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# Mathematical Representation of Traits

Aug 30, 2022

## Key Concepts

• Natural selection
• Charles Darwin- the founder of natural selection
• The process of natural selection
• Industrial melanism
• Increase and decrease of traits in a population due to natural selection

### Introduction:

Natural selection occurs when organisms with traits that are best suited to their environments survive and reproduce successfully. This process is sometimes called the “survival of the fittest”.

Natural selection is one of the major mechanisms of evolutionary change and is the process responsible for the evolution of adaptive features. It is a force that causes groups of organisms to change over time.

## Explanation:

### How does natural selection work?

Natural selection depends on the environment. It does not select the superior trait but selects the traits that are beneficial for survival and reproduction in a specific area and condition. Characteristics that are useful in a particular habitat may be harmful to another. For example, this deer mouse can blend in a forest but will be easy prey in desert areas.

Natural selection acts only on the existing heritable traits and not on the acquired traits. This heritable variation acts as a starting material for natural selection to act upon. The heritable variations can result in random changes or mutations in the genes. The random mutations of genes result in new variants of traits that are heritable.

Whereas acquired traits are the changes developed within the body of an organism in response to the changes occurring in the environment, or in the functioning of organs, in their own life to fulfill their new needs.

For example, the muscular strength of a wrestler is an acquired trait and cannot be passed on to the next generation.

### Who proposed natural selection?

The process of natural selection was first described by Charles Darwin in 1859, in his book named “On the Origin of Species”. Darwin was an English naturalist of the 19th century whose ideas helped explain how the many varied species on Earth could be descended from a single ancestral species.

### The process of natural selection:

Natural selection is a mechanism that occurs whenever certain conditions (size, color, etc.] exist. This mechanism explains how populations evolve (undergo descent with modification) in such a way that they become better suited to their environments over time.

The mechanism of natural selection involves the following steps:

First, more individuals are born than can survive. Organisms are capable of producing more offspring than their environments can support. This results in competition for the limited resources in every generation.

Second, there is a heritable variation in the population. We know that offspring vary in traits such as size, color, etc. These variations are inherited from parents to offspring.

The sources of genetic variation include mutations, the formation of gametes, and sexual reproduction. Genetic variation is necessary for evolution by natural selection to occur.

Third, some individuals have traits that are favored by their environment, i.e., such traits favor survival and successful reproduction.

For example, in the above image natural selection favors the trait that produces brown color in beetles and as a result, their number increases over time.

### Example of natural selection:

Populations keep evolving as they become better adjusted to their surroundings. Populations can change if their environment changes.

Traits that were once well suited to the old environment may not work as well in the new environment. Due to this, new adaptations may evolve. This can be explained by the example of industrial melanism and peppered moths.

Before industrialization, the grey-white-winged moths (Biston betularia) outnumbered the black-winged moths (Biston carbonaria) in Britain. These moths are nocturnal and rest on tree trunks during the day. White-winged moths can blend in well with lichen-covered trees, allowing them to avoid predatory birds.

On the other hand, the black-winged moths resting on lichen-covered tree trunks were easy prey for the predatory birds and so their number was reduced. During the industrial revolution, numerous industries emerged in Great Britain. The industries emitted black sooty smoke that killed the lichens and turned the tree black due to pollution.

This change benefitted the black-winged moth as it blended well with the black tree trunks, and their number increased while the white-winged moth became the prey for predatory birds resulting in a decline in their population.

The inherited traits that favor an organism’s survival and reproduction in a specific environment are called adaptations. Adaptations only spread through a population in future generations if natural selection favors them.

Variations or adaptations that are beneficial for an organism’s survival and reproduction increase over time in the population.

Darwin postulated that if groups of organisms having a common ancestor are isolated from other organisms of the same species, natural selection acts on them to become different over generations. The separated groups develop adaptations to different environmental conditions, and this process can develop a new species.

With enough time, this could explain the large number of species on Earth today.

### Natural Selection – Increase or decrease in specific traits

Let us see – How does natural selection result in the increase or decrease of specific traits in a population?

Darwin gave the example of the Galapagos finches to explain his theory. He stated that the different finch species on different islands evolved from a common ancestor. The variations were developed due to the different environmental conditions of different islands.

Darwin also stated that natural selection results in the increase or decrease of specific traits in a population. The medium ground finch has a wide and strong beak to crack open big, hard seeds. However, a variation is seen in the size of the beak in the finch population.

During drought, when there is less availability of food, the beak size increases in the population. When there I enough rainfall and abundant food available, the size of the beak tends not to increase in the population.

Thus, we can say that natural selection leads to the increase and decrease of certain traits in a population.

## Summary

• Natural selection occurs when organisms with traits that are best suited to their environments survive and reproduce successfully.
• Natural selection depends on the environment. It does not select the superior trait but selects the traits that are beneficial for survival and reproduction in a specific area and condition.
• Natural selection acts only on the existing heritable traits and not on the acquired traits.
• Populations keep evolving as they become better adjusted to their surroundings.
• The inherited traits that favor an organism’s survival and reproduction in a specific environment are called adaptations.
• Natural selection leads to the increase and decrease of certain traits in a population.

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