Question

Define evolution. Describe Darwin’s theory of evolution.

Answer 1

Hint: The phenomenon that is responsible for the generation of new species or helps the fittest species to survive. It is said to be the result of various factors involved like environment, accumulation of genetic variation, etc.

Complete answer:
Evolution refers to the change in the heritable characteristics of a population over successive generations. These characteristics are due to the expression of genes that are passed on from parent to offspring during reproduction. These variations are occurring due to changes in the environmental conditions and also these variations help the organism to survive in this challenging environment.
Darwin’s theory of evolution- It is popularly known as Darwinism, a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others.
-This theory of Darwin is very popularly known as "survival of the fittest”. Here, "fitness" refers to reproductive fitness i.e. an organism's ability to survive and reproduce.
-It also states that phenotypic variation exists among individuals and the variation is heritable.
-According to this theory, the population has variations and only those organisms will be able to survive in the environment, which will perfectly fit in the environmental situations. That's why this theory is also known as the survival of fittest.
-Darwin defined evolution as "descent with modification". According to him, species sharing common ancestors, change over time, and give rise to new species.
-Darwin in his book, On the Origin of Species, set forth his ideas about evolution and natural selection. These ideas were largely based on direct observations from Darwin's travels around the globe. From 1831 to 1836, he sailed on the ship HMS Beagle, in an expedition covering South America, Australia, and the southern tip of Africa.

Note: Darwin's concept of natural selection was based on several key observations:
-Traits are often heritable.
-Because the helpful traits are heritable, and because organisms with these traits leave more offspring, the traits will tend to become more common in the next generation.
-Over the generations, the population will become adapted to its environment.