Natural Selection Introduction
Natural selection theory was given, by "Charles Darwin" in 1859 in a book called On The Origin of Species Natural Selection has two main points.
Given Condition- The given condition means a present-day condition.
Better than Others- Because most of the individuals reproduce by sexual reproduction because of the sexual reproduction when two parent are going to produce gamut they are many changes in the DNA.
Due to recombination, due to mutation, due to genetic drift, due to arrangements of the chromosome at the metaphase plate, they are certain processes by which the gamut are going to have a variety of DNA when such gamit fuse.
The next progeny is each slightly different than the previous generation so that next-generation we can say is each slightly different promise parental generation and this generation is having a variety of genome such a population known as polymorphic population.
The polymorphic population is the population which is having variety in phenotype and this variety in phenotype is created due to the variety of genotype. They are certain for allele Gene.
And when multiple alleles are present they are going to cause variation in the population. So in a population, they are variations such as population known as polymorphic population.
Suppose all of the individuals are some species and they are living together in a given time in a given space to all of these individuals are collectively known as population. All the members of the population are facing some kind of temperature.
They are also facing some range of light. They are also getting the rainfall in a certain range we side all these abiotic factors they are certain animals, plants, microbes extra. These come under biotic forms. So all these organisms are now going to interact with each other.
And this interaction could be beneficial this interaction could be natural and most of the time these interactions are harmful to each other. When they are going to compete for saving resources interactions are very harmful.
Under such interactions among all the of the population, we can observe that some of them are performing better than others. Some of them are competing well in a given condition that candidates who are competing well in better than others.
Natural Selection Definition
Such individuals are going to survive in nature in the future and those who are surviving. The future will get a chance to reproduce and to produce than next generation and producing next generation the variation they are having in themselves will be passed in the next generation. So the next generation will be better than the previous one.
And that's how in every generation these changes are passed. So the heritable changes which going to be passed in next to next generation will fix in the population and after then a long time is observed better population than the previous one. This is known as natural selection.
So finally under given conditions when individuals are interacting with each other some of the individuals can better interact and, these individuals are set to fit. Those who can interact better are known as fit.
And fit individuals will survive in nature. And fit they are going to survive to be can say that nature has selected us over those individuals, who could survive in the given saturation.
So natural selection is simply a process of nature that is operating on a given condition in this the better candidate, the fit candidate than the others are going to survive and because those who are surviving will reproduce nature so they will live better progenies.
It is known as natural selection, however a very time in taking process. Is a very long process and no one can predict.
Types of Natural Selection
there three types of natural selection
1. Stabilizing Selection/Centripetal Selection/Balancing Selection
Suppose we are having a population and in this population, let's focus on a particular gene known as A gene there is a population of deployed organisms.
In which we are focusing on gene A sense the population is deployed so every candidate of the population is going to have two copies of the gene and if they are only two genes in population we can get three genotypes.
So for gene A three genotype. The allele is going to form a normal protein. So those babies with AA genotype are having weight more than the normal one.
Under such a situation these human babies which are having AA genotypes are not going to survive. Because these babies are overweight and they will die those babies who are having (aa) phenotype.
They are can also not survive because they are underweight so among the three types of genotype Aa that mean heterozygote that means the intermediate is much better than both of homozygotes Aa better than AA and aa under such scenario the Aa is better than both the homozygotes so Aa going to survive.
If it going to survive we say that nature has selected Aa when is about the bodyweight such, the selection is known as stabilizing selection.
Directional Selection
In human genetics, the direct selection is a natural bias in which excessive phenotype is more popular than other phenotypes, causing allele frequency to change over time in that phenotype.
Under the direction of selection, the beneficial allele increases due to differences in survival and productivity between different phenotypes. The increase is independent of the allele rule, and even if the allele repeats, it will eventually, be corrected.
The choice of direction was first described by Charles Darwin in the book On the Origin of Species as a matter of natural selection. Other types of natural selection include stability and distraction. Each type of selection contains the same principles but is slightly different.
Disruptive selection prefers both extreme phenotypes, which differ from the extreme one, indirect selection. Selection stability prefers a moderate phenotype, which results in a decrease in population variability over time.
The choice of guidelines occurs mostly under environmental change and when people move to new areas with different environmental pressures. Selecting directions allows for rapid changes in allele frequency, and plays a major role in speciation.
QTL effect analysis was used to evaluate the impact of direct selection options on phenotypic differentiation. These analyzes showed that the genetic area associated with target selection was higher than expected; which means that direct selection is a major cause of phenotypic variability, leading to speciation.
Method of Direction Selection
Various statistical tests can be performed to test the existence of direct demographic options. A few tests include QTL signal testing, Ka / Ks rating test, and related rating test. QTL mark testing compares the QTL counting number with a neutral model and allows for testing of genetic guidance against genetic predisposition.
The Ka / Ks rating test compares the negative number with the same exchange, and a rating greater than 1 indicates directional selection. Related measurement studies look at the accumulation of benefits against a neutral model, but require a phylogenetic tree to compare.
Example of Direction Selection
An example of direct selection of fossil records shows that the size of European bears in Europe during the winter solstice, but increased during each winter season. Another example is the size of the beak in a flock of birds.
Throughout the wet years, small seeds were so common and there was so little seed available that birds rarely ate large seeds. During the dry years, no seeds were plentiful, but birds often ate very large seeds. Changes in bird food have affected the depth of bird mouths in future generations. Their beaks range from large and strong to small and smooth.
African cichlids are known to be one of the most diverse fish and are emerging very quickly. These fish came from the same area, but have a wide variety of morphology, especially those related to the mouth and jaw. Albertson et al.
In 2003 he explored this by crossing two species of African cichlids with very different oral morphology. The cross between Labeotropheus and the Metriaclima zebra allowed for the QTL mapping of food morphology.
Using QTL signal testing direct evidence was presented to prove that direct selection, was performed on the oral machine.
However, this was not the case with the suspensorium or skull. Sockeye Salmon Set
Sockeye salmon is one of the many species of anadromous fish. People move to the same rivers where they were born to breed.
These migrations occur at the same time each year, but Quinn et al. 2007 show that sockeye salmon found in the waters of Bristol Bay in Alaska has recently been selected straightforwardly during migration.
In this study, two sockeye salmon communities were identified. Data from 1969-2003 provided by the Alaska Department of Fish and Animals are divided into five seven-year sets and are scheduled to reach the fishery.
After analyzing the data it was determined that in both residents the migration date rate was pre-determined and was selected by reference.
The population of Egegik received a strong selection and changed in 4 days. The water temperature is thought to date to the previous migration, but in this study, there were no statistically significant correlations.
This paper suggests that fishing may be a factor in driving this choice because fishing occurs more frequently in recent migratory seasons, which prevents those fish from breeding.
Disruptive Selection
Disruptive selection, also called variability, describes changes in human genes in which the overprotective values of a factor are higher than average values. In this case, the diversity of the feature increases, and the population is divided into two distinct groups.
In this case, most people find the value of the peripheral character in both ends of the distribution gap.
Suppose there are many rabbits. The rabbit color is governed by two imperfect elements: black fur, represented by "B", and white fur, represented by "b". A rabbit in this tribe with a genotype of "BB" will have a phenotype of black fur, a genotype of "Bb" may have gray hair, and a type of "bb" will be white. fur.
If this number of rabbits occurs in areas with black and white rock areas, black-haired rabbits will be able to hide from predators in the dark rocks, and white-haired rabbits are equally among whites. stones. gray-haired rabbits, however, would stand out in all habitats, and thus would be more prone to attack.
As a result of this type of selected pressure, our estimated number of rabbits can be randomly selected by the extreme values of the fur color feature: white or black, but not gray. This is an example of uncontrollable that leads to disruptive choices.
