Evolution and Taxonomy
1. What is evolution?
Evolution is the change in a kind of organism over time based on descending from ancient ancestors. Although evolution is "just a theory" there have been countless studies that have led to believe that this "theory" is actual reality. In other words, evolution is based off of survival of the fittest (natural selection by which those fittest ( best adapted to environment) survive and repopulate, while those who have not adapted die off. For example, Charles Darwin, the theory of common descent discovered proof while visiting the Galapagos Islands. While he was their he observed that on one island one species of finch dominated the area while on a different island a new species of finch was found without the other one in sight. Although this may seem normal Charles believed that all these finches descended from one type of finch. Each finch had a different beak shape and size for a specific use such as cracking open a nut. However, since different varieties were found on each island Charles believed that that specific finch on that island was best suitable to survive their because its beak was able to gather food on that terrain more efficiently. Also, some may think that these changes occur quickly but in fact these changes take many years. Some may ask why we aren't changing as humans? However, humans are changing it is just hard to prove this because we have only lived on this planet for a spec of earths existence. Overall, evolution is the change in organisms over time. Although you may think evolution is hard to prove, the evidence is standing all around you. Another example of evolution came from Jean Baptiste Lamarck. He posed the theory of Inheritance of acquired characteristics. This was the idea that during an organisms life time it was able to grow or stretch some part of its body to help it survive. Then as that changed organism found another changed organism with in the same species they would mate and produce offspring that also shared those characteristics that its parents gathered.
2. 5 ways a gene pool can change (micro-evolution)
A) Natural Selection- this is where those who are best suited for their environment survive and are able to reproduce and pass their genes on to the next generation. This allows the next generation organism a greater chance to survive because by having the better genes they are more likely to strive and survive in their environment.
B) Mutations- This is where there is a change in DNA in an organism which is caused by a coding error. This can have a positive, neutral, or negative effect on the organism. This gene mutation will then be passed on to the next generation and could change the gene pool. Most of these mutations don't have a great effect on their species but those who do can greatly effect the gene pool.
C) Genetic Drift- This is when there is a change in the gene pool which occurred after a random event which caused some genes to leave the gene pool (Drift away). When this occurs it ruins or totally destroys your chances of developing specific genes. For example, it their were 10 red bugs, 10 blue bugs and 2 yellow bugs and one day a natural disaster washed away the 2 yellow bugs then those genes would be eliminated from the gene pool. This would then destroy the chances of a yellow bug being reproduced until say another mutation occurs. Also genetic drift greater effects small gene pools as oppose to large gene pool.
D) Gene Flow- This is the transfer of alleles (genes) from one population to another. This can slowly, after generations change the genes of one organism and completely change it. For example, if a brown bug enters a white bug community over time the genes from the brown bug will most likely change the color of the white bug to a slightly more darker color.
E) Sexual Selection- This is non-random mating in which organisms choose who they want to mate with based on who has the greater, better amount of genes to pass on to the next generation. Although this can be how strong or big an organism is it can also be who plays the best song or who has the best color. For example, in a bug community the bugs have to hide in tiny holes from their predators. And most bugs are small but some are too big. Although the bigger and stronger bugs seem to be more "fit", those who are smaller actually have the better genes to pass on to the next generation.
B) Mutations- This is where there is a change in DNA in an organism which is caused by a coding error. This can have a positive, neutral, or negative effect on the organism. This gene mutation will then be passed on to the next generation and could change the gene pool. Most of these mutations don't have a great effect on their species but those who do can greatly effect the gene pool.
C) Genetic Drift- This is when there is a change in the gene pool which occurred after a random event which caused some genes to leave the gene pool (Drift away). When this occurs it ruins or totally destroys your chances of developing specific genes. For example, it their were 10 red bugs, 10 blue bugs and 2 yellow bugs and one day a natural disaster washed away the 2 yellow bugs then those genes would be eliminated from the gene pool. This would then destroy the chances of a yellow bug being reproduced until say another mutation occurs. Also genetic drift greater effects small gene pools as oppose to large gene pool.
D) Gene Flow- This is the transfer of alleles (genes) from one population to another. This can slowly, after generations change the genes of one organism and completely change it. For example, if a brown bug enters a white bug community over time the genes from the brown bug will most likely change the color of the white bug to a slightly more darker color.
E) Sexual Selection- This is non-random mating in which organisms choose who they want to mate with based on who has the greater, better amount of genes to pass on to the next generation. Although this can be how strong or big an organism is it can also be who plays the best song or who has the best color. For example, in a bug community the bugs have to hide in tiny holes from their predators. And most bugs are small but some are too big. Although the bigger and stronger bugs seem to be more "fit", those who are smaller actually have the better genes to pass on to the next generation.
3. What is stabilizing selection, directional selection and disruptive selection?
Stabilizing Selection- This is when there is something harming only the extreme variations in a population. When this happens the common variation has the highest survival advantage therefore making in even more common. While this is happening the extreme variations are starting to lose their percentage in the population. For example, say you have 3 colors of beetle ; black, white, and yellow and the environment is covered in dark rock and dirt and in this case the black beetles are most common. And in this environment lizards dominate the area in which they easily spot the white and yellow lizards. This lowers the amount of the extreme variations ( Yellow and White Beetles ) from the population while the black beetles grow in even more population.
Directional Selection- This is when the extreme variation at one end of the graph gets favored over time. Although at the start the most common variation had the most population, over time the extreme variation gained the survival advantage to survive in its environment. For example, during the industrial revolution the trees became dark, covered in soot. Although at the time the white peppered moths had more population, the extreme variation ( black peppered moths) over time became the most common because they were camouflaged while the white moths were not.
Disruptive Selection- This is when the extreme variations at both ends of the graph are favored over the in between variation. In other words, the extreme variations both contain traits which enable them to more likely survive over the intermediate variation. For example, If humans had a battle to the death, the small humans could avoid fighting by hiding, the strongest/biggest humans could fight while the medium sized humans couldn't hide or fight very well. Therefore the small and large humans would survive while the medium sized humans would most likely die.
4. Punctuated Equilibrium vs. Gradualism
Punctuated equilibrium was first thought of by Eldridge and Gould. This was the idea that members of a population were pushed or carried away from their original location to a less desirable or harsher environment. For example, the water levels in an ocean could drop leaving some members of a population stuck against a underwater mountain unable to swim overtop to its original location. Since this new location was more "extreme" , then the population would have to adapt quicker in order to survive. Then later over a long period of time when the water levels rise and the 2 populations meet again, those who were in the harsher environment would be more evolved allowing them to out compete the others. So in short terms punctuated equilibrium is quick, major changes in a population then is slowly changed from there on.
Gradualism on the other hand is based off of Darwin's theory of evolution. This is the idea that over time, the population will undergo changes but not major changes. As shown in the example above gradualism would be the population that didn't get pushed away from the others. This would be those who didn't have to live in harsher environments meaning that they didn't have to undergo major changes. However, eventually the gradual population will undergo changes due to surrounding changes but these changes will be minor.
Gradualism on the other hand is based off of Darwin's theory of evolution. This is the idea that over time, the population will undergo changes but not major changes. As shown in the example above gradualism would be the population that didn't get pushed away from the others. This would be those who didn't have to live in harsher environments meaning that they didn't have to undergo major changes. However, eventually the gradual population will undergo changes due to surrounding changes but these changes will be minor.
5. 5 Pieces of evidence that support the theory of evolution
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Fossil Records- By having fossil records it allows scientists to compare and contrast rock layers to see if life on earth has changed over time. Also these fossils are physical evidence that supports the theory of evolution. In similar fossils scientists are able to determine whether or not they are from the same species thus being able to find intermediate stage proof that life has changed slowly, with small steps in between. Although there are still many gaps in fossil findings, each year many more pieces of the puzzle are being fit due to fossils. Overall, by having fossils records it proves that ancient life exists and shows how there is change over time (evolution).
Geographical Distribution of Living Species- This as well also drove scientists to believe that Darwin's theory was true. During Darwin's voyage around the globe he found that in the same or different continents around the world were great examples of descent with modification. For example, the 13 different species of finch all had their own special traits but what Darwin believed was that they all came from a common ancestor on the mainland of South America. This takes place over many years as the birds travel and start adapting to knew environments that they encounter. Another example is that Darwin noticed how on Australia and South America were completely different species. However, in similar environments on both continents were different species that have both developed similar traits to match the surroundings. Overall, this is another reason that proves the theory of evolution.
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Comparative Anatomy- Scientists have also found similar body structures within different species to help prove Darwin's theory. These species that have similar body structures such as limbs are all used for different purposes which they have adapted over time to their environment. For example, humans, reptiles and birds all contains limbs but they all have different forms and functions such as legs, wings and flippers. Depending on how similar body structures within species are it groups species and determines how recently they shared a common ancestor. A good example of this is humans and monkeys which are different species but have many similar structures proves that they both share a recent common ancestor and are both classified in the same group "mammals". Overall these similar body structures prove that species, including plants all originated from a common ancestor at some point. Also, by having similar organs as other species can also help prove the theory.
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Similarities in Embryology- As scientists have found, in early stages as embryos they have found that many backbones animals are similar. This doesn't mean that they will develop the same but they do follow the same pattern and process. This is because they all develop the major body features first such as a heart and spinal cord but soon after they each start developing their own features that are unique to them. By having similar embryos this proves that many species share a more recent common ancestor and over time have changed and adapted to different environments. Also by seeing and studying these different species as embryos it is much easier to see relationships between them as oppose to when they look completely different after birth.
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Molecular Evidence- The DNA evidence found in species also helps support the idea of evolution. If the DNA from two different species is similar than the more recently they have shared a common ancestor. On the other hand the more different the DNA between the two species is means that they don't share a more recent ancestor but do in fact share one a long time ago. For example at first the African and American vulture were both classified in the falcon family because they looked similar and were seemed to be closely related. But, soon after scientists found that the African Vulture was more closely related to storks due to similar DNA and the fact that they are the only 2 birds that urinate on their own legs to cool down. Overall, by having similar DNA it proves you both have a more recent common ancestor. Another example of this is molecular clocks which shows how over time different DNA mutations can determine how long ago the gene pools have been separated. If the 2 populations or gene pools have been separated for a long time then the greater difference they will have between them. This is because within the same population the DNA will mutate at the same rate but as they separate so will the DNA mutations causing change over time (evolution).
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