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What is the relationship between genetic drift and the founder effect?
- A. Founder effect is a cause of genetic drift within a small population
- B. Genetic drift is a cause of the founder effect in new populations
- C. They are the same phenomenon with different names
- D. They are unrelated concepts.
Correct Answer: A
Rationale: - The founder effect is a specific type of genetic drift that occurs when a small group of individuals establishes a new population, leading to a loss of genetic variation.
- Genetic drift, on the other hand, is a broader concept that refers to random changes in allele frequencies in a population over time due to chance events.
- Therefore, the founder effect is a specific scenario within the broader concept of genetic drift, where the establishment of a new population by a small number of individuals leads to genetic changes in the population.
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In the reaction 2Na + 2H2O → 2NaOH + H2, what is the limiting reactant when 3 moles of sodium react with 2 moles of water?
- A. Na
- B. H2O
- C. NaOH
- D. H2
Correct Answer: A
Rationale: The balanced chemical equation indicates that 2 moles of sodium react with 2 moles of water to yield 2 moles of sodium hydroxide and 1 mole of hydrogen gas. When 3 moles of sodium react with only 2 moles of water, sodium becomes the limiting reactant as it is present in excess compared to the available water molecules. This situation arises because not all sodium atoms can fully react with the limited amount of water, resulting in sodium being the limiting reactant in this specific case. Choice B (H2O), choice C (NaOH), and choice D (H2) are incorrect as they are not the limiting reactant in the given reaction scenario.
What property of a substance remains constant regardless of its location in the universe?
- A. Mass
- B. Weight
- C. Density
- D. Volume
Correct Answer: A
Rationale: Mass is a measure of the amount of matter in an object and remains constant regardless of its location in the universe. Weight, on the other hand, is the force of gravity acting on an object and can vary depending on the gravitational pull at different locations. Density and volume can also change based on the environment in which an object is placed, making mass the property that remains constant universally. Therefore, the correct answer is mass. Weight changes with the gravitational force of a particular location, density varies with mass and volume, and volume can change depending on the shape or size of the object.
What is the principle behind the phenomenon of refraction, where waves bend when entering a new medium?
- A. Change in wavelength
- B. Change in frequency
- C. Change in wave speed
- D. None of the above
Correct Answer: C
Rationale: Refraction occurs due to a change in wave speed when waves enter a new medium. As waves travel from one medium to another, their speed changes, causing them to bend. This change in speed is responsible for the bending of waves during refraction. It is not the change in wavelength or frequency that causes refraction, but rather the change in speed as waves move through different mediums. Therefore, the correct answer is the change in wave speed (Choice C). Choices A and B are incorrect as refraction is not primarily influenced by changes in wavelength or frequency, but by changes in wave speed. Choice D is also incorrect as there is a specific principle, which is the change in wave speed, behind the phenomenon of refraction.
Which of the following is a pair of nerves that originates from the brain?
- A. Spinal nerves
- B. Olfactory nerves
- C. Sciatic nerve
- D. Optic nerve
Correct Answer: B
Rationale: The olfactory nerves, choice B, are a pair of cranial nerves that originate from the brain. They are responsible for the sense of smell and are the only cranial nerves that directly connect to the cerebrum. Spinal nerves, choice A, originate from the spinal cord, the sciatic nerve, choice C, is a large nerve that originates in the lower back, and the optic nerve, choice D, originates from the retina of the eye. Therefore, choices A, C, and D are incorrect as they do not originate directly from the brain.
What is the process of breaking down glucose into pyruvate called?
- A. Glycolysis
- B. Gluconeogenesis
- C. Krebs cycle
- D. Oxidative phosphorylation
Correct Answer: A
Rationale: A) Glycolysis is the process of breaking down glucose into pyruvate. This occurs in the cytoplasm of cells and is the first step in cellular respiration.
B) Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, such as amino acids or glycerol, and is the opposite of glycolysis.
C) The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that occur in the mitochondria and is involved in the oxidation of acetyl-CoA to produce ATP and other energy carriers.
D) Oxidative phosphorylation is the final stage of cellular respiration where ATP is produced through the transfer of electrons in the electron transport chain.