Biology Ch. 16

Sexual selection in males usually results in an increased ability to 1. ________ for mates, whereas sexual selection in females usually involves 2._________ a mate with the best fitness.

1. compete 2. selecting/choosing

When natural selection favors the ratio of two or more 1. ____________ over multiple generations, it is called 2. _________ _________.

1. phenotypes 2. balanced polymorphism

Because only alleles that are 1. _____________ expressed are subject to the pressures of 2. ___________, heterozygotes can be protectors of 3. _____________ alleles that could possibly be lost otherwise.

1. phenotypically 2. natural selection 3. recessive

_1. _________ is generated through 2. ______________, recombination, independent assortment, and gene flow.

1. variation 2. mutations

Match the letter on the left with the correct type of natural selection on the right.

A ----> stabilizing selection B -----> directional selection C -----> disruptive selection

Hardy-Weinberg principle

A mathematical model that proposes that the genotypic frequencies of a nonevolving population can be described by the expression p2 + 2pq + q2.

Most adaptations resulting from natural selection are perfectly suited to the environment. True or False

False

What does p represent in the Hardy-Weinberg principle?

Frequency of the dominant allele

Hardy-Weinberg equilibrium (HWE)

Genotypic and allele frequencies will remain constant (no evolution will occur) in a population from generation to generation when there are no other evolutionary influences. Influences include nonrandom mating, selection, migration, and genetic drift.

Population

Group of organisms of the same species occupying a certain area and sharing a common gene pool.

Which genotype is most prevalent in regions of Africa that have high rates of malaria?

HbAHbS (dominant allele carries disease)

Which of the following is an example of stabilizing selection?

High frequency of intermediate birth weight in humans

inbreeding

Mating between closely related individuals; influences the genotype ratios of the gene pool.

allele frequency

Relative proportion of each allele for a gene in the gene pool of a population. The percentage of each allele in a populations gene pool.

gene flow

Sharing of genes between two populations through interbreeding. movement of alleles between populations.

sexual dimorphism

Species that have distinct differences between the sexes, resulting in male and female forms. The males and females differ in size and other characteristics.

Match the form of natural selection on the left with the correct description on the right. Stabilizing Directional Disruptive

Stabilizing -----> Increases the frequency of an intermediate form of a trait. Directional ------> Increases the frequency of an extreme form of a trait. Disruptive -----> Maintains high levels of two different forms of a trait.

population genetics

The study of gene frequencies and their changes within a population. studies the diversity of a population at the level of a gene. It measures the diversity of a population by allele and genotype frequencies over generations.

gene pool

Total of the alleles of all the individuals in a population. The alleles of all the genes of all the individuals in a population.

bottleneck effect

Type of genetic drift; loss of diversity due to natural disasters, human interference, disease, overhunting, overharvesting, habitat loss.

founder effect

Type of genetic drift; similar to bottleneck effect; genetic variation is lost when a few individuals break away from a large population and form a new population.

mutation

a change to the DNA sequence that creates a new genetic variation

Natural selection favors the phenotype that is most _________.

adaptive

sexual selection

adaptive changes in males and females that increase ability to secure a mate/mate successfully. Best fitness, better ability to compete with other males.

A gene pool includes all of the ________ of all of the genes of a species.

alleles

Gene flow causes microevolution by introducing new or rare _____ into a population.

alleles

Gene flow is the movement of __________ between populations.

alleles/genes

A type of mating that occurs when individuals choose a mate with a preferred trait is called ______ mating.

assortative

Gonorrhea is becoming more difficult to treat because antibiotic resistance is developing in the ______ that causes gonorrhea.

bacterium

Which of the following are types of genetic drift?

bottleneck effect founder effect

genetic drift

changes in the allele frequency of a gene pool due to random events; events remove organism and genes from population at random without regard for phenotype or genotype. Mechanism of evolution due to random changes in the allelic frequencies of a population.

No mutations, no migration, random mating, no selection, and a large gene pool are required to maintain Hardy-Weinberg ________________.

equilibrium

directional selection

extreme phenotype/trait is favored/more successful, distribution curve shifts toward one of the extremes

The ability to produce surviving offspring is called ______.

fitness

If the frequency of an allele reaches 1.0, the allele is said to be

fixed

A type of genetic drift in which a small number of individuals form a new population away from the original one is called the ______.

founder effect

The percentage of each allele in a population's gene pool is referred to as an allele __________

frequency

Population genetics studies the diversity of a population at the level of the ________.

gene

A Canada goose leaving it's population in order to mate with a goose from another population is an example of _______ ________.

gene flow

The movement of alleles between populations is referred to as ______.

gene flow

All of the alleles of all of the genes in a population is known as the _______.

gene pool

The bottleneck effect is a type of ______.

genetic drift

When chance causes only certain members of a population to reproduce and pass on their alleles to the next generation it is called

genetic drift

If a scientist studies the diversity of genes in a population they are studying population __________.

genetics

The hypothesis regarding sexual selection that states that females choose mates on the basis of traits that increase a male's chance of survival is called the _______ hypothesis.

good genes

Sickle-cell disease is caused by an abnormal form of ____ in red blood cells.

hemoglobin (recessive allele carries disease)

The maintenance of genetic diversity of future generations is often maintained through the _____________ advantage.

heterozygous

The heterozygote advantage means that the heterozygote for a trait has an advantage over the two ______________.

homozygotes

Which of the following are conditions that a population must meet in order to maintain Hardy-Weinberg principle?

no new members can join the population and no existing members can leave no selection (no random mating) no mutation no migration/genetic drift large gene pool

The allele frequency is ______.

the percentage of each allele in a population

polygenic trait

traits controlled by multiple genes

Assortative mating is a type of ______ mating in which an individual is chosen because of a preferred trait

nonrandom

When individuals mate based upon preferences it is known as ____________ breeding

nonrandom/assortive

Which equation describes the genotype frequencies of a non-evolving population?

p2 + 2pq + q2

If a trait is controlled by more than one gene, the trait is referred to as being ______.

polygenic

A group of organisms of a single species living in the same geographic area is called a _____________.

population

All of the western blue birds living in a 100 hectare forest would be an example of a(n) ______.

population

The STD gonorrhea is becoming more difficult to treat due to the development of antibiotic ____________.

resistance

The hypothesis regarding sexual selection that states that females choose mates on the basis of appearance is called the _______ hypothesis

runaway

Male deer growing extremely large antlers that require excessive amounts of energy is due to _______ selection

sexual

List the ways diversity is maintained in a population

sexual reproduction mutations that create new alleles the presence of subspecies occasional interbreeding between adjacent populations

An abnormal form of hemoglobin causes __________ ___________ disease.

sickle cell

monogenic trait

single gene trait

Types of Natural Selection

stabilizing selection, directional selection, disruptive selection

stabilizing selection

when an intermediate phenotype/trait is the most adaptive to the given conditions/most successful

disruptive selection

when two or more extreme traits are favored over the intermediate phenotype/trait

The allele and genotype changes occurring within a population is known as __________

microevolution

The raw material for evolutionary change, which introduces new variations among members of a population is caused by _______.

mutation

Microevolution

Change in gene frequencies between populations of a species over time

Mutations serve as a source of new genetic variation and are caused by changes to an organisms ____________ sequence.

DNA/genetic/allele

The alleles in nonrandom mating assort according to ______.

mating behavior