All Free Biology MCQs with Answers

1991. A condition in which there is a decrease of oxygen to the tissue despite adequate blood flow to the tissue is_________?

• A. Aphasia
• B. Dysphasia
• C. Hypoxia
• D. None

Explanation: Hypoxia means inadequate oxygen availability to body tissues; it can occur even when blood flow is adequate if oxygen delivery or cellular use is impaired. Students may choose one of the aphasia terms because both describe functional problems, but aphasia and dysphasia concern language, not tissue oxygen deficiency.

1992. Parabronchi are present in__________?

• A. cockroach
• B. frog
• C. fish
• D. birds

Explanation: Parabronchi are the fine respiratory passages in bird lungs, where air flows continuously and gas exchange occurs through surrounding air capillaries. Students may choose frog because frogs have lungs, but frog lungs contain larger chambers and lack the parabronchial system of birds.

1993. Vocal cords are stretched across_______?

• A. Larynx
• B. Pharynx
• C. Golttis
• D. None of these

Explanation: The vocal cords are stretched across the glottis, which is the opening of the larynx through which air passes. The larynx contains the vocal cords, but the cords specifically span the glottis. Students often choose larynx because it is the voice box, but larynx is the structure containing the glottis.

1994. In most birds air sacs are ____________ in number?

• A. 10
• B. 3
• C. 4
• D. 9

Explanation: Most birds have nine air sacs: cervical, clavicular, anterior thoracic, posterior thoracic and abdominal sacs. These sacs act as bellows and maintain a continuous flow of air through the lungs. The common mistake is choosing 10 by confusing the number of air sacs with the number of lungs or air passages.

1995. Parabronchi are open at ______________ end/s?

• A. Single
• B. Both
• C. Do not have opening
• D. None of these

Explanation: Parabronchi are the fine respiratory tubes in bird lungs, and they are open at both ends. Air flows through them continuously, while capillaries around them receive oxygen by cross-current exchange. A student may choose single because many ordinary air passages are described as having one inlet and one outlet without recognising that both ends of a parabronchus are open.

1996. Respiratory distress syndrome is common especially for infants with a__________?

• A. Less than 7 month
• B. Less than 8 month
• C. Less than 9 month
• D. More than 9 month

Explanation: Respiratory distress syndrome is especially common in very premature infants, particularly those born before about seven months of gestation, because their lungs have insufficient surfactant. Surfactant prevents alveoli from collapsing during expiration. Students may choose less than 8 months because prematurity at that stage is also risky, but the traditional threshold used in this question is seven months.

1997. Gaseous exchange through the skin is known as ______________ respiration?

• A. Cuticular
• B. Cutaneous
• C. Skin
• D. Pulmonary

Explanation: Gaseous exchange through the skin is called cutaneous respiration. Oxygen diffuses through the moist skin into blood and carbon dioxide diffuses out, as seen prominently in earthworms and amphibians. Cuticular respiration is a tempting choice because it refers to exchange through a cuticle, not the skin itself.

1998. All of the following contain cartilage except:___________?

• A. Larynx
• B. Trachea
• C. Bronchi
• D. Bronchioles

Explanation: The trachea, bronchi and larynx contain cartilage that keeps their air passages open. Bronchioles have no cartilage rings and instead contain smooth muscle, so their diameter can change during breathing. Students often select bronchi because they are smaller than the trachea, but bronchi still possess cartilage plates.

1999. Voice box is another name used for___________?

• A. Buccal cavity
• B. Pharynx
• C. Larynx
• D. Chest Cavity

Explanation: The larynx is called the voice box because it contains the vocal cords, which vibrate as air passes between them. The pharynx is a shared passage for food and air but does not contain the vocal cords. The likely mistake is choosing pharynx because it lies just above the larynx in the throat.

2000. Which of the following animals has a respiratory system with one way flow of the air through the lungs, and the air is renewed after inspiration?

• A. Cockroach
• B. Earthworm
• C. Aves
• D. Frogs

Explanation: Birds have a unidirectional respiratory system in which air sacs drive air through the parabronchi during both inhalation and exhalation. This keeps fresh air moving across the respiratory surfaces and makes gas exchange highly efficient. Students may choose cockroach because it also has a specialised respiratory system, but cockroach tracheae do not produce the bird-like one-way lung flow.