Question

Lamarck, Darwin and Wallace were all unaware of Mendel’s work on genetics. Yet Darwin and Lamarck had different ideas about inheritance. How did Lamarck and Darwin’s ideas differ?

Explain why directional selection tends to reduce genetic variation in a population over time.

Answer 1

Question:- How did lamarck and Darwin ideas differ?

Sol:- Lamarckism- Jean baptiste de Lamarck, a French biologist, and his theory of evolution is Use and disuse or inheritance of acquired characteristics. According to this theory character changes brought out by the environment during the life of an individual become heredity and thus can be transmitted to the next generation.

Example - The long neck of the modern giraffe could be explained by the lamarckian theory. During times when food was scarce, the short necked ancestors needed to stretch their necks to get leaves higher up in the trees. In this way they stretched their neck. In each generation the exercising of the neck in this fashion caused an increment in the length of the neck, which becomes genetically fixed.

Darwinism: Charles Robert Darwin theory of evolution is natural selection. First, Darwin stated that variation exists among individuals of a species. Second, he stated that scarcity of resources in a burgeoning population would lead to competition between individuals of the same species because all use the same limited resources( struggle for existence).

Example- Heritable variation in neck length giraffe exists in the ancestral population. During times of food scarcity, the longer necked individuals are able to exploit food resources that are unavailable to the Shorted necked individuals. In this way longer necked individuals perpetuates their kind in much greater numbers than the shorter necked individuals.

Question: why directional selection reduces genetic variation in a population over time?

Sol:- Under directional selection, individuals at one end of the frequency distribution do especially well, and so the frequency distribution of the trait in the in the subsequent generation is shifted from where it was in the parental generation. And eliminate normal or average individuals.