Natural Selection

Natural selection theory explains how traits that enhance an organism’s survival and reproduction become more common in a population over time. This theory explains the process of evolution. Understanding the types of natural selection and its mechanism helps in learning how various environmental pressures shape the evolution and adaptation of species over time. In this article, we will read about natural selection theory in detail.

Natural selection is a fundamental process in evolution that describes how organisms with advantageous traits are more likely to survive and reproduce in their environment thereby passing those traits to their offspring. This process acts as the external pressure on the species to evolve.

Natural selection acts on the principle of “survival of the fittest.” Here, individuals who are better adapted to their surroundings have a higher chance of passing on their genes to future generations. Over time, this process leads to the gradual accumulation of beneficial traits within a population, resulting in the adaptation of species to their specific habitats and ecological niches.

Also Read: What are Darwin’s four Postulates?

In other words, animals are adapted to their habitat. Over time, due to changes in the environment the conditions of that habitat change. Only those animals will survive and reproduce which are better able to adapt to the changing conditions. This process of natural selection ensures that the traits beneficial for survival become more common in a population over generations, while traits less suited to the environment decrease. As a result, species gradually evolve to better fit their ecological niche. This external pressure on the species is termed Natural Selection. If the species can survive in nature, then they will live. Otherwise, they have to go extinct from nature.

Also Read: Darwin Postulates

The mechanism of natural selection is a process that can be divided into five sub-processes. These are the subprocesses that play an important role in the Evolution process. Sub-processes might not be any specific process, but they have importance in natural selection. That is why they are accepted as a step in natural selection. The mechanism process of natural selection is termed the VISTA process. The processes involved are:

Variation (V)

Natural selection is not the beginning of the variation process. It is an integrated mechanism that acts upon existing variations within species. Variations arise primarily from genetic mutations and environmental changes. These variations can lead to the emergence of different subspecies within a species. Variation is crucial because it sets the stage for natural selection. When a species possesses numerous variations, competition for survival increases, especially in challenging and harsh environments. This competition initiates the natural selection process

Inheritance (I)

Now, this process marks the beginning of natural selection. As competition among various variations increases, there arises a need for species to acquire new traits to survive in their challenging environment. Through the collective efforts of the species, new traits are acquired. However, this isn’t the end of the process; these acquired traits need to be passed on to the next generation. This transfer occurs through the inheritance process. Any new trait gained by the species must be inherited by the next generation to continue the subsequent steps of natural selection.

Also Read: Mendel’s Laws of Inheritance

Selection (S)

This is the core process of the natural selection process. When a species acquires a new trait, this process begins. It signifies the species’ readiness to face nature’s challenges. Now, it is the time to prove the fittest to survive. Among the variations within the species, those inheriting advantageous traits stand a chance to survive in nature, while others may go extinct. This is the selection process of nature. This is the main vital step among all of these steps.

Time (T)

This phase is not seen as a direct part of natural selection. The term “Time step” simply refers to a normal period. During this time, surviving species have a chance to stabilize. Following the selection process, where many variations vanish from nature, a period is allowed for them to stabilize. This timeframe can span millions of year

Adaptation (A)

Now, as species survive in nature and spend considerable time in harsh environments, it’s crucial to adapt to changes. This means that inherited traits are adopted by the species. This ensures the next generation carries traits vital for survival in nature for millions of years. These adaptations help them endure harsh conditions and may lead to significant changes, possibly evolving into entirely new forms. This process, known as natural selection, is the fundamental mechanism driving evolution, shaping the diversity of life on Earth.

Also Read: What is Adaptation?

There are three types of Natural Selection which are discussed below:

Stabilizing Selection

Stabilizing selection is a type of natural selection that favors the average traits within a population, maintaining the existing condition and reducing genetic variation. In this process, extreme variations are selected against, while traits close to the population average are favored, ensuring that the population remains well-adapted to its current environment. This type of selection is common in stable environments where there is minimal change, leading to the preservation of existing traits over time.

Directional Selection

Directional selection is a type of natural selection where individuals with traits that are at one extreme of the range are favored over other individuals in the population. This leads to a shift in the average phenotype of the population towards that extreme trait over time. Essentially, directional selection occurs when environmental conditions change, favoring individuals with specific traits that confer an advantage for survival and reproduction. As a result, the frequency of those advantageous traits increases in the population while the frequency of other traits decreases.

Disruptive Selection

Disruptive selection is a type of natural selection where extreme traits are favored over intermediate traits, leading to the divergence of a population into two distinct phenotypic groups. This occurs when environmental conditions create selective pressures that benefit individuals at both ends of the trait spectrum, resulting in the reduced fitness of individuals with intermediate traits. Disruptive selection can drive the evolution of new species or the maintenance of existing diversity within a population

Some of the examples of natural selection are:

Eggs of Robin Bird

The eggs of the robin bird are also an example of natural selection. There might be some similarities with the process of the human baby. As they both work on the same type of natural selection. Robin birds lay four eggs at a time. Among those four eggs, some eggs have large clutches. In some eggs, the clutches are very small. In the intermediate class, the eggs are in the appropriate size. So, the intermediate-sized eggs will only survive.

As the large-sized eggs will produce malnutrition chicks. On the other hand, the small eggs might not produce chicks properly. So, the intermediate-sized eggs will only produce chicks. As the intermediate parameter survives in nature, it is also an example of Stabilizing Selection.

White-Black Peppered Moth

This is another example of natural selection. Before the industrial revolution in the UK, there is a large number of white peppered moths present. By comparing with the black peppered moth, their number is much more. So, there are several deficiencies of the black peppered moth. But during and after the industrial revolution in the UK, the pollution level gets high. As a result, the bark of the trees becomes blackish due to the release of coal ashes from the industry chimneys.

In that background, white peppered moths are more rarely attacked by predators. But the black peppered moth can able to camouflaged in that background. As a result, the white-peppered moth becomes less in number and the black-peppered moth starts growing rapidly. So, it seems that there is a change in direction. Earlier, the white peppered moth was dominant. But now the black peppered moth is dominant. So, this is an example of Directional Selection.

Himalayan Squirrel

Himalayan squirrels are another example of natural selection. Here also, the three parameters will be discussed. Here, the parameter is the color, so three will be three types of colored squirrels are present. There are black-colored, white-colored, and gray-colored squirrels present. In the Himalayas due to sudden changes in nature, there is a change in the number of squirrels. The black-colored squirrels can able to hide in the shadow of the rocks. Where the white-colored squirrels can able to hide in the snow.

But the gray-colored squirrel can’t able to hide either in the shadow of the rock or in the snow. So, they started getting the target of the predators. So, the number of gray-colored squirrels started decreasing. Where two extreme parameters can able to survive in nature. As the intermediate parameter can able to survive in nature. So, it is an example of Disruptive Selection.

In conclusion, natural selection is a fundamental driver of evolution, ensuring that organisms with advantageous traits are more likely to survive and reproduce, thus passing those traits to future generations. This process, often referred to as “survival of the fittest,” acts as an external pressure on species to adapt to changing environments. Through mechanisms like variation, inheritance, selection, time, and adaptation, natural selection shapes the diversity of life on Earth. Understanding its types, such as stabilizing, directional, and disruptive selection, provides insights into how species evolve and adapt to their environments. Examples like the eggs of the robin bird, the white-black peppered moth, and Himalayan squirrels illustrate the mechanisms and outcomes of natural selection in different ecosystems.

Also Read:

• Difference Between Adaptation and Natural Selection
• Evolution Notes for Class 12 Chapter 6
• Evolution Of Life Forms – A Theory
• Interesting Facts About Evolution
• Theory Of Organic Evolution

What are 4 Examples of Natural Selection?

Four examples of natural selection are the eggs of the robin bird, the white-black peppered moth, Himalayan squirrels, and finch beak size variation in the Galapagos Islands

What are the Causes of Natural Selection?

The causes of natural selection include genetic variation, environmental changes, competition for resources, and adaptation to changing conditions.

What are the 3 Types of Natural Selection?

The three types of natural selection are stabilizing selection, directional selection, and disruptive selection.

What is Darwin’s Theory of Natural Selection?

Darwin’s theory of natural selection proposes that organisms with advantageous traits for survival and reproduction are more likely to pass those traits to their offspring, leading to gradual changes in species over time.

What is the Simple Definition of Natural Selection?

The simple definition of natural selection is the process by which organisms with beneficial traits for survival and reproduction are more likely to pass those traits to future generations, leading to the evolution of species.