Process of Natural Selection and Evolution

Key Concepts

• Natural selection

• Variation

• Adaptation

• Process of natural selection

Introduction

Natural selection is one of the important mechanisms of evolutionary change and is the process responsible for the evolution of adaptive features in various species. It is a force that causes groups of organisms to change over time and it leads to evolution.  

Natural selection means that organisms with traits that are best suited to their environment are more likely to survive and reproduce. These favourable traits are passed on to the next generation. 

Explanation:

Charles Darwin described the process of natural selection in his book “On the Origin of Species” in 1859. He was a well-known English naturalist of the 19th century. His thoughts on evolution explained how the many varied species on Earth could be descended from a single ancestral species. 

Darwin was very young when he went on a journey around the world. He went on a voyage on the HMS Beagle, a British military ship that sailed from England to South America and other parts of the world in December 1831. 

Throughout his journey, Darwin made a note of the new plants and animals that he saw. He kept a journal and noted all his observations. After the voyage, Darwin returned to England and continued to think about his observations. He collected more evidence on inherited traits.  

Darwin developed a theory of evolution in the mid-1800s 

 that is accepted by most scientists today. He published his ideas in his book called “On the Origin of Species”, which was published in 1859. 

After several years, Darwin’s ideas became known as the theory of evolution by natural selection. The theory says that species can change over time and that new species arise from pre-existing species.  

Hence, species share a common ancestor that gradually diverged from the original species and became a new species. 

Fundamentals of Darwin’s theory: 

Darwin’s theory of evolution encompasses the following fundamental ideas: 

1. Species change over time. 

2. All organisms are descended by the process of branching from common ancestors. For example, humans shared a common ancestor with chimpanzees around eight million years ago, with whales around 60 million years ago, and with kangaroos around 100 million years ago.  

3. Evolution is a slow process that takes a long time to complete. 

4. Natural selection is the mechanism of evolution. 

The process of natural selection: 

Natural selection depends on the environment. It does not select the superior trait but selects the traits that are beneficial for the survival and reproduction in a specific area and condition. Characteristics that are useful in a particular habitat may be harmful to another. 

Natural selection acts on the existing heritable traits. This heritable variance serves as a starting material for natural selection to act upon. The heritable variations come from random changes or mutations from the genes. The random mutations of genes lead to new variants of traits that are heritable. 

These heritable variations come from random mutations or changes from the genes. The random mutations result in new variants of traits that are heritable. 

There are four principles of natural selection which are as follows: 

1. Overproduction of offspring 

2. Inherited variation and adaptation 

3. Struggle for existence 

4. Natural selection 

1. Overproduction: 

All organisms produce more offspring so that more can survive to adulthood and reproduce. This means that many of those offspring will die without reproducing. Only the survivors are able to reproduce pass their traits on to their offspring. 

For example, grasshoppers can lay more than 200 eggs at a time. However, only a few of these offspring survive to reproduce. Salmon fish produces around 28 lakh eggs in one season. 

2. Variation and adaptation: 

Most characteristics that an organism has are passed from parent to offspring. Every individual has their own combination of traits. There is variation in nature. Offspring vary in traits such as color and size, etc 

Variation: 

A variation is an inherited trait or character that makes an individual unique from other members of the species. Variations can result from permanent changes, or mutations, in an organism’s genes.  

e gene changes produce small variations, such as differences in the texture of human hair. Other gene changes can produce large variations, such as an albino squirrel in a population of gray squirrels. Over time, a large number of individuals of the species might inherit these variations.  

If individuals with such variations continue to survive and reproduce over a lot of generations, a new species can evolve. It may take hundreds, thousands, or millions of generations for a new species to develop. 

Adaptation: 

Some variations are more useful than others. An adaptation is a type of variation that makes an organism better suited to its environment and increases its chances of survival and reproduction. 

Camouflage is a type of adaptation. A camouflaged organism blends into its environment and is more likely to stay alive and reproduce. 

3. Struggle to survive: 

Environmental factors like predators, food supply, disease, and climate affect the size of a population. We know that a species produces too many offspring, and only a certain number survive; the survivors are better adapted to their environment than those who die. 

Offspring of the survivors would inherit the favorable adaptations. Organisms with unfavorable adaptations die before they can pass them to progeny.  

4. Natural selection: 

Individuals with favorable variations survive better and reproduce in a particular environment and are thus selected by nature. Whereas those with unfavorable variations perish. As a result, they will have more offspring and pass on these favorable traits compared to individuals without those features.  

Example of natural selection: 

Let’s take the example of a grasshopper. A grasshopper lays more than 200 eggs at a time but not all of them are able to survive. This struggle for existence is created due to competition for resources like food, water, space, mates, etc.  

In this population of grasshoppers. The body color is inherited and variation is observed – some are yellow and some are green in color. The green color is an adaptation that allows the grasshoppers to blend into their environment and thus escape predation. 

The green color acts as a form of camouflage making it harder for predators to see green grasshoppers compared to yellow grasshoppers. Therefore, we can say that green grasshoppers have higher fitness than yellow grasshoppers. In this environment, green grasshoppers are able to survive and reproduce more than yellow grasshoppers. 

Over time, the population of green grasshoppers increases compared to yellow grasshoppers. 

Summary

• Natural selection means that organisms with traits that are best suited to their environment are more likely to survive and reproduce. These favorable traits are passed on to the next generation.

• Charles Darwin described the process of natural selection in his book “On the Origin of Species” in 1859.

• In December 1831, Darwin went on a voyage on a British military ship that sailed from England to South America and other parts of the world.

• After the voyage, Darwin returned to England and continued to think about his observations. He collected more evidence on inherited traits and developed his theory of evolution in the mid-1800s.

• He published his ideas in a book called “On the Origin of Species”, which was published in 1859.

• Darwin’s theory of evolution encompasses the fundamental ideas that species change over time, all organisms are descended from common ancestors, evolution is a slow process and natural selection is the mechanism of evolution.

• The process of natural selection depends on the following four principles:

1. Overproduction of offspring: organisms produce more offspring than can survive.
2. it Inherited variation and adaptation: organisms develop adaptations according to their environment The favorable variations are inherited while the unfavorable ones perish.
3. Struggle for existence: organisms compete for resources.
4. Natural selection: nature selects organisms that are best adapted to their environment

FAQs 

1. In which natural selection depends? 

Ans) The environment affects natural selection. Instead, then choosing the best features, it chooses those that will help an organism survive and reproduce in a certain environment. 

2. What are the four principles of natural selection? 

Ans) Overproduction of offspring, Inherited variation and adaptation, Struggle for existence, Natural selection they are the four principals of natural selection.  

3. What is variation? 

Ans) An inherited trait or characteristic that distinguishes an individual from other members of the species is called a variation.