Natural Selection

The mice living in an area changed from having brightly colored fur to having darkly colored fur.

How did natural selection most likely result in this evolutionary change?

• Bright mice were not able to blend into their environment as easily as dark mice, so they did not continue to survive and reproduce.

• Bright mice produced fewer offspring than dark mice, so the bright mice became outnumbered within days.

• Random changes in the genetics of bright mice produced more dark mice, so the bright mice quickly died off.

• Random changes in the genetics of dark mice produced fewer bright mice, so the dark mice took over the population.

Which are characteristics of natural selection? Select three options.

• It affects populations.

• It affects only individuals.

• It occurs when there is genetic variation.

• It occurs when organisms are genetically identical.

• It selects organisms with certain traits to survive.

The process by which the organisms that are better adapted to the environment survive and reproduce is called

• Extinction

• Evolution

• Natural Selection

• variation

Which statement best describes how reproduction leads to natural selection in a population?

• Organisms do not produce many offspring, so all of them can survive and pass on their traits.

• Organisms overproduce offspring; consequently, all of them are likely to survive and pass on traits.

• Organisms overproduce offspring, so only some survive and pass on their traits.

• Organisms do not overproduce offspring; therefore, those that are produced will develop the best traits.

Organisms must have variation within a population in order for natural selection to occur.

Which situation is an example of this variation?

• A frog living in a pond is eaten by a predator, while others in the same population survive.

• A snake living in a desert produces more offspring than other snakes in the same population.

• Some rabbits living in a forest have short, spotted ears, while others have long white ears.

• Some birds living in a grassland eat less than other birds who eat the same food.

Answer explanation

Variation is what makes some organisms different in the same species.

Which statement describes how favorable traits in a population relate to natural selection?

• They are the only traits that ever exist in the population.

• They build in the population over time.

• They are rarely passed on to offspring.

• They are found only in a few individuals within the population.

Which conditions are required for natural selection? Select three options.

• Populations have genetic variation.

• Organisms overproduce offspring.

• Environmental conditions remain stable.

• Traits are passed on to only some of the offspring.

• Nature selects favorable adaptations.

A genetic mutation causes a squirrel to be born with much darker fur than its parents.

• Because the trait was caused by a mutation, it will not be passed on to any offspring, resulting in the disappearance of the trait.

• Because the trait was caused by a mutation, it will be passed on to offspring over many generations, resulting in a population of darker squirrels.

• If the trait is unfavorable, it will be passed on to offspring over many generations, resulting in a population of darker squirrels.

• If the trait is favorable, it will be passed on to offspring over many generations, resulting in a population of darker squirrels.

Answer explanation

If the mutation helps the organism survive, it will pass those genes on to its offspring.

Due to a genetic mutation, a deer is born with a missing toe. This makes it difficult for the deer to escape from predators.

• The deer with the mutation will not survive, and the trait will disappear from the population.

• The deer with the mutation will survive and reproduce, but it will not pass this trait on to its offspring.

• The deer with the mutation will not survive, but the trait will appear again in the next generation.

• The deer with the mutation will survive and reproduce, and the trait will commonly appear in future generations.

Answer explanation

If the mutation doesn't help the organism to survive, it will die, and not pass it on to its offspring.

In a mouse population, some mice have thicker fur than others, but there are more mice with thinner fur. The climate in which these mice live has slowly gotten colder.

• The adaptation of thinner fur will be selected over thicker fur, and the population will remain unchanged.

• The adaptation of thicker fur will be selected over thinner fur, and the population will remain unchanged.

• The adaptation of thicker fur will be selected over thinner fur, and the population will evolve.

• The adaptation of thinner fur will be selected over thicker fur, and the population will evolve.