Identify the correct statement regarding trophic hormones and the regulation of body temperature.

Question 33: Trophic hormones are hormones that stimulate other endocrine glands to produce and secrete their own hormones. i. Growth hormone and prolactin: Growth hormone has some trophic effects, but prolactin is not primarily a trophic hormone for other glands. ii. Prolactin and FSH: FSH is a trophic hormone, but prolactin is not. iii. LH, TSH and ACTH: Luteinizing Hormone (LH), Thyroid-Stimulating Hormone (TSH), and Adrenocorticotropic Hormone (ACTH) are all classic examples of trophic hormones, stimulating the gonads, thyroid gland, and adrenal cortex, respectively. iv. ACTH and Human placental lactogen: ACTH is a trophic hormone, but Human placental lactogen is not. The correct option is iii. Question 34: The heat loss center in the hypothalamus is activated when the body temperature rises above the set point. Its functions are to promote heat loss and reduce heat production. i. Increases vasoconstriction: This is a heat conservation* mechanism, reducing blood flow to the skin to prevent heat loss. ii. Inhibits sweating and panting: The heat loss center stimulates* sweating and panting to increase heat loss. iii. Increases thickness of air layer by contraction of hair muscles, making hair stand erect: This is piloerection, a heat conservation* mechanism that traps an insulating layer of air. iv. Decreases metabolic activities: Reducing metabolic rate decreases the internal production of heat, thus aiding in overall heat loss. The correct statement is iv. Question 37: The "shotgun" approach in molecular biology typically refers to a method of DNA sequencing or cloning where the entire genome is randomly fragmented. i. Involves chopping up the DNA and searching for the piece with the required gene: This is a key step in shotgun cloning or sequencing. ii. Makes use of restriction endonucleases: Restriction enzymes are commonly used to cut DNA into fragments. iii. Makes use of gel electrophoresis and auto radiography: These techniques are used to separate and visualize DNA fragments, which is essential for analyzing the results of a shotgun approach. iv. Does not produce "split genes": This statement is not directly related to the methodology of the shotgun approach itself. "Split genes" refer to genes containing introns. Statements i, ii, and iii are correct. Question 38: The description indicates a chemical that binds to an enzyme at a site away from the active site and inhibits its action. i. It is an end product inhibitor: This is often true for allosteric inhibitors in metabolic pathways, where the end product inhibits an enzyme early in the pathway (feedback inhibition). ii. It is a competitive inhibitor: Competitive inhibitors bind to the active site*, which contradicts the description. iii. It binds to the allosteric site of the enzyme: The description states it binds "at a site away from the active site," which is the definition of an allosteric site. iv. It brings about a positive feedback mechanism: The chemical inhibits* the enzyme, indicating negative feedback, not positive. Statements i and iii are correct. Question 39: Cell-cell recognition involves molecules on the cell surface that act as markers for cells to identify each other. A. Carrier and channel proteins: These are primarily involved in transporting substances across the membrane. B. Glycoproteins and glycolipids: These molecules, with their carbohydrate chains extending from the cell surface, form the glycocalyx and are crucial for cell-cell recognition and adhesion. C. Glycoproteins and cholesterol: While glycoproteins are involved, cholesterol primarily regulates membrane fluidity. D. Glycerolipids: These are a type of lipid, but not the primary molecules for cell-cell recognition. The correct option is B. Question 40: Genetic drift is the random fluctuation of allele frequencies in a population. Its impact is inversely proportional to population size. A. Large populations: Genetic drift has a minimal effect in large populations because random events are averaged out. B. Changing environments: While environmental changes can drive evolution, they are not the primary factor determining the power of genetic drift. C. Small populations: In small populations, random events (like which individuals reproduce or survive) can lead to significant changes in allele frequencies, making genetic drift most powerful. D. Stable environments: Environmental stability does not directly influence the power of genetic drift. The correct option is C. Question 41: The Hardy-Weinberg principle describes a theoretical population that is not evolving, meaning allele and genotype frequencies remain constant from generation to generation. A. Degree of evolution: This is a measure, not a tool to know if evolution is occurring. B. Genetic drift: Genetic drift is a mechanism of evolution, not a tool to detect it. C. Gene pool: The gene pool is the total collection of genes in a population, but observing it alone doesn't tell you if evolution is happening without a baseline. D. Hardy Weinberg equation: By comparing observed allele and genotype frequencies to those predicted by the Hardy-Weinberg equation, scientists can determine if a population is evolving (i.e., if its frequencies deviate from equilibrium). The correct option is D. Question 42: Variations can be categorized based on their distribution in a population. A. Independent variations: This term is not standard for describing the type of variation based on gene number. B. Discontinuous variations: These are distinct categories with no intermediates (e.g., blood types), typically controlled by one or a few genes. C. Continuous variations: These show a range of phenotypes that blend into one another (e.g., height, skin color), typically controlled by multiple genes (polygenic inheritance). D. Discrete variations: This is another term for discontinuous variations. The correct option is C. 3 done, 2 left today. You're making progress.