Ch 25 Second Study Module

Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, which develop from similar embryonic tissues. These structural similarities are an example of __________.

homology

Darwin and Wallace were the first to propose __________.

natural selection as the mechanism of evolution

Pseudogenes are __________.

nonfunctional vestigial genes

evelopmental homologies most likely occur because __________.

of genetic homologies

Refer to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change. Which of these is/are the extant (that is, living) species that are least related to species X?

Z and Y

During a study session about evolution, one of your fellow student's remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement is most likely to be helpful in correcting this student's misconception?

Characteristics acquired during an organism's life are generally not passed on through genes.

Which of these conditions are always true of populations evolving due to natural selection? Condition 1: The population must vary in traits that are heritable. Condition 2: Some heritable traits must increase reproductive success. Condition 3: Individuals pass on most traits that they acquire during their lifetime.

Conditions 1 and 2

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. Which pair of scientists below would probably have agreed with the process that is depicted by this tree?

Darwin and Wallace

Which of the following must exist in a population before natural selection can act upon that population?

Genetic variation among individuals

If Darwin had been aware of genes and their typical mode of transmission to subsequent generations, with which statement would he most likely have been in agreement?

If natural selection can change gene frequency in a population over generations, given enough time and genetic diversity, then natural selection can cause sufficient genetic change to produce new species from old ones.

In the mid-1900s, the Soviet geneticist Lysenko believed that his winter wheat plants, exposed to increasingly colder temperatures, would eventually give rise to more cold-tolerant winter wheat. Lysenko's attempts in this regard were most in agreement with the ideas of __________.

Lamarck

Currently, two extant elephant species (X and Y) are classified in the genus Loxodonta, and a third species (Z) is placed in the genus Elephas. Thus, which statement should be true?

Species X and Y share a greater number of homologies with each other than either does with species Z.

A biologist studied a population of squirrels for fifteen years. During that time, the population was never fewer than thirty squirrels and never more than forty-five. Her data showed that over half of the squirrels born did not survive to reproduce, because of both competition for food and predation. In a single generation, 90% of the squirrels that were born lived to reproduce, and the population increased to eighty. Which inference(s) about this most recent surge in the population size might be true?

The amount of available food may have increased and/or the predators that prey upon squirrels may have decreased.

Refer to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change. Which of these is the extant (that is, living) species most closely related to species X?

V

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. Which of the five species, labeled V-Z, is the common ancestor of the fewest number of species?

V

The question below refers to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change. Which species is most closely related to species W?

V is most closely related to species W.

Which of the following scientists argued that variation among individuals allows evolution to occur?

Wallace

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. Which of the five common ancestors, labeled V-Z, is the common ancestor of the greatest number of species, both living and extinct?

Y

If two modern organisms last shared a common ancestor fifty million years ago, we expect that they __________.

have fewer homologous structures than two modern organisms that last shared a common ancestor one million years ago

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. Evolutionary trees such as this are properly understood by scientists to be __________.

hypotheses

It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that __________.

island forms are descended from mainland forms

In a hypothetical environment, fishes called pike-cichlids are visual predators of large, adult algae-eating fish (in other words, they locate their prey by sight). The population of algae-eaters experiences predatory pressure from pike-cichlids. Which of the following is least likely to occur in the algae-eater population in future generations?

selection for larger female algae-eaters, bearing broods composed of more, and larger, young

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. How many distinct species, both living and extinct, are depicted in this tree?

six