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.

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.

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.

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.

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.

37. Divergence in morphology that is a result of competition between species is termed (A) competitive exclusion. (B) resource partitioning. (C) character displacement. (D) amensalism. (E) mutualism.

38. When each female in the population mates with several males, but each male mates with only one female, the mating system is referred to as (A) polygamy. (B) polyandry. (C) polygyny. (D) monogamy. (E) harem mating.

39. Which of the following cannot be determined using a fecundity schedule combined with a life table? (A) per capital rate of increase. (B) net reproductive rate. (C) mean generation time. (D) dispersal rates. (E) geometric rate of increase.