All Free Biology MCQs with Answers

• A. option A
• B. Option B
• C. Option C
• D. Option D

Explanation: The marked cells are neutrophils because they have multilobed nucleus. Neutrophils are white blood cells with a multi-lobed nucleusSo A is the correct option.

• A. Absence of blood capillaries
• B. Regulation of blood pressure
• C. Absence of respiratory pigments
• D. Flow of haemolymph in cavities

Explanation: In a closed circulatory system, blood circulates within a network of vessels, allowing for efficient regulation of blood pressure. This system enables precise control over the distribution of nutrients and oxygen to various tissues. Unlike open systems, closed systems have capillaries that connect arteries and veins. Option B is correct as it highlights the regulation of blood pressure as a characteristic feature. Options A and C are incorrect because blood capillaries and respiratory pigments are present in closed systems. Option D describes an open circulatory system, where haemolymph flows in cavities, not a closed system.

• A. Haemorrhage
• B. Atherosclerosis
• C. Arteriosclerosis
• D. Myocardial infarction

Explanation: The correct answer is haemorrhage. A haemorrhage is the medical term for the escape of blood from a ruptured blood vessel. This can occur in any part of the body. The other options describe different medical conditions: atherosclerosis involves the buildup of substances in arteries; arteriosclerosis refers to the hardening of the arteries; and myocardial infarction is a heart attack caused by blocked blood flow, not by a ruptured vessel.

• A. 24o
• B. 90o
• C. 144o
• D. 270o

Explanation: To determine the angle of the sector for blood group B, calculate it using the formula: (Number of students with blood group B / Total number of students) × 360°.=6/15×360°=144°So option C is correct.A, B and D mentions wrong angles.

• A. Aorta
• B. Veins
• C. Arteries
• D. Capillaries

Explanation: Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. The aorta is the largest artery of the body that carries oxygenated blood from the left ventricle of the heart to the rest of the body. Blood pressure is highest in the aorta because this is the location where the blood is ejected from the heart with the greatest force. As the blood moves away from the heart, the blood pressure gradually decreases

• A. 10
• B. 20
• C. 25
• D. 55
• E. 75

Explanation: Albumins constitute around 75% of the plasma proteins. They are the smallest of the plasma proteins and play an important role in maintaining the osmotic pressure of blood, which is necessary for the proper distribution of fluids between the blood and tissues.

• A. Non-nucleated
• B. In deficiency, cancer is caused
• C. Manufactured in thymus
• D. Can squeeze through blood capillaries

Explanation: The correct answer is that WBCs can squeeze through blood capillaries. This is due to their amoeboid shape and the process known as diapedesis. This ability allows them to move to areas of the body where they are needed, such as sites of infection or injury. The other options are incorrect: WBCs are nucleated, so 'non-nucleated' is false. While a deficiency in WBCs can weaken the immune system, it does not directly cause cancer; instead, an overproduction of WBCs is associated with leukemia, a type of cancer. Lastly, while some WBCs mature in the thymus, they are primarily produced in the bone marrow.

• A. Spleen
• B. Red bone marrow
• C. Kidney
• D. Liver

Explanation: Erythropoiesis is the formation of red blood cells (erythrocytes) which occurs in the red bone arrow. Proerythroblast is the earliest precursor which gives rise successively to the early erythroblast, intermediate erythroblast and late erythroblast. Then, the nucleus is forced out and a biconcave, enucleated cell called reticulocyte is formed, which is released into blood. In blood, it develops into mature erythrocytes. Red bone marrow, found in certain bones of the body, is the primary site for erythropoiesis. It is responsible for producing red blood cells (erythrocytes), along with other blood cell types like white blood cells and platelets. Red bone marrow contains stem cells known as hematopoietic stem cells that give rise to various blood cell lineages, including red blood cells.

• A. X: stroke, Y: haemorrhage,
• B. X: haemorrhage, Y: stroke,
• C. X: haemorrhage, Y: arteriosclerosis,
• D. X: stroke, Y: arteriosclerosis,

Explanation: Option A correctly identifies X as stroke (blood flow to brain stops) and Y(bleeding from a vessel) as haemorrhage, which align with the typical characteristics of these conditions in diagrams. Option B,C and D are incorrect.

• A. Thalamus
• B. Amygdala
• C. Hippocampus
• D. Hypothalamus

Explanation: The correct answer is the hippocampus, which plays a vital role in the formation and retrieval of long-term memories. It is part of the limbic system and is essential for memory consolidation. The other options are incorrect because they serve different primary functions: the thalamus is a relay station for sensory and motor signals, the amygdala is involved in emotion and emotional memory, and the hypothalamus regulates autonomic functions such as temperature and hunger.