Which of the following are the first organisms to have a one-way digestive system? A. roundworms
B. flatworms
C. jellyfish
D. sponges

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.

In which situations is the principle of cross-cutting relationship useful in determining relative age?

If bacteria are much too small to see, what is one reason why can we see colonies in the petri dishes that have plenty of food to eat after only a few days?