Practice Questions

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.

Strictly applied, Lamarck's inheritance of acquired characters suggests that any physical change, including a lost limb, would be passed down (though Lamarckians later tried to exclude random accidents).

Morgan's work proved that hereditary traits are carried on chromosomes inside the cell nucleus, which are not altered by the somatic activities or "urges" of the animal.

Lamarckism explains webbed digits as physical structures acquired through repeated stretching of the skin during swimming (use), which is then inherited.

Regressive evolution (simplification) contradicts the idea of an unstoppable, innate "internal vital force" that always drives organisms toward greater complexity and perfection.

Lamarckism relies on individual-level somatic adaptation during a single lifetime, whereas modern evolutionary biology relies on population-level changes in allele frequencies over generations.

"Soft inheritance" refers to the inheritance of acquired characters, where the genetic material is not fixed but can be modified directly by environmental influences during an organism's life.