All Free Biology MCQs with Answers

• A. Ethene
• B. Gibberellins
• C. Cytokinins
• D. Abscisic acid

Explanation: Stomatal closure is a common adaptation response of plants to the onset of drought condition

• A. Somatotropin hormone
• B. Thyroid stimulating hormone
• C. Antidiuretic hormone
• D. Gonadotrophic hormone

Explanation: ADH is produced by the hypothalamus in the brain and stored in the posterior pituitary gland at the base of the brain. The anterior pituitary gland produces six major hormones: (1) prolactin (PRL), (2) growth hormone (GH), (3) adrenocorticotropic hormone (ACTH), (4) luteinizing hormone (LH), (5) follicle-stimulating hormone (FSH), and (6) thyroid-stimulating hormone (TSH). The somatotropin hormone is also called the growth hormone.

• A. ADH
• B. Thyroxin
• C. Cortisone
• D. Insulin

Explanation: Steroid hormones are fat-soluble molecules made from cholesterol. Among these are the three major sex hormone groups: estrogens, androgens, and progesterones. Males and females make all three, just in different amounts. The steroids that are made almost exclusively in the adrenal glands are cortisol, 11-deoxycortisol, aldosterone, corticosterone, and 11-deoxycorticosterone. Most other steroid hormones, including estrogens, are made by the adrenal glands and the gonads.

• A. Nervous stimulation
• B. Chemical stimulation
• C. Both chemical and nervous stimulation
• D. None of the given options

Explanation: The diameter of any given vessel may also change frequently throughout the day in response to neural and chemical signals that trigger vasodilation and vasoconstriction.

• A. Adrenaline
• B. Non adrenaline
• C. Thyroxin
• D. Insulin

Explanation: Adrenaline triggers the body's fight-or-flight response. This reaction causes air passages to dilate to provide the muscles with the oxygen they need to either fight danger or flee. Adrenaline also triggers the blood vessels to contract to re-direct blood toward major muscle groups, including the heart and lungs.

• A. Auxins
• B. Gibberellins
• C. Abscisic acid
• D. Cytokinins
• E. All of the above

Explanation: Phytohormones are critical for plant growth, development, and responses to stimuli. Auxins are directly involved in tropisms, which are movements towards or away from stimuli. Gibberellins, while primarily growth hormones, also influence tropic movements by modulating growth patterns. Abscisic acid is more related to stress responses but contributes to movement by regulating stomatal closure. Cytokinins affect growth and cell division, indirectly influencing movement. Thus, all these hormones together play a role in plant movements and responses.

• A. Pituitary
• B. Adrenal gland
• C. Thyroid
• D. Parathyroid
• E. Pancreas

Explanation: The adrenal glands are often referred to as the "glands of emergency" because they play a crucial role in the body's stress response. These glands produce hormones such as adrenaline and cortisol, which prepare the body to respond to stressful situations by increasing heart rate, raising blood pressure, and mobilizing energy resources.

• A. Trypsin
• B. Pepsin
• C. Chymotrypsin
• D. Amylase
• E. Lipase

Explanation: Secretin is a hormone that primarily stimulates the pancreas to release digestive enzymes such as trypsin, chymotrypsin, amylase, and lipase. These enzymes are crucial for the digestion of proteins, carbohydrates, and fats in the small intestine. However, pepsin is an enzyme produced in the stomach and is not under the regulatory influence of secretin. Instead, pepsinogen (the inactive form of pepsin) is activated in the acidic environment of the stomach. Therefore, blocking secretin production affects all listed pancreatic enzymes but does not influence pepsin levels. Hence, the correct answer is Pepsin, as it would not be affected by the blockage of secretin.

• A. To increase the rate of breathing
• B. To increase the heart rate
• C. To increase the level of calcium in blood
• D. Both A and B

Explanation: Adrenaline is released in a fight or flight situation. In flight or fight conditions, both the breathing rate and the heart rate increase in order to increase alertness.

• A. Cushing's syndrome
• B. Addison's disease
• C. Diabetes Mellitus
• D. Goiter
• E. Epilepsy

Explanation: Addison's disease is the result of insufficient production of hormones from the adrenal glands, particularly cortisol and aldosterone. This condition leads to symptoms such as fatigue, muscle weakness, and low blood pressure. Cushing's syndrome, in contrast, is caused by excessive cortisol. Diabetes Mellitus involves insulin issues and not adrenal hormones. Goiter relates to thyroid gland issues, and epilepsy is a neurological disorder, both unrelated to adrenal insufficiency.