Evolution Time
I know we have all heard of evolution, maybe you learned it as change over time. But evolution is more properly known as the change of allele frequency. An allele is a version of a trait. That sounds confusing but it is actually just the number of times there is a change of a trait. Allele frequency can change in three different ways: Mutation, Genetic Drift, Migration, Natural Selection. Lets break each one of these down.
1. "Mutation is the only way new alleles are created. Gene mutations occur in two ways: they can be inherited from a parent or acquired during a persons life time." [1] Alleles formed by mutation can either be harmful of helpful. Mutations can occur from exposure to radiation, certain chemicals or a mistake when crossing-over. For the mutation to be able to be passed on to the next generation, it has to be heritable. For a mutation to be heritable it has to be present in the gametes or sex cells not just in the skin cells.
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This image shows how a mutation can help a species.
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2. The next way evolution can change is by Genetic Drift. This is a random change in the allele frequency in a gene pool or small population. The bottleneck effect is a term commonly used when talking about genetic drift. How that works is an event that extremely reduces the size of a breeding population, which greatly decreases genetic variability and increases genetic drift when they begin to reproduce. "This might sound like natural selection but that works on mutations which impact survival, whereas, genetic drift, on the other hand, works on all mutations, including those which offer no survival advantages."[2]
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This diagram represents the bottleneck and how in the end it increases genetic drift. You can see there are much less yellow marbles in the end.
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3. The third way evolution can happen is by migration. A well-known example of this is the founder effect. This is when out of a large population a few individuals decide to move and start a new population of their own. The allele frequencies that were present in the first group would un-likely be present in the new population. This may sound similar to the bottleneck effect but remember that bottleneck happens when a disaster results in a surviving population that is unlike the original. Founder is when a group of individual decide to move and the new population is unlike the original.
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4. The last way allele frequency can change is by natural selection. This is where organisms that are more adapted to their environment will be able to survive and produce. Natural selection is also broken down into three different groups. First is variation in populations, like different colors or body size. The next is some of those variations are heritable, where some traits are consistently passed on and others are not. The third is there is a high reproductive success where more offspring are produced than would typically survive. The last are traits that help the species to survive and reproduce. They need to have traits that will help them survive the obstacles in their habitat.
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Evidence of Evolution
Evolution might seem very hard to believe but there is some evidence to help you out. For instance scientists have found out about continental drift. A long time ago the earths surface was basically one big continent. This is why we have found the same fossils of animals on completely different continents. This shows that there could have been a single species in one place opposed to separate species evolving in different continents. (see the image to the right)
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Another piece of evidence to guide you along is that humans and other animals share similar embryos during a certain stage of development. At one point in our mothers womb we might have looked just like the embryo of a pig of fish. We resemble many of these other animals because we all share and carry the same ancient gene. That means we are all related and have common ancestors.
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The final piece of evidence i will give you for evolution are vestigial structures. Vestigial structures are structures in an organisms body that have lost function or purpose due to evolution. But why would we have useless structures still in our bodies then? The answer to that question is evolution, because at one point we must have needed them to help us survive but eventually we have evolved to not need them. The reason why they stay in our body is because they do not harm us so we don't get rid of them. Examples in humans are: appendix and tailbone and wisdom teeth. Bonus: inside a whales flipper there is the vestigial structure of an hand an pelvic bone.
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But is this true for wombats!?!?!?!
Here are some adaptation wombats have:
The wombat Vombatus hacketti began to go extinct about 12,000 years ago when the climate changed to quickly for it to adapt to. While there used to be many species of wombat there are now only 3.
- Their front legs are have with sharp claws for digging.
- Wombats are one of only a few species of marsupial that have a backward-facing pouch. This protects their young from dirt. [3]
- Wombats teeth never stop growing
- They have a very thick behind so when a predator attacks them it is hard to bite the skin and may actually hurt the attacker.
The wombat Vombatus hacketti began to go extinct about 12,000 years ago when the climate changed to quickly for it to adapt to. While there used to be many species of wombat there are now only 3.