4.4: Genetic diversity & adaptation

Question 1

List 4 sources of genetic variation

Answer 1

mutation - new alleles
crossing over of chromatids
independent assortment
random fertilisation

Question 2

What is another source of variation other than genetic variation

Answer 2

environmental variation

Question 3

List and explain the 6 principles of natural selection

Answer 3

1- Mutation - A DNA mutation results in the formation of a new allele of a gene
2 - Genetic variation arises within the population
3 - Selective pressure - changes in environment
4 - Differential survival + reproduction - individuals with favourable phenotype, have a selective advantage therefore will survive + reproduce
5 - Inheritance - favourable allele passes on to some of the offspring
6 - Gene pool - Frequency of favourable allele will increase in gene pol

Question 4

What may cause extinction of a species

Answer 4

as natural selection occurs over many generations, if the environmental changes occur rapidly, species may be unable to adapt in time, and become extinct

Question 5

Describe and explain directional selection

Answer 5

when conditions favour individuals expressing one extreme of a phenotypic range, there is a shift in the population’s frequency distribution and mean for the phenotypic character in one direction or the other
therefore, one range is selected against and one range (on other side of distribution) is selected for

Question 6

Describe and explain stabilising selection

Answer 6

When there is an optimal value for the trait of interest, means that selection favours intermediate variants and selects against both extreme phenotypes. Mean frequency stays the same, but frequency distribution decreases