MCQs

Evolutionary fitness is defined by reproductive success; an organism must not only survive but also successfully pass its genetic material to fertile offspring.

Malthus's work on human populations made Darwin realize that in nature, overproduction of offspring coupled with limited food and space leads to a struggle for survival.

Natural selection is context-dependent; a trait that is highly beneficial in one environment (e.g., thick fur in the Arctic) may be detrimental in another (e.g., a hot desert).

Disruptive (or diversifying) selection occurs when environmental conditions favor individuals at both extremes of a phenotypic range over those with intermediate phenotypes.

Darwin noted that organisms have a massive reproductive potential (overproduction), yet environmental resources remain stable and limited. This discrepancy inevitably leads to competition or a struggle for existence.

Lamarck was a pioneer who proposed the first fully formed, systematic theory of organic evolution, paving the way for evolutionary thought despite his proposed mechanisms being incorrect.

Since the offspring of the salt-stressed plant reverted to normal thin leaves when grown in normal soil, the acquired trait (thick leaves) was not inherited, refuting Lamarck's theory.

Lamarck's theory is widely known as the "Theory of Inheritance of Acquired Characters" or simply "Lamarckism."

Lamarck believed that all living organisms possess an innate, vital force that drives them to become more complex, organized, and structurally perfect over time.

Hypertrophy from physical work is a somatic adaptation (phenotypic plasticity). It does not alter germ-line DNA, so the children must still build their own muscles through work.

Weismann established that only the genetic material in germ cells (sperm and egg) is passed to offspring; changes in somatic cells (like muscle or nerve) die with the individual.

Lamarck's "Philosophie Zoologique" was published in 1809, which is in the early 19th century.

The kiwi bird lives on the ground with few predators; its lack of flight led to the disuse of wings, causing them to shrink and become vestigial over generations.

Herons stretched their legs constantly to stay dry while wading in water. Under Lamarck's "use" principle, this stretching elongated the limbs, a trait passed to subsequent generations.

The Central Dogma states that genetic information cannot flow backward from proteins (somatic phenotype) to DNA (germline genotype), making Lamarckian inheritance of somatic changes molecularly impossible.

Students often mistakenly believe Lamarck proposed that organisms consciously or voluntarily change their "genes", whereas Lamarck wrote about physiological adaptations to environmental "besoins" long before genes were discovered.

Lamarckism posits that the environmental stress (insecticide) induced an active, physiological adaptation in the individual insects, which was then directly inherited.

Lamarck's third postulate states that active use of an organ strengthens and enlarges it, while continuous disuse leads to its structural decay and eventual loss.

In Lamarckism, the environment forces the organism to change its physiology/behavior. In Darwinism, the environment simply "selects" which pre-existing variations survive.