Natural selection is a process that leads to the adaptation of an organism to its environment. This adaptation occurs as a consequence of changes in the genetic make-up of the organism that are preferentially reproduced.
An organism is more likely to thrive under the influence of natural selection when there is a difference in the rates of individual survival and reproduction. These heritable modifications are handed down from generation to generation, which serves as a driving force in the process of evolution.
the correct answer is option: C.
Charles Darwin, a British biologist, was the one who first introduced the idea that biological evolution occurs via natural selection.
The process of natural selection is an orderly and non-random one in which the features or qualities of an organism gradually become either more prevalent or less common through time.
During the process of natural selection, significant advantageous variations that occurred in an organism’s genetic constitution or genotype that increased the chances of an organism for survival and reproduction are preserved and proliferated from generation to generation at the expense of variations that were less advantageous. These changes occurred in the genetic constitution or genotype that increased the chances of an organism for survival and reproduction.
Over long periods of time, natural selection causes populations to become more adapted to the conditions of their respective surroundings. Natural selection is a process that is wholly dependant on the surrounding environment, and as a result, a population has to have some heritable variation already present. This lends credence to the notion that the unit of natural selection is the person, given that the genetic make-up operates on an individual level.
Several distinct methods of evolution have previously been shown to you. Genetic drift, migration, mutation, and so on are only some of the examples. All of these methods together have the potential to cause a population to evolve, or undergo a change in its genetic composition over the course of successive generations.
Natural selection, on the other hand, is the one process of evolution that has gained more notoriety than the others throughout the course of time. What is it about natural selection that makes it so unique? It is the only method of evolution that has the potential to continually make populations more adapted, or better fitted, for their environment throughout the course of time.
You may already be familiar with Darwin’s theory of evolution, which incorporates the concept of natural selection. In this post, we are going to go much further — in fact, we are going to delve even deeper than Darwin himself could. We are going to look at natural selection through the lens of population genetics, specifically in terms of the frequencies of alleles, genotypes, and phenotypes.
To review, natural selection causes the following changes to occur in a population over time:
It is common for organisms that have heritable (genetically determined) characteristics that aid them in surviving and reproducing in a specific environment to generate a greater number of offspring than their contemporaries.
If this pattern persists over several generations, the characteristics that are heritable and help individuals survive and reproduce will become more prevalent in the population.
The population will not only change through time in terms of its genetic make-up and the characteristics it inherits, but it will also alter in such a manner that it adapts, or becomes better suited, to the environment in which it lives.
The phenotype, sometimes known as an organism’s outward appearance, is what is targeted by natural selection. The phenotype is often and significantly influenced by the genotype (the alleles, or gene versions, the organism carries).
Natural selection may generate microevolution when a phenotype produced by particular alleles helps organisms live and reproduce better than their contemporaries. This is because natural selection can raise the frequency of advantageous alleles from one generation to the next.
Consider, for the sake of illustration, a population of brown and white rabbits, the coat color of which is controlled by the presence of a single gene that contains both dominant brown (B) and recessive white (b) alleles.
If a potential predator like a hawk has an easier time detecting white rabbits (genotype bb) than brown rabbits (genotypes BB and Bb) against the background of a grassy field, then brown rabbits have a better chance of avoiding being eaten by hawks than white rabbits do. It is likely that the following generation will have a higher frequency of B alleles since there will be a greater number of brown rabbits that will survive to breed than white rabbits.
Through the process of working through an example, we may show this to ourselves. Let’s begin by looking at the allele and phenotypic frequencies, which are shown in the graphic below. Then, let’s observe how these frequencies shift over the course of one generation if half of the white rabbits are bred (but none of the brown rabbits)
It’s not always the case that the phenotypes and genotypes that are preferred by natural selection are the ones that are the most successful at surviving. They are, rather, the individuals who have the greatest overall fitness levels. The ability of an organism to live and reproduce successfully is referred to as its fitness, with a focus on the word “reproduce.”
Officially, fitness is defined as the number of children that organisms with a certain genotype or phenotype leave behind on average in comparison to others in the population. This number is compared to the average number of offspring left behind by others in the community.
The ability to survive is an essential part of being physically fit. It is necessary for an organism to reach the age of reproduction in order for it to have any chance of passing on its genes to the next generation. In the previous illustration, for instance, brown rabbits had a higher fitness than white rabbits because a greater proportion of brown rabbits than white rabbits lived to breed.
This meant that brown rabbits were more likely to pass on their genes. It is possible that an organism will be able to reproduce more independently if it is able to live for extended periods of time (e.g., with more mates or in multiple years).
However, survival is not the only factor that goes into determining a species’ fitness. Additionally, fitness is determined by an individual’s capacity to entice a mate and the amount of children that may be generated from a single mating. An organism with a very (zero) poor fitness would be one that lived for a significant amount of time but never managed to effectively attract a partner or produce children.
It is dependent on the environment to determine which characteristics are preferred by natural selection (that is, which characteristics make an organism more fit). In a terrain that is mostly brown and grassy and is inhabited by predators with acute vision, for instance, a brown rabbit could be more physically fit than a white rabbit.
On the other hand, in environments with a lot of light-colored vegetation, such as sand dunes, white rabbits may be better at evading predators than brown rabbits. And if there were no dangerous animals around, it’s possible that any coat color would be OK!
In many instances, a characteristic is also associated with tradeoffs. That is to say, it is possible that it will have both beneficial and bad consequences on one’s fitness. If a rabbit’s coat is a certain hue, for example, it may be less noticeable to prospective predators, but it may also be less appealing to potential mates.
Since fitness is a function of both survival and reproduction, determining whether or not the coat color is a net “win” will rely on the relative strengths of the predation and the mate preference. Since fitness is a function of both survival and reproduction,
One gene may be responsible for a population’s wide variety of phenotypes, depending on the circumstances. For instance, this was the situation with the rabbits in our hypothetical scenario. It is also true in certain real-world instances of natural selection for coat color (for example, in mice)1,2 start superscript, 1, comma, 2, end superscript.
However, in many instances, phenotypes are regulated by numerous genes, each of which contributes a relatively little amount to the final outcome. Such phenotypes are sometimes referred to as polygenic characteristics, and they generally take the shape of a spectrum, manifesting themselves in a variety of subtly altered ways.
A graph with the shape of a bell curve is often produced when one plots the frequency of the many types that exist within a population. There are several genes that contribute to human characteristics, including height (see the graph below).
Keeping an eye on how the phenotypic distribution in the population changes over the course of time allows us to determine whether or not natural selection is at work on a polygenic trait. Even while we do not know which genes specifically govern a certain feature, we may determine that selection is taking place based on variations in certain characteristics.
Natural selection may have an effect on the distribution of phenotypes for polygenic characteristics in a population in one of three fundamental ways. As an example of these different kinds of selection, let’s consider a made-up population of beetles. In this population, the color of the beetles is determined by a large number of genes and ranges from light to dark green along a spectrum.
The process of stabilizing selection favors intermediate phenotypes over extreme ones as the most fit. On a forest floor that is covered with medium-green plants, for instance, medium-green beetles may have the greatest opportunity to conceal themselves, and so have the highest chance of surviving. The curve may be made more steep by using stabilizing selection.
There is one extreme phenotype that is superior to all the other phenotypes in terms of fitness. For instance, if a colony of beetles goes into a new location with dark soil and plants, the dark green insects may be better concealed and survive better than the medium or light bugs. This is because dark green beetles have a darker coloration. The curve is shifted toward the desirable phenotype as a result of directional selection.
Those that fall into either of the two extreme phenotypes have superior fitness than those who are in the center. For instance, if the beetles go into a new habitat that has patches of bright-green moss and dark-green bushes, the light and dark insects may be better concealed (and live better) than the medium-green beetles. This is because light and dark beetles are less noticeable to predators. The curve has several peaks when there is a diverse array of options.
Because genes operate on an individual basis, the person is the basic building block of natural selection. Therefore, the option C is the one that should be chosen.
The individual organism is regarded as the fundamental building block of selection in traditional Darwinian theory.
Natural selection can only take place if the following four requirements are met: reproduction, heredity, variation in the fitness of organisms, and variation in the individual characteristics of individuals of the population. If those conditions are satisfied, natural selection will take place spontaneously.
Therefore, the most easy method for estimating the intensity of selection is to concentrate on a single generation and compare the performance of various phenotypes or genotypes at surviving to the next generation and reproducing successfully. This method necessitates the collection of data about the level of physical fitness possessed by individuals (or groups of persons) within a community.
shifts in the frequency of genes among gene pools
the cause of the genetic differences that exist between different people
shifts in the frequency of genes among gene pools
the cause of the genetic differences that exist between different people
a phenotype of a certain person
a populations’s gene frequency
selection by natural processes
Variability in the sequence of nucleotides is the source of every new allele.
Before natural selection can have any effect on a population, it must first be present within that population.
Natural selection may lead to microevolution, often known as a shift in the frequencies of different alleles over the course of time. This results in fitness-enhancing alleles being more prevalent in the population as time passes. Fitness may be thought of as a measurement of one’s relative level of reproductive success.
It is a measure of how many offspring organisms of a certain genotype or phenotype leave in the following generation in comparison to those of the other members of the group.
Both features that are controlled by various alleles of a single gene and traits that are determined by several genes may be subject to the influence of natural selection (traits determined by many genes).
The distribution of polygenic characteristics in a population often takes the shape of a bell curve. The following are some examples of the forms that natural selection on polygenic characteristics might take:
The bell curve tends to decrease as fitness increases, which indicates that intermediate genotypes have the maximum fitness.
The greatest level of fitness is associated with one of the extreme phenotypes. The bell curve moves in the direction of phenotypes that are more fit.
The fitness of both extreme phenotypes is much greater than that of the intermediate genotypes. The bell curve has two peaks at different points.