All Free Biology MCQs with Answers

• A. 6-8 days
• B. 9-15 days
• C. 16-22 days
• D. 22-28 days

Explanation: This is generally considered the fertile window in the menstrual cycle.

• A. Skeletal muscles
• B. Smooth muscles
• C. Cardiac muscles
• D. All of the above

Explanation: Smooth muscles are uniquely adapted to sustain long-term contractions with minimal energy consumption.

• A. Released from the sarcoplasmic reticulum into the sarcoplasm
• B. Transported back from the sarcoplasm into the sarcoplasmic reticulum
• C. Further released from the sarcoplasmic reticulum into the sarcoplasm
• D. Remain constant without any movement

Explanation: During muscle relaxation, calcium ions are actively transported back from the sarcoplasm into the sarcoplasmic reticulum, which decreases…

• A. I-Line
• B. A-Line
• C. Z-Line
• D. M-Line

Explanation: Option C is correct. The sarcomere is the region of a myofibril between two successive Z-lines.

• A. Sodium
• B. Calcium
• C. Magnesium
• D. Potassium

Explanation: Option B is correct. According to the sliding filament hypothesis, the release of calcium ions from the sarcoplasmic reticulum causes the…

• A. Adenosine triphosphate, Lactic acid
• B. Adenosine triphosphate, Ionic imbalance
• C. Glucose, Lactic acid
• D. Glucose, Ionic imbalance

Explanation: Muscle fatigue occurs when muscles are unable to generate force or contract due to a combination of factors. The two main factors are: 1.

• A. Striped
• B. Unstriped
• C. Cardiac
• D. Triceps

Explanation: The correct answer is 'Cardiac' because cardiac muscles are uniquely adapted to contract continuously throughout a person's life without…

• A. Tendon
• B. Ligaments
• C. Elastic fibers
• D. Areolar

Explanation: The correct answer is 'Tendon'. Tendons are strong bands of connective tissue that connect muscles, like the bicep, to bones such as the…

• A. Bone
• B. Connective tissue
• C. Muscles
• D. Cartilage

Explanation: Myoglobin is a protein found in muscle fibers, responsible for storing oxygen and facilitating its availability during muscle contraction.

• A. Afferent neuron
• B. Efferent neuron
• C. Associative neuron
• D. Interneuron

Explanation: Afferent neurons, also known as sensory neurons are responsible for establishing a link between the sensory organ and the central nervous…

• A. Areolar tissue
• B. Tendon
• C. Neuron
• D. Ligament

Explanation: Neurons are specialized cells that make up nervous tissue, which is responsible for transmitting signals throughout the body.

• A. 8 pairs
• B. 10 pairs
• C. 12 pairs
• D. 31 pairs

Explanation: Humans have 12 pairs of cranial nerves that emerge directly from the brain, each designated with a specific function.

• A. Thicker the nerve fiber-less resistance to flow of current-faster the nerve impulse.
• B. Thicker the nerve fiber-more resistance to flow of current-slower the nerve impulse
• C. Thinner the nerve fiber-less resistance to flow of current-slower the nerve impulse
• D. None of the above

Explanation: The correct answer is that thicker nerve fibers have less resistance to the flow of current, leading to faster nerve impulse transmission.

• A. 5
• B. 10
• C. 15
• D. 20

Explanation: The Na+/K+ pump, also known as Na+/K+-ATPase, is crucial in maintaining the resting membrane potential of cells by actively transporting…

• A. Para sympathetic
• B. Sympathetic
• C. Somatic
• D. Peripheral

Explanation: The parasympathetic nervous system predominates in quiet "rest and digest" conditions while the sympathetic nervous system drives the…

• A. Na+ into the axon and K+ out of the axon
• B. K+ into the axon and Na+ out of the axon
• C. Na+ and K+ within the axon toward the axon terminal
• D. Increased Na+ permeability leading to an influx of Na+

Explanation: When a neuron fiber is stimulated by a stimulus of adequate strength (threshold stimulus), the stimulated area of the fiber becomes…

• A. Respiratory system
• B. Nervous system
• C. Circulatory system
• D. Bones and muscles

Explanation: Tetanus is an infection of the nervous system caused by Clostridium tetani bacteria.

• A. Myofibrils
• B. Lines
• C. Sarcolemma
• D. Dendrites

Explanation: Dendrites are specialized extensions of nerve cells that receive electrical signals from other nerve cells and transmit them towards the…

• A. All leaves
• B. A few leaves
• C. All branches except one
• D. All floral bud except one

Explanation: Removing all floral buds except one is the correct method to promote the growth of larger chrysanthemum flowers.

• A. 15.5 hours
• B. 9 hours
• C. 11 hours
• D. 13 hours

Explanation: Hyoscyamus, like many plants, has a specific photoperiod requirement known as the critical day length, which is the minimum daylight hours…