Natural selection II

Question 1

Examples of natural selection

Answer 1

Peppered moth
-Typical form (++)
-Melanic form (MM & M+)
-Genetics controlled by a single gene with two alleles
-Melanic allele (M) is dominant over the typical allele (+)

Rock pocket mice
-Coat colour determined by (MC1R) gene
-D (dark) dominant to d (light)
-Light = dd
-Dark = DD and Dd

Question 2

Understand different forms of natural selection

Answer 2

Positive selection
-A process of natural selection that increases the frequency of a beneficial allele in a population
-E.g. peppered moths, rock pocket mice
-Evidence from phenotype and genotype
-Drive advantageous phenotypes and genotypes to high frequencies
-Loss of variation

Balancing selection
-A type of natural selection that maintains genetic diversity in a population by preserving different alleles of a gene. It occurs when natural selection favours heterozygous individuals over homozygous individuals, or when different alleles confer advantages in different environments or under different conditions
-When heterozygotes are fitter than homozygotes
-Maintains variation

Question 3

How natural selection can affect allele frequencies

Answer 3

Alleles that increase an organism’s fitness are more likely to be passed on to future generations, resulting in an increase in their frequency in the population.

alleles that decrease an organism’s fitness are less likely to be passed on, resulting in a decrease in their frequency in the population.

Over time, this process can lead to significant changes in allele frequencies, and eventually, the evolution of new traits or adaptations.

Additionally, natural selection can also act on different types of selection, such as directional, stabilising, and disruptive selection, which can have different effects on allele frequencies