Nokea
What is the stage of mitosis during which the nuclear envelope reforms?
- A. Prophase
- B. Metaphase
- C. Telophase
- D. Cytokinesis
Correct Answer: C
Rationale: During telophase, the nuclear envelope reforms around the separated sister chromatids at opposite poles of the cell. This stage marks the reversal of the processes that occurred during prophase, where the nuclear envelope breaks down. Metaphase is characterized by the alignment of chromosomes along the metaphase plate in the cell's center. Cytokinesis is the final step of cell division involving cytoplasmic division to form two daughter cells, but it does not involve the reformation of the nuclear envelope. Therefore, choice C (Telophase) is the correct answer as it specifically involves the reformation of the nuclear envelope, distinguishing it from the other stages of mitosis.
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What is the valve that prevents blood from flowing back from the left ventricle into the left atrium?
- A. Tricuspid valve
- B. Mitral valve
- C. Aortic valve
- D. Pulmonic valve
Correct Answer: B
Rationale: The correct answer is the Mitral valve. The mitral valve is located between the left atrium and the left ventricle of the heart. Its function is to prevent the backflow of blood from the left ventricle into the left atrium during ventricular contraction. Choice A, the Tricuspid valve, is incorrect as it is located between the right atrium and right ventricle. Choice C, the Aortic valve, and Choice D, the Pulmonic valve, are also incorrect as they are involved in the circulation of blood leaving the heart rather than preventing backflow within the atria and ventricles.
Scientists compare the DNA of different organisms to understand evolutionary relationships. What is this type of evidence called?
- A. Morphological evidence (comparing body structures)
- B. Biochemical evidence (comparing molecules like proteins)
- C. Geographic distribution evidence (where organisms live)
- D. Genetic evidence (comparing DNA sequences)
Correct Answer: D
Rationale: A) Morphological evidence involves comparing body structures of organisms, which can provide information about evolutionary relationships based on physical similarities and differences. However, DNA comparison is a more direct and accurate method for understanding evolutionary relationships.
B) Biochemical evidence involves comparing molecules like proteins, which can also provide insights into evolutionary relationships. However, DNA comparison is considered more reliable due to the direct relationship between DNA sequences and genetic information.
C) Geographic distribution evidence refers to where organisms live and how their distribution may provide clues about evolutionary history. While this can be informative, it is not as direct or specific as comparing DNA sequences.
D) Genetic evidence involves comparing DNA sequences of different organisms to understand their evolutionary relationships. DNA comparison is a powerful tool in evolutionary biology because it provides direct information about genetic similarities and differences, offering precise insights into evolutionary relationships.
What is the outermost layer of the dermis, rich in collagen and elastin fibers that provide elasticity to the skin?
- A. Papillary layer
- B. Reticular layer
- C. Stratum basale
- D. Stratum corneum
Correct Answer: B
Rationale: The correct answer is the reticular layer. This layer is the outermost layer of the dermis that contains abundant collagen and elastin fibers, providing elasticity to the skin. The papillary layer is located beneath the epidermis and is responsible for supplying nutrients to the epidermis, not the outermost layer. The stratum basale is the deepest layer of the epidermis where new skin cells are produced, not part of the dermis. The stratum corneum is the outermost layer of the epidermis composed of dead skin cells, not a layer of the dermis.
Where does fertilization of the egg by sperm typically occur?
- A. Ovary
- B. Fallopian tube
- C. Uterus
- D. Vagina
Correct Answer: B
Rationale: Fertilization of the egg by sperm typically occurs in the fallopian tube. After ovulation, the egg is released from the ovary and travels through the fallopian tube, where it may encounter sperm for fertilization. The fallopian tube provides the ideal environment, including necessary nutrients and conditions, for fertilization to take place before the fertilized egg moves towards the uterus for implantation. Choices A, C, and D are incorrect because fertilization does not occur in the ovary, uterus, or vagina. The ovary releases the egg, the uterus is the site for implantation, and the vagina is part of the birth canal but not the typical site for fertilization.
Which of these organs is NOT involved in the production of digestive enzymes?
- A. Mouth
- B. Stomach
- C. Pancreas
- D. Small intestine
Correct Answer: A
Rationale: A) Mouth: The mouth is involved in the mechanical breakdown of food through chewing and the initiation of carbohydrate digestion by the enzyme amylase in saliva, but it does not produce digestive enzymes. The salivary amylase in the mouth helps in breaking down carbohydrates. However, it is not an organ that produces digestive enzymes. B) Stomach: The stomach produces gastric juices containing enzymes like pepsin that help break down proteins. C) Pancreas: The pancreas produces various digestive enzymes such as amylase, lipase, and proteases that aid in the digestion of carbohydrates, fats, and proteins. D) Small intestine: The small intestine produces enzymes such as peptidases, sucrase, lactase, and maltase that further break down proteins, carbohydrates, and fats for absorption. Therefore, the mouth is the organ that is NOT involved in the production of digestive enzymes.