How many different species have been identified by science? How many are estimated to exist?

If the feathers of extant flying birds originally arose as thermoregulatory devices in ancestral reptiles, then flight feathers could be accurately described as __________.

In the species selection model, __________ is to macroevolution as __________ is to microevolution.

Which of the listed examples is a current hypothesis regarding the Cambrian explosion?

Which of the following occurred during the Mesozoic era?

Fossilized stromatolitesa. formed around deep-sea vents.b. resemble structures formed by bacterial communities that are found today in some shallow marine bays.c. provide evidence that plants moved onto land in the company of fungi around 500 million years ago.d. contain the first undisputed fossils of eukaryotes.

A cell is placed in a solution that is hypotonic to the cell. Which of the following best describes movement of water in this situation?a. Water will only flow into the cell.b. Water will only flow out of the cell.c. Water will flow into and out of the cell, but the overall net movement will be out of the cell.d. Water will flow into and out of the cell, but the overall net movement will be into the cell.

Choose the best definition of a fossil.a. a rock that contains information about an organismb. a bone, tooth, shell, or other hard part of an organism that has been preservedc. any trace of an organism that lived in the pastd. any part of a dead organism

Which of the following results provided evidence of a discrete nuclear localization signal somewhere on the nucleoplasmin protein?a. The nucleoplasmin protein was small and easily slipped through the nuclear pore complex.b. After cleavage of the nucleoplasmin protein, only the tail segments appeared in the nucleus.c. Removing the tail from the nucleoplasmin protein allowed the core segment to enter the nucleus.d. The SRP bound only to the tail of the nucleoplasmin protein, not the core segment.