Lecture Ten - Adaptations to environmental stress

Question 1

What is the old world hypothesis about the effect of the environment on phenotypes?

Answer 1

Genotype + environment = phenotype.

Simply an additive effect (does not depend on anything else).

Question 2

In what way is the link between phenotype and genotype complex?

Answer 2

The effect that a genotype has on the phenotype is often contingent on the environment that the individual lives.
The genotype interacts with the environment to form the phenotype.
Effects of genotypes are not usually additive across environments.
The fitness of say two genotypes depend on the environment.
A single genotype is unlikely to be superior across all environments.

Question 3

What is the reaction norm and phenotypic plasticity?

Answer 3

Reaction norm = the environmental sensitivity of a genotype/gene.
Essentially, the amount a phenotypes abundance and therefore fitness changes as the environment changes.
Genotypes with environment-specific expression are said to be ‘plastic.’
Phenotypic plasticity = enables individuals to make short term responses to environmental change.
Generally in juvenile development, but also at other life stages.
Responses can be physiological, morphological, behavioural or developmental etc.
When the direction or magnitude of this change depends on the genotype, then the plasticity is underpinned by genotype x phenotype interactions.

Question 4

What is genotype-by-environment interaction?

Answer 4

Genotype x Environment.

Is the phenotypic effect of interactions between genes and the environment.

Question 5

What is Bergmann’s rule?

Answer 5

Individuals of a given species increase in size with increasing latitude.
Smaller near equator and larger in cooler climates.

Question 6

Define what occurs when there are long term responses to environmental change.

Answer 6

Evolution involves changes in the DNA sequence. Specifically in alelle frequencies across generations (from one generation to the next).