Nokea
What phenomenon explains the formation of rainbows in the sky?
- A. Diffraction
- B. Interference
- C. Refraction and dispersion of sunlight by water droplets
- D. Reflection from clouds
Correct Answer: C
Rationale: Rainbows are formed due to the refraction and dispersion of sunlight by water droplets in the atmosphere. When sunlight enters a water droplet, it is refracted, then internally reflected, and finally refracted again as it exits the droplet. This dispersion of light into its component colors creates the beautiful rainbow we see in the sky. Choice A, diffraction, involves bending of light around obstacles or through narrow openings, not the splitting of light into colors as seen in rainbows. Choice B, interference, refers to the phenomenon where two or more light waves overlap and interact, producing a pattern of light and dark bands, which is not the case with rainbows. Choice D, reflection from clouds, does not accurately describe the process involved in the formation of rainbows through refraction and dispersion of light by water droplets.
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Which of the following is an example of stabilizing selection?
- A. Selection that favors extreme traits in a population
- B. Selection that removes individuals with extreme traits
- C. Selection that maintains the current average trait in a population
- D. Selection that favors one specific trait over all others
Correct Answer: C
Rationale: - Stabilizing selection is a type of natural selection that favors the intermediate variants in a population, while selecting against the extreme traits. This results in the maintenance of the current average trait in the population.
- Option A is incorrect because stabilizing selection does not favor extreme traits; instead, it favors the average trait.
- Option B is incorrect because stabilizing selection does not remove individuals with extreme traits; it acts against extreme traits by favoring the intermediate variants.
- Option D is incorrect because stabilizing selection does not favor one specific trait over all others; it favors the average trait by selecting against extreme traits.
What is the unit of measurement for momentum?
- A. Newton-second (N·s)
- B. Kilogram-meter (kg·m)
- C. Joule (J)
- D. Meter per second (m/s)
Correct Answer: A
Rationale: The correct unit of measurement for momentum is Newton-second (N·s). Momentum is calculated as the product of an object's mass and its velocity. The unit of mass is kilograms (kg) and the unit of velocity is meters per second (m/s). Therefore, the unit of momentum is kilogram-meter per second (kg·m/s). By Newton's second law of motion (F = ma), force is measured in Newtons (N), which is equivalent to kg·m/s². Multiplying the unit of force (N) by the unit of time (s) gives the unit of momentum as Newton-second (N·s). Choice B, Kilogram-meter (kg·m), is incorrect because it represents the unit of work or energy, not momentum. Choice C, Joule (J), is incorrect as it is a unit of energy. Choice D, Meter per second (m/s), is incorrect as it represents velocity alone, not momentum which is a vector quantity involving mass and velocity.
What is the process by which a cell divides to produce two daughter cells?
- A. Mitosis
- B. Meiosis
- C. Differentiation
- D. Transformation
Correct Answer: A
Rationale: Mitosis is the correct answer because it is the process of cell division that results in the production of two daughter cells with identical genetic material to the parent cell. Meiosis, while also involving cell division, leads to the formation of gametes with half the number of chromosomes as the parent cell. Differentiation is the specialization of cells for specific functions, not the process of cell division. Transformation involves a cell incorporating foreign DNA into its genome, which is unrelated to the division of a cell into two daughter cells.
What checkpoint mechanism ensures all chromosomes are attached to the spindle fibers before anaphase begins?
- A. Prometaphase
- B. Metaphase
- C. Cyclin degradation
- D. Sister chromatid cohesion
Correct Answer: A
Rationale: A) Prometaphase is the correct answer because it is the stage of mitosis where all chromosomes are attached to the spindle fibers before anaphase begins. During prometaphase, the nuclear envelope breaks down, allowing the spindle fibers to attach to the kinetochores of the chromosomes. This attachment is necessary for proper chromosome alignment and segregation during anaphase.
B) Metaphase is incorrect because it is the stage where chromosomes are aligned at the metaphase plate but do not necessarily have all spindle fibers attached.
C) Cyclin degradation is incorrect because it is a regulatory mechanism that controls the progression of the cell cycle but is not specifically related to ensuring all chromosomes are attached to spindle fibers.
D) Sister chromatid cohesion is incorrect because it refers to the physical connection between sister chromatids that is maintained until anaphase, but it does not ensure that all chromosomes are attached to spindle fibers.
Which neurotransmitter is associated with mood regulation, sleep, and appetite?
- A. Acetylcholine
- B. Dopamine
- C. Serotonin
- D. GABA (Gamma-aminobutyric acid)
Correct Answer: C
Rationale: The correct answer is C: Serotonin. Serotonin is a neurotransmitter that plays a crucial role in mood regulation, sleep, and appetite. It helps regulate emotions, mood, and behavior. Imbalances in serotonin levels have been associated with conditions such as depression, anxiety, and eating disorders.
Choice A, Acetylcholine, is primarily involved in muscle control and memory functions. Choice B, Dopamine, is associated with reward, motivation, and motor control. Choice D, GABA (Gamma-aminobutyric acid), is an inhibitory neurotransmitter that helps reduce neuronal excitability and is not directly linked to mood regulation, sleep, or appetite.