Biology Test (2-14)

What is a gene pool?

A gene pool is the complete genetic makeup of of a population. It consists of all the genes of all the members of the population, including all the alleles for each gene.

Describe the timing of evolutionary change according to the punctuated equilibrium model.

According to the punctuated equilibrium model, evolution is characterized by long periods of little change that are interrupted by bursts of rapid change.

How did Alfred Russel Wallace influence Darwin?

Alfred Russel Wallace influenced Darwin by developing essentially the same theory of evolution as Darwin's. Wallace sent Darwin an article that outlined his theory, and this confirmed Darwin's ideas. It also pushed Darwin to finish and publish his book, On the Origin of Species

Describe how allopatric speciation occurs.

Allopatric speciation occurs when some members of a species become geographically sepa- rated from the rest of the species. If they remain separated long enough, they may evolve genetic differences. If the differences become significant and prevent them from interbreeding with members of the original species, speciation has occurred. They have become a new species.

What is artificial selection? How does it work?

Artificial selection is a method of breeding domestic plants and animals to have traits that are useful to humans. It involves humans selecting which plants or animals are allowed to reproduce and pass their traits to the next generation.

Define biogeography.

Biogeography is the study of how and why plants and animals live where they do.

Compare and contrast homologous and analogous structures. What do they reveal about evolution?

Both homologous and analogous structures are structures that are similar in different organisms. However, the reasons for the similarities are different. Homologies are similar because they were inherited from a common ancestor in closely related species. Analogies are similar because they evolved to do the same job in unrelated species, not because they were inherited from a common ancestor.

Why does comparative embryology show similarities between organisms that do not appear to be similar as adults?

Comparative embryology shows similarities between organisms that do not appear to be similar as adults because many features of embryos disappear by adulthood. For example, all vertebrate embryos have a tail and gill slits, but these disappear by adulthood in many vertebrates, including humans. It is only by comparing embryos that the similarities are apparent.

Why did Darwin's observations of Galápagos tortoises cause him to wonder how species originate?

Darwin's observations of Galápagos tortoises caused him to wonder how species originate because he saw that each island had its own type of tortoise. He wanted to know how tortoises had diverged into these different types.

State Darwin's theory of evolution by natural selection.

Darwin's theory of evolution by natural selection states that organisms change through time because individuals with beneficial traits produce more offspring than others do. As a result, their beneficial traits become more common.

Describe what fossils reveal about the evolution of the horse.

Fossils reveal that the earliest horses were about the size of a fox and had four long toes. They lived in wooded marshlands and probably ate soft leaves. Through time, their environment became drier, and grasslands replaced the marshes. Later fossils show that horses also changed to adapt to the new environment. They became taller and evolved a single large toe that eventually became a hoof. They also evolved longer molars that were covered with cement.

What is gradualism? When is it most likely to apply?

Gradualism is a model of the timing of evolution that was accepted by Charles Darwin. According to this model, evolution occurs at a slow and steady pace. Gradualism is most likely to apply when geologic and climatic conditions are stable.

Explain how the writings of Charles Lyell and Thomas Malthus helped Darwin develop his theory of evolution by natural selection.

In his Principles of Geology On Population gave Darwin the idea that there is overproduction of offspring relative to the environmental resources they depend on. This leads to a struggle for existence, with the weaker organisms being less likely to survive and reproduce. This was the basis for Darwin's ideas of fitness and natural selection.

What is the inheritance of acquired characteristics? What scientist developed this mistaken idea?

Inheritance of acquired characteristics is Lamarck's mistaken idea of how evolution occurs. It posits that traits an organism develops in its own lifetime are passed on to its offspring.

Humans and apes have five fingers they can use to grasp objects. Do you think these are analogous or homologous structures? Explain.

It is a homologous structure. A homologous structure is a structure that is similar in different organisms because it was inherited from a common ancestor. Humans and apes are closely related. They inherited five grasping fingers from a common ancestor.

Why is mutation needed for evolution to occur, even though it usually has little effect on allele fre- quencies?

Mutation creates new genetic variation in a gene pool. It is how all new alleles first arise. Although mutation usually has little effect on allele frequencies, it provides the genetic variation needed for other forces of evolution to act.

How do paleontologists learn about evolution?

Paleontologists learn about evolution by finding and studying fossils of organisms that lived in the past. From the fossils, they can learn what extinct ancient organisms were like and how they lived.

Why are populations, rather than individuals, the units of evolution?

Populations, rather than individuals, are the units of evolution because evolution is a change in allele frequencies over time. An individual's alleles do not change, but the allele frequencies in a population may change from one generation to the next.

Define speciation.

Speciation is the process by which a new species evolves.

Describe an example of island biogeography that provides evidence of evolution.

The distribution of different species of finches on the Galápagos Islands is an example of island biogeography that provides evidence of evolution. It shows that adaptive radiation occurred. One original finch species evolved into many species, each with adaptations for a different type of food.

Identify the four forces of evolution.

The four forces of evolution are mutation, gene flow, genetic drift, and natural selection.

Identify three types of natural selection for a polygenic trait.

Three types of natural selection for a polygenic trait are: stabilizing selection, in which both extremes of the phenotypic distribution are selected against, narrowing the range of variation; directional selection, in which one of the extremes is selected for, shifting the distribution toward that extreme; and disruptive selection, in which genotypes in the middle are selected against, leading to two overlapping phenotypes, one at each end of the distribution.

What are vestigial structures? Give an example.

Vestigial structures are structures that are no longer used and have become reduced in size through evolution. Examples are the human tailbone and appendix.