Natural selection is a process that describes how a species gives rise to a new species that possesses characteristics that make them better adapted to a specific environment that may increase their chance of survival.
Key steps in natural selection:
The key steps in natural selection are described in five terms:
- Variation
- Inheritance
- Competition
- Selection
- Adaption
Variation:
The process of natural selection begins with the concept that more individuals are produced than the environment can support and that these individuals have variations (differ from each other). Some variations may increase the chances of survival in the individual over other variations in that specific environment. Basically, some variations will give individuals a competitive advantage.
Inheritance:
Individuals that possess advantageous variations have an increased chance of reproducing and passing on these traits to their offspring. This will then increase the chances of the offspring’s survival and allow these genes to be passed on to the following generation.
Competition:
The individuals in a population compete with each other for resources (food, shelter, and mates). Individuals that have an advantage over others possess an increased ability to compete for a resource. Some competitive situations do not involve resources but may be competing to escape from a predator or not be killed by a disease. Individuals that possess an advantageous variation that allows them to evade predators and disease would have a better chance of survival over those that did not.
Selection:
Organisms live within ecosystems which consist of biotic (living) and abiotic (non-living) factors. These factors help select which variations provide the individual with an increased chance of survival. These factors are known as selective pressures or selective agents. Biotic factors that act as selective pressures include predators, disease, competitors, prey and mating partners. Abiotic factors would include temperature, shelter, sunlight, water and nutrients.
Adaption:
If the variation continues to provide an advantage, over time, more of the population will possess the variation. Individuals that possess variations that are not advantageous are not as well suited to that environment and cannot compete as effectively. They may die young or produce little or no offspring, therefore providing little to the gene pool of the next generation. The number of individuals that possess this variation will decrease in the population.
Key steps in natural selection:
The key steps in natural selection are described in five terms:
- Variation
- Inheritance
- Competition
- Selection
- Adaption
Variation:
The process of natural selection begins with the concept that more individuals are produced than the environment can support and that these individuals have variations (differ from each other). Some variations may increase the chances of survival in the individual over other variations in that specific environment. Basically, some variations will give individuals a competitive advantage.
Inheritance:
Individuals that possess advantageous variations have an increased chance of reproducing and passing on these traits to their offspring. This will then increase the chances of the offspring’s survival and allow these genes to be passed on to the following generation.
Competition:
The individuals in a population compete with each other for resources (food, shelter, and mates). Individuals that have an advantage over others possess an increased ability to compete for a resource. Some competitive situations do not involve resources but may be competing to escape from a predator or not be killed by a disease. Individuals that possess an advantageous variation that allows them to evade predators and disease would have a better chance of survival over those that did not.
Selection:
Organisms live within ecosystems which consist of biotic (living) and abiotic (non-living) factors. These factors help select which variations provide the individual with an increased chance of survival. These factors are known as selective pressures or selective agents. Biotic factors that act as selective pressures include predators, disease, competitors, prey and mating partners. Abiotic factors would include temperature, shelter, sunlight, water and nutrients.
Adaption:
If the variation continues to provide an advantage, over time, more of the population will possess the variation. Individuals that possess variations that are not advantageous are not as well suited to that environment and cannot compete as effectively. They may die young or produce little or no offspring, therefore providing little to the gene pool of the next generation. The number of individuals that possess this variation will decrease in the population.
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What natural selection proposes:
Natural selection proposes:
- There is variation in the inherited characteristics in a species and some of these variations may increase the chance of the survival of the species in a certain environment.
- In the struggle to survive, those who possess more favourable characteristics have a better chance of surviving over others of their species.
- Members with an increased chance of survival have a better chance of reproducing and passing on these inherited advantageous traits to their offspring.
- Over a long period of time, organisms will have traits that make them better suited to the environment they inhabit, increasing their chances of survival.
Evolution by natural selection of the British Peppered Moth:
The Peppered Moth is found all over Britain and Ireland and is the most well-known example of evolution by natural selection. Peppered moths are usually white with black specks all over their wings which allows them to camouflage against lichen-covered trees. A naturally occurring mutation causes some moths to have wings that are almost completely black. Yet the moths with this mutation are not able to camouflage as well as the normal ‘peppered’ moths so they are more likely to be eaten by predators. This means that the black forms of this moth do not survive to reproduce and are less common in the population than the Peppered Moth. Though in the nineteenth century, the black form of the moth was more common than the Peppered Moth in towns and cities. Domestic coal fires and industrialisation produced sooty air pollution that killed off the lichen of trees and blackened their trunks. This made the Peppered Moth unable to camouflage and more likely to be eaten by a predator and the black form of the moth more likely to survive to reproduce. The black moth made up more the population than the Peppered Moth over generations in towns and cities. Because moths have such a short lifespan, this process of evolution by natural selection occurred at a very fast rate. The first black Peppered Moth was recorded in 1848 in Manchester. 98% of Peppered Moths in the city were black by 1895. Controls were established to reduce air pollution in the mid-twentieth century which increased the quality of air. This caused the tree trunks to improve and start growing lichen again. The normal Peppered Moths had a better camouflaging ability again and the black moths were more easily seen. Now in both city and country areas, the paler Peppered Moth are more common than the black form of the species. This observation has allowed us to see the process of natural selection occur in both ways, in which the moth that was best suited to the environment had a better chance of survival.
Natural selection proposes:
- There is variation in the inherited characteristics in a species and some of these variations may increase the chance of the survival of the species in a certain environment.
- In the struggle to survive, those who possess more favourable characteristics have a better chance of surviving over others of their species.
- Members with an increased chance of survival have a better chance of reproducing and passing on these inherited advantageous traits to their offspring.
- Over a long period of time, organisms will have traits that make them better suited to the environment they inhabit, increasing their chances of survival.
Evolution by natural selection of the British Peppered Moth:
The Peppered Moth is found all over Britain and Ireland and is the most well-known example of evolution by natural selection. Peppered moths are usually white with black specks all over their wings which allows them to camouflage against lichen-covered trees. A naturally occurring mutation causes some moths to have wings that are almost completely black. Yet the moths with this mutation are not able to camouflage as well as the normal ‘peppered’ moths so they are more likely to be eaten by predators. This means that the black forms of this moth do not survive to reproduce and are less common in the population than the Peppered Moth. Though in the nineteenth century, the black form of the moth was more common than the Peppered Moth in towns and cities. Domestic coal fires and industrialisation produced sooty air pollution that killed off the lichen of trees and blackened their trunks. This made the Peppered Moth unable to camouflage and more likely to be eaten by a predator and the black form of the moth more likely to survive to reproduce. The black moth made up more the population than the Peppered Moth over generations in towns and cities. Because moths have such a short lifespan, this process of evolution by natural selection occurred at a very fast rate. The first black Peppered Moth was recorded in 1848 in Manchester. 98% of Peppered Moths in the city were black by 1895. Controls were established to reduce air pollution in the mid-twentieth century which increased the quality of air. This caused the tree trunks to improve and start growing lichen again. The normal Peppered Moths had a better camouflaging ability again and the black moths were more easily seen. Now in both city and country areas, the paler Peppered Moth are more common than the black form of the species. This observation has allowed us to see the process of natural selection occur in both ways, in which the moth that was best suited to the environment had a better chance of survival.