Week 5: Adaptation to Environmental Stress

Question 1

In complex traits, offspring tend to…

Answer 1

Resemble parents but regress towards the population mean

Question 2

Offspring mean height lies between parental mean height and population mean height because of what 3 factors?

Answer 2

1. During meiotic cell division, segregation and recombination break up combinations of genes leading to extreme phenotypes
2. Parental phenotype is a result of both genetic and environmental factors
3. Offspring phenotype is a result of both genetic and environmental factors

Question 3

Define heritability

Answer 3

How well genetics can account for differences in one’s phenotypic expression ( a number between 0-1)
E.g. Height: heritability = 0.88 meaning genetic factors dictate this largely although environmental factors have some effect
E.g. Sleep: heritability = ~0.15 meaning it is largely environmental although some genetic effect is present

Question 4

What is the estimated % of species loss per annum?

Answer 4

~0.25% per year

This is 5000 - 25,000 species a year dependant on how many species actually exist which is definitively unknown

Question 5

Describe Bergmann’s rule

Answer 5

Larger species are found towards the poles (colder environments) with a decrease is size as one moves towards equatorial regions (warmer regions).
Low latitude organisms are smaller
High latitude organisms are larger

Question 6

Why is this?

Answer 6

Surface area to volume ratio - larger organisms retain heat better and are thus better equipped cope with colder environments. This is a genetic adaption over time.