Biology Chapter 16: Evolution of Populations

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Questions and Answers

What is a gene pool?

The combined genetic information of all the members of a particular population.

What are relative frequencies?

The number of times a certain allele occurs in a gene pool compared with the number of times the other alleles occur.

What defines a single-gene trait?

A trait controlled by a single gene.

What is a polygenic trait?

A trait controlled by two or more genes. Signup and view all the answers

What is directional selection?

Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. Signup and view all the answers

What is stabilizing selection?

Individuals near the center of the curve have higher fitness than individuals at the end. Signup and view all the answers

What is disruptive selection?

Individuals at the upper and lower end of the curve have higher fitness than individuals near the middle. Signup and view all the answers

What is genetic drift?

Random changes in allele frequencies in small populations. Signup and view all the answers

What is the founder effect?

A situation in which allele frequencies change as a result of the migration of a small subgroup of a population. Signup and view all the answers

What is the Hardy-Weinberg principle?

Allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. Signup and view all the answers

What does genetic equilibrium mean?

The situation in which allele frequencies remain constant. Signup and view all the answers

What are the 5 conditions required to maintain genetic equilibrium?

Random mating, large population, no movement in/out of population, no mutations, no natural selection. Signup and view all the answers

What is speciation?

Species in a genetically isolated organism capable of reproducing. Signup and view all the answers

What is reproductive isolation?

The members of two populations cannot interbreed and produce fertile offspring. Signup and view all the answers

What is behavioral isolation?

Two populations are capable of interbreeding but have differences in courtship rituals or other types of behavior. Signup and view all the answers

What is geographical isolation?

Two populations are separated by geographic barriers such as rivers, mountains, or bodies of water. Signup and view all the answers

What is temporal isolation?

Two or more species reproduce at different times. Signup and view all the answers

Study Notes

Key Concepts in Population Evolution

Gene Pool: Represents the total genetic diversity within a population; includes all alleles present.
Relative Frequencies: Measures how often a specific allele appears in comparison to others within the gene pool; essential for tracking genetic variations.

Types of Traits

Single-Gene Trait: Influenced by a single gene, resulting in distinct phenotypic expressions.
Polygenic Trait: Governed by multiple genes, leading to a range of phenotypes and continuous variation among individuals.

Selection Mechanisms

Directional Selection: Favors individuals at one extreme of the phenotypic spectrum, shifting the population's trait distribution over time.
Stabilizing Selection: Enhances traits around the average phenotype, reducing variation by favoring intermediate phenotypes.
Disruptive Selection: Promotes extreme phenotypes at both ends, potentially leading to speciation when intermediates are selected against.

Genetic Variability and Population Dynamics

Genetic Drift: Random fluctuations in allele frequencies often observed in small populations, which can lead to significant evolutionary changes over time.
Founder Effect: Occurs when a new population is established by a very small number of individuals, resulting in a limited gene pool and altered allele frequencies.

Principles of Population Genetics

Hardy-Weinberg Principle: Maintains that allele frequencies in a large, randomly mating population will remain constant in the absence of evolutionary influences.
Genetic Equilibrium: Refers to the stability of allele frequencies; a population in genetic equilibrium does not evolve.
Conditions for Genetic Equilibrium: Requires random mating, a large population size, no immigration/emigration, no mutations, and the absence of natural selection.

Speciation Processes

Speciation: The evolutionary process through which new biological species arise; involves genetic isolation.
Reproductive Isolation: Describes the inability of two populations to interbreed and produce viable, fertile offspring; can occur through various mechanisms.

Types of Reproductive Isolation

Behavioral Isolation: Differences in mating rituals or behaviors prevent interbreeding among populations despite potential compatibility.
Geographical Isolation: Physical barriers, like mountains or rivers, separate populations, leading to divergent evolutionary paths.
Temporal Isolation: Different breeding times prevent species from mating, maintaining distinct genetic lines.

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Test your knowledge on the evolution of populations with these flashcards. You'll explore key terms and concepts such as gene pool, relative frequencies, single-gene traits, and polygenic traits. Perfect for biology students looking to reinforce their understanding of population genetics.