Nokea
Adaptive radiation refers to the evolutionary process where:
- A. A single ancestral species diversifies into multiple descendant species due to ecological pressures in a heterogeneous environment.
- B. Two unrelated species evolve similar adaptations in response to similar environments, leading to convergent evolution.
- C. A population becomes increasingly well-adapted to its current environment through continued natural selection.
- D. The fossil record exhibits gaps or missing links in the evolutionary history of a lineage.
Correct Answer: A
Rationale: - Adaptive radiation is a process where a single ancestral species diversifies into multiple descendant species to exploit different ecological niches within a heterogeneous environment.
- This diversification occurs due to the different selective pressures present in various habitats, leading to the evolution of distinct traits and adaptations in different descendant species.
- Option A accurately describes the process of adaptive radiation, where the initial species undergoes rapid speciation to occupy different ecological roles and adapt to diverse environmental conditions.
- Options B, C, and D do not accurately describe adaptive radiation but refer to other evolutionary processes such as convergent evolution, natural selection, and gaps in the fossil record, respectively.
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Muscles that work in opposition to each other, producing opposing movements, are called:
- A. Synergists
- B. Antagonists
- C. Agonists
- D. Fixators
Correct Answer: B
Rationale: Antagonist muscles are pairs of muscles that work in opposition to each other, producing opposing movements. When one muscle contracts, the other relaxes to allow the movement to occur smoothly. Synergists are muscles that work together to create a movement, not in opposition. Agonists are muscles primarily responsible for producing a specific movement, not opposing each other. Fixators are muscles that stabilize joints to allow other movements to take place, providing a stable base for muscle actions but do not produce opposing movements.
Where does most of the chemical digestion and absorption of nutrients occur?
- A. Mouth
- B. Stomach
- C. Small intestine
- D. Large intestine
Correct Answer: C
Rationale: The small intestine is the primary site for both chemical digestion and absorption of nutrients in the digestive system. The lining of the small intestine is equipped with villi and microvilli, which significantly increase the surface area available for absorption. Enzymes from the pancreas and bile from the liver play crucial roles in further breaking down food into absorbable molecules that can pass through the intestinal wall into the bloodstream. While the stomach assists in mechanical breakdown and initial protein digestion, it is not the main site of nutrient absorption. The large intestine, on the other hand, mainly absorbs water and electrolytes from undigested food particles. The mouth aids in initial mechanical breakdown and some carbohydrate digestion, but the majority of nutrient absorption occurs in the small intestine, making it the correct answer.
Why is the electrical conductivity of a strong acid solution higher than that of a weak acid solution?
- A. Strong acids are more concentrated.
- B. Strong acids release more hydrogen ions.
- C. Weak acids are better at dissolving salts.
- D. Strong acids have a lower pH.
Correct Answer: B
Rationale: The correct answer is B because strong acids release more hydrogen ions compared to weak acids. This higher concentration of ions in the solution leads to a higher electrical conductivity. Strong acids ionize completely in solution, producing a higher concentration of ions that can conduct electricity, whereas weak acids only partially ionize, resulting in a lower concentration of ions and lower electrical conductivity. Choice A is incorrect because the concentration of the acid does not directly determine its electrical conductivity. Choice C is incorrect as the ability to dissolve salts is not directly related to electrical conductivity. Choice D is incorrect because the pH of the solution, although related to acidity, does not directly determine the electrical conductivity.
Which vitamin requires intrinsic factor for proper absorption?
- A. Vitamin A
- B. Vitamin C
- C. Vitamin D
- D. Vitamin B12
Correct Answer: D
Rationale: Vitamin B12 requires intrinsic factor, a glycoprotein secreted by the parietal cells of the stomach, for proper absorption in the small intestine. Intrinsic factor binds to vitamin B12 and facilitates its absorption in the ileum. Deficiency in intrinsic factor can lead to pernicious anemia, a condition characterized by a lack of vitamin B12 absorption. Options A, B, and C are incorrect. Vitamin A is absorbed in the small intestine with the help of bile salts; Vitamin C is absorbed in the small intestine via active transport; Vitamin D is absorbed in the small intestine through a process involving bile salts and micelles. It is essential for students to understand this relationship as it highlights the importance of intrinsic factor in the absorption of specific vitamins and the consequences of its deficiency.
What is the function of the pituitary gland?
- A. Produces hormones that regulate growth and metabolism
- B. Filters blood and removes waste products
- C. Stores and releases bile
- D. Produces red blood cells
Correct Answer: A
Rationale: The correct answer is A: Produces hormones that regulate growth and metabolism. The pituitary gland is often referred to as the 'master gland' because it produces and releases hormones that regulate various bodily functions, including growth, metabolism, reproduction, and stress response. It does not filter blood or remove waste products (option B), store and release bile (option C), or produce red blood cells (option D). The pituitary gland's primary role is in hormone production and regulation, influencing many essential functions in the body.