Natural Selection
What is evolution?
Well, evolution is a change in allele frequency in a population. It is a change over time. It's how animals obtain adaptations, or traits that an organism has evolved, that help them survive in an environment.
There are four factors that drive a change in allele frequency:
1) Mutation is the only way new alleles are created. It can be a harmful or helpful allele. It must be heritable in order for offsprings to get it, and it may or may not affect the reproductive success.
2) Genetic Drift is a random change in allele frequency. There are two examples: the founder effect, and population bottleneck. The founder effect is when a small population breaks away from a larger one to colonize a new area, but it is most likely not genetically representative of the original larger population, like the Amish people of Lancaster, Pennsylvania (many have extra fingers and toes). Population bottleneck effect is when Natural disasters reduce the size of a population nonselectively and randomly, resulting in loss of genetic variation.
3) Migration, aka Gene Flow, is when a group of individuals move from one population to another. For example, pollen from one valley can be carried by the wind across a mountain to another valley.
4) Natural Selection is the "survival of the fittest," when organisms best suited to the environment survive and reproduce. This was described by Charles Darwin, when he first saw natural selection in the Galapagos Islands with finches and their different types of beaks.
Darwin shows three conditions needed for natural selection to occur:
1) There has to be variation for a trait. The running speed in a population has to vary in individuals.
2) It has to be heritable. The running traits have to be passed on to offsprings.
3) It has to have differential reproductive success. Slow running speed traits are not passed on because organisms with slow running speed die out.
Well, evolution is a change in allele frequency in a population. It is a change over time. It's how animals obtain adaptations, or traits that an organism has evolved, that help them survive in an environment.
There are four factors that drive a change in allele frequency:
1) Mutation is the only way new alleles are created. It can be a harmful or helpful allele. It must be heritable in order for offsprings to get it, and it may or may not affect the reproductive success.
2) Genetic Drift is a random change in allele frequency. There are two examples: the founder effect, and population bottleneck. The founder effect is when a small population breaks away from a larger one to colonize a new area, but it is most likely not genetically representative of the original larger population, like the Amish people of Lancaster, Pennsylvania (many have extra fingers and toes). Population bottleneck effect is when Natural disasters reduce the size of a population nonselectively and randomly, resulting in loss of genetic variation.
3) Migration, aka Gene Flow, is when a group of individuals move from one population to another. For example, pollen from one valley can be carried by the wind across a mountain to another valley.
4) Natural Selection is the "survival of the fittest," when organisms best suited to the environment survive and reproduce. This was described by Charles Darwin, when he first saw natural selection in the Galapagos Islands with finches and their different types of beaks.
Darwin shows three conditions needed for natural selection to occur:
1) There has to be variation for a trait. The running speed in a population has to vary in individuals.
2) It has to be heritable. The running traits have to be passed on to offsprings.
3) It has to have differential reproductive success. Slow running speed traits are not passed on because organisms with slow running speed die out.
Evidence of Evolution
1) Fossils show past organisms and how they are related to modern species. For example, with fossils, scientists have figured out that wooly mammoths and elephants are related. Fossils also can determine the age of organisms and how the environment was around the organism. It also shows that extinction occured, and that it did not adapt to environment changes.
2) Vestigial organs are organs with no function or purpose. For example, our appendixes were for digesting tough plants, which shows our ancestors' diet and habitat. Whales and snakes have a "pelvis", which shows that they once had feet and lived on land. Humans also have a tailbone. What would this conclude?
3) Convergent evolution shows how unrelated species have similar traits. The penguin, shark, and dophin all have flippers due to similar environments. Penguins and orcas have pelagic coloring because they are also in similar environments.
4) Divergent evolution shows how once related species turn into different species. For example, the mammals and the marsupials were on the same land. But now, marsupials only are in Australia. Finches on the Galapagos started out on the same land, but because of the separated Galapagos Islands, they became different.
5) Biochemistry shows genetic evidence and amino acid similarities. Using biochemistry, scientists saw that humans had 98% similar genetic evidence and amino acid similarities with chimps.
6) Homologous structures show the same structures of body and skeleton in different species. The cat, the human, the whale, and the bat all have the same bone structures in their legs/arms/flippers/wings.
7) Embryology shows how different organisms' embryos look similar to one another. The fish, the whale, the bird, and the turtle all look the same when they are embryos. Fish and humans also start out with gills when they are embryos, but the human DNA gets rid of the gills because we don't need them. Remember, DNA codes development, and certain genes are turned on or off. This proves that they shared a common ancestor.
2) Vestigial organs are organs with no function or purpose. For example, our appendixes were for digesting tough plants, which shows our ancestors' diet and habitat. Whales and snakes have a "pelvis", which shows that they once had feet and lived on land. Humans also have a tailbone. What would this conclude?
3) Convergent evolution shows how unrelated species have similar traits. The penguin, shark, and dophin all have flippers due to similar environments. Penguins and orcas have pelagic coloring because they are also in similar environments.
4) Divergent evolution shows how once related species turn into different species. For example, the mammals and the marsupials were on the same land. But now, marsupials only are in Australia. Finches on the Galapagos started out on the same land, but because of the separated Galapagos Islands, they became different.
5) Biochemistry shows genetic evidence and amino acid similarities. Using biochemistry, scientists saw that humans had 98% similar genetic evidence and amino acid similarities with chimps.
6) Homologous structures show the same structures of body and skeleton in different species. The cat, the human, the whale, and the bat all have the same bone structures in their legs/arms/flippers/wings.
7) Embryology shows how different organisms' embryos look similar to one another. The fish, the whale, the bird, and the turtle all look the same when they are embryos. Fish and humans also start out with gills when they are embryos, but the human DNA gets rid of the gills because we don't need them. Remember, DNA codes development, and certain genes are turned on or off. This proves that they shared a common ancestor.
Speciation
Speciation is the creation of new species, which is a group of interbreeding individuals.
There are two types of speciation:
1) Allopatric - speciation due to geographic isolation.
2) Sympatric - speciation with no geographic isolation. For plants, polyploidy occurs, which is like self pollination. Polyploidy is a random mutation that causes plants to become bigger and more unusual.
There are two types of speciation:
1) Allopatric - speciation due to geographic isolation.
2) Sympatric - speciation with no geographic isolation. For plants, polyploidy occurs, which is like self pollination. Polyploidy is a random mutation that causes plants to become bigger and more unusual.