Chapter 13 Core Content: How Populations Evolve

offspring

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

unity

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

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.

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.

Why was Darwin's acceptance of an ancient, continuously changing Earth so important in his development of his ideas about evolution?

Darwin hypothesized that species changed gradually, over long spans of time, in response to diverse and changing habitats. Correct Darwin recognized that descendants of a common ancestor adapted to a diversity of habitats through natural selection. To produce current life-forms, this process required a great deal of time within a dynamic Earth environment.

natural selection

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

Selective Pressure

Green beetles are more visible to birds than brown beetles, so birds eat more green beetles.

Remember that color is an inherited trait in beetles. Which of the following is an example of natural selection?

Green beetles leave more offspring than brown beetles because they are better at finding food. Correct Natural selection occurs when organisms with one inherited trait survive and reproduce more than organisms with other traits.

Sometimes critics charge that evolution is based on mere speculation because it cannot be directly observed or experimentally induced. Is this true of evolution by natural selection?

No. Natural selection changes the traits of some organisms quite quickly, in ways that are clearly adaptive. Scientists have documented such changes in thousands of studies. Correct In species with short generation times, natural selection is particularly swift.

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.

diversity

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

modification

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

Natural selection is best described as _____.

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

The evolution of populations due to chance is

genetic drift. Correct Genetic drift describes the evolution of a population due to chance.

In a population with brown and green alleles for color, genetic drift

has more effect on the evolution of a small population. Correct Genetic drift affects the evolution of small populations more than it affects the evolution of large populations.

In artificial selection, humans provide the selective pressure for species to change and shape the evolution of various breeds. What provides the selective pressure in natural selection?

the environment Correct The organisms best adapted to a particular environment have the greatest reproductive success.

If color is an inherited trait in beetles, and birds are more likely to eat brown beetles than green beetles,

the frequency of the green allele will increase. Correct If birds are more likely to eat brown beetles than green beetles, then green beetles will survive and reproduce more than brown beetles. This causes the frequency of the green allele to increase.

Darwin found that many of the species on the Galápagos islands

resembled species on the nearest mainland.

When they were first sold, certain insecticides were highly effective in killing mosquitoes. Today, dozens of mosquito generations later, a much smaller proportion of these insects die when sprayed with the same chemicals. Fewer insects are killed today because _____.

many mosquitoes today are descendants of mosquitoes with insecticide-resistant characteristics Correct Individuals whose characteristics best fit them to their environment are likely to leave more offspring than are less fit individuals. This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations.

Which of the following list of assumptions was part of Charles Darwin's theory of natural selection?

1. Organisms vary in heritable ways. 2. Some traits improve the survival and reproduction of individuals who possess them. 3. Populations produce more offspring than their environment can support, so individual organisms must compete for limited resources. 4. Earth and its life are very old. Correct Suggestion: Make a checklist of the key elements that come together to support Darwin's concept of evolution by natural selection.

Environmental Change

A drought causes a habitat to turn dry and brown.

How are adaptations beneficial to organisms?

Adaptations help organisms survive and reproduce in a particular environment. Correct Adaptations result from the evolution of populations through natural selection as a result of interactions with their environment.

Change in Population

Brown beetles survive to reproductive more than green beetles do. The brown allele increases in frequency.

adaptations

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

inherited traits

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.

Who developed a theory of evolution almost identical to Darwin's?

Wallace

HIV has become an important source of mortality for humans. If AIDS persists as a major factor for humans for many generations in the future, natural selection theory predicts that _____.

any heritable traits that help humans survive and reproduce in the presence of AIDS should become more frequent over time

In natural selection, _____ determine which phenotypes are successful.

current conditions in the local environment. Correct Natural selection occurs through an interaction between the environment and the variability inherent among individual organisms making up a population.

Which of the following best expresses the concept of natural selection?

differential reproductive success based on inherited characteristics

Color is an inherited trait in beetles. If brown beetles move into a population from a nearby island, which of the following statements is correct?

Gene flow causes the frequency of the brown allele to increase. Correct Gene flow occurs when individuals move into or out of a population, changing the allele frequencies in the population. In this case, new brown beetles in the population cause the frequency of the brown allele to increase.