Natural Selection

Which of the following best illustrates natural selection?

• An organism with favorable genetic variations will tend to survive and breed successfully. 
• A population monopolizes all of the resources in its habitat, forcing other species to migrate.
• A community whose members work together utilizing all existing resources and migratory routes.
• The largest organisms in a species receive the only breeding opportunities.

 According to fossil records, the horses that lived 50 million years ago were much smaller, weaker and slower than modern horses. Which process is most likely responsible for the changes that have led to the increased size, strength, and speed in horses?

• commensalism
•  inbreeding
• migration 
• evolution by natural selection

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?

• Organisms produce more offspring than can survive.
• Disease and natural disaster will limit population growth.
• Species today descended with modifications from ancestral species.
• Organisms with advantages will survive and reproduce.

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?

• available niches
• existing predators
• chromosome number
• available food resources

Mutations within a DNA sequence are

• natural processes that produce genetic diversity
• natural processes that always affect the phenotype
• unnatural processes that always affect the phenotype
• unnatural processes that are harmful to genetic diversity

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?

• It will accelerate the appearance of new traits.
• It will promote the survival of chimpanzees with beneficial traits.
• It will increase the number of alleles for specific traits.
  
•  It will reduce genetic diversity.

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?

• Environments with more organisms tend to have more successful species.
• Species with greater genetic diversity adapt more easily to changing environments.
•  Changing environments prevent species from adapting and surviving.
•  Species in a stable environment are more resistant to a changing environment.

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?

• fewer mutations
• limited food resources
• limited beak variations
• overproduction of offspring

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

• genetic drift
• mutation rate
• natural selection
• genetic variation

Survival of at least a few members of a population after a major environmental change is most dependent on

• the population having an individual that is adapted to the original environment
• the population having an individual that is adapted to great changes in the temperature in its environment
• variations in many different traits in many individuals in the population
• no variations in the color of the fur, skin, or feathers of the individuals in the population