Question

Define natural selection. What is the essential difference between natural selection and the selection practiced by plant and animal breeders? What special adaptive challenges are posed by variable environments? What are the major factors that constrain the process of natural selection?

Answer 1

Solution-Natural selection is the process that is the basis of evolution.A process which prefers the individuals with advantageous traits and that advantageous traits are heritable and also lead to betterment of the species and also removal of the individuals which are at disadvantage(Not able to survive the environmental pressure). Whenever a species is subjected to a environmental pressure(like climate , resources or predation) it has to survive that particular condition, where no two individuals in the species are same and contain some useful traits that help them survive.So natural selection is process that positively selects individuals that are fit for the the changing environment ,in survival, reproduction etc.Its a directed , non random and a gradual process.

Selection practiced by plant and animal breeders is artificial selection. Main differences between artificial and natural selection are-  

Artificial selection is a type of selective breeding, where you select a particular species for its beneficial and economical role, whereas natural selection acts on each and every individual facing environmental pressure.

Artificial selection tends to select only few traits which are beneficial but have no role in survival, whereas natural selection only select individuals with traits that help them survive.

Artificial selection is done in labs , natural selection is a natural gradual process.

Major factors that constrain the process of natural selection are-

Variation- Mutation is the ultimate source of variation. As no two individuals are same , they posses different traits which help them in different manner to survive a environment. Only the individual with better trait survive and continue evolving.

Gene flow-That advantageous character must be heritable from generation to generation, only the the process of natural selection will occur.

Differential reproduction- Individuals who are the fittest ,reproduce better and leave offsprings have more chances to be positively selected for in the environment.