1. During gas exchange in the alveoli, what happens to oxygen?

A. Oxygen is released from the bloodstream into the alveoli.
B. Oxygen is absorbed from the alveoli into the bloodstream.
C. Oxygen is converted into carbon dioxide.
D. Oxygen is stored in the alveoli for later use.

Correct answer: B

Rationale: During gas exchange in the alveoli, oxygen is absorbed from the alveoli into the bloodstream. In the alveoli, oxygen diffuses across the thin walls of the alveoli and into the surrounding capillaries where it binds to hemoglobin in red blood cells. This oxygen-rich blood is then transported to the body's tissues for cellular respiration. Therefore, option B is correct as it accurately describes the direction of oxygen movement during the process of gas exchange in the lungs.

2. 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: 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

3. Which hormone, produced by the thyroid gland, plays a crucial role in regulating the body's metabolism, growth, and development?

A. Calcitonin
B. Parathyroid hormone (PTH)
C. Thyroxine
D. Insulin

Correct answer: c

Rationale: The correct answer is C: Thyroxine. Thyroxine, also known as T4, is a hormone produced by the thyroid gland that plays a crucial role in regulating the body's metabolism, growth, and development. It controls how the body uses energy, affects heart rate, and influences other vital functions. Calcitonin (A) is involved in calcium regulation, not metabolism. Parathyroid hormone (PTH) (B) is produced by the parathyroid glands and regulates calcium and phosphorus levels in the body. Insulin (D) is a hormone produced by the pancreas that regulates blood sugar levels, not metabolism or growth.

4. Which of the following is NOT a common symptom of lactose intolerance?

A. Gas
B. Bloating
C. Diarrhea
D. Nausea

Correct answer: D

Rationale: Rationale: A) Gas: Gas is a common symptom of lactose intolerance. When lactose is not properly digested, it can ferment in the colon, leading to the production of gas. B) Bloating: Bloating is another common symptom of lactose intolerance. The buildup of gas in the digestive system can cause bloating and discomfort. C) Diarrhea: Diarrhea is a common symptom of lactose intolerance. When lactose is not broken down in the small intestine, it can draw excess water into the colon, resulting in diarrhea. D) Nausea: Nausea is not a common symptom of lactose intolerance. While some individuals may experience mild stomach discomfort or cramps, nausea is not typically associated with lactose intolerance.

5. Which blood vessels carry oxygenated blood from the heart to the rest of the body?

A. Pulmonary arteries
B. Pulmonary veins
C. Systemic arteries
D. Systemic veins

Correct answer: C

Rationale: The correct answer is C: Systemic arteries. Systemic arteries carry oxygenated blood from the heart to the rest of the body, delivering vital nutrients and oxygen to tissues and organs. Pulmonary arteries carry deoxygenated blood from the heart to the lungs for oxygenation. Pulmonary veins carry oxygenated blood from the lungs back to the heart. Systemic veins return deoxygenated blood from the body to the heart. It's important to differentiate between pulmonary and systemic vessels in understanding the circulation of blood throughout the body.

6. What is the difference between a sensory neuron and a motor neuron?

A. Sensory neurons carry signals away from the brain, while motor neurons carry signals towards the brain.
B. Sensory neurons control voluntary muscles, while motor neurons control involuntary muscles.
C. Sensory neurons are located in the peripheral nervous system, while motor neurons are located in the central nervous system.
D. Sensory neurons detect light, while motor neurons detect sound.

Correct answer: A

Rationale: The correct answer is A because sensory neurons are responsible for carrying signals from sensory receptors towards the central nervous system (brain and spinal cord), allowing us to perceive sensations such as touch, taste, smell, sight, and sound. On the other hand, motor neurons carry signals from the central nervous system to muscles and glands, enabling movement and responses. Therefore, sensory neurons carry signals away from the brain, while motor neurons carry signals towards the brain, making option A the most accurate choice among the options provided.