Chapter 16 Biology

Post-zygotic

reproductive isolation that occurs after fertilization

Pre-zygotic

reproductive isolation that occurs before fertilzation

What is a gene pool? How are allele frequencies related to gene pools?

A gene pool is the combined genetic information of all members of a particular population. Allele frequencies are the number of times certain alleles occur in a particular gene pool compared with other alleles.

Describe three patterns of natural selection on polygenic traits. Which one leads to two distinct phenotypes?

Directional selection favors one extreme; stabilizing selection favors the middle of the range; disruptive selection favors both extremes and leads to two phenotypes.

Sexual Selection

Females choosing mates based on certain elaborate traits

How is reproductive isolation related to the formation of new species?

For new species to evolve, populations must be reproductively isolated from each other.

Sickle Cell Anemia

Genetic disease that causes red blood cells to become misshaped and not able to take up oxygen

How does genetic drift lead to a change in a population's gene pool?

Genetic drift causes random changes in allele frequencies in small populations.

What type of isolating mechanism was important in the formation of Galápagos finch species?

Geographic isolation

Species

Group of interbreeding organisms that look similar and can produce fertile offspring

Describe how natural selection can affect traits controlled by single genes.

It can lead to changes in allele frequencies and the evolution of traits.

Gene flow

Movement of genes from one population to another

What two processes can lead to inherited variation in populations?

Mutations and the genetic shuffling that results from sexual reproduction

Evaluate the significance of mutations to the process of biological evolution. (Hint: How does mutation affect genetic variation?)

Mutations increase genetic variation, which is needed for natural selection to bring about evolutionary change.

Allopatric Speciation

New species evolve because the population is geographically isolated

Sympatric Speciation

New species evolve because the population is reproductively isolated.

Suppose that a drought on an island eliminates all but plants that produce large, tough seeds. All the finches on the island have very small beaks. How might this environmental change impact the survival of this finch population?

Only those finches that can find another food source or those with beaks large enough to crack the seeds will survive.

What recent research findings support Darwin's theory of evolution?

Peter and Rosemary Grant have provided evidence of the process of evolution through their studies of changes of beak size and shape in Galápagos finches.

Allele frequency

Ratio of a particular allele divided by the total number of alleles in a population

Phenotype frequency

Ratio of individuals with a particular phenotype divided by the total number of individuals in the population

Assortative Mating

Selecting a mate with similar traits

How does the range of phenotypes differ between single-gene traits and polygenic traits?

Single-gene traits have only two distinct phenotypes. Polygenic traits can have many possible phenotypes.

Population Genetics

Study of evolution from a genetic point of view

Gradualism

Theory that speciation happens over a long period of time through the accumulation of small changes

Punctuated Equilibrium

Theory that speciation happens suddenly, followed by periods of no change or evolution.

In genetic terms what indicates that evolution is occurring in a population?

When there is a change in the relative frequency of alleles in a population.

Mutation

A change in DNA

What is the Hardy-Weinberg principle?

Allele frequencies in a population remain constant unless one or more factors cause the frequencies to change.

Explain how behavior can play a role in the evolution of species.

Behavioral isolation can occur when two populations that could otherwise interbreed do not because of differences in behavior. This can lead to the evolution of different species.

How are directional selection and disruptive selection similar? How are they different?

Both are types of selection on polygenic traits in which the curve shifts away from the middle. In directional selection, the curve shifts toward one end, and in disruptive selection, toward both ends.

Malaria

Disease caused by a protists that is transmitted by mosquitoes

Immigration

organisms moving INTO a new population

Emigration

organisms moving OUT of a population

Genetic Drift

phenomenon where allele frequencies in a small population change as a result of random events.

Gene Pool

total genetic information in a population