Evolutionary Mechanisms

Question 1

Natural Selection
Define and examples

Answer 1

Definition: Process where individuals with advantageous traits survive and reproduce more successfully, passing those traits to offspring.

Examples:

Directional Selection: Favors one extreme phenotype; Development of antibiotic-resistant bacteria.

Stabilizing Selection: Favors the intermediate phenotype; Human birth weight (extremes are less viable).

Disruptive Selection: Favors both extremes over the intermediate phenotype; Beak sizes in Darwin’s finches.

Sexual Selection: Traits that improve mating success are selected; Peacock tails.

Question 2

Balancing Selection
Define and examples

Answer 2

Definition: Maintains genetic diversity by favoring heterozygous individuals.

Example: Sickle cell trait (HbA/HbS) in malaria-endemic regions provides a survival advantage.

Question 3

Genetic Drift define and examples

Answer 3

Definition: Random changes in allele frequencies due to chance, more significant in small populations.

Examples:

Founder Effect: A small group breaks off from a larger population and establishes a new one.
Example: High prevalence of genetic disorders in Amish populations.

Population
Bottleneck: A drastic reduction in population size reduces genetic variation.
Example: Northern elephant seals reduced genetic diversity after overhunting.

Question 4

Conservationists’ Concerns with Population Bottleneck

Answer 4

Reduced Genetic Diversity:
Limits adaptability to environmental changes or disease.

Inbreeding Depression:
Increased likelihood of harmful recessive traits.
Example: Cheetahs have low genetic diversity, making them vulnerable to extinction.