Microevolution

Question 1

What two scales does evolution occur?

Answer 1

1) microevolution: is the process that changes the frequency of an allele within a single population (small scale).

Ex: foxes and dogs have evolved from wolves

2) Macroevolution: refers to larger evolutionary changes that results in new species.

Ex: humans have evolved from apes, apes have evolved from other living organisms.

Question 2

1) What is a genotype frequency?
2) what is an allele frequency?
3) what is a gene pool

Answer 2

1) the frequency between 0 &1 of a single genotype with a population.

Ex: PP = 0.6, PQ = 0.2, QQ = 0.2

2) It is the frequency between 0 & 1 of a single allele within a population

Ex:
P + Q = 1 -> 0.7 + 0.3 = 1

IMPORTANT: The frequencies for all genotypes, or alleles must add up to 1.

3) the set of all genes of a population pooled together.

Question 3

What is the Hardy-Weinberg equation?

Answer 3

It is used to calculate the percent of genotypes in a population at equilibrium (where alleles are equally likely to combine).

P^2 + 2PQ + Q^2 =1

REFER TO SLIDE 10-11 FOR EXAMPLE

Question 4

1) What is the Hardy- Weinberg Principle?

2) what are two things to remember about Hardy Weinberg?

Answer 4

1) In the absence of evolutionary process, the genotype frequencies in a large population do not change from generation to generation.

2)
1 - OBSERVED = EXPECTED (at equilibrium) : The gene is not being affected by evolutionary process

2 - OBSERVED (not equal to) EXPECTED (evolution occurs): An evolutionary process is altering the allele frequencies.

REFER TO SLIDE 12

Question 5

What are four evolutionary processes, their descriptions and the factors affecting allele frequencies?

Answer 5

1) natural selection: certain alleles are favoured and increase in frequency over others

Factors:

• directional selection: favours an extreme phenotype over other phenotypes, and changes the average value of a trait.

Ex: a large body size provides fitness benefits so the average body size increases.

• stabilizing selection: reduces the amount of variation in a trait. ( to provide fitness benefits)

Ex: very small and very large babies (extreme phenotypes) are most likely to die, leaving a narrower distribution of birth weights. So intermediate phenotypes had higher fitness.

• disruptive selection: increases the amount of variation in a trait. (To provide fitness benefits)

Ex: very long or very short beaks of a bird species survived long enough to breed. So the extreme phenotypes had higher fitness.

• balancing selection: it maintains genetic variation. No single phenotype is favoured at all times, so there is a diversity of phenotypes maintained in the population.

Ex:
heterozygous individuals have higher fitness than homozygotes:
heterozygous sickle cell anemia has some protection from malaria

variation in the environment favour different phenotypes:
Seeds germinate in environments with different conditions

rare alleles provide fitness benefits:
A predator consume the most common type of prey, so the rare allele survives.

2) genetic drift: random changes in allele frequencies which can lead to fixation ( where an allele becomes the only one in a population) this mainly occurs in small populations.

Factors:

• founder effect: occurs when a new population is formed with different allele frequencies, due to immigration and forms new populations.
• genetic bottleneck: occurs when a sudden decrease in population size reduces the number of alleles.
  3) gene flow: movement of alleles between populations; reduces differences between populations.

Factors:
Immigration & emigration. For example Pollen is dispersed everywhere which reduces variation between populations.

4) mutation: random production of new alleles is produced when DNA is permanently changed.

Factors:
- genome duplications in plants, the copy of these gene can accumulate mutations without decreasing fitness.

• errors in meiosis can duplicate whole genome.

EXTRA:
5) Non-random mating: individuals may prefer mates with particular alleles, making it non-random.

Factors:
-sexual selection

Question 6

What is adaptive evolution?

Answer 6

Evolution that results in better fit between individuals and their environment.

Question 7

What is non-adaptive evolution?

Answer 7

Evolution that has random effects on fitness. Individuals are not better adapted.