We impact our life, hunting, and habitat degradation. So we lose the vast majority of a species, and we see this in white rhinos and many big cats. If you look at genetics, you see a clear sign that most genes are relatively diverse. But in genes that are only inherited from the seeds.
So those would be maternal genes. They have very low diversity. So the pollen coming in from the father is coming from very long distances can bring in lots of genetic diversity. The seeds that can’t disperse very far mean only limited genetic diversity in the genome’s maternal portions.
Genetic drift is a mechanism of evolution responsible for random changes in a gene pool. It happens to all populations but has a much more visible and drastic effect on small populations. It’s driven by chance and not selection. So evolutionary fitness doesn’t matter here. It’s all random, and natural selection doesn’t come into play when looking at genetic drift.
What is founder effect?
The founder effect happens by emigration, which is the colonization of a new location. Whenever a group moves from one place to a new location, it’s known as immigration. Specific habitats may not be continuous in the environment. So, for example, coral reefs may be separated by open seafloor without corals. Mountains or rivers or oceans can separate forested regions.
Therefore, populations may be restricted to certain geographic areas. If a population member expands into a new region very often, a limited number of individuals do this, sometimes only one. So the representatives who reach the island are a small subset of the original population. Or those who cross the river or the mountain range.
This may be a small subset of the original population. Therefore, the new population’s characteristics will be determined by the features present in that population’s founders. This is known as the founder effect. So a change in an overall allele frequency can occur if a small population finds a new larger population whose alleles will now be determined by the subset of alleles present in the founders.
Explanation with an example: In South Africa, the population is named after the African people. Few Dutch people found that population. They went there to South Africa start to colonize there at the very beginning time. There are only 20 people who go there and start the population and colonize there slowly. Thousands of people living there in South Africa originated from the original twenty people-founded population.
Now that population when founded at a very early time with only 20 people. Tiny population changes have been constructed since there are many differences in allele frequency. At that time, though, in those 20 people, many of them have a disease known as Huntington’s disease.
As they have Huntington’s disease in most people in that 20 founding population throughout the year, the rate of Huntington’s disease is very high in South Africa. The percentage of Huntington’s disease becomes very high. The reason for that is the founding population. Many of the founding population already had that this is earlier. So it is known as a founder effect. Because, at that early time, some of the alleles carried Huntington’s disease.
Some of these alleles remain changed, and their population is that their frequency is also changing. It might get increased over time. So individuals in the present times get those diseases quite often in that particular population in South Africa.
Let’s think about a small island and a small group of seven people. 43% of them have an unattractive condition that causes them to be bald. In the mainland population, the percentage of bald people is much lower, only about 10%.
The small population of humans arrives on the secluded island far away from any mainland. Keep in mind that this group of people accurately represents the percentage of people in the normal population with this hairless condition.
The small group of founders arrives on the island and begins to know one another. The small number of humans procreate until their population grows to a number supported by the island’s conditions. As procreation continues, notice the increasingly high number of bald people.
After another population survey, there’s a much higher percentage of all island people. This is a result of the founder effect. If descendants do, the island founders had a much higher percentage of people with the genetic condition. Suddenly a natural disaster comes and wipes out all of the population except for a few survivors.
As rubble is washed away, life begins to flourish again on the island. The survivors begin to rebuild their population with an even higher percentage of people than before. This is a result of the bottleneck. There was already a high percentage of the condition on the island before the disaster.
When nearly all the population is wiped out, the survivor’s genetics are passed on to their descendants. Also, they represent an even higher percentage of all people than before the disaster.
At this point, we have a small population inhabiting our fictional island. Due to the absence of natural disasters, the population exists freely. However, the factor of randomness has yet to be examined. As chance will happen gradually, more and more people with air survive. Subsequently, reproduce on the island. Due to the small population, the allele frequencies slowly change over time.
We have a mother group. A portion of this group essentially branches off and goes and creates a new colony elsewhere. Their genetic makeup may differ from the mother group or the original group. There’s a lot of variability in genetics, and there’s a lot of individuals. A portion of this mother group branches off. So this is what humans do. In history, we’ve seen Europeans, a certain number of them, branch off and colonize other areas in the world.
In this case, when humans go off and colonize another area, they may have alleles. They may possess alleles in their genetics that could negatively impact and because they were originally living. Their population was originally living in a mother group. Also, This group was large and had a lot of genetic variabilities. Their genetics may have almost been hidden!
Suppose you have a gene that needs to be homozygous to be expressed. But you’re in a genetically variable group. Then technically, you will see a lot of heterozygosity. There’s a lot of gene variability, so it won’t be expressed. You won’t see the genetic defect or the illness that gene or allele may entail.
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Provine. “Ernst Mayr: Genetics and speciation.” Genetics.
Templeton, A. R. “The theory of speciation via the founder principle.” Genetics.
Hartwell, Leland; Hood, Leroy. Genetics: From Genes to Genomes.
Raven, Peter, Susan. Biology of Plants. W H Freeman and Company.