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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What is the correct way to represent 8,600,000,000,000 in scientific notation with two significant figures?
- A. 8.6 x 10^12
- B. 8.6 x 10^-12
- C. 8.6 x 10^11
- D. 8.60 x 10^12
Correct Answer: A
Rationale: The correct way to represent 8,600,000,000,000 in scientific notation with two significant figures is 8.6 x 10^12. Scientific notation involves expressing a number as a decimal (with one non-zero digit before the decimal point) multiplied by a power of 10. In this case, 8,600,000,000,000 is correctly written as 8.6 x 10^12 to maintain two significant figures and the appropriate magnitude. Choice B (8.6 x 10^-12) is incorrect as it represents a very small number due to the negative exponent. Choice C (8.6 x 10^11) is incorrect as it does not account for the magnitude of the original number. Choice D (8.60 x 10^12) is incorrect because it unnecessarily adds a zero after the decimal point, which is not warranted by the original number's precision.
What is an alteration in the normal gene sequence called?
- A. DNA mutation
- B. Gene migration
- C. Polygenic inheritance
- D. Incomplete dominance
Correct Answer: A
Rationale: A DNA mutation is the correct term used to describe an alteration in the normal gene sequence. It refers to changes in the DNA sequence that can result in different traits or characteristics. Gene migration involves the movement of genes between populations, polygenic inheritance refers to the inheritance of traits controlled by multiple genes, and incomplete dominance is a pattern of inheritance where neither allele is dominant.
What is the process of cell division in somatic (most body) cells called?
- A. Mitosis
- B. Meiosis
- C. Respiration
- D. Cytogenesis
Correct Answer: A
Rationale: Mitosis is the correct answer. It is the process of cell division in somatic cells, leading to the formation of two identical daughter cells with the same number of chromosomes as the parent cell. Meiosis, on the other hand, is the type of cell division that occurs in sex cells, leading to the formation of gametes with half the number of chromosomes. Respiration is a completely different biological process related to energy production, and cytogenesis is not a recognized term for cell division.
Which of the following serves as a standard or series of standards for comparing the results of an experiment?
- A. A control
- B. A variable
- C. A constant
- D. Collected data
Correct Answer: A
Rationale: A control is a standard used to compare the outcomes of an experiment and is crucial for determining the effect of the variables being tested. It helps isolate and measure the impact of the independent variable by providing a baseline for comparison. While variables may change, constants remain consistent, and collected data is the information obtained from the experiment. A control specifically serves as the standard for comparison in an experiment, making it the correct choice. Variables, although important, are what are being altered and tested in an experiment, constants are factors that are kept consistent throughout the experiment, and collected data is the information gathered from the experiment, none of which specifically serve as the standard for comparison.
What is the sensory threshold?
- A. The smallest amount of stimulus required for an individual to feel a sensation
- B. The amount of stimulus required for an individual to feel pain
- C. The amount of stimulus required to cause an individual to move away from the stimulus
- D. The place from which the stimulus is coming
Correct Answer: A
Rationale: The sensory threshold refers to the smallest amount of stimulus required for an individual to perceive or feel a sensation. It is the minimum level of stimulus intensity that is detectable by an individual. Choice B is incorrect because the sensory threshold is not specifically related to feeling pain but rather to perceiving any sensation. Choice C is incorrect as the sensory threshold is about perception and not necessarily physical reaction. Choice D is incorrect as it describes the source of the stimulus, not the threshold for perception.