Nokea
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.
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What type of inheritance pattern results in a 3:1 ratio of dominant to recessive phenotypes in the F2 generation?
- A. Incomplete dominance
- B. Codominance
- C. Sex-linked inheritance
- D. Autosomal dominant inheritance
Correct Answer: D
Rationale: Autosomal dominant inheritance results in a 3:1 ratio of dominant to recessive phenotypes in the F2 generation. This inheritance pattern occurs when a single copy of the dominant allele is enough to express the dominant phenotype.
A) Incomplete dominance: In incomplete dominance, the heterozygous phenotype is a blend of the two homozygous phenotypes, and it does not lead to a 3:1 ratio of dominant to recessive phenotypes in the F2 generation.
B) Codominance: In codominance, both alleles are fully expressed in the heterozygous phenotype, but this pattern also does not result in a 3:1 ratio of dominant to recessive phenotypes in the F2 generation.
C) Sex-linked inheritance: Sex-linked inheritance involves genes located on the sex chromosomes and does not typically lead to a 3:1 ratio of dominant to recessive phenotypes in the F2 generation.
What is the common name for the compound CH₃COOH?
- A. Acetic acid
- B. Formic acid
- C. Butyric acid
- D. Propionic acid
Correct Answer: A
Rationale: The compound CH₃COOH is commonly known as acetic acid. Acetic acid is a clear, colorless liquid with a sour taste and a pungent smell. It is a weak acid found in vinegar and is used in the production of various chemicals. Formic acid, butyric acid, and propionic acid are different organic acids with distinct chemical structures and properties, but they are not the common name for the compound CH₃COOH.
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.
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.
Which of the following processes breaks down cellular components for recycling or waste removal?
- A. Photosynthesis
- B. Cellular respiration
- C. Cell division
- D. Phagocytosis
Correct Answer: D
Rationale: The correct answer is D: Phagocytosis. Phagocytosis is the process by which cells engulf and break down cellular components or foreign particles for recycling or waste removal. It is a vital mechanism used by cells to maintain homeostasis and remove waste materials. Photosynthesis (A) is the process by which plants convert light energy into chemical energy to produce food, not for breaking down cellular components. Cellular respiration (B) is the process by which cells generate energy from nutrients, not for waste removal. Cell division (C) is the process by which cells replicate and divide to form new cells during growth, repair, or development, not for breaking down cellular components.