Free Evolution MCQs with Answers

1. The forelimb of a whale, a bat and a human have the same arrangement of bones but perform different functions. Such organs are described as

• A. analogous
• B. homologous
• C. vestigial
• D. acquired

Explanation: Homologous organs share a common structural plan and a common embryonic origin because they were inherited from a shared ancestor, and their different uses are the result of divergent evolution. Analogous organs are the opposite case: same job, different structure and origin. Vestigial organs are reduced remnants that have lost their original function altogether.

2. The wing of an insect and the wing of a bird are said to be analogous because they

• A. develop from the same embryonic tissue
• B. contain the same bones in the same order
• C. perform the same function but differ in structure and origin
• D. are both reduced and non functional

Explanation: Both are used for flight, but a bird wing is a modified vertebrate forelimb with bone inside while an insect wing is an outgrowth of the body wall with no bone at all, so the resemblance is functional only. This is convergent evolution, in which unrelated groups meeting the same environmental demand arrive at similar solutions. Analogy therefore tells us about the environment, whereas homology tells us about ancestry.

3. Which of the following is a vestigial structure in the human body?

• A. Vermiform appendix
• B. Pancreas
• C. Diaphragm
• D. Thymus gland

Explanation: The appendix is the reduced remains of a large caecum that digests cellulose in herbivorous ancestors, and it can be removed with no loss of digestive function. Vestigial organs are evidence of evolution precisely because a designed structure would not carry a useless remnant. The pancreas and diaphragm are fully functional, and the thymus, though it shrinks after puberty, is essential for training T lymphocytes.

4. The most direct evidence for the course of evolution comes from

• A. comparative embryology
• B. vestigial organs
• C. biochemical similarity between proteins
• D. the fossil record

Explanation: Fossils are the only evidence that shows extinct organisms themselves, arranged in dated rock layers, so they give an actual sequence of change over time rather than an inference drawn from living species. The other three lines are powerful but indirect, since they compare organisms alive today and reason backwards. The fossil record is incomplete, which is its main limitation, not its reliability.

5. Archaeopteryx is regarded as a connecting link between

• A. fishes and amphibians
• B. amphibians and reptiles
• C. reptiles and birds
• D. reptiles and mammals

Explanation: Archaeopteryx had feathers and a wishbone like a bird but also teeth in its jaws, a long bony tail and clawed fingers like a reptile, so it carries characters of both classes. Such transitional fossils are exactly what common descent predicts and what a theory of separately created fixed types does not. The fish to amphibian link is filled by fossils such as Ichthyostega instead.

6. The fewer the differences in the amino acid sequence of cytochrome c between two species, the

• A. more distantly related they are
• B. more closely related they are
• C. larger their genomes must be
• D. faster their mutation rate must be

Explanation: Sequence differences accumulate by mutation after two lineages separate, so a small number of differences means little time has passed since they shared an ancestor. Human and chimpanzee cytochrome c is identical, while human and yeast differ at dozens of positions, and the pattern matches the tree built from anatomy and fossils. Genome size is unrelated to relatedness, as many amphibians have genomes far larger than ours.

7. The central idea of Lamarck's theory of evolution is that

• A. variations arise at random and are then selected
• B. characteristics acquired during an individual's lifetime are passed on to its offspring
• C. species are fixed and do not change
• D. populations evolve by chance changes in allele frequency

Explanation: Lamarck proposed that an organism changes during its own life in response to need and environment, and that these changes are transmitted to the next generation, so evolution is directed by use rather than by selection. Random variation followed by selection is Darwin's very different mechanism. Lamarck did accept that species change, so fixity of species is the view he was arguing against.

8. Lamarck explained the long neck of the giraffe by suggesting that

• A. giraffes with longer necks survived and left more offspring
• B. a mutation in a growth gene lengthened the neck
• C. chance alone lengthened necks in a small isolated population
• D. each generation stretched its neck to reach higher leaves and the gain was inherited

Explanation: In Lamarck's account the effort of stretching lengthens the neck within the animal's own lifetime and the longer neck is then handed to the offspring, so the trait grows a little in every generation. Darwin's explanation, offered in the first option, starts from neck length varying at birth and lets the environment select among those variations. The two theories are distinguished by this exact contrast in almost every exam.

9. Lamarckism was finally rejected mainly because

• A. changes in body cells do not alter the genes carried in the germ cells
• B. organisms were found not to vary at all
• C. the fossil record showed no change over time
• D. no organ was ever found to degenerate through disuse

Explanation: Weismann's germ plasm idea, supported by his experiment of cutting off the tails of mice for many generations without shortening the tails of their offspring, showed that somatic changes leave the gametes untouched. Since only the gametes carry information to the next generation, an acquired character cannot be inherited. Variation and fossil change are both real and are the very evidence evolution rests on.

10. Lamarck's law of use and disuse states that

• A. an organ that is constantly used becomes better developed while a disused organ degenerates
• B. all organs of the body remain unchanged throughout life
• C. organs change only when their genes mutate
• D. an organ once lost can never reappear in any descendant

Explanation: This is the first of Lamarck's two laws, and he used it to explain the strong limbs of a blacksmith, the webbed feet of water birds and the loss of eyes in cave dwellers. His second law, the inheritance of acquired characters, is what turns these lifetime changes into evolution. Modern biology accepts that use develops an organ but denies that the development reaches the offspring.