times better at acquiring carotenoids, and they indicate this in their red hue.
• Females show a mate choice preference for red.

This is directional selection for more efficient acquisition of carotenoids under stress of lack of carotenoids

• The capacity of Kokanee salmon to acquire carotenoids was cryptic until they stayed in freshwater all the time and were put under environmental stress

Question 8

Differential fixing of alternative phenotypes

Answer 8

1. Selection can eliminate plasticity fixed
2. Genetic assimilation (AKA the Baldwin effect), caused by genetic drift or mutational degradation gives environmental stimulus no longer required to produce the trait

Question 9

importance for environment

Answer 9

1. Phenotypic plasticity allows fast, adaptive responses to environmental change
2. Change to current environment (e.g. anthropogenic climate change)
3. Invasion of new environment (invasive species)

Question 10

Parental Effects

Answer 10

Effects of parents on the phenotype of offspring that are not caused by gene transmission. It is a type of environmental effect.

Question 11

Parental Effects - Environment matching

Answer 11

For those developing in both good and poor environments, fitness is the highest when the adult and developmental environments match.

Question 12

Parental Effects - The silver spoon model

Answer 12

receiving good early care is always beneficial to the fitness of the offspring.

Question 13

A combination of the silver spoon and environmental matching.

Answer 13

1. For both those born in the good environment, fitness improves as the quality of the adult environment improves.
2. For those born in the poor environment, fitness declines as the resources in the adult environment increase.
3. However, whatever the adult environment, those born in the good environment always have higher fitness.

Question 14

Transgenerational Phenotypic Plasticity

Answer 14

It is a type of adaptive evolution, where the cue eliciting parental response also predicts offspring environment.
It is a type of parental effect.

Question 15

Water flea

Answer 15

pos phototactic- swim away from light
neg phototactic- swim towards the light
shows phenotypic plasticity is trait that can evolve