30. Which of the following represents a difference between viruses and viroids?
(A) Viruses contain introns; viroids have only exons.
(B) Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.
(C) Viruses always have genomes composed of DNA, whereas viroids always have genomes composed of RNA.
(D) Viruses have capsids composed of protein, whereas viroids have no capsids.
(E) Viruses cannot pass through plasmodesmata; viroids can.

26. Assume that excessive consumption of ethanol increases the influx of negative chloride ions into "common sense" neurons whose action potentials are needed for you to act appropriately and not harm yourself or others. Thus, any resulting poor decisions associated with ethanol ingestion are likely due to (A) increased membrane depolarization of "common sense" neurons. (B) more action potentials in your "common sense" neurons. (C) decreased membrane depolarization of "common sense" neurons. (D) fewer IPSPs in your "common sense" neurons. (E) more EPSPs in your "common sense" neurons.

27. Which is one of the two laws of inheritance identified by Mendel? (A) The law of priority. (B) The law of independent assortment. (C) The law of neutralism. (D) The law of paternity. (E) The law of polarity.

28. In glycolysis, for each molecule of glucose oxidized to pyruvate (A) 4 molecules of ATP are used and 2 molecules of ATP and 4 molecules of NADH are produced. (B) 2 molecules of ATP are used and 4 molecules of ATP and 2 molecules of NAD are produced. (C) 2 molecules of ATP are used and 4 molecules of ATP and 2 molecules of NADH are produced. (D) 2 molecules of ATP are used and 4 molecules of ATP and 1 molecules of NADH are produced. (E) 2 molecules of ATP are used and 2 molecules of ATP and 2 molecules of NADH are produced.

29. In vertebrate animals, brown fat tissue's color is due to abundant mitochondria. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few mitochondria. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue? (A) to allow other membranes of the cell to perform mitochondrial function. (B) to increase the rate of oxidative phosphorylation from its few mitochondria. (C) to allow the animals to regulate their metabolic rate when it is especially hot. (D) to regulate temperature by converting energy from NADH oxidation to heat. (E) to increase the production of ATP synthase.

31. What may lead to alternations of chromosome number? (A) nondisjunction during meiosis. (B) hybridization. (C) chromosome breakage. (D) genetic recombination. (E) genetic exchange.

32. A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of (A) the influence of environment on development. (B) paedomorphosis. (C) a change in a developmental gene or in its regulation that altered the spatial organization of body parts. (D) heterochrony. (E) gene duplication.

33. The chain lengths in food webs are limited by (A) the amount of energy such as sunlight available in an ecosystem. (B) the efficiency of energy transfers that occur between trophic levels. (C) catastrophes. (D) all of the above. (E) A and B only.

34. _________ is the ability of a community or ecosystem to maintain structure in the face of potential disturbance. (A) Resilience (B) Elasticity (C) Resistance (D) Plasticity (E) Flexibility

35. Some bacteria are metabolically active in hot springs because (A) they are able to maintain a cooler internal temperature. (B) high temperatures make catalysis unnecessary. (C) their enzymes have high optimal temperatures. (D) their enzymes are completely insensitive to temperature. (E) they use molecules other than proteins or RNAs as their main catalysts.

36. The Shannon diversity index is a measure of (A) the number of different species in a community. (B) the abundance of a species in a community. (C) the types of species found in a typical climate. (D) the number of different species and their relative abundance in a community. (E) the distribution of members of a species in a community.