AP Biology Exam Question and Answers Verified 100% A+ 2024, With Rationale.

AP Biology Exam Question and Answers Verified 100% A+ 2024, With Rationale. The resting membrane potential depends on which of the following? I. Active transport II. Selective permeability III. Differential distribution of ions across the axonal membrane A. III only B. I and II only C. II and III only D. I, II, and III D The resting potential depends on active transport (the Na+K+-ATPase pump) and the selective permeability of the axon membrane to K+ than to Na+, which leads to a differential distribution of ions across the axonal membrane. The Krebs cycle in humans occurs in the A. mitochondrial matrix B. inner mitochondrial membrane C. outer mitochondrial membrane D. intermembrane space A The Krebs cycle occurs in the mitochondrial matrix. Don't forget to review the site of each stage of aerobic respiration. Glycolysis, the first step in aerobic respiration, occurs in the cytoplasm. The electron transport chain occurs along the inner mitochondrial membrane. Oxidative phosphorylation occurs as protons (H+ ions) move from the intermembrane space to the mitochondrial matrix. A heterotroph A. obtains its energy from sunlight, harnessed by pigments B. obtains its energy by oxidizing organic molecules C. makes organic molecules from CO2 D. obtains its energy by consuming exclusively autotrophs B A heterotroph obtains its energy from organic molecules. An autotroph obtains energy from sunlight utilizing pigments such as chlorophyll, and uses CO2 and water to make organic molecules. Therefore, (A) and (C) can be eliminated. Heterotrophs can obtain their energy from ingesting autotrophs, but they can also consume other heterotrophs. Regarding meiosis and mitosis, one difference between the two forms of cellular reproduction is that in meiosis A. there is one round of cell division, whereas in mitosis there are two rounds of cell division B. separation of sister chromatids occurs during the second division, whereas in mitosis separation of sister chromatids occurs during the first division C. chromosomes are replicated during interphase, whereas in mitosis chromosomes are replicated during prophase D. spindle fibers form during prophase, whereas in mitosis the spindle fibers form during metaphase B In meiosis, the sister chromatids separate during the second metaphase of meiosis (Meiosis II), whereas the sister chromatids separate during metaphase of mitosis. A feature of amino acids NOT found in carbohydrates is the presence of A. carbon atoms B. oxygen atoms C. nitrogen atoms D. hydrogen atoms C Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen, so eliminate (A), (B), and (D). Don't forget to associate amino acids with nitrogen because of the amino group (NH2). Which of the following is NOT a characteristic of bacteria? A. Circular double-stranded DNA B. Membrane-bound cellular organelles C. Plasma membrane consisting of lipids and proteins D. Ribosomes that synthesize polypeptides B Unlike eukaryotes, prokaryotes (which include bacteria) do not contain membrane-bound organelles. Bacteria contain circular double-stranded DNA, ribosomes, and a cell wall, so (A) and (D) are incorrect. Also eliminate (C) because bacterial cell membranes are made up of a bilipid layer with proteins interspersed. Which of the following best explains why a population is described as the evolutionary unit? A. Genetic changes can only occur at the population level. B. The gene pool in a population remains fixed over time. C. Natural selection affects individuals, not populations. D. Individuals cannot evolve, but populations can. D Populations can be described as the evolutionary unit because changes in the genetic makeup of populations can be measured over time. Eliminate (A), as genetic changes occur only at the individual level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in a population. However, this statement does not explain why the population is the evolving unit, so (B) is incorrect. Choice (C) is true but does not address the question. The endocrine system maintains homeostasis using many feedback mechanisms. Which of the following is an example of positive feedback? A. Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk production. B. An enzyme is allosterically inhibited by the product of the reaction it catalyzes. C. When ATP is abundant the rate of glycolysis decreases. D. When blood sugar levels decrease to normal after a meal, insulin is no longer secreted. A Positive feedback occurs when a stimulus causes an increased response. Choices (B), (C), and (D) are examples of negative feedback. A large island is devastated by a volcanic eruption. Most of the horses die except for the heaviest males and heaviest females of the group. They survive, reproduce, and perpetuate the population. Since weight is highly heritable and the distribution of weights approximates a binomial distribution, the offspring of the next generation would be expected to have A. a higher mean weight compared with their parents B. a lower mean weight compared with their parents C. the same mean weight as members of the original population D. a higher mean weight compared with members of the original population D The mean weight of the offspring in the next generation will be heavier than the mean weight of the original population because all the lighter horses in the original population died off. The normal distribution for weight will therefore shift to the heavier end (to the right of the graph). During the period when life is believed to have begun, the atmosphere on primitive Earth contained abundant amounts of all the following gases EXCEPT A. oxygen B. hydrogen C. ammonia D. methane A The primitive atmosphere lacked oxygen (O2). It contained methane (CH4), ammonia (NH3), and hydrogen (H2). Villi and microvilli are present in the small intestine and aid in reabsorption by A. increasing the surface area of the small intestine B. decreasing the surface area of the small intestine C. making the small intestine more hydrophilic D. making the small intestine more hydrophobic A Villi and microvilli are fingerlike projections present in the small intestine that dramatically increase the surface area available for nutrient absorption. Which of the following does NOT take place in the small intestine? A. Pancreatic lipase breaks down fats to fatty acids and glycerol. B. Pepsin breaks down proteins to amino acids. C. Pancreatic amylase breaks down carbohydrates into simple sugars. D. Bile emulsifies fats into smaller fat particles. B Pepsin works in the stomach (not the small intestine) to break down proteins to peptides. Complete digestion occurs in the small intestine. Pancreatic lipase breaks down fats into three fatty acids and glycerol, so eliminate (A). Pancreatic amylase breaks down carbohydrates into simple sugars, so (C) can also be eliminated. Bile emulsifies lipids and makes them more accessible to lipase, so get rid of (D). In animal cells, which of the following represents the most likely pathway that a secretory protein takes as it is synthesized in a cell? D Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with ribosome. So eliminate (A) and (C). The polypeptide then moves through the rough ER to the Golgi apparatus, where it is modified and packaged into a vesicle. The vesicle then floats to the plasma membrane and is secreted. Choice (D) is your answer. Which of the following adaptive features would least likely be found in an animal living in a hot arid environment? A. Long loops of Henle to maximize water reabsorption B. Storage of water in fatty tissues C. Large ears to aid in heat dispersion D. Short loops of Henle to maximize water secretion D The main challenge for organisms residing in hot arid environments is water loss. Long loops of Henle and storage of water in fatty tissues conserve water resources and large ears help disperse heat. Secretion is the elimination of water in the kidneys, which would not be advantageous for an organism in a dry environment. Which of the following best accounts for the ability of legumes to grow well in nitrogen-poor soils? A. These plants make their own proteins. B. These plants have a mutualistic relationship with nitrogen-fixing bacteria. C. These plants are capable of directly converting nitrogen gas into nitrates. D. These plants do not require nitrogen to make plant proteins. B Legume plants are able to live in nitrogen-poor soil because they obtain nitrogen from nitrogen-fixing bacteria. These plants cannot make their own proteins without nitrogen from nitrogen-fixing bacteria, so eliminate (A), (C), and (D). All of the following are examples of events that can prevent interspecific breeding EXCEPT A. the potential mates experience geographic isolation B. the potential mates experience behavioral isolation C. the potential mates have different courtship rituals D. the potential mates have similar breeding seasons D If potential mates have similar breeding seasons they will most likely mate. Use common sense to eliminate the other answer choices. If the organisms don't meet, they won't reproduce; eliminate (A). Also eliminate (B) and (C): If potential mates do not share the same behaviors (such as courtship rituals), they may not mate. Transpiration is a result of special properties of water. The special properties of water include all of the following EXCEPT A. cohesion B. adhesion C. capillary action D. hydrophobicity D Cohesion, adhesion, and capillary action are special properties of water that are necessary for transpiration to occur. Water is a hydrophilic, polar molecule. A plant grows in the opposite direction of the gravitational force. This is an example of A. positive thignotropism B. negative phototropism C. positive phototropism D. negative gravitropism D Tropism describes the reaction of plants to a stimulus. Gravitropism specifies a reaction to gravity, and negative specifies that the reaction is away from the stimulus. In most ecosystems, net primary productivity is important because it represents the A. energy available to producers B. total solar energy converted to chemical energy by producers C. biomass of all producers D. energy available to heterotrophs D The net primary productivity is what the energy producers have left for storage after their own energy needs have been met. Energy stored = (Total energy produced) - (energy used in cellular respiration). Choice (A) is incorrect; it is not the energy available to producers. You can also eliminate (B) because it is not the total chemical energy in producers—it's the gross primary productivity. Get rid of (C) as well because it is not the biomass (total living material) among producers. Hawkmoths are insects that are similar in appearance and behavior to hummingbirds. Which of the following is LEAST valid? A. These organisms are examples of convergent evolution. B. These organisms were subjected to similar environmental conditions. C. These organisms are genetically related to each other. D. These organisms have analogous structures. C Choice (A) and (B) are incorrect: These organisms exhibit the same behavior because they were subjected to the same environmental conditions and similar habitats. This is an example of convergent evolution. However, they are not genetically similar, so (C) is the answer. (One is an insect and the other a bird.) They are analogous, so (D) is also incorrect. They exhibit the same function but are structurally different. Which of the following describes a symbiotic relationship? A. A tapeworm feeds off of its host's nutrients causing the host to lose large amounts of weight. B. Certain plants grow on trees in order to gain access to sunlight, not affecting the tree. C. Remora fish eat parasites off of sharks; the sharks stay free of parasites, and the remora fish are protected from predators. D. Meerkats sound alarm calls to warn other meerkats of predators. C A symbiotic relationship is a relationship among two organisms in which both benefit. Choice (A) describes parasitism, and (B) describes commensalism. Choice (D) is an example of altruistic behavior. Destruction of all beta cells in the pancreas will cause which of the following to occur? A. Glucagon secretion will stop and blood glucose levels will increase. B. Glucagon secretion will stop and blood glucose levels will decrease. C. Glucagon secretion will stop and digestive enzymes will be secreted. D. Insulin secretion will stop and blood glucose levels will increase. D Beta cells secrete insulin. Destruction of beta cells in the pancreas will halt the production of insulin. Therefore, eliminate (A), (B), and (C). This will lead to an increase in blood glucose levels. All of the following are stimulated by the sympathetic nervous system EXCEPT A. dilation of the pupil of the eye B. constriction of blood vessels C. increased secretion of the sweat glands D. increased peristalsis in the gastrointestinal tract D The sympathetic division is active during emergency situations. This leads to a decrease in peristalsis in your gastrointestinal tract. (Your stomach shuts down.) Stimulation of the sympathetic nervous system leads to (A), pupils dilating, (B), peripheral blood vessels constricting, and (C), sweating. The calypso orchid, Calypso bulbosa, grows in close association with mycorrhizae fungi. The fungi penetrate the roots of the flower and take advantage of the plant's food resources. The fungi concentrate rare minerals, such as phosphates, in the roots and make them readily accessible to the orchid. This situation is an example of A. parasitism B. commensalism C. mutualism D. endosymbiosis C This is an example of mutualism. Both organisms benefit. Choice (A), parasitism, is an example of a symbiotic relationship in which one organism benefits and the other is harmed. Choice (B), commensalism, is when one organism benefits and the other is unaffected. Choice (D), endosymbiosis, is the idea that some organelles originated as symbiotic prokaryotes that live inside larger cells. The synthesis of new proteins necessary for lactose utilization by the bacterium E. coli using the lac operon is regulated A. by the synthesis of additional ribosomes B. at the transcription stage C. at the translation stage D. by differential replication of the DNA that codes for lactose-utilizing mechanisms B This question tests your understanding of what stage is responsible for the synthesis of new proteins for lactose utilization. The region of bacterial DNA that controls gene expression is the lac operon. Structural genes will be transcribed to produce enzymes, which produce an mRNA involved in digesting lactose. Which of the following statements about trypsin is NOT true? A. It is an organic compound made of proteins. B. It is a catalyst that alters the rate of a reaction. C. It is operative over a wide pH range. D. The rate of catalysis is affected by the concentration of substrate. C Trypsin is an enzyme, which are proteins and organic catalysts that speed up reactions without altering them. They are not consumed in the process. Therefore, you can eliminate (A) and (B). The rate of reaction can be affected by the concentration of the substrate up to a point, so (D) can be eliminated. The energy given up by electrons as they move through the electron transport chain is used to A. break down glucose B. make glucose C. produce ATP D. make NADH C Electrons passed down along the electron transport chain from one carrier to another lose energy and provide energy for making ATP. Glucose is decomposed during glycolysis, but this process is not associated with energy given up by electrons; eliminate (A). Glucose is made during photosynthesis, so eliminate (B). NADH is are energy-rich molecule, which accepts electrons during the Krebs cycle. Therefore, (D) is incorrect as well. If a photosynthesizing plant began to release 18O2 instead of normal oxygen, one could most reasonably conclude that the plant had been supplied with A. H2O containing radioactive oxygen B. CO2 containing radioactive oxygen C. C6H12O6 containing radioactive oxygen D. NO2 containing radioactive oxygen A The oxygen released during the light reaction comes from the splitting of water. (Review the reaction for photosynthesis.) Therefore, water must have originally contained the radioactive oxygen. Carbon dioxide is involved in the dark reaction and produces glucose, so eliminate (B). Glucose is the final product and would not be radioactive unless carbon dioxide was the radioactive material, so (C) is incorrect. Finally, eliminate (D), because nitrogen is not part of photosynthesis. All of the following statements describe the unique characteristics of water EXCEPT A. it is a polar solvent B. it forms hydrogen bonds with disaccharides C. it can dissociate into hydrogen ions and hydroxide ions D. it is a hydrophobic solvent D Hydrophobic means "water fearing," so water cannot be a hydrophobic solvent. Water is a polar solvent; it contains both negatively and positively charged ends that can form hydrogen bonds with other polar substances. Water can break up into H+ and OH- ions. Chemical substances released by organisms that elicit a physiological or behavioral response in other members of the same species are known as A. auxins B. hormones C. pheromones D. enzymes C Pheromones act as sex attractants, alarm signals, or territorial markers. Auxins are plant hormones that promote growth, so eliminate (A). Hormones are chemical messengers that produce a specific effect on target cells within the same organism, so eliminate (B). Enzymes are catalysts that speed up reactions, so eliminate (D). Homologous structures are often cited as evidence for the process of natural selection. All of the following are examples of homologous structures EXCEPT A. the wings of a bird and the wings of a bat B. the flippers of a whale and the arms of a man C. the pectoral fins of a porpoise and the flippers of a seal D. the forelegs of an insect and the forelimbs of a dog D Homologous structures are organisms with the same structure but different functions. The forelegs of an insect and the forelimbs of a dog are not structurally similar. (One is an invertebrate and the other a vertebrate.) They do not share a common ancestor. However, both structures are used for movement. All of the other examples are vertebrates that are structurally similar. The sliding action in the myofibril of skeletal muscle contraction requires which of the following? I. Ca2+ II. ATP III. Actin A. I only B. II only C. II and III D. I, II, and III D Muscle contractions require calcium ions, so (I) is required. You need energy order to have a muscle contraction, so (II) is required. And actin is one of the proteins involved in muscle contractions, so (III) is required. The answer is (D).