The graph shows how the activity of an enzyme changes at different temperatures. Which statement best describes what happens to the enzyme when the temperature of the reac-
tion increases to 45 degrees Celsius?
X = optimal temperature
Rate of reaction
20 30 40 50
Temperature / "C
А
The enzyme is used up and the reaction stops.
B
The enzyme begins to decrease the rate of the reaction.
С
The enzyme continues to increase the rate of the reaction.
D
The enzyme changes shape and can no longer speed up the reaction.

Examine the two squirrel populations in the accompanying figure. the populations are separated by a geographic barrier. if after a long period of time the two species are no longer separated, what evidence is needed to determine if speciation has occurred? the figure shows two populations of squirrels separated by a geographic barrier. examine the two squirrel populations in the accompanying figure. the populations are separated by a geographic barrier. if after a long period of time the two species are no longer separated, what evidence is needed to determine if speciation has occurred? the figure shows two populations of squirrels separated by a geographic barrier. polyploidy is creating new species. the two populations are not interbreeding freely. hybrid offspring of the two populations begin to appear. one species will increase into a population size twice as large as the other species.

Match the description of each organism to the appropriate category

Explain how scientists use geologic time to determine the age of landforms.