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SC.912.L.15.13 Natural Selection

What You Need To Know

  • You need to know the conditions required for natural selection to occur. These include: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success. 
  • You need to understand genetic drift and gene flow.
  • You need to know how mutation and genetic recombination increase genetic variation. 

Example One

Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur?

A. fewer mutations

B. limited food resources

C. limited beak variations

D. overproduction of offspring


Example Two

Which of these would have the least effect on natural selection in a subspecies of giraffes that is geographically isolated from other subspecies of giraffes? 

A. available niches

B. existing predators

C. chromosome number

D. available food resources


Example Three

Mutations within a DNA sequence are

A. natural processes that produce genetic diversity

B. natural processes that always affect the phenotype

C. unnatural processes that always affect the phenotype

D. unnatural processes that are harmful to genetic diversity


Example Four

Which of the following best illustrates natural selection? 

A. An organism with favorable genetic variations will tend to survive and breed successfully. 

B. A population monopolizes all of the resources in its habitat, forcing other species to migrate.

C. A community whose members work together utilizing all existing resources and migratory routes.

D. The largest organisms in a species receive the only breeding opportunities.


Example Five

A small population of chimpanzees lives in a habitat that undergoes no changes for a long period. How will genetic drift probably affect this population? 

A. It will accelerate the appearance of new traits.

B. It will promote the survival of chimpanzees with beneficial traits.

C. It will increase the number of alleles for specific traits.

D. It will reduce genetic diversity.


Example Six

A small portion of the population that is geographically isolated from the rest of the population runs the risk of decreased.

A. genetic drift

B. mutation rate

C. natural selection

D. genetic variation


Example Seven

In his book On the Origin of the Species, Charles Darwin described how species change over time. Which of the following is NOT part of his observations that describes the mechanisms of natural selection? 

A. Organisms produce more offspring than can survive.

B. Disease and natural disaster will limit population growth.

C. Species today descended with modifications from ancestral species.

D. Organisms with advantages will survive and reproduce.


Example Eight

Theodosius Dobzhansky discovered that successful species tend to have a wide variety of genes that do not appear to be useful to the species in its present environment. What did this discovery help explain about genetics and the changes that occur in a species over time? 

A. Environments with more organisms tend to have more successful species.

B. Species with greater genetic diversity adapt more easily to changing environments.

C. Changing environments prevent species from adapting and surviving.

D. Species in a stable environment are more resistant to a changing environment.


video tutorials.jpg

Introduction to Natural Selection

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How Does Evolution Really Work?

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Natural Selection and the Owl Butterfly

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Natural Selection

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Genetic Drift

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Gene Flow

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In Your Book

General Biology - Chapter 11, pg. 326

Honors Biology - Chapter 17, pg. 404

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