Nursing Elites

1. Decomposers in an ecosystem play a vital role by:

• A. Photosynthesizing and producing organic matter
• B. Breaking down dead organisms and returning nutrients to the environment
• C. Preying on herbivores and controlling their populations
• D. Fixing nitrogen from the atmosphere and making it available to plants

Correct answer: B

Rationale: Decomposers are organisms that break down dead organic matter, such as dead plants and animals, into simpler substances. By doing so, they help to recycle nutrients back into the environment, making them available for other organisms to use. This process is essential for the functioning of ecosystems, as it ensures that nutrients are not lost but instead are continuously cycled through the ecosystem. Photosynthesis (option A) is the process by which plants and some other organisms convert light energy into chemical energy in the form of glucose, and it is not a role of decomposers. Preying on herbivores (option C) is a role typically carried out by predators, not decomposers. Fixing nitrogen from the atmosphere (option D) is a process carried out by nitrogen-fixing bacteria, not decomposers.

2. The hypothalamus, a part of the brain, plays a crucial role in endocrine regulation. It secretes GnRH (Gonadotropin-releasing hormone) which stimulates the pituitary gland to produce FSH and LH. What is the MAIN function of FSH and LH?

• A. Regulate blood sugar levels
• B. Control growth and development
• C. Stimulate the fight-or-flight response
• D. Maintain calcium homeostasis

Correct answer: B

Rationale: FSH (Follicle-stimulating hormone) and LH (Luteinizing hormone) are hormones produced by the pituitary gland in response to GnRH from the hypothalamus. FSH plays a key role in the growth and development of ovarian follicles in females and sperm production in males. LH is essential for the maturation of the ovarian follicle, ovulation, and the formation of the corpus luteum in females, as well as the production of testosterone in males. Therefore, the main function of FSH and LH is to control growth and development in the reproductive system. Choices A, C, and D are incorrect as they do not align with the roles of FSH and LH in reproductive physiology. Regulating blood sugar levels is primarily the function of insulin and glucagon, controlling the fight-or-flight response involves hormones like adrenaline and noradrenaline, and maintaining calcium homeostasis is mainly regulated by parathyroid hormone and calcitonin.

3. Molecular clocks utilize the accumulation of mutations in DNA sequences to estimate the evolutionary divergence time between species. This method relies on the assumption that:

• A. The rate of mutation is constant across all genes and all species.
• B. Species with more morphological similarities diverged more recently.
• C. Mutations are always beneficial and contribute to increased fitness.
• D. The fossil record provides the most accurate estimates of evolutionary relationships.

Correct answer: A

Rationale: A molecular clock is a method used to estimate the time of divergence between species by measuring the accumulation of mutations in DNA sequences. This method relies on the assumption that mutations occur at a relatively constant rate over time. If the rate of mutation were not constant, it would be challenging to accurately estimate the evolutionary divergence time between species. Therefore, option A is the most appropriate choice as it aligns with the fundamental principle underlying the molecular clock hypothesis. Option B is incorrect because the assumption that species with more morphological similarities diverged more recently does not directly relate to the concept of molecular clocks and the accumulation of mutations in DNA sequences. Option C is incorrect because mutations are not always beneficial and do not always contribute to increased fitness. Mutations can be neutral or deleterious as well, and their accumulation is what is used to estimate evolutionary di

4. In the human skeleton, which of the following lists some of the vertebrae in descending order?

• A. Atlas, axis, thoracic, lumbar, sacral, coccyx.
• B. Axis, sacral, coccyx, atlas, lumbar, thoracic.
• C. Thoracic, sacral, lumbar, axis, coccyx, atlas.
• D. Coccyx, lumbar, axis, sacral, thoracic, atlas.

Correct answer: A

Rationale: The correct order of some of the vertebrae in the human skeleton in descending order is Atlas, Axis, Thoracic, Lumbar, Sacral, Coccyx. This sequence follows the typical arrangement from the top of the spine down towards the pelvis. Choice B is incorrect as it does not follow the descending order of vertebrae. Choice C is incorrect as it starts with Thoracic which is not the first vertebra in the descending order. Choice D is incorrect as it starts with Coccyx which is the last vertebra in the descending order.

5. Which of the following is produced by Natural Killer Cells to create pores for target cell rupture?

• A. Interferon
• B. Apoptosis
• C. Perforin
• D. Antibody

Correct answer: C

Rationale: The correct answer is C, Perforin. Natural Killer cells release perforin, which forms pores in the membrane of target cells, leading to their lysis. Interferon (choice A) is a protein released by cells in response to viral infections, apoptosis (choice B) is programmed cell death, and antibodies (choice D) are produced by B cells to neutralize pathogens but are not directly involved in creating pores for cell rupture like perforin.

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