1. Negative feedback mechanisms are crucial in the endocrine system to:

A. Increase hormone production continuously
B. Maintain hormone levels within a specific range
C. Cause a constant release of hormones
D. Disrupt communication between glands

Correct answer: B

Rationale: The correct answer is B: 'Maintain hormone levels within a specific range.' Negative feedback mechanisms in the endocrine system are essential for regulating hormone levels. These mechanisms work to counteract any deviations from the set point, ensuring that hormone levels remain balanced and within the optimal range for proper physiological function. Continuous hormone production (A) or constant release of hormones (C) would lead to imbalances and potential harm to the body. Disrupting communication between glands (D) would hinder the coordination necessary for maintaining homeostasis. Therefore, option B is the best choice as it highlights the critical role of negative feedback in keeping hormone levels stable and regulated.

2. What is the function of introns in eukaryotic genes?

A. They code for protein sequences.
B. They are involved in gene regulation.
C. They are removed during mRNA processing.
D. They are non-functional remnants of ancient DNA.

Correct answer: C

Rationale: Rationale: A) Introns do not code for protein sequences. Exons are the segments of DNA that code for proteins. B) While introns can indirectly influence gene regulation, their primary function is not directly involved in gene regulation. C) Introns are non-coding regions of DNA that are transcribed into pre-mRNA but are removed during mRNA processing through a process called splicing. This allows only the exons to be included in the mature mRNA that will be translated into proteins. D) While introns were once thought to be non-functional remnants of ancient DNA, research has shown that they can have regulatory functions and play a role in gene expression.

3. he adrenal cortex produces a group of steroid hormones called corticosteroids. What is a MAJOR function of corticosteroids?

A. Regulate insulin sensitivity and blood sugar levels
B. Control blood pressure and electrolyte balance
C. Stimulate the immune system and inflammatory response
D. Promote growth and development during puberty

Correct answer: B

Rationale: The correct answer is B: 'Control blood pressure and electrolyte balance.' Corticosteroids, produced by the adrenal cortex, play a major role in regulating blood pressure and electrolyte balance in the body. These hormones, such as aldosterone, act on the kidneys to control the reabsorption of sodium and water, which in turn affects blood pressure and electrolyte levels. While corticosteroids can have effects on other physiological processes, their primary function is to regulate blood pressure and electrolyte balance, making option B the most appropriate choice in this context.

4. Which structure connects the two hemispheres of the brain, allowing communication and coordination between them?

A. Corpus callosum
B. Thalamus
C. Hypothalamus
D. Medulla oblongata

Correct answer: a

Rationale: The correct answer is A: Corpus callosum. The corpus callosum is a broad band of nerve fibers that connects the left and right hemispheres of the brain, allowing them to communicate and coordinate with each other. It enables the transfer of information between the two hemispheres, which is essential for various functions such as sensory processing, motor coordination, and cognitive processes. The thalamus (B) is a different brain structure responsible for relaying sensory signals to the cerebral cortex, while the hypothalamus (C) regulates various vital functions such as body temperature, hunger, and hormone release. The medulla oblongata (D) is located in the brainstem and controls vital autonomic functions like breathing and heart rate. Therefore, the corpus callosum is the correct answer as it directly connects the two hemispheres of the brain for communication and coordination.

5. During which phase of the cardiac cycle do the atria contract, pushing blood into the ventricles?

A. Atrial diastole
B. Ventricular systole
C. Atrial systole
D. Ventricular diastole

Correct answer: C

Rationale: The correct answer is C: Atrial systole. During the cardiac cycle, the atria contract during atrial systole, pushing blood into the ventricles. This phase occurs after atrial diastole when the atria fill with blood. Ventricular diastole (option D) is when the ventricles relax and fill with blood, preparing for ventricular systole (option B), which is when the ventricles contract to pump blood out of the heart. Atrial systole is crucial for ensuring efficient filling of the ventricles before they contract, making it a key phase in the cardiac cycle.

6. In plant cells, what structure provides rigidity and support?

A. Cell membrane
B. Golgi apparatus
C. Plastid
D. Cell wall

Correct answer: D

Rationale: The correct answer is D: Cell wall. The cell wall is a rigid structure found in plant cells that provides support and protection. It is composed of cellulose and other materials, forming a tough outer layer that helps maintain the cell's shape and prevents it from bursting under pressure. The cell membrane (option A) is a semi-permeable barrier that surrounds the cell but does not provide rigidity. The Golgi apparatus (option B) is involved in sorting and packaging proteins. Plastids (option C) are organelles responsible for functions like photosynthesis and storage, but they do not provide rigidity and support like the cell wall does.