Selection Pressure Explained
Selection Pressures (Taken and edited from Geek website)
Selection pressure is a force of nature that causes a particular organism to evolve in a certain direction. It is not a physical force, but an interaction between natural variation in a species and factors in its environment that cause a certain form to have an advantage over the others.
This can be thought of as a “pressure” that pushes the evolution of that organism toward a greater prevalence (greater numbers) of this variation.
Evolution and Natural Selection
When organisms reproduce, random mutations can occur, which cause the offspring to vary in some way from their parents. These changes may be
damaging, but they may give an advantage.
A favourable mutation may increase an individual’s chances of surviving long enough to reproduce and pass this new trait on to its offspring, and so it will become more common. Eventually, all members of the species may have this characteristic. Unfavourable mutations quickly disappear, as they are less likely to be passed on to the next generation.
These changes in the populations of different forms of a species are known as natural selection: the form of a species that is best adapted to its environment is the one that survives. This is sometimes referred to as “survival of the fittest.” The term “fittest,” in this context, does not mean the strongest or fastest, but the variant that is the best fit for its environment. Strength and speed may play a role, but other factors, such as intelligence or colouration may be more important, depending on the circumstances. Natural selection is the outcome of selection pressures and drives evolution: as favourable mutations accumulate, organisms evolve into new species.
How Selection Pressures Operate
A selection pressure can come from practically anything, as long as it acts in a relatively consistent fashion over reasonably long timeframes, and actually impacts the reproductive or survival rates of a species. Potential pressures may include availability of prey, presence of predators, environmental stresses, competition with other species — including humans — and competition between members of a species. In the eyes of evolution, the likelihood of reproduction is all that matters: if, for example, a certain predator only consumes old animals that are already incapable of reproducing, the predator will have no impact on the evolution of the prey
species.
An organism’s colour may affect its survival chances. For example, insects with colours that blend in to their surroundings are less likely to be seen by predators such as birds. A mutation that produces coloration similar to an insect’s usual background, for example, a green colour in a species that spends most of its time eating the leaves of plants, will increase its chances of successful reproduction, and over a number of generations, this will become the normal form. Mutations that produce a different colour will quickly disappear from the population.
It is important to note that selection pressure has no intelligence, foresight, rhyme, or reason. Selection operates at individual, not species, level. A new adaptation does not appear "for the good of the species": it only becomes fixed in a population if it is good for each individual that has it, even if it collectively makes life worse for the species.
Selection pressure can operate quite quickly, in fact within only a few generations
Selection pressure is a force of nature that causes a particular organism to evolve in a certain direction. It is not a physical force, but an interaction between natural variation in a species and factors in its environment that cause a certain form to have an advantage over the others.
This can be thought of as a “pressure” that pushes the evolution of that organism toward a greater prevalence (greater numbers) of this variation.
Evolution and Natural Selection
When organisms reproduce, random mutations can occur, which cause the offspring to vary in some way from their parents. These changes may be
damaging, but they may give an advantage.
A favourable mutation may increase an individual’s chances of surviving long enough to reproduce and pass this new trait on to its offspring, and so it will become more common. Eventually, all members of the species may have this characteristic. Unfavourable mutations quickly disappear, as they are less likely to be passed on to the next generation.
These changes in the populations of different forms of a species are known as natural selection: the form of a species that is best adapted to its environment is the one that survives. This is sometimes referred to as “survival of the fittest.” The term “fittest,” in this context, does not mean the strongest or fastest, but the variant that is the best fit for its environment. Strength and speed may play a role, but other factors, such as intelligence or colouration may be more important, depending on the circumstances. Natural selection is the outcome of selection pressures and drives evolution: as favourable mutations accumulate, organisms evolve into new species.
How Selection Pressures Operate
A selection pressure can come from practically anything, as long as it acts in a relatively consistent fashion over reasonably long timeframes, and actually impacts the reproductive or survival rates of a species. Potential pressures may include availability of prey, presence of predators, environmental stresses, competition with other species — including humans — and competition between members of a species. In the eyes of evolution, the likelihood of reproduction is all that matters: if, for example, a certain predator only consumes old animals that are already incapable of reproducing, the predator will have no impact on the evolution of the prey
species.
An organism’s colour may affect its survival chances. For example, insects with colours that blend in to their surroundings are less likely to be seen by predators such as birds. A mutation that produces coloration similar to an insect’s usual background, for example, a green colour in a species that spends most of its time eating the leaves of plants, will increase its chances of successful reproduction, and over a number of generations, this will become the normal form. Mutations that produce a different colour will quickly disappear from the population.
It is important to note that selection pressure has no intelligence, foresight, rhyme, or reason. Selection operates at individual, not species, level. A new adaptation does not appear "for the good of the species": it only becomes fixed in a population if it is good for each individual that has it, even if it collectively makes life worse for the species.
Selection pressure can operate quite quickly, in fact within only a few generations