Topic 7.3 - Artificial Selection

Artificial selection is a major piece of evidence for evolution. The concept of human selection practices as evidence for the theory of natural selection was so significant to Darwin that it is the subject of the first chapter of On the Origin of Species.

Which of the following is an example of artificial selection?

• Male peacocks with longer tails and more eyespots have more offspring than males with shorter tails and fewer eyespots.

• Urban animals, such as raccoons, may scavenge dumpsters as their primary food source.

• The bloodhound dog breed was bred in the middle ages for an excellent sense of smell to be used for hunting.

• Zebra mussels are freshwater mussels native to Russia. They were accidentally introduced to North America when they were transported in ballast tanks of ships from Europe. The species is invasive and has had a significant effect on native species of the Great Lakes.

Several different types of selection can act on a population at a given time.

Which of the following is a role that humans play in the process of artificial selection?

• To perform operations on organisms that increase survival.

• To determine which organisms live and which organisms die.

• To determine which organisms breed and which organisms do not breed.

• To create novel genetic mutations, which nature then selects.

Humans have had major impacts, both intentional and unintentional, on populations and ecosystems. Human actions have driven change in ways that provide evidence for evolution. Darwin used examples of human impacts on organisms to support the concept of natural selection.

Which of the following human activities, according to Darwin, demonstrates that selection can cause significant changes to species?

• DNA sequencing.

• Domestication of plants and animals.

• Overhunting.

• Use of microscopes.

A new bacterial infection is spreading through a city. Doctors start prescribing penicillin, but they soon find that the bacteria is resistant to the antibiotic.

Testing reveals that a penicillin resistance gene is located on a plasmid that is increasing in the bacteria population through conjugation and selection due to the use of penicillin. Doctors start using rifampicin, another antibiotic that works through a different mechanism than penicillin.

Which of the following is MOST likely to occur in the bacteria population?

• All bacteria without the penicillin resistance plasmid will be eliminated from the population by the use of rifampicin.

• The penicillin resistance plasmid will be eliminated from the population in several generations due to lack of use.

• The penicillin resistance plasmid will continue to increase in the population because it will protect against rifampicin.

• The spread of the penicillin plasmid will slow, but it will remain in the population.

Maize (corn) was domesticated about 10,000 years ago. Genetic evidence suggests that maize developed from a wild plant called teosinte. Early farmers in what is now Mexico artificially selected maize to increase traits, such as number of ears produced, number of kernels, and size of kernels.

How does the genetic diversity of a modern corn field compare to the genetic diversity of a population of teosinte?

• Less diversity.

• More diversity.

• More genetic diversity, but less phenotypic variation.

• The same amount of diversity.

The phenotype of an organism can change over multiple generations by artificially selecting for a particular trait. One such example is the manipulation of trichome density on the petioles (leaf stalks) of the Wisconsin fast plant, Brassica rapa.

If a horticulturalist developed a variant stock of the fast plant that expressed a low density of trichomes and grew it in the wild, which of the following would be a major deficiency in the plant’s ability to adapt to its environment?

• The “hairless” plant would lose its ability to attract pollinators.

• A low density of trichomes would diminish the plant’s ability to absorb nutrients.

• A low density of trichomes decreases the plant’s ability to exchange gases such as and .

• The “hairless” plant would not be able to ward off insect predators.

What is the definition of natural selection?

• The process in which genes are chosen by humans such as farmers and ranchers

• The process in which organisms are chosen by environmental pressures such as climate, available food, predators and habitat.

• If an organism changes during their life in order to adapt to its environment, those changes are passed on to its offspring.

• The process in which genes are chosen by scientist and academics.

Which statement is true comparing natural selection and artificial selection?

• In natural selection, traits benefit humans and in artificial selection, the traits benefit the species

• In natural selection, traits benefit the species and in artificial selection, the traits benefit humans

• In natural and artificial selection, the process takes hundreds of years to occur

• In natural and artificial selection, nature determines what traits will be passed down to offspring.

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Artificial selection takes

• a shorter period of time than natural selection

• a longer period of time than natural selection

• the same amount of time as natural selection

Artificial selection is also known as

• natural selection

• selective hearing

• genetic manipulation

• selective breeding

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