Mastering Biology Chapter 13: How Populations Evolve

Observation of Natural Selection in Action

- Development of Pesticides Resistant in Insects - Changes in Average Beak Size in Finches Following Dry or Wet Years

Fossil Record

- Discovery of bones from many different dinosaur species - Transitional forms that link whales with land-dwelling ancestors that are now extinct

Natural selection is best described as _________.

A filtering process that fine-tunes the traits of populations by sorting among existing, randomly produced variations.

Stabilizing Selection

Favors intermediate phenotypes, selecting against phenotypes at both ends of a range and reducing variation.

Disruptive Selection

Favors phenotypes at both ends of a range over intermediate phenotypes. This type of selection may occur when the habitat is varied.

In a type of sexual selection often called ________________, individuals of one sex (usually females) are choosy in selecting their mates. This choice is often based on the showy appearance or behavior of the male.

Mate Choice

In sexual selection, individuals with certain inherited characteristics are more likely to obtain mates than other individuals. This often results in __________________, differences between the sexes in size, appearance, and behavior.

Sexual Dimorphism

The human immune system cannot effectively suppress the HIV virus on its own. What key feature of HIV makes it so hard to beat?

The HIV virus has an extremely high rate of mutation.

Anatomical and Molecular Homologies

- Same genetic language of DNA and similar genes in yeasts, fruit flies, & humans. - Similar forelimb anatomy in different species of mammals.

Biogeography

- Unique collection of marsupial mammals in Australia - Resemblance of island species to nearby mainland species

Imagine that four people are infected with HIV from a common source (an infected blood sample). Initially, the patients' HIV populations are genetically identical. By the time they develop full-blown AIDS, how would the viral populations of the fourpatients compare?

Each patient's viral population would be unique, specifically adapted to deal with—and overcome—his or her unique immune system responses.

The phrase Darwin used to describe his broad theory of evolution is ''descent with __________."

Modification

Darwin proposed a mechanism for how evolution occurs, which he called __________.

Natural Selection

Directional Selection

Favors phenotypes at one end of a range and is common in periods of environmental change.

As proposed by Darwin, what sorts of traits are favored by natural selection?

Heritable traits that help individuals survive and reproduce more successfully than others in the same population.

Two key observations underlying natural selection are that members of a population vary in their ________________ and that all species can produce more offspring than the environment can support.

Inherited Traits

Intrasexual Selection

Is a type of sexual selection in which individuals of one sex (usually males) compete directly for mates. This may involve ritualized displays or physical combat.

The _________ of life arises from the adaptation of species to different habitats over long spans of time.

Diversity

This unequal reproduction in a population leads to the gradual accumulation of ______________ to the environment.

Adaptations

Darwin inferred that those organisms with traits best suited to the environment tend to leave more ______________ than other members of a population.

Offspring

All of life is related through common ancestry, accounting for the _________ of life.

Unity