Every year, adult salmon swim upstream to a spawning area. To get to the area, salmon have to swim against strong currents for a long time. Only the strongest salmon successfully complete the journey. What concept is represented in this example?

• climax community

• succession

• mutualism

• survivial of the fittestsurvival

Which most likely explains the change in the mouse population?

• The lighter mice were more visible to predators than the darker mice, which resulted in fewer of the lighter mice reaching reproductive age.

• The darker mice did not require as many resources as the lighter mice, which resulted in more of the darker mice reaching reproductive age.

• The lighter mice were less successful in finding food in the environment than the darker mice, which resulted in fewer of the lighter mice being able to survive.

• The darker mice were able to find more nesting places in the environment than the lighter mice, which resulted in more of the darker mice being able to survive.

A new species of finch with long beaks is introduced to an island with a limited food supply. The long beaks allow the finches to gather food more easily compared to the native finches. What will be the most likely outcome in 30 years?

• Both finch populations will increase.

• The native-finch population will decrease and the long-beak finch population will increase.

• The native-finch population will increase and the long-beak finch population will decrease.

• Both finch populations will decrease.

Certain types of tree frogs live in habitats with a lot of green, leafy vegetation. What color of tree frog would have the best chance of passing on its traits to successive generations in this habitat?

• yellow

• blue

• black

• green

Why do characteristics that are not beneficial to a species tend to decrease in frequency over time?

• The characteristics have a high survival rate.

• The characteristics are inherited by other individuals.

• The characteristics have a low survival rate.

• The characteristics take time to spread into the population.

Four hundred beetles of the same species were sprayed with an insecticide. Several weeks later, nearly all the beetles were dead. A few, however, survived. Which statement best describes the future generations of these beetles?

• The future generations of beetles will likely survive the insecticide if it is sprayed again. 

• The beetles in future generations will have no immunity to the insecticide. 

• The majority of beetles in future generations will also die from the insecticide. 

• The surviving beetles will not pass on their favorable traits to future generations. 

In some species of birds, males with bright colors and long feathers are usually picked by dull-colored, female birds for mating. If this is true, what will happen to the males in future generations?

• There will be a greater population of dull-colored males.

• There will be a greater population of brightly colored males. 

• There will be equal numbers of dull-colored and brightly colored males. 

• There will be a decline in brightly colored males each generation. 

A population of dark- and light-colored mice move into a new area that has a lot of dark-colored rocks. The light mice are more easily visible to hawks hunting for them. What will happen to the genes of this mice population over time?

• The genes for the mice will stay the same throughout successive generations.

• The genes for light-colored fur will increase with every generation.

• The genes for dark-colored fur will increase with every generation.

• The genes for dark-colored fur will slowly disappear through successive generations. 

According to Darwin's theory of evolution, differences in the fossils between species may be the result of

• natural selection

• mutagens

• the use and disuse of body structures

• the transmission of acquired traits

Which of the following is true of certain physical characteristics that are passed from generation to generation?

• All of the physical characteristics passed down are needed for the survival of the species.

• Many of the physical characteristics passed down are needed for the survival of the species.

• Many of the physical characteristics are passed down, but none of them are needed for the survival of the species.

• All of the physical characteristics are passed down, but none of them are needed for the survival of the species.