Nursing Elites

1. A keystone species plays a critical role in an ecosystem because its removal would:

• A. Lead to a decrease in competition among other species
• B. Cause a slight increase in primary productivity
• C. Have a minimal impact on the overall ecosystem structure
• D. Disrupt the food web and cause cascading effects on other populations

Correct answer: D

Rationale: Rationale: Keystone species are species that have a disproportionately large effect on their environment relative to their abundance. They play a critical role in maintaining the structure and function of an ecosystem. If a keystone species is removed from an ecosystem, it can disrupt the food web by causing imbalances in predator-prey relationships. This disruption can lead to cascading effects on other populations within the ecosystem, potentially causing population declines or even extinctions. Therefore, the removal of a keystone species would have significant impacts on the overall ecosystem structure, making option D the correct answer.

2. Which of the following is an example of a chemical property of matter?

• A. Boiling point
• B. Flammability
• C. Density
• D. Conductivity

Correct answer: b

Rationale: Chemical properties describe how a substance reacts with other substances, such as its ability to burn (flammability) or react with acids or bases.

3. In the phrase "a drop in the bucket," "bucket" represents:

• A. A literal container
• B. A large quantity
• C. A specific goal
• D. An obstacle

Correct answer: B

Rationale: The phrase signifies that something is insignificant compared to a much larger amount.

4. Which of the following is a weak acid commonly found in citrus fruits?

• A. Sulfuric acid (Hâ‚‚SOâ‚„)
• B. Hydrochloric acid (HCl)
• C. Citric acid
• D. Nitric acid (HNO₃)

Correct answer: c

Rationale: Citric acid is a weak acid commonly found in citrus fruits. The other choices are strong acids.

5. 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: 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.

6. Which of these pairs represents an example of convergent evolution?

• A. Humans and chimpanzees
• B. Bats and birds
• C. Dolphins and sharks
• D. Snakes and earthworms

Correct answer: B

Rationale: Rationale: Convergent evolution refers to the process by which different species independently evolve similar traits or characteristics due to similar environmental pressures. In the case of bats and birds, both have evolved wings for flight despite not sharing a recent common ancestor with wings. Bats are mammals, while birds are avians, yet they both have wings adapted for flight, which is a classic example of convergent evolution. A) Humans and chimpanzees share a common ancestor and have not independently evolved similar traits. C) Dolphins and sharks are not closely related, and their similarities are due to adaptations to their aquatic environment rather than convergent evolution. D) Snakes and earthworms belong to different classes (reptiles and annelids, respectively) and do not share recent common ancestors, making their similarities not a result of convergent evolution.

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