Which of the following steps has not yet been accomplished by scientists studying the origin of life?a. synthesis of small RNA polymers by ribozymesb. formation of molecular aggregates with selectively permeable membranesc. formation of protocells that use DNA to direct the polymerization of amino acidsd. abiotic synthesis of organic molecules

Adaptive radiations can be a direct consequence of three of the following four factors. Select the exception.a. vacant ecological nichesb. genetic driftc. colonization of an isolated region that contains suitable habitat and few competitor speciesd. evolutionary innovation

Ancient photosynthetic prokaryotes were very important in the history of life because theya. 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 (see Ch. 3, Figure 3.2) would likely be found in the portion that crosses the lipid bilayer? a. acidicb. basicc. polar unchargedd. nonpolar

Scientists studying the origin of life have accomplished which of the following steps?(A)abiotic synthesis of protocells with self-replicating, catalytic RNA(B)formation of vesicles that use RNA as a template for DNA synthesis(C)formation of protocells that use DNA to direct the polymer-ization of amino acids(D)abiotic synthesis of RNA's bases (A, C, G, U)

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.

Adaptive radiations may be promoted by all of the following except one. Which one?a. mass extinctions that result in vacant ecological nichesb. colonization of an isolated region with few competitorsc. a gradual change in climated. 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; and (3) a lactose carrier.