34. The ability of the mammalian kidney to produce urine that is much more concentrated than blood is primarily due to:
(A) The active transport of water in the collecting duct.
(B) The presence of a short loop of Henle in cortical nephrons.
(C) The establishment and maintenance of a steep osmolarity gradient in the renal medulla by the loops of Henle of juxtamedullary nephrons.
(D) The selective reabsorption of all solutes, including urea, in the proximal tubule.

30. Imagine you want to study a human crystallin protein. To obtain a sufficient amount of this protein, you decide to clone its gene. Assuming you know the gene sequence, which approach would allow you to produce the protein in a suitable system like bacteria?(A) Isolate lens cells, extract genomic DNA, and insert the entire gene directly into a bacterial expression vector.(B) Isolate lens cells, extract mRNA, use reverse transcriptase to make cDNA, and insert the cDNA into a bacterial expression vector.(C) Directly synthesize the protein from its known amino acid sequence using a chemical synthesizer.(D) Use PCR to amplify the gene from a brain cell and insert it into a eukaryotic yeast expression vector.

31. Which statement accurately distinguishes Ulva from Caulerpa regarding their multicellular organization?(A) Ulva is a colonial protist, while Caulerpa is a true multicellular alga with specialized tissues.(B) Ulva forms true multicellular bodies through cell division and differentiation, whereas Caulerpa achieves largesize via repeated nuclear division without cytoplasmic division, making it not truly multicellular.(C) Caulerpa exhibits alternation of generations, while Ulva only has a single-celled haploid stage.(D) Both are truly multicellular, but Ulva has a simpler organizational plan compared to Caulerpa's complex thallus.

32. All chordates, at some point during their life cycle, are characterized by which of the following derived traits?(A) Notochord, dorsal hollow nerve cord, pharyngeal slits or clefts, and muscular post-anal tail.(B) Jaws, mineralized skeleton, lungs, and four limbs.(C) Vertebrae, cranium, a two-chambered heart, and paired fins.(D) Hair, mammary glands, endothermy, and a highly developed brain.

33. Put the following milestones in animal evolution in order from oldest to most recent: (a) origin of mammals, (b) earliest evidence of terrestrial arthropods, (c) Ediacaran fauna, (d) extinction of large, nonflying dinosaurs.(A) c, b, a, d (B) a, b, c, d (C) d, c, b, a (D) c, a, b, d

35. What are the four main stages of food processing in animals, in order?(A) Digestion, ingestion, absorption, elimination(B) Ingestion, digestion, absorption, elimination(C) Ingestion, absorption, digestion, elimination(D) Digestion, absorption, ingestion, elimination

36. Given that sponges lack true tissues and organs, how do they accomplish vital functions such as gas exchange, nutrient transport, and waste disposal?(A) They possess a gastrovascular cavity that handles all internal transport.(B) Through specialized, but rudimentary, circulatory and excretory systems.(C) By simple diffusion across the surfaces of their cells, which are in direct contact with the water environment.(D) They rely on symbiotic bacteria to perform these functions for them.

37. In a closed circulatory system, where does chemical exchange occur between the blood and interstitial fluid?(A) Arteries (B) Veins (C) Capillaries (D) Ventricles

38. If a plant detects increased levels of light reflected from the leaves of encroaching neighbors, it typically responds with stem elongation, production of erect leaves, and reduced lateral branching. How do these responses help the plant compete?(A) They allow the plant to store more water in its stems.(B) They enhance the plant's ability to produce defensive chemicals.(C) They enable the plant to grow taller and capture more light, reducing shading from competitors.(D) They promote earlier flowering and seed production.

39. Which type of immunity is active immediately upon exposure to a pathogen and is the same whether or not the pathogen has been encountered previously?(A) Adaptive immunity (B) Acquired immunity(C) Innate immunity (D) Humoral immunity

40. If a complete ring of bark is removed from around a tree trunk (a technique called girdling), the tree will die, but typically slowly (in weeks) rather than quickly (in days). Which of the following best explains this observed timeframe?(A) Girdling only disrupts the xylem, and the tree's roots can store enough water to survive for a few days.(B) Girdling severs the phloem, cutting off sugar transport to the roots, which leads to root starvation and eventual death, a process that takes weeks.(C) Girdling directly kills all the living cells in the trunk, but the leaves can continue photosynthesis until stored carbohydrates are depleted.(D) The tree can regenerate the phloem within days, thus preventing rapid death, but the energy cost is high.