Natural Selection. In science, theories are statements or models that have been tested and confirmed many times. . In science, the term "Theory" does not express doubt. They explain a wide variety of data and observations They can be used to make predictions
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In science, theories are statements or models that have been tested and confirmed many times.
A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.
Photo courtesy of ucumari, creative commons, flickr
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass those advantages to their children
5. Species alive today are descended with modifications from common ancestors
1. Variation exists among individuals in a species.2. Individuals will compete for resources (food, mates, and space)3. Competition would lead to the death of some individuals while others would survive4. Individuals that had advantageous variations are more likely to survive and reproduce.
This process came to be known as Natural SelectionThe favorable variations are called Adaptations
Photo courtesy of digitalART2, flickr creative commons
Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes.
While natural selection involves interactions between individual organisms and their environment, it is populations, not individuals that evolve.
Say in a species of blob….there exists blobs of all shapes and sizes (variation)
Blobs eat the little purple organisms that live underground and on the surface.
During a particularly hot year, food became less abundant (competition), blobs that had the ability to dig into the soil to get food had a better chance of survival.
Many blobs died that year…….
The ones that survived mated and passed their genes to the next generation. (reproduction)
The next generation had move blobs with the pointed noses. That is NATURAL SELECTION.