All Free Biology MCQs with Answers

2241. Types of behaviour enabling pillbugs to reach moist area is___________?

• A. Kinesis
• B. Taxes
• C. Instinct
• D. Learning

Explanation: Pillbugs respond to humidity by changing the speed of their movement, moving more rapidly in dry conditions and slowing in moist conditions; this is kinesis. Kinesis is a non-directional response whose rate depends on stimulus intensity, whereas taxis involves movement directly toward or away from a stimulus. The likely alternative is taxis, but pillbugs do not need to detect and move in a fixed direction toward moisture.

2242. ____________ was first to propose an objective definition of instinct.

• A. Thorpe
• B. Darwin
• C. Pavlov
• D. Kohler

Explanation: Darwin gave one of the earliest objective biological descriptions of instinct as an inherited behavioural tendency rather than a conscious decision. This placed instinct within evolutionary biology and distinguished it from behaviour acquired through learning. The likely alternative is Thorpe, who later made important contributions to ethology, but he was not the first in the usual textbook account.

2243. ____________ is simplest form of learning.

• A. Imprinting
• B. Habituation
• C. Insight learning
• D. Latent learning

Explanation: Habituation is the simplest form of learning because an organism gradually stops responding to a repeated, harmless stimulus. The response decreases without requiring reward, punishment, or complex reasoning. The likely alternative is imprinting, but imprinting is a more specialized form of learning that occurs during a sensitive developmental period.

2244. Which type of sensory structures carry deep pressure and vibration sensations______________?

• A. Hair end organs
• B. Meissner's Corpuscles
• C. Pacinian corpuscles
• D. none of these

Explanation: Pacinian corpuscles are rapidly adapting mechanoreceptors located deep in the skin and subcutaneous tissues, where they detect deep pressure and high-frequency vibration. Meissner's corpuscles mainly detect light touch and low-frequency vibration near the skin surface. The likely alternative is Meissner's corpuscles because they also sense touch, but they are not the main receptors for deep pressure.

2245. Which type of sensory structures carrying the touch sensations are present in papillae extending into ridges of the fingertips___________________?

• A. Hair end organs
• B. Meissner's Corpuscles
• C. Pacinian corpuscles
• D. None of these

Explanation: Meissner's corpuscles lie in the dermal papillae of sensitive skin, including the ridges of the fingertips, and detect fine or light touch. Their superficial position makes them suitable for detecting small movements across the skin. The likely alternative is Pacinian corpuscles, but those are deeper and specialize in vibration and deep pressure.

2246. Type of sensations carried by nociceptors are_________________?

• A. Touch.
• B. Temperature.
• C. Pressure.
• D. Pain

Explanation: Nociceptors are free nerve endings that respond to potentially damaging mechanical, thermal, or chemical stimuli and produce the sensation of pain. They are responsible for warning the body about tissue injury rather than detecting ordinary touch or pressure. The likely alternative is temperature, because extreme heat or cold can activate nociceptors, but their characteristic sensation is pain.

2247. Which type of the receptors are present in the ear__________________?

• A. Chemoreceptors
• B. Mechanoreceptors
• C. Photoreceptors
• D. Thermoreceptors

Explanation: Hearing and balance depend on hair cells that respond to mechanical displacement caused by sound waves or movement of fluid in the inner ear. Therefore, the receptors of the ear are mechanoreceptors. The likely alternative is photoreceptors, but photoreceptors detect light in the retina, not mechanical vibrations in the ear.

2248. Reflex actions below the neck are under control of____________?

• A. Brain
• B. Spinal cord
• C. Hypothalamus
• D. none of these.

Explanation: Most reflex actions below the neck are integrated through reflex arcs in the spinal cord, allowing rapid responses without waiting for conscious processing by the brain. Students may choose the brain because it can receive information about the reflex, but the immediate coordination is performed by the spinal cord.

2249. There are mainly __________ types of tRNA?

• A. 170
• B. 20
• C. 25
• D. 15

Explanation: In the basic genetic code, there are mainly 20 functional types of tRNA, each associated with one of the 20 standard amino acids. Some cells have additional isoacceptor tRNAs for the same amino acid, but the standard classification is based on 20 amino acids. Students may choose 25 by counting extra tRNA varieties rather than the main amino-acid-specific types.

2250. rRNA constitutes ____________% of the total cellular RNA?

• A. 3-4 %
• B. 10-20%
• C. 80%
• D. 90%

Explanation: Ribosomal RNA makes up about 80% of the total RNA in a typical cell because ribosomes contain a large amount of rRNA and cells have many ribosomes. Messenger RNA and transfer RNA form much smaller fractions. Students may choose 90% by overestimating the dominance of rRNA or confusing total cellular RNA with ribosomal RNA within a ribosome.