Module B - 2

Which of the following is a result of cheetahs having gone through a population bottleneck?

• The cheetah species is more likely to become extinct.

• Mutations occur more frequently in the cheetah genome.

• Individual cheetahs have different alleles for many genes.

• The cheetah population cannot increase past a certain size.

Answer explanation

A population bottleneck reduces genetic variation. If variation is low, natural selection is less able to cause a change in allele frequencies in response to environmental change.

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NGSS.MS-LS4-4

Which is one way that natural selection differs from genetic drift?

• Natural selection causes the frequencies of alleles in a population to change.

• Natural selection affects smaller populations more often than larger populations.

• Natural selection results from some individuals producing more offspring than others.

• Natural selection depends on some traits helping individuals survive in their environment.

Answer explanation

Natural selection is a result of survival of the fittest. Fitness is dependent upon traits or adaptations that result in individuals having a higher survival rate. Genetic Drift is random, survival is not related to traits.

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NGSS.HS-LS4-4

Recently, bears have been found in the Arctic Circle that are hybrids between grizzly bears and polar bears. Which type of isolating mechanism keeps these species from producing offspring?

• mating and breeding in different habitats

• production of a nonviable embryo or fetus

• inability of sperm to reach the egg during mating.

• failure of the fertilized egg to implant in the uterus.

Answer explanation

Isolating mechanisms keep organisms from interbreeding from one another. Polar bears and grizzly bears occupy different habitats so their contact is limited which stops them from interbreeding.

A particular gene has two alleles, G and g. Each allele has a frequency of 50% in a population. Which is most likely to preserve these allele frequencies?

• The population doubles in size over several generations.

• A number of individuals with one allele migrate from the population.

• One allele results in a phenotype that better enables organisms to reproduce.

• A popoulation bottleneck temporarily reduces the population size by one-tenth.

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NGSS.MS-LS4-4

Under which of the following conditions would a dominant allele that coded for a fatal disease most likely remain in a population?

• The allele is acted on by natural selection.

• The gene is expressed only in members of one sex.

• The gene is expressed in individuals late in their lives.

• The allele mutates to a nonfatal form during an individual's lifetime.

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Imagine that DNA replication and cell division were completely error-free and that cell DNA were completely protected from substances that cause mutation. How would natural selection be affected?

• It would become more efficient, since it removes mutations from the populations.

• It would become ineffective, since it depends of variations within populations.

• It would become unnecessary, since organisms would be better adapted to their environments.

• It would become more obvious, since it would improve on organisms with better cell processes.

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NGSS.HS-LS4-4

Which statement best describes the significance of Archaeopterix fossils?

• They revealed the direct ancestor of birds.

• They prove that dinosaurs were fearthered.

• They provided the first evidence for evolution.

• They show that birds and dinosaurs have a common ancestor.

Answer explanation

This fossil is an example of a transition fossil, which shows the relationship between current organisms and other ancient extinct species.

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Which of the following structures are not homologous?

• The wings of a fly and the wings of a pigeon.

• The gills of a goldfish and the gills of a shark.

• The arms of a human and the arms of a chimpanzee.

• The roots of a white oak tree and the roots of a red oak tree.

Answer explanation

Homologous structures are found in organisms that share a relatively common ancestor.

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NGSS.MS-LS4-2

The spotted touch-me-not, a flowering plant, has seed pods that burst open when touched and forcefully eject their seeds.  Such an adaptation is favorable because it

          

• Aids in the dispersal of the species

• Prevents germination within the seed pods  

• attracts insects that aid in pollination      

• it looks cool

Answer explanation

This adaption will increase the fitness of the plants by spreading out the seeds. This will decrease competition among the offspring for resources.

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NGSS.MS-LS1-4

Fossils of species such as Basilosaurus have been discovered in the deserts of the Middle East. Which term best describes this fossil in relation to the evolution of the modern baleen whale?

• analogous

• homologous

• transitional

• vestigial

Answer explanation

Basilosaurus has structural features of current whales and "walking" whales/ancient whales. This shows the link between current whale species and their ancient ancestors.

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