Nokea
What is the first event to occur in a primary immune response?
- A. Macrophages phagocytose pathogens and present their antigens.
- B. Neutrophils aggregate and act as cytotoxic, nonspecific killers of pathogens.
- C. B lymphocytes make pathogen-specific antibodies.
- D. Helper T cells secrete interleukins to activate pathogen-fighting cells.
Correct Answer: A
Rationale: The correct answer is A. The initial event in a primary immune response is the phagocytosis of pathogens by macrophages and the subsequent presentation of their antigens, which is crucial for initiating the adaptive immune response. Neutrophils (Choice B) are also involved in the innate immune response, but they typically respond after macrophages. B lymphocytes (Choice C) produce antibodies later in the adaptive immune response, and Helper T cells (Choice D) help in coordinating the immune response but are not the first cells to act in a primary immune response.
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How many daughter cells are formed from one parent cell during meiosis?
- A. One
- B. Two
- C. Three
- D. Four
Correct Answer: D
Rationale: During meiosis, one parent cell produces four genetically distinct daughter cells. This occurs through two rounds of cell division, resulting in four haploid cells with half the number of chromosomes as the parent cell. Each daughter cell is genetically unique due to processes like crossing over and independent assortment during meiosis. Choice A is incorrect because meiosis results in multiple daughter cells. Choice B is incorrect because meiosis yields more daughter cells. Choice C is incorrect because meiosis produces four, not three, daughter cells.
Which type of chemical reaction produces a salt?
- A. An oxidation reaction
- B. A neutralization reaction
- C. A synthesis reaction
- D. A decomposition reaction
Correct Answer: B
Rationale: The correct answer is B, a neutralization reaction. In a neutralization reaction, an acid and a base react to produce a salt and water. This process involves the combination of H+ ions from the acid and OH- ions from the base to form water, while the remaining ions combine to form a salt. Therefore, a neutralization reaction is the specific type of chemical reaction that produces a salt. Choices A, C, and D are incorrect. An oxidation reaction involves the loss of electrons, a synthesis reaction involves the formation of a compound from simpler substances, and a decomposition reaction involves the breakdown of a compound into simpler substances. None of these reactions directly lead to the production of a salt, making them incorrect choices in this context.
How do organisms maintain homeostasis?
- A. By increasing their body temperature, blood pH, and fluid balance.
- B. By undergoing biochemical processes and absorbing energy to increase entropy.
- C. By undergoing biochemical processes to maintain the order of their external environment.
- D. By using free energy and matter via biochemical processes to work against entropy.
Correct Answer: D
Rationale: Organisms maintain homeostasis by utilizing free energy and matter through biochemical processes to counteract entropy, which helps in preserving internal stability. This process involves maintaining a balance within the organism's internal environment despite external changes, ensuring proper functioning and survival. Choice A is incorrect because increasing body temperature, blood pH, and fluid balance alone do not define the comprehensive process of maintaining homeostasis. Choice B is incorrect as absorbing energy to increase entropy goes against the concept of maintaining internal stability. Choice C is incorrect as maintaining the order of the external environment does not directly contribute to the organism's internal stability and balance.
Which blood component is chiefly responsible for clotting?
- A. Platelets
- B. Red blood cells
- C. Antigens
- D. Plasma cells
Correct Answer: A
Rationale: The correct answer is A: Platelets. Platelets are small cell fragments in the blood that play a crucial role in clotting. When there is an injury, platelets adhere to the site and release chemicals that help form a clot to prevent excessive bleeding. Red blood cells transport oxygen, antigens are substances that trigger an immune response, and plasma cells are a type of white blood cell involved in producing antibodies, none of which are primarily responsible for clotting.
When testing how quickly a rat dies based on the amount of poison it eats, which of the following is the independent variable and which is the dependent variable?
- A. How quickly the rat dies is the independent variable; the amount of poison is the dependent variable.
- B. The amount of poison is the independent variable; how quickly the rat dies is the dependent variable.
- C. Whether the rat eats the poison is the independent variable; how quickly the rat dies is the dependent variable.
- D. The cage the rat is kept in is the independent variable; the amount of poison is the dependent variable.
Correct Answer: B
Rationale: The correct answer is B. In this experiment, the independent variable is the amount of poison because it is what is being manipulated by the researcher. The dependent variable is how quickly the rat dies, as it is the outcome that is being measured based on the different amounts of poison administered. Choice A is incorrect because the independent variable should be what is being manipulated or changed, which is the amount of poison in this case. Choice C is incorrect because whether the rat eats the poison is not being varied or controlled by the researcher. Choice D is incorrect because the cage the rat is kept in is not relevant to the relationship being studied between the amount of poison and the rat's survival time.