All Free Biology MCQs with Answers

1391. Which of the following is true about hearts of earthworm?

• A. There are 5-7 pairs of heart.
• B. They are present between 1-7th segments.
• C. They are present lateral to the oesophagus.
• D. They pump blood from ventral to dorsal vessel.Standardized & Admissions Tests

Explanation: Earthworms have several pairs of muscular aortic arches, commonly called hearts, located around the oesophagus in the anterior segments. These vessels lie lateral to the oesophagus and connect the dorsal and ventral blood vessels. Students may choose option a because earthworms are often described as having five pairs, but the location given in option c is the more reliable identifying feature and the number can vary with the description used.

1392. Open circulatory system can contain_________?

• A. Red Blood Cells
• B. White Blood Cells
• C. Haemoglobin
• D. All of these

Explanation: Open circulatory systems contain hemolymph, which may include circulating cells called hemocytes that perform functions comparable to white blood cells. Red blood cells and haemoglobin are characteristic of vertebrate blood and are generally absent from the hemolymph of animals with open circulation. Students may choose all of these because they are familiar components of vertebrate blood, but open systems do not generally contain red blood cells or haemoglobin.

1393. 95% of the cytoplasm of red blood cells is the___________?

• A. Antibodies
• B. Hemoglobin
• C. Enzymes
• D. Proteins

Explanation: Haemoglobin makes up most of the dry protein content of a red blood cell and occupies much of its cytoplasm, allowing the cell to transport oxygen. Antibodies and enzymes are present in much smaller amounts and are not the main cytoplasmic component. Students may choose proteins because haemoglobin is a protein, but the question asks for the specific protein that predominates, namely haemoglobin.

1394. _________ give rise to macrophages, which destroy larger particles by phagocytosis.

• A. Nautrophils
• B. Basophila
• C. Monocyte
• D. Lymphocyte

Explanation: Monocytes leave the bloodstream and differentiate into macrophages in tissues, where they engulf and digest large particles and pathogens by phagocytosis. Neutrophils also perform phagocytosis, but they do not normally give rise to macrophages. Students may choose neutrophils because they are abundant phagocytic white blood cells, but macrophages develop specifically from monocytes.

1395. Cooley's anemia is another name used for___________?

• A. Leucemia
• B. Thalassaemia
• C. Sickle cell anemia
• D. None of these

Explanation: Cooley's anaemia is beta-thalassaemia major, an inherited disorder in which defective beta-globin production causes severe anaemia. Students may choose sickle-cell anaemia because both are inherited haemoglobin disorders, but sickle-cell disease results from abnormal haemoglobin shape rather than reduced beta-globin synthesis.

1396. Which of the following have thickest walls?

• A. Arteries
• B. Veins
• C. Capillaries
• D. None of these

Explanation: Arteries have the thickest and most muscular and elastic walls because they receive blood at high pressure directly from the ventricles. Students may choose veins because they are larger and may appear substantial, but veins carry blood at lower pressure and therefore have thinner walls.

1397. It is the measure of force with which blood pushes up against the walls of blood vessels.

• A. Stroke volume
• B. Cardiac output
• C. Blood pressure
• D. Blood flow

Explanation: Blood pressure is the force exerted by circulating blood against the walls of blood vessels, usually expressed in mmHg. Students may choose blood flow, but flow means the movement or volume of blood, not the pressure causing force on vessel walls.

1398. All of the follwing are blood clots except:___________?

• A. Thrombus
• B. Embolus
• C. Atheroma
• D. Hematoma

Explanation: An atheroma is a fatty, cholesterol-rich plaque in an arterial wall, not a blood clot. Students may choose an embolus because it can block a vessel, but an embolus is often a travelling clot or other material, whereas an atheroma is a plaque.

1399. It is the discharge of blood from blood vessels?

• A. Myocardial infarction
• B. Cerebral infarction
• C. Cerebral Hemorrhage
• D. Thromboembolism

Explanation: Cerebral haemorrhage is bleeding caused by rupture of a blood vessel in or around the brain. Students may choose thromboembolism because it also involves blood vessels, but thromboembolism is blockage by a travelling clot, not discharge of blood.

1400. All of the following veins carry deoxygenated blood except

• A. Superior vena cava
• B. Inferior vena cava
• C. Hepatic vein
• D. Pulmonary vein

Explanation: The pulmonary vein carries oxygen-rich blood from the lungs to the left atrium, making it the exception among these veins. The likely mistake is the hepatic vein, but it carries oxygen-poor blood away from the liver toward the inferior vena cava.