All Free Biology MCQs with Answers

2151. Which of the followings is missing from the nervous system of planaria_____________?

• A. Ganglia
• B. Longitudinal nerves
• C. Lateral nerves
• D. none of these

Explanation: Planaria has cerebral ganglia, paired longitudinal nerve cords, and transverse lateral connections, giving it a ladder-like nervous system. Students may choose ganglia because planaria is a simple animal, but it does possess a pair of anterior cerebral ganglia.

2152. Co-ordination in man is brought about by___________?

• A. Nervous system
• B. Endocrine system
• C. Both of these
• D. none of these.

Explanation: Coordination in humans involves rapid electrical control by the nervous system and slower, longer-lasting chemical control by the endocrine system. Choosing only the nervous system ignores hormonal coordination, while choosing only the endocrine system ignores nerve impulses.

2153. Hydra has___________?

• A. Brain
• B. Nerves
• C. Neuron-cells
• D. All of these

Explanation: Hydra has a diffuse network of nerve cells, called a nerve net, but it has no brain or central nervous system. The likely mistake is selecting all of these by assuming every animal with neurons also has a brain.

2154. Which of the followings are effectors______________?

• A. Muscles
• B. Glands
• C. Sensory organs
• D. Both 'a' & 'b'

Explanation: Effectors are muscles and glands because they produce a response to nerve or hormonal signals, such as contraction or secretion. Sensory organs are receptors, not effectors, so choosing only option c confuses detection of a stimulus with execution of a response.

2155. Co-ordination results in_____________?

• A. Regulation of body functions
• B. Organization of body functions
• C. Integration of body functions
• D. All of these

Explanation: Coordination integrates information and organizes body activities so that functions are regulated and produce a suitable overall response. Students may select only integration because it is the central definition, but regulation and organization are also outcomes of coordination.

2156. Maximum speed of nerve impulse transmission is____________?

• A. 100 m/sec
• B. 110 m/sec
• C. 120m/sec
• D. 130 m/sec.

Explanation: The fastest impulses in heavily myelinated neurons travel at about 120 m/sec, or 120 metres per second, because myelin allows saltatory conduction between nodes of Ranvier. Students may choose 100 m/sec because it is a commonly quoted approximate speed, but it is not the maximum value used here.

2157. Which of the following has no central nervous system?

• A. Hydra
• B. Man
• C. Planaria
• D. Cockroach

Explanation: Hydra has a diffuse nerve net but no central nervous system, brain, or spinal cord. Planaria, cockroach, and humans all possess central concentrations of nervous tissue, so choosing planaria overlooks its cerebral ganglia and longitudinal nerve cords.

2158. Number of pairs of cranial nerves is__________?

• A. 10
• B. 11
• C. 12
• D. 13

Explanation: Humans have 12 pairs of cranial nerves, arising from the brain and mainly serving the head and neck. Students may choose 10 pairs because some older simplified lists or confusion with spinal nerve groups lead to an undercount.

2159. Normal resting membrane potential of a neuron is_____________?

• A. - 50 mv
• B. - 60 mv
• C. - 70 mv
• D. - 80 mv

Explanation: A neuron's resting membrane potential is approximately -70 mV because the membrane is more permeable to K+ than Na+ and the Na+-K+ pump maintains unequal ion distributions. Students may choose -60 mV or -80 mV because the exact value varies slightly among cells, but -70 mV is the standard value.

2160. Cell membrane under resting conditions is impermeable to all the ions except_____________?

• A. Na+
• B. K+
• C. Cl-
• D. PO4-2

Explanation: At rest, the neuronal membrane has many potassium leak channels and is therefore much more permeable to K+ than to Na+ or large intracellular anions. K+ tends to diffuse outward, helping establish the negative resting potential inside the cell. The likely alternative is Na+, because sodium is important during the action potential, but resting permeability to Na+ is relatively low.