All Free Biology MCQs with Answers

1961. heart beats 72 times in a male and _________Times in female in one minute.?

• A. 60 Times
• B. 70 Times
• C. 80 Times
• D. 85 Times

Explanation: A commonly taught comparison gives an average adult male heart rate of about 72 beats per minute and an adult female rate of about 80 beats per minute, making option c the intended answer. Students may choose 70 beats per minute by treating the male average as the female value, although actual heart rate varies with age, fitness and health rather than sex alone.

1962. from right ventricle the blood is pushed into________?

• A. pulmonary trunk
• B. brain
• C. aorta
• D. None of these

Explanation: The right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary trunk, which carries it toward the lungs. Students may choose the aorta because it is a major artery leaving the heart, but the aorta receives blood from the left ventricle, not the right ventricle.

1963. Life span of Red Blood Cells_____?

• A. 150 Days
• B. 120 Days
• C. 80 Days
• D. 100 Days

Explanation: Red blood cells circulate for about 120 days before ageing changes their membranes and they are removed mainly by the spleen and liver. Students may choose 150 days because RBCs survive for several months, but the standard average lifespan is 120 days.

1964. How many hearts does an Octopus have?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: An octopus has three hearts: two branchial hearts pump blood to the gills, while one systemic heart pumps oxygenated blood to the rest of the body. Students may choose one because humans have one heart, but the octopus has a specialised three-heart circulatory system.

1965. When the Left Ventricle in the human heart contracts, the blood moves to the_________ ?

• A. Brain
• B. Pulmonary Artery
• C. Aorta
• D. Lungs

Explanation: The left ventricle pumps oxygenated blood into the aorta, which distributes it through the systemic circulation to the body. The pulmonary artery leaves the right ventricle and carries deoxygenated blood to the lungs. Students may choose the brain because it receives blood from the aorta, but the ventricle first ejects blood into the aorta.

1966. Single circuit heart is found in_________?

• A. Fishes
• B. Amphibians
• C. Reptiles
• D. Mammals

Explanation: Fish have a two-chambered heart and a single circulatory circuit: heart to gills, gills to body tissues, and body tissues back to the heart. Amphibians, reptiles and mammals have double circulation, although reptiles and amphibians may have incomplete separation. Students may choose amphibians because their hearts are less completely divided, but they still possess pulmonary and systemic circuits.

1967. Tricuspid valve is present_____________?

• A. Between right atrium and right ventricle
• B. Between left atrium and left ventricle
• C. At base of pulmonary artery
• D. At base of aorta

Explanation: The tricuspid valve lies between the right atrium and right ventricle and prevents blood from flowing back into the atrium during ventricular contraction. Students may choose the left atrium and left ventricle because that pair also has an atrioventricular valve, but that valve is the bicuspid or mitral valve.

1968. The blood enters the ________________ side of heart ?

• A. Posterior
• B. Anterior
• C. Lateral
• D. All possible

Explanation: In the usual anatomical description, blood enters the heart from the posterior side through the atria and leaves through vessels located more anteriorly. The venae cavae and pulmonary veins bring blood into the atria, while the ventricles pump it out through the arteries. Students may choose anterior because the major arteries are prominent at the front, but those vessels carry blood away rather than into the heart.

1969. Deoxygenated blood first enters in _________ part in fishes?

• A. Sinus venosus
• B. Right atrium
• C. Left atrium
• D. Conus arteriosus

Explanation: In fish, blood returning from body tissues first enters the sinus venosus, which passes it to the atrium and then the ventricle. Fish have a single atrium rather than separate right and left atria, so students may incorrectly select right atrium by applying the mammalian heart plan.

1970. 95% of the cytoplasm of RBCs is____________?

• A. Hemoglobin
• B. Enzymes
• C. Salts
• D. Other proteins

Explanation: About 95% of the dry cytoplasmic content of a red blood cell is hemoglobin, the iron-containing protein that binds and transports oxygen. Enzymes and salts are present in smaller amounts, so students may choose d by treating all non-hemoglobin proteins as the major component.