All Free Biology MCQs with Answers

911. Allopatric speciation requires

• A. Same habitat
• B. Geographic isolation
• C. Polyploidy
• D. Sympatric conditions

Explanation: Allopatric speciation occurs when populations are separated by a geographic barrier, leading to reproductive isolation.

912. Analogous structures result from

• A. Common ancestry
• B. Convergent evolution
• C. Divergent evolution
• D. Vestigial development

Explanation: Analogous structures (different origin, same function) result from convergent evolution, e.g., wings of bats and insects.

913. The modern synthesis combines

• A. Darwin and Mendel
• B. Lamarck and Darwin
• C. Mendel and Morgan
• D. Watson and Crick

Explanation: The modern evolutionary synthesis combines Darwin's natural selection with Mendelian genetics and population genetics.

914. Vestigial organs are

• A. Essential for survival
• B. Reduced non-functional remnants
• C. Newly evolved structures
• D. Only found in embryos

Explanation: Vestigial organs (appendix, coccyx) are reduced remnants of structures functional in ancestors.

915. Gene flow between populations

• A. Increases genetic differences
• B. Decreases genetic differences
• C. Has no effect
• D. Causes speciation

Explanation: Gene flow (migration) decreases genetic differences between populations by exchanging alleles.

916. Punctuated equilibrium proposes

• A. Constant slow change
• B. Rapid change followed by stability
• C. No change over time
• D. Only gradual change

Explanation: Eldredge and Gould's punctuated equilibrium proposes long periods of stability interrupted by rapid speciation events.

917. The functional unit of the kidney is

• A. Nephron
• B. Neuron
• C. Glomerulus
• D. Collecting duct

Explanation: The nephron is the functional unit of the kidney, consisting of glomerulus, tubules, and associated structures.

918. Ultrafiltration occurs in the

• A. Proximal convoluted tubule
• B. Bowman's capsule
• C. Loop of Henle
• D. Collecting duct

Explanation: Ultrafiltration occurs in the glomerulus/Bowman's capsule, where blood is filtered under pressure.

919. ADH acts on the

• A. Proximal tubule
• B. Descending limb
• C. Collecting duct
• D. Glomerulus

Explanation: ADH (vasopressin) increases water permeability of the collecting duct by inserting aquaporins.

920. The loop of Henle creates

• A. Blood pressure
• B. Concentration gradient in medulla
• C. Glomerular filtrate
• D. Urea

Explanation: The counter-current multiplier in the loop of Henle establishes a hypertonic gradient in the renal medulla.