Nokea
During which phase of meiosis do chiasmata structures form?
- A. Prophase I
- B. Prophase II
- C. Metaphase I
- D. Metaphase II
Correct Answer: A
Rationale: Chiasmata structures, where crossing over occurs, form during Prophase I of meiosis. This phase is characterized by homologous chromosomes pairing up and crossing over, leading to the exchange of genetic material between non-sister chromatids. Chiasmata are visible points of contact where genetic material has been exchanged, and they play a critical role in genetic diversity. Prophase II is the phase where chromosomes condense again in the second meiotic division, but chiasmata formation occurs in Prophase I. Metaphase I is the phase where homologous chromosomes align at the metaphase plate, not where chiasmata form. Metaphase II is the phase where replicated chromosomes align at the metaphase plate in the second meiotic division, but chiasmata formation occurs earlier in Prophase I.
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A scientist wants to measure how far a person can run in 30 minutes. Which of the following units should be used to record this measurement as a small number?
- A. Gigameters
- B. Kilometers
- C. Megameters
- D. Terameters
Correct Answer: B
Rationale: Kilometers are commonly used for shorter distances and would provide a small and practical number to measure distance in this context. Gigameters, Megameters, and Terameters are much larger units of measurement and would result in very large numbers, making them impractical for measuring the distance a person can run in 30 minutes. Therefore, the correct choice is Kilometers as it is a suitable unit for measuring such distances within a reasonable range.
What is the most basic unit of structure in living things?
- A. Cell
- B. Organelle
- C. Oxygen
- D. Pigment
Correct Answer: A
Rationale: The cell is indeed the most basic unit of life, forming the foundation of all living organisms. Cells are the building blocks of all living things, containing organelles that perform specific functions. While oxygen is essential for life, it is not a structural unit. Similarly, pigment is a component found within cells but is not the fundamental unit of structure. Therefore, the correct answer is 'A: Cell.'
Which statement confirms that the cell membrane is selectively permeable?
- A. Receptors are found on a cell's surface.
- B. Cells communicate with each other using cell signals.
- C. Environmental changes can cause a cell to expand or shrink.
- D. Sodium ions must travel through ion channels to enter the cell.
Correct Answer: D
Rationale: The correct answer is D because selective permeability is demonstrated by the fact that specific ions, such as sodium, require ion channels to cross the cell membrane. This process allows the cell to control what substances can enter or exit, highlighting the selective nature of the cell membrane. Choices A, B, and C do not directly relate to the concept of selective permeability of the cell membrane. Receptors on a cell's surface (Choice A) are involved in cell signaling rather than selective permeability. Cell communication through signals (Choice B) and environmental changes affecting cell size (Choice C) are not directly related to the selective permeability of the cell membrane, which specifically refers to the regulation of substances passing through the membrane.
In an experiment where five tropical plants are kept at varying humidity levels in a greenhouse for three months, while one plant is left outside in normal conditions, with plant height measured weekly, what serves as the control of the experiment?
- A. Plant height for each tropical plant
- B. The plant left outside in normal conditions
- C. Humidity level readings in the greenhouse
- D. Amount of time used to study plant height
Correct Answer: B
Rationale: The correct answer is B. The plant left outside in normal conditions acts as the control in the experiment. It provides a standard reference point for comparison to assess the impact of the varying humidity levels on the growth of the tropical plants. Choice A is incorrect because it refers to the dependent variable being measured, not the control. Choice C is incorrect as humidity levels in the greenhouse are part of the experimental conditions, not the control. Choice D is incorrect as the time used for studying plant height is a parameter of the experiment and not the control.
If a doctor diagnoses a patient with an impaired posterior pituitary gland, which of the following symptoms related to kidney function does the patient display?
- A. Thirst
- B. Tiredness
- C. Weight gain
- D. Concentrated urine
Correct Answer: D
Rationale: When the posterior pituitary gland is impaired, there is decreased secretion of antidiuretic hormone (ADH). ADH plays a crucial role in regulating water reabsorption by the kidneys. A deficiency of ADH leads to the inability of the kidneys to concentrate urine, resulting in the production of dilute urine. Therefore, 'Concentrated urine' is the correct symptom associated with impaired posterior pituitary gland. Choices A, B, and C are incorrect. Thirst is more commonly associated with diabetes insipidus, tiredness could be a general symptom but not specifically related to kidney function, and weight gain is not a typical symptom of impaired posterior pituitary gland affecting kidney function.