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. The ball-and-socket joint, which allows for wide range of motion, is found in the connection between:

• A. Upper arm and shoulder blade (scapula)
• B. Collarbone (clavicle) and breastbone (sternum)
• C. Two vertebrae in the spine
• D. Ribs and sternum

Correct answer: A

Rationale: The correct answer is A: 'Upper arm and shoulder blade (scapula).' The ball-and-socket joint is found in the connection between the humerus (upper arm bone) and the scapula (shoulder blade). This joint allows for a wide range of motion, including flexion, extension, abduction, adduction, and rotation. The collarbone (clavicle) and breastbone (sternum) are connected by a cartilaginous joint, not a ball-and-socket joint. Two vertebrae in the spine are connected by facet joints, and the ribs and sternum are connected by cartilaginous joints and the costovertebral joints. Therefore, the ball-and-socket joint is uniquely found in the connection between the upper arm and the shoulder blade, allowing for the shoulder's impressive range of motion.

3. Which of the following phases of mitosis is characterized by the separation of sister chromatids and their movement to opposite poles?

• A. Metaphase
• B. Anaphase
• C. Anaphase
• D. Cytokinesis

Correct answer: B

Rationale: Rationale: During anaphase of mitosis, the sister chromatids, which are duplicated copies of a chromosome, separate and move towards opposite poles of the cell. This movement is facilitated by the shortening of microtubules attached to the chromatids. As a result, each pole of the cell receives a complete set of chromosomes, ensuring that the daughter cells produced after cell division will have the correct number of chromosomes. Metaphase is characterized by the alignment of chromosomes at the cell's equator, not their separation. Telophase is the phase following anaphase, where the separated chromatids reach the opposite poles and nuclear envelopes start to form around them. Cytokinesis is the final stage of cell division, where the cytoplasm is divided to form two separate daughter cells.

4. Dandruff is caused by

• A. Excessive sebum production (This can contribute to oily dandruff)
• B. Bacterial infection (This can cause scalp folliculitis, not dandruff)
• C. Overgrowth of a specific type of fungus on the scalp
• D. Lack of proper skin hydration

Correct answer: C

Rationale: Dandruff is primarily caused by an overgrowth of a specific type of fungus called Malassezia on the scalp. This fungus feeds on the natural oils produced by the hair follicles, leading to an inflammatory response in some individuals, resulting in flaking and itching. Excessive sebum production can contribute to oily dandruff by providing more food for the fungus. Bacterial infections, such as scalp folliculitis, can cause symptoms similar to dandruff but are not the primary cause. Lack of proper skin hydration can contribute to dry scalp conditions but is not the main cause of dandruff.

5. Which of the following is NOT a factor affecting the rate of a chemical reaction?

• A. Concentration of reactants
• B. Temperature
• C. Presence of a catalyst
• D. Color of the reaction mixture

Correct answer: D

Rationale: Color of the reaction mixture. While color change can sometimes be an indicator of a reaction, it doesn't directly influence the reaction rate.

6. What information can be obtained directly from the element's atomic number?

• A. Its atomic mass
• B. Its position on the periodic table
• C. Its position on the periodic table
• D. Its chemical properties

Correct answer: B

Rationale: The atomic number of an element represents the number of protons in the nucleus of an atom. This number determines the element's unique identity and its position on the periodic table. The atomic mass (option A) is not directly determined by the atomic number but is a weighted average of the isotopes of an element. The position on the periodic table (option C) is directly related to the atomic number, as elements are arranged in order of increasing atomic number. The chemical properties of an element (option D) are influenced by the number of protons in the nucleus, which is determined by the atomic number.

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