All Free Biology MCQs with Answers

631. Lamarck proposed that new structures arise because of

• A. the inner needs and desires of the organism
• B. random mutation
• C. genetic drift
• D. hybrid sterility

Explanation: Lamarck imagined that a new need creates a new habit, the habit uses or abandons an organ, and the change is then inherited. Mutation and drift are modern concepts he could not have known.

632. Lamarck would explain the tiny useless wings of the kiwi bird as the product of

• A. natural selection
• B. disuse of wings over many generations
• C. genetic engineering
• D. mutation only

Explanation: In Lamarck's scheme, ground living birds stopped flying, their wings weakened from disuse and the reduction was passed on. Today we explain the kiwi's wings through selection, but the question tests the Lamarckian logic itself.

633. Lamarck's theory of evolution appeared

• A. after Darwin's Origin of Species
• B. at exactly the same time as Darwin's
• C. about half a century before Darwin's
• D. in the twentieth century

Explanation: Philosophie Zoologique appeared in 1809 and the Origin of Species in 1859, so Lamarck preceded Darwin by fifty years. Knowing the order stops the common slip of crediting Darwin with the first theory.

634. Darwin gathered much of the evidence for his theory during a five year voyage on the ship

• A. Endeavour
• B. Mayflower
• C. Santa Maria
• D. HMS Beagle

Explanation: The Beagle surveyed South American coasts from 1831 to 1836, giving Darwin fossils, finches and biogeography to think about for the next twenty years. Without the voyage, the evidence base of the Origin would not have existed.

635. Darwin's concept of the struggle for existence was inspired by the essay on population written by

• A. Thomas Malthus
• B. Herbert Spencer
• C. Charles Lyell
• D. Alfred Wallace

Explanation: Malthus argued that human populations grow faster than food supply, and Darwin saw the same pressure in nature: far more offspring are born than can survive. Lyell's geology shaped Darwin's timescale, but the struggle came from Malthus.

636. Natural selection is best described as

• A. the survival of the largest individuals
• B. the differential survival and reproduction of the individuals best suited to their environment
• C. the deliberate breeding of the best plants by farmers
• D. the migration of animals to better habitats

Explanation: What matters is leaving more offspring, not mere survival or size, so the fittest are those whose inherited traits match the environment. Deliberate breeding is artificial selection, the human guided version of the same idea.

637. Darwin noted that populations produce far more offspring than the environment can support, which leads to

• A. universal survival
• B. genetic uniformity
• C. competition, the struggle for existence
• D. instant formation of new species

Explanation: Overproduction plus limited food and space means only some individuals survive to breed, and which ones depends on their traits. This competition is the engine that makes natural selection operate.

638. The phrase survival of the fittest was coined by

• A. Charles Darwin
• B. Alfred Wallace
• C. Charles Lyell
• D. Herbert Spencer

Explanation: Spencer, the philosopher, coined the phrase after reading Darwin, and Darwin later adopted it in later editions of the Origin. The wording is often credited to Darwin himself, which is the trap here.

639. In natural selection, the selecting agent is

• A. human beings
• B. parasites only
• C. the largest individual in the population
• D. the environment

Explanation: Climate, food, predators and disease together decide which variants survive and reproduce. When humans do the choosing, as in crop breeding, the process is called artificial selection instead.

640. The resemblance of a stick insect to the twig on which it rests is best explained by

• A. natural selection favouring camouflaged variants over many generations
• B. the insect stretching its body towards twigs
• C. Lamarck's inner need for safety
• D. pure chance in every individual

Explanation: Birds removed the conspicuous insects generation after generation, leaving the better disguised to breed, until resemblance became remarkable. The insect does not change on purpose; selection filters what variation offers.