Topic 4

Question 1

Without ___________, _________ and _______, evolution will not occur. Why?

Answer 1

Without inheritance, variation and fitness, evolution will not occur.

1. Inheritance
   
   • advantageous traits must be capable of being passed down to the next generation
   • otherwise, the advantage disappears and allele frequencies remain the same = no evolution
2. Variation
   
   • if all individuals are identical, natural selection is not able to act
3. Fitness
   
   • if all individuals achieve the same reproductive success, allele frequencies remain the same = no evolution

Question 2

What is genetic drift?

Answer 2

Genetic drift: the change in allele frequencies due to random chance rather than natural selection.

Question 3

What is the effect of genetic drift?

Answer 3

Genetic drift reduces variation among a population. It’s impact increases as the population size decreases (fewer individuals = less genetic diversity).

Question 4

Drift tends to increase/decrease genetic variation between populations? Why?

Answer 4

Drift tends to increase genetic variation between populations. Because genetic drift acts randomly, separate populations experience different random changes in allele frequencies.

Question 5

Increased/decreased homozygosity leads to increased/decreased fitness, causing an increase/decrease in genetic diversity. Why?

Answer 5

Increased homozygosity leads to decreased fitness, causing a decrease in genetic diversity. Many harmful mutations are recessive (aa), meaning that when the a is paired with A, the impact is lessened.

Question 6

Variation is lost more/less rapidly in small/large populations.

Answer 6

Variation is lost more rapidly in small populations.

Question 7

What is the founder effect?

Answer 7

• A small group of individuals breaks off from a larger population
• They bring a select amount of alleles with them
• The resulting population ends up differing greatly from the original population in terms of genetics (i.e some alleles are very common while others are entirely absent).

Question 8

If natural selection is not causing evolution, does this mean that evolution can not take place at all? Why?

Answer 8

If one of the conditions for evolution by natural selection is broken, evolution can still occur by way of genetic drift.

Question 9

What is directional selection?

Answer 9

Occurs when the fitness of an organism increases or decreases as the frequency of the trait increases.

Question 10

Stabilizing selection: _______ individuals have a higher fitness than _______ individuals.

Answer 10

Stabilizing selection: average individuals have a higher fitness than extreme individuals.

Question 11

Disruptive selection: _______ phenotype is favoured over _______ phenotype.

Answer 11

Disruptive selection: extreme phenotype is favoured over average phenotype.

Question 12

What is frequency-dependent selection?

Answer 12

Fitness of each phenotype depends on how common it is within a population (i.e level of competition).

Question 13

Gametic asymmetry tends to lead to other asymmetries such as:

Answer 13

1. Differences in parental investment
2. Differences in parental care
3. Differences in reproductive success

Question 14

Sexual dimorphism occurs when _______ _________ takes place, leading to ___________ _________ between males and females.

Answer 14

Sexual dimorphism occurs when extreme selection takes place, leading to substantial differences between males and females.

Question 15

Intrasexual selection: fitness differences resulting from _________ _________ of members of the ____ ___ to compete for mating opportunities.

Answer 15

Intrasexual selection: fitness differences resulting from differing abilities of members of the same sex to compete for mating opportunities.

Question 16

Intersexual selection: fitness differences resulting from __________ ______ between specific _____ ___ _______.

Answer 16

Intersexual selection: fitness differences resulting from preferential mating between specific males and females.

Question 17

Selection is defined as ___-_______ association between the phenotypic/genotypic traits and _______.

Answer 17

Selection is defined as non-random association between the phenotypic traits and fitness.

Question 18

Assortative mating: individuals with _______ genotypes and or phenotypes mate with one another more or less frequently than expected. It can be positive (____ with ____) or negative (______ with _______).

Answer 18

Assortative mating: individuals with similar genotypes and or phenotypes mate with one another more or less frequently than expected. It can be positive (like with like) or negative (unlike with unlike).

Question 19

What are two form of assortative breeding?

Answer 19

1. Inbreeding
2. Outbreeding

Question 20

Inbreeding depression results in _______ _______. Why?

Answer 20

Inbreeding depression results in reduced fitness.
- A greater proportion of your offspring will be homozygous
- Could produce a greater amount of homozygous recessives
- Leads to a greater chance of deleterious mutations.