All Free Biology MCQs with Answers

1021. Which one of the following biomolecules is a polymer/polysaccharide?

• A. Sucrose
• B. Pentose
• C. Lactose
• D. Glycogen

Explanation: Glycogen is a highly branched polymer of thousands of glucose units, stored in liver and muscle as the animal energy reserve. Sucrose and lactose are disaccharides of just two units and pentose is a single five carbon sugar, so none of them is a polymer. The test is whether the molecule can be hydrolysed into many repeating units.

1022. Olfactory receptors are the type of:

• A. photoreceptors
• B. mechanoreceptors
• C. thermoreceptors
• D. chemoreceptors

Explanation: Smell depends on molecules dissolving in the mucus and binding receptor proteins in the nasal epithelium, so olfactory receptors respond to chemicals and are chemoreceptors, as are the taste buds. Photoreceptors detect light in the retina and mechanoreceptors detect pressure, touch and sound. Classifying a receptor means asking which form of energy or signal it transduces.

1023. Which of the following organisms eliminate nitrogenous waste mainly in the form of uric acid?

• A. Freshwater Fish
• B. Amphibians
• C. Birds
• D. Mammals

Explanation: Uric acid is almost insoluble, so it can be excreted as a paste with very little water, which suits birds both for flight and for developing inside a shelled egg where waste must be stored safely. Freshwater fish excrete ammonia directly into the surrounding water, and mammals and adult amphibians make urea. The choice of waste product tracks how much water the animal can afford to lose.

1024. Which of the following cells possess Nissl's granules?

• A. Nerve cells
• B. WBC
• C. RBC
• D. Platelets

Explanation: Nissl granules are stacks of rough endoplasmic reticulum in the cell body of a neurone, supporting the heavy protein synthesis a nerve cell requires. Mature red blood cells have no nucleus and almost no organelles at all, and platelets are only cell fragments. Their loss after injury, called chromatolysis, is a recognised sign of neuronal damage.

1025. Which part of human brain is involved in maintaining the posture and balance of the body?

• A. Cerebrum
• B. Cerebellum
• C. Hypothalamus
• D. Medulla oblongata

Explanation: The cerebellum receives information from muscles, joints and the balance organs of the inner ear and smooths the commands issued by the cerebrum, so damage to it leaves movement clumsy and unsteady even though strength is normal. Alcohol depresses it, which is why an intoxicated person staggers. The medulla controls heart rate and breathing instead.

1026. Arthritis is:

• A. Inflammation of joints
• B. Herniation of intervertebral disc
• C. Fusion of vertebral joint
• D. Tingling along the length of legs

Explanation: The word itself means inflammation of a joint, from arthron for joint and itis for inflammation, and it covers osteoarthritis, rheumatoid arthritis and gout despite their very different causes. A herniated disc is a slipped disc pressing on a nerve, which produces the tingling described in the last option. Reading the suffix is often enough with medical terms of this kind.

1027. Which type of joint is present in pubis?

• A. Fibrous joints
• B. Immoveable joints
• C. Cartilaginous joints
• D. Freely moveable joints

Explanation: The pubic symphysis is a cartilaginous joint, its two bones joined by a pad of fibrocartilage that allows slight movement, which becomes important during childbirth when the ligaments soften. Fibrous joints such as the skull sutures allow no movement at all, and freely movable synovial joints have a fluid filled cavity. Cartilaginous joints sit between these two extremes.

1028. Which type of neurons stimulate muscles to contract in a reflex arc?

• A. Motor neurons
• B. Sensory neurons
• C. Interneurons
• D. Afferent neurons

Explanation: Motor, or efferent, neurones carry impulses away from the central nervous system to the effector, which in this case is a muscle that contracts. Sensory and afferent are two names for the same thing, neurones carrying impulses inwards, which is why both appear as options. Interneurones link the two inside the spinal cord but do not reach the muscle.

1029. Which of the following statements best compares cell division in prokaryotic and eukaryotic cells?

• A. Eukaryotes divide by budding; prokaryotes by mitosis
• B. Eukaryotes use binary fission; prokaryotes by meiosis
• C. Eukaryotes divide by mitosis; prokaryotes by binary fission
• D. Both use mitosis by cell division

Explanation: Mitosis needs a spindle and organised chromosomes, which only eukaryotes possess, while a prokaryote simply replicates its single circular chromosome and splits by binary fission. This is much faster, which is why bacteria can divide every twenty minutes. Meiosis is confined to eukaryotes producing gametes.

1030. Which of the following best describes "acquired characteristics" according to Lamarckism?

• A. Traits caused by mutation
• B. Traits inherited from parents
• C. Traits developed by use or disuse
• D. Traits selected by nature

Explanation: Lamarck held that an organ strengthens with use and withers with disuse during an individual's own lifetime, and that this change is then passed on. Weismann's germ plasm work disproved the inheritance step, since changes to body cells never reach the gametes. Mutation and natural selection belong to the modern account that replaced it.