The animals and plants of India are very different from the species in nearby Southeast Asia. Why might this be true?
a. India was once covered by oceans and Asia was not.
b. India is in the process of separating from the rest of Asia.
c. Life in India was wiped out by ancient volcanic eruptions.
d. India was a separate continent until about 45 million years ago.

Ancient photosynthetic prokaryotes were very important in the history of life because they

a. Produced the oxygen in the atmosphere.

b. Are the oldest-known archaea.

c. Were the first multicellular organisms.

d. Showed that life could evolve around deep-sea vents.

Which of the following groups of amino acid residues would likely be found in the portion that crosses the lipid bilayer?

a. Acidic

b. Basic

c. Polar uncharged

d. Nonpolar

Which of the following steps has not yet been accomplished by scientists studying the origin of life?

a. Synthesis of small RNA polymers by ribozymes

b. Formation of molecular aggregates with selectively permeable membranes

c. Formation of protocells that use DNA to direct the polymerization of amino acids

d. Abiotic synthesis of organic molecules

Adaptive radiations may be promoted by all of the following except one. Which one?

a. Mass extinctions that result in vacant ecological niches

b. Colonization of an isolated region with few competitors

c. A gradual change in climate

d. A novel adaptation

Consider the endosymbiosis theory for the origin of the mitochondrion. How did each endosymbiotic partner benefit from the relationship?

Draw and label the plasma membrane of a cell that is placed in a solution with concentrations of calcium ions and lactose that are greater than those on the inside of the cell. Use arrows to show the relevant gradients and the activity of the following membrane proteins:

(1) A pump that exports protons

(2) A calcium channel

(3) A lactose carrier

Most of the proteins that enter the nucleus possess a nuclear localization signal (NLS), even if they are small enough to pass through the nuclear pore complex unhindered. Why would a small protein have an NLS, when it naturally diffuses across the nuclear pore complex without one?