Biology Chapter 16 Flashcards

Questions and Answers

What is a gene pool?

Consists of all genes, including all the different alleles, that are present in a population.

What is relative frequency?

Number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.

What is a single-gene trait?

A trait that is controlled by a single gene that has two alleles.

What is a polygenic trait?

A trait that is controlled by two or more genes that each have two or more alleles. Signup and view all the answers

What are the sources of genetic variation, and which one contributes the most to variation in inheritable traits?

Two sources are mutation and gene shuffling; gene shuffling contributes the most. Signup and view all the answers

Which type of gene trait contributes to the most phenotypes?

Polygenic. Signup and view all the answers

What type of graph does a polygenic trait produce?

A bell-shaped curve. Signup and view all the answers

What is directional selection?

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

What is stabilizing selection?

Form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end. Signup and view all the answers

What is disruptive selection?

Occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle. Signup and view all the answers

What is genetic drift?

Random change in allele frequencies that occurs in small populations. Signup and view all the answers

What is the founder effect?

Change in allele frequencies 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?

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

What is genetic equilibrium?

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

What are the two types of genetic drift?

The founder effect and bottleneck. Signup and view all the answers

What are some similarities between natural selection and genetic drift?

The offspring are genetically different from the original population; Certain alleles occur more often because the individuals that carry the allele may have more descendants than others. Signup and view all the answers

What are some differences between natural selection and genetic drift?

Genetic drift is caused by chance; Natural selection affects a population through directional, stabilizing, or disruptive selection. Signup and view all the answers

What are the 5 requirements of the Hardy-Weinberg principle?

<ol> <li>There must be random mating. 2. The population must be very large. 3. There can be no movement into or out of the population. 4. No mutations. 5. No natural selection.</li> </ol> Signup and view all the answers

What are the 5 steps to solving a Hardy-Weinberg equilibrium problem?

<ol> <li>Find the frequency of the 'aa' genotype (q^2). 2. Find the frequency of the 'a' allele (the square root of q^2). 3. Find the frequency of the 'A' allele (p; p + q = 1.0 - solve for p). 4. Find the frequency of the 'AA' genotype (p^2). 5. Find the frequency of the 'Aa' genotype (2pq).</li> </ol> Signup and view all the answers

What is speciation?

Formation of a new species. Signup and view all the answers

What is reproductive isolation?

Separation of a species or population so that they cannot interbreed and produce fertile offspring. Signup and view all the answers

What is behavioral isolation?

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding. Signup and view all the answers

What is geographic isolation?

Form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water. Signup and view all the answers

What is temporal isolation?

Form of reproductive isolation in which two populations reproduce at different times. Signup and view all the answers

How does geographic isolation change alleles in an organism's gene pool?

Because they are separated physically, natural selection that worked for one group will be different than for the other; different experiences will mean different offspring. Signup and view all the answers

How can behavior play a role in the evolution of species?

A difference in rituals can prevent some subgroups of a species from interbreeding with others, therefore their genes are not passed to the other groups and vice versa. Signup and view all the answers

What is evolution in genetic terms?

Any change in the relative frequency of alleles in a population. Signup and view all the answers

Study Notes

Genetic Concepts

Gene Pool: Represents all the genetic information, including various alleles, found within a population.
Relative Frequency: Refers to how often a specific allele appears in a gene pool compared to other alleles for that gene.
Single-Gene Trait: A characteristic determined by one gene with two possible alleles.
Polygenic Trait: A characteristic influenced by two or more genes, each potentially exhibiting multiple alleles.

Genetic Variation

Sources of Genetic Variation: Include mutations and gene shuffling, with gene shuffling being the primary contributor to variability in inheritable traits.
Dominance in Phenotypes: Polygenic traits lead to a broader range of phenotypes compared to single-gene traits.
Graph Representation: Polygenic traits typically display a bell-shaped curve in graphical representations due to their diverse expression.

Natural Selection Types

Directional Selection: Favors individuals at one extremity of a trait distribution, enhancing fitness at that end.
Stabilizing Selection: Maintains the status quo by favoring individuals near the average trait value, reducing variation.
Disruptive Selection: Prefers extreme values of a trait, leading to two or more contrasting phenotypes.

Population Dynamics

Genetic Drift: Involves random changes in allele frequencies, particularly influential in small populations.
Founder Effect: Occurs when a small subgroup migrates, resulting in altered allele frequencies compared to the original population.
Hardy-Weinberg Principle: States that allele frequencies in a population will remain stable barring external influences.

Equilibrium and Drift

Genetic Equilibrium: A state where allele frequencies remain unchanged across generations.
Types of Genetic Drift: Includes founder effect and bottleneck effect.

Natural Selection vs. Genetic Drift

Similarities: Both processes lead to genetic variability among offspring and can enhance the frequency of certain alleles.
Differences: Genetic drift is attributed to chance events, whereas natural selection is driven by environmental pressures and results in specific adaptive traits.

Hardy-Weinberg Requirements

Conditions for maintaining Hardy-Weinberg equilibrium include:
- Random mating within the population
- Large population size
- No immigration or emigration
- Absence of mutations
- Lack of natural selection pressures

Hardy-Weinberg Equation Steps

Compute the frequency of genotypes and alleles through a sequential process involving:
- Identifying the frequency of the homozygous recessive genotype (q²)
- Calculating the allele frequency of the recessive allele (q) and then the dominant allele (p)
- Finding homozygous dominant (p²) and heterozygous (2pq) frequencies to apply in the equation p² + 2pq + q² = 1.

Speciation and Isolation Mechanisms

Speciation: The emergence of new species from existing species.
Reproductive Isolation: Mechanisms that prevent populations from interbreeding, maintaining species integrity.
Types of Isolation:
- Behavioral Isolation: Differences in mating behaviors prevent interbreeding.
- Geographic Isolation: Physical barriers separate populations, leading to divergent evolutionary paths.
- Temporal Isolation: Species reproduce at different times, preventing mating opportunities.

Impact of Isolation on Evolution

Geographic isolation alters allele frequencies due to varying selective pressures in each environment, potentially leading to different adaptations.
Behavioral differences in mating rituals can inhibit gene flow between subgroups, promoting genetic divergence.

Evolution Definition

Refers to changes in allele frequency distribution within a population over time.

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Explore key concepts from Biology Chapter 16 with flashcards covering essential terms such as gene pool, relative frequency, and single-gene traits. This quiz will help reinforce your understanding of genetic variation within populations.