How is natural selection related to evolution?
How did life in a constantly changing earth manage to survive for millions of years?
One of the reasons lies in the process of "natural selection"!
The term selection comes from the Latin word "selectio" and means selection. Natural selection means that living beings are "selected" by the existing environmental conditions. Living beings that are better adapted to their environment have a higher chance of survival than others.
This is best done on one example explain:
A group of people lived on a desert island. One day when the food supply ran out, there was a famine.
In our example, the group consisted of fat people (good feed converters) and thinner people (poor feed converters). Because of the low food supply, the thin people became weaker and weaker, while the fat people used up their fat reserves. After a while, the thin people died of malnutrition. Now only those people lived on the island who were already good feed converters by nature. Thus, through natural selection, there were only thicker people.
During evolution, selection leads to a better adaptation of living beings to their environment. Because the adapted people reproduce better through better feed conversion, they can introduce more alleles (= expression of a single gene) into the gene pool (= accumulation of genes) of the next generation. So they prevail in the population. This is not possible for the thin people in our example.
A distinction is made between three different types of natural selection:
The directed selection is directed against individuals with characteristics that differ greatly from the average. For example against stub wings in fruit flies. Fruit flies with stub wings are incapable of flying. So they differ significantly from an average fly. Thus they are eaten more often than flyable flies. This means that they can only reproduce less frequently (see Fig. 1).
There are also those disruptive selectiondirected against individuals with the average trait. Like the finches, for example. Finches with large beaks can crack large grains and nuts. Finches with small beaks can only pick up smaller seeds. Disruptive selection therefore turns against finches with medium-sized beaks, as they can neither crack large seeds nor pick seeds that are too small. As a result, they have major nutritional problems and of course this also has a massive influence on the chances of reproduction (see Fig. 2).
There is also the stabilizing selectionwhich supports the spread of individuals with an average trait. For example, birds with extremely large or extremely small wings in relation to their body size have less ability to fly. This means that birds with extremely small wings have difficulty keeping their own body weight in the air. In contrast, birds with extremely large wings have to use more force to move their wings. This means that the mean value stabilizes in the long term. So for the distribution of medium-sized wings in relation to body size (see Fig. 3).
The selection depends on various factors. The biotic selection factors (animate), which include all selection factors emanating from the animate environment. These include natural predators, competition for food, mating partners and habitat.
In addition, from the abioticSelection factors (inanimate), which encompass the physical conditions. Here z. B. Climate, salinity of the water and nutrient content of the soil play a role.
There is also selection forced measure instead of. Through the always existing Selection pressure Adaptation is inevitably made necessary, so that species that are not closely related can show an adaptation similarity if they are in the same environment (for example the mole and the mole cricket).
Through selection, the living beings are chosen that are particularly well adapted to their environment. Individuals who live longer can inherit more. Those who no longer fit in with their environment are dying out.
© Leonie Oelmeier & Analena Büsse
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