Lamarckism

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 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.

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.

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

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

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

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.

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).

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

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.

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

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.

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.

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 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.

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

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.

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.

"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.