31. Which one of the following statements is NOT true?
(A) Not every organism is able to exchange gas, nutrients, and waste with its environment directly.
(B) Some small molecules can move between cells and their surroundings by diffusion.
(C)Both arthropods and human beings have closed circulatory systems.
(D) A circulatory system includes a circulatory fluid, a set of interconnecting vessels, and a muscular pump.
(E)All of the above.

27. Bacterial conjugation is an example of _______ .(A) Transduction (B) Vertical gene transfer (C)Horizontal gene transfer (D) Bacterial transformation (E)None of the above.

28. Which enzyme is responsible for reverse transcription in retroviruses? (A) RNA polymerase (B) DNA polymerase (C)Reverse transcriptase (D) Ligase (E)Protease

29. Which of the following distinguishes cardiac muscle from both smooth and skeletal muscles? (A) Its cells contract. (B) Its cells are striped. (C)It generally cannot be contracted at will. (D) It generally can be contracted at will. (E)Its cells are branched.

30. Which of the following organs belongs to both the lymphatic and endocrine systems? (A) Pancreas (B) Kidney (C)Thymus (D) Spleen (E)Thyroid gland

32. Which of the following is an example of a tissue? (A) blood (B) the heart (C)a red blood cell (D) the respiratory system (E)the spleen

33. _______ produces the alkaline solution to neutralize the acidity of chyme. (A) Pancreas (B) Liver (C)Gallbladder (D) Small intestine (E)Stomach

34. The _______ carries nutrient-rich blood from the capillaries of the villi to the liver, then to the heart. (A) hepatic portal artery (B) hepatic portal vein (C)superior vena cava (D) hepatic vein (E)common carotid artery

35. Which one of the following statements is NOT true? (A) Fish gills use a countercurrent exchange system to increase blood flow. (B) In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface. (C)In human lungs, cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx. (D) Respiratory surfaces are always thin and moist. (E)All of the above.

36. Which one is secreted by cytotoxic T cells? (A) histamine (B) perforin (C)IgG (D) IL-1β (E)None of the above.

37. Which of the following is true of innate behaviors? Innate behaviors __________.(A) are only weakly influenced by genes (B) occur in invertebrates and some vertebrates but not mammals (C)are limited to invertebrate animals (D) are expressed in most individuals in a population (E)None of the above.