This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.
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Here are the solutions to the questions: 19. The pyramid is that of Step 1: Analyze the pyramid structure. The pyramid shows decreasing numbers at successive trophic levels (1500 at the base, then 140, 15, and 5 at the top). This represents the quantity of organisms at each level. Step 2: Evaluate the options. A. energy: Energy pyramids show energy flow, usually in units like Joules. B. biomass: Biomass pyramids show the total mass of organisms, usually in units like kg/m^2. C. numbers: Pyramids of numbers show the count of individual organisms at each trophic level. The given numbers are counts. D. herbivores: Herbivores represent a trophic level, not a type of pyramid. Step 3: Conclude the type of pyramid. Given the raw counts of organisms, this is a pyramid of numbers. The correct option is C. C. numbers 20. Which of the following organisms could occupy the position with number 5? Step 1: Identify position 5. Position 5 is the lowest level of the pyramid, which has 1500 individuals. This represents the producer trophic level. Step 2: Evaluate the options for producers. A. Grasses: Producers, typically numerous and small. B. Trees: Producers, but usually fewer in number than grasses in a typical ecosystem represented by such a pyramid. C. Eagles: Consumers (carnivores). D. Lizards: Consumers (carnivores or omnivores). Step 3: Select the most appropriate producer. Given the large number (1500) at the base, grasses are a more suitable representation of producers than trees in this context. The correct option is A. A. Grasses 21. The process by which manufactured food is transported from the leaves to the roots of plants is Step 1: Understand the question. The question asks about the transport of sugars (manufactured food) within a plant. Step 2: Define the options. A. transpiration: Loss of water vapor from leaves. B. capillarity: Movement of water in narrow tubes due to surface tension and adhesion. C. translocation: The process of transporting sugars and other organic nutrients through the phloem. D. guttation: Exudation of xylem sap from the tips or edges of leaves. Step 3: Identify the correct process. Translocation is the specific process for transporting manufactured food (sugars) from source (leaves) to sink (roots, storage organs, growing parts). The correct option is C. C. translocation 22. The statement that is not correct about exchange of gases in the lungs is Step 1: Analyze gas exchange in the lungs. Gas exchange occurs in the alveoli, which are thin-walled air sacs surrounded by capillaries. Step 2: Evaluate each statement. A. the epithelium is impermeable: This is incorrect. The alveolar epithelium is very thin and permeable to allow rapid diffusion of gases. B. gases diffuse through capillary walls: This is correct. Gases move between the alveoli and blood across the capillary walls. C. the alveoli is well supplied with blood: This is correct. A dense network of capillaries surrounds the alveoli to maximize gas exchange efficiency. D. gases diffuse through the epithelium: This is correct. Gases diffuse across the alveolar epithelium. Step 3: Identify the incorrect statement. The statement that the epithelium is impermeable is false. The correct option is A. A. the epithelium is impermeable 23. The functional unit of the kidney is Step 1: Recall kidney structure and function. The kidney filters blood to produce urine. Step 2: Define the options. A. renal vein: A blood vessel that carries deoxygenated blood away from the kidney. B. renal artery: A blood vessel that carries oxygenated blood to the kidney. C. cortex: The outer region of the kidney. D. nephron: The microscopic structural and functional unit of the kidney responsible for filtering blood, reabsorbing useful substances, and forming urine. Step 3: Identify the functional unit. The nephron is the functional unit of the kidney. The correct option is D. D. nephron 24. The chemical substance produced by endocrine glands is Step 1: Understand endocrine glands. Endocrine glands are ductless glands that secrete substances directly into the bloodstream. Step 2: Define the options. A. hormone: Chemical messengers produced by endocrine glands that regulate various bodily functions. B. trypsin: An enzyme produced by the pancreas (an exocrine and endocrine gland, but trypsin is an exocrine secretion). C. adenine: A nitrogenous base found in DNA and RNA. D. enzyme: Biological catalysts, most of which are proteins. While some hormones are proteins, enzymes are generally secreted by exocrine glands or function intracellularly. Step 3: Identify the correct substance. Endocrine glands are characterized by their production and secretion of hormones. The correct option is A. A. hormone 25. The diet that would produce the least amount of glucose is Step 1: Understand glucose production. Glucose is primarily derived from the breakdown of carbohydrates. Proteins can also be converted to glucose through gluconeogenesis, but fats generally yield very little glucose. Step 2: Evaluate the carbohydrate content of each option. A. maize flour: High in carbohydrates (starch). B. sweet bean: Contains carbohydrates and protein. C. cassava flour: High in carbohydrates (starch). D. cooked beef: Primarily composed of protein and fat, with very minimal carbohydrates. Step 3: Determine the option yielding the least glucose. Cooked beef, being predominantly protein and fat, will produce the least amount of glucose compared to the other carbohydrate-rich options. The correct option is D. D. cooked beef 26. When a nerve impulse reaches the end of an axon, a chemical substance that would be secreted by the synaptic knob is Step 1: Recall synaptic transmission. At the synapse, nerve impulses are transmitted from one neuron to another (or to an effector cell) via chemical messengers. Step 2: Define the options. A. choline: A precursor molecule for acetylcholine, not the neurotransmitter itself. B. acetylcholine: A well-known neurotransmitter that is released at many synapses. C. potassium: An ion involved in nerve impulse propagation, not a secreted chemical messenger at the synapse. D. amylase: An enzyme involved in carbohydrate digestion. Step 3: Identify the secreted chemical. Neurotransmitters are secreted from the synaptic knob. Acetylcholine is a common example. The correct option is B. B. acetylcholine 27. Chemical impulses are transmitted from sensory cells to the central nervous system by the Step 1: Understand the flow of nerve impulses. Nerve impulses travel from sensory receptors to the central nervous system (CNS), and then from the CNS to effector organs. Step 2: Define the types of neurons. A. afferent neurons: Also known as sensory neurons, they carry impulses from sensory receptors towards the CNS. B. efferent neurons: Also known as motor neurons, they carry impulses from the CNS to muscles or glands. C. association neurons: Also known as interneurons, they connect neurons within the CNS. D. relay neurons: Another term for interneurons. Step 3: Identify the correct neuron type. Sensory information is carried to the CNS by afferent neurons. The correct option is A. A. afferent neurons 28. Which of the following structures does not protect the human eye? Step 1: Consider the protective mechanisms of the eye. The eye has several structures designed to protect it from injury and environmental factors. Step 2: Evaluate each option's role. A. Conjunctiva: A thin membrane that covers the front of the eye (except the cornea) and lines the inside of the eyelids, providing lubrication and protection. B. Retina: The light-sensitive layer at the back of the eye responsible for vision. Its primary function is not protection. C. Eyelid: Protects the eye from foreign objects, excessive light, and helps keep it moist. D. Eye socket: The bony cavity (orbit) in the skull that surrounds and protects the eyeball. Step 3: Identify the non-protective structure. The retina's main function is vision, not protection. The correct option is B. B. Retina 29. The developmental stage found only in incomplete metamorphosis is Step 1: Differentiate between complete and incomplete metamorphosis. Complete metamorphosis: Egg → Larva → Pupa → Adult. Incomplete metamorphosis: Egg → Nymph → Adult. Step 2: Evaluate the options. A. larva: Found in complete metamorphosis. B. nymph: Found only in incomplete metamorphosis. C. pupa: Found in complete metamorphosis. D. egg: Found in both types of metamorphosis. Step 3: Identify the unique stage. The nymph stage is characteristic of incomplete metamorphosis. The correct option is B. B. nymph 30. The offspring produced from asexual reproduction is a Step 1: Understand asexual reproduction. Asexual reproduction involves a single parent producing offspring that are genetically identical to itself. Step 2: Define the options. A. clone: An organism that is genetically identical to its parent. B. gamete: A reproductive cell (sperm or egg) involved in sexual reproduction. C. hybrid: The offspring of two different species or varieties, typically from sexual reproduction. D. larva: An immature form of an animal that undergoes metamorphosis. Step 3: Identify the correct term. Offspring from asexual reproduction are clones. The correct option is A. A. clone 31. The organism that exists as a particle and replicates only inside living cells is Step 1: Analyze the characteristics described. The organism exists as a particle (meaning it's not a full cell) and is an obligate intracellular parasite (replicates only inside living cells). Step 2: Evaluate the options. A. bacterium: A single-celled prokaryotic organism that can replicate independently. B. alga: A photosynthetic eukaryotic organism that can replicate independently. C. protozoon: A single-celled eukaryotic organism that can replicate independently. D. virus: A non-cellular infectious agent that can only replicate inside the living cells of other organisms. It exists as a virion (particle) outside a host cell. Step 3: Identify the organism. This description perfectly matches a virus. The correct option is D. D. virus Got more? Send 'em.