39. The descending portion of the loop of Henle is
(A)permeable to water and impermeable to sodium.
(B)permeable to water and permeable to sodium.
(C)impermeable to water and permeable to sodium.
(D)impermeable to water and impermeable to sodium.
(E)the site of active transport of water

35. Estivation in animals is an example of what specific phenomenon? (A)sleep (B)rest (C)torpor (D)hiding (E)activity

36. ______ do NOT depend on the circulatory system to deliver oxygen to the tissues. (A)Insects (B)Molluscs (C)Mammals (D)Birds (E)Amphibians

37. The volume of air normally breathed in and out of the lungs in a single breath at rest is referred to as the _____ volume. (A)tidal (B)total (C)reserve (D)inspiratory reserve (E)expiratory reserve

38. The bulk of the reabsorption of useful materials by the kidney takes place in the (A)renal corpuscle. (B)proximal convoluted tubule. (C)loop of Henle. (D)distal convoluted tubule. (E)collecting ducts.

40. ________ is a water-soluble hormone derived from the nervous system that regulates blood volume and blood pressure? (A)Antidiuretic hormone (B)Aldosterone (C)Cortisol (D)Oxytocin (E)Adrenocorticotropic hormone

41. The ectoderm is to the central nervous system as the mesoderm is to the (A)epidermis. (B)respiratory tube. (C)digestive tract. (D)skeletal muscle. (E)peripheral nervous system. 

42. The clonal selection theory is an explanation for (A)how a single type of stem cell can produce both red blood cells and white blood cells. (B)how antibody proteins can be molded to fit antigens after the antigen interacts with the antibody-producing type of cell. (C)how an antigen can induce the multiplication of very few cells to result in production of high levels of specific antibodies. (D)how HIV can disrupt the immune system. (E)how macrophages can recognize specific T cells and B cells.

43. Which of following is NOT true? (A)Amino acid neurotransmitters are active in the vertebrate CNS and PNS. (B)Binding of GABA to receptors in postsynaptic cells increases membrane permeability to potassium. (C)The biogenic amine serotonin made from tryptophan. (D)In the PNS, CO acts as an inhibitory neurotransmitter that hyperpolarized the plasma membrane of intestinal smooth muscle cells. (E)In the CNS, the amino acid glutamate is the most common neurotransmitter.

44. Patterns of species change and succession are one focus of (A)behavioral ecology. (B)environmental science. (C)biological control. (D)community ecology. (E)physiological ecology.

45. What is the process through which many animals develop irreversible species-specific behavior patterns? (A)altruism (B)taxis (C)operant conditioning (D)cognitive learning (E)imprinting