Question

A colleague of yours states that natural selection merely eliminates unfit mutants rather than creating “new” characters. Thus, he concludes that natural selection could not account for the evolution of new types of organisms. Do you agree? Explain your rationale.

Answer 1

Ans:- No natural selection perform the role in evolution of new types of organisms.

Natural selection is a pressure that causes groups of organisms to change over time. Animals inherit their genetics from their parents or ancestors, and the environment is constantly changing. So, no organism is perfectly adapted to its environment. Thus, natural selection is constantly influencing the evolution of species.

Even if a parent were perfectly adapted to the environment, the environment will change, leaving the offspring maladapted to the environment. Because there are many animals and few resources, only the best and most fit organisms can reproduce. Natural selection works against all organisms, and it can be thought of as the environment and forces acting to stop organisms from surviving and reproducing. Therefore, organisms which are able to survive can also pass on their DNA to the next generation. This “selects” for those DNA sequences.

Luckily for all organisms, genetic variability causes each individual to be slightly different. These slight differences in performance can lead to differences in the amount each individual reproduces. By reproducing more, an individual creates more of the genetic variations that helped it succeed. The offspring of these individuals will also benefit from the genetic variations that allowed their parents to succeed. Organisms without these genetic adaptations will not reproduce as much, and in this way, their lines will someday cease to exist. Nature constantly exerts a selective force on the different genetic combinations that try to reproduce, and in this way, natural selection is the major driving force of evolution.

Natural Selection Examples

Example of Stabilizing Selection

For stabilizing selection, imagine a population of mice that lives in the woods. Some of the mice are black, some are white, and some are grey. If the mice had no predators, and no other forces acting on the color of their coat, it would have no reason to change and would only change randomly in response to certain mutations in the DNA. However, that is not the case with these mice. They have lots of predators.

Foxes and house cats prey on the mice during the day. In the nighttime, the owls and other predators scour the dark for dinner. Either way, the mice are in a tough position. But not all the mice face the same risk at all times. In the daytime, the black mice are much easier to spot, and predators eat more black mice. The white mice stand out at night. This means owls eat more white mice at night. The grey mice are the only ones who survive more both during the day and at night. By the next generation, there will be many less black and white mice to reproduce.

After a few generations of strong selective pressure, the entire population could be grey. It depends entirely on the genetic makeup of the trait, but in some cases, a single trait is selected for and the rest are lost from the population. In other cases, the black and white coat colors could just become rarely seen traits. Retaining the traits can be an advantage when the predators change. For instance, if all the owls and night predators disappeared, it would be more beneficial to be black. The black mice would then take off, and become more frequent in the population.