A Brief History of Evolution

like 849 Posted By : SHRISHTI KULKARNI, Class 7, Vidyarthi Vigyan Manthan

Evolution basically suggests that the populations of all living beings and species change over time. And when we think of evolution, most of us think of Charles Darwin. Charles Darwin explained his theory of evolution in a book called “On the Origin of Species”, in which he proposed that species evolve and all living things descend from a common ancestor.

Not only did Darwin suggest the theory of evolution, he also suggested a method of evolution- natural selection. Natural selection allowed the traits that helped organisms survive in their conditions to pass on to next generations and become more common in a population over many years.

Darwin’s Natural selection theory was based on several observations:

<!--[if !supportLists]-->·         <!--[endif]-->Characteristics are heritable and passed on from parents to offspring, and now we know this occurs due to passing on of genes.

<!--[if !supportLists]-->·         <!--[endif]-->Very few of the produced offspring actually survive. Organisms are capable of producing more offspring than the environment can support, which leads to competition for the limited resources in each generation.

<!--[if !supportLists]-->·         <!--[endif]-->Offspring differ in their heritable traits. Any generation’s offspring will be different (at least slightly) from one another in their characteristics, and many of their traits will be heritable.

Based on these observations, Darwin concluded that in a population, some offspring will have specific traits that help them survive and reproduce in their environment, and will produce more offspring, which will also have these helpful traits, than others. Since these traits are hereditary, these offspring will also reproduce and survive better, leading to another generation, most of which will contain these traits. Over many generations, these traits will continue passing on, till the whole population becomes adapted to their environment.

Natural selection depends on the environment, as it favors the traits beneficial to the species in their environment. For natural selection to act on a trait, there must first be a difference in traits of a species, which have to be heritable. These variations come from random mutations or changes in the DNA sequence.

Groups of a single population may get isolated from one another due to geographical barriers, and they can no longer interbreed. Their environments also differ from one another. So in each environment, natural selection will favour different traits, and over many generations, the difference in traits can be so vast that the two groups are considered separate species.

Scientists think that this process has repeated numerous times over millions of years, which led to the diversity of life on Earth.

 

References: Khan Academy, “The Magic of Reality”- Richard Dawkins

 

-Shrishti Kulkarni

Class 8G

GEAR Innovative International School