Back To CourseHigh School Biology: Help and Review
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Devin has taught psychology and has a master's degree in clinical forensic psychology. He is working on his PhD.
Evolutionary Fitness is how well a species is able to reproduce in its environment. If they're no longer reproducing then they are no longer evolutionarily fit. For example, you did not ride a Tyrannosaurus rex to the store. Why not? They're all gone. In their environment they were extremely fit as they ate, reproduced, and continued their species on. But what most often stops evolutionary fitness, and your pet T. rex , is a shift in the environment.
Your pet T. rex died out because the environment could no longer support it. The sun was blotted out resulting in a massive decrease in the amount of plants, causing the oxygen level to drop so the environment could no longer support large creatures. The plants died because there was less sun, resulting in the bottom of the food chain shrinking. With fewer plants the large herbivores starved to death, and with no herbivores to eat the predators starved to death.
The well known term 'survival of the fittest' was not actually said by Charles Darwin. The phrase was actually coined by Herbert Spencer, who used it for Social Darwinism, a concept we will not be exploring here. Survival of the Fittest is actually impossible, because fittest implies an end. If the fittest critter existed it would be a massive predator that feared nothing and could not possibly mate, because by mixing its perfect genes, or internal blueprints, with anything it would then become less fit.
Charles Darwin is best known for his work on evolutionary theory. He was not, however, the first to propose an evolutionary theory. The first would be Anaximander of 600 BCE Ionia, who noticed human limbs and fish limbs bear a striking similarity, leading him to believe that land-based animals must have originated in the sea. Darwin described the two mechanisms of evolution in his book, On the Origin of Species.
Another researcher by the name of Alfred Wallace came to similar conclusions as Darwin. However, Darwin's ideas and writings were more thorough and published, resulting in the scientific community attributing the evolutionary mechanisms to him. Darwin and Wallace's evolutionary mechanisms actually support the idea of survival of the fit: those who are fit enough to reproduce will pass on their genes, and those that do not work will die out.
Natural selection is the process by which the critter with the best adaptions survives long enough to reproduce. Let us take 200 people, and divide them into two groups. Each group of 100 is going to live on a different island for the next 100 years.
Island A is near the equator, which means it will get a lot of sunshine and will be very warm and very humid. This type of climate is very similar to what is seen in the Philippines. Because it is very warm, the vegetation tends to produce very little edible plant matter, and the animals tend to be very small. If there is very little food, the larger people will be hungry while the smaller people will be able to survive off the smaller food. In addition, the bright sun will give light-skinned people some nasty sunburn, while those with darker pigmentation in their skin will be better off. After 100 years the 100 people we put on Island A are now smaller and darker-skinned. This is seen in a person with Filipino heritage.
Island B will be nearer the Arctic Circle, with heavy cloud cover resulting in tougher vegetation, but larger sea animals that stay warm because of their blubber. To hunt big sea beasts like walruses you need big people who can hunt. In addition, because this island receives less light, people on this island will need lighter skin so they can more efficiently process sunlight into Vitamin D. After 100 years you will have large, pale-skinned people who look very Scandinavian. This is the process of natural selection; what works best in the environment will endure. Natural selection works by having traits that are useful continue on to the next generation and what does not work will be bred out.
Sexual Selection works by selecting what is passed on to the next generation by having those with desirable traits breed more. This works regardless of how useful the trait is. If you think of a peacock, you think of the large fan of very colorful feathers. Why do peacocks have those feathers? They do not ward off predators, they do not have any defensive properties to help protect them from predators, and they do not help them find food. They actually do just the opposite, since the male peacock must carry around this very large bundle of feathers, making it difficult to run away from predators and move through plants.
The reason the male peacock has such a large feather bundle is because the females mate with the males with the largest and brightest feathers. If within each generation only the largest feather-bundled peacocks get to make babies, then those babies will only have the genes for large feather bundles. This repetition at each level adds up, and the feather bundles are now a burden because they are so large. Sexual selection works by having females or males determine what is desirable and passing whatever that may be on to the next generation.
Does Homo sapien's greatest tool, the brain, evolve as well? Can a mind and brain show evolutionary fitness? A study by Sharps, Villegas, Nunes, and Barber (2002) looked at how well humans memorized new information, but they added an evolutionary twist. What do average college students with no outdoor experience memorize faster: animal tracks or military equipment and vehicles? Which option will allow humans in a non-modern society to survive?
If you had two hunter-gatherers and one was able to remember and track animals, a vital component of hunting, then he will survive and be able to have more children. Generation after generation allows the hunter-gatherers who can track and hunt better survive and have more children. This study demonstrates that evolutionary fitness is not just in claws, skin, or feathers but in the brain and in how a species thinks.
Evolutionary fitness is how well a species is able to survive and reproduce in its environment. Charles Darwin outlined the mechanisms of how species change, by natural selection and sexual selection. Natural selection is when the traits of a creature, such as size, skin color, or other features make it better able to survive. Sexual selection is when a species has a trait it finds desirable, resulting in individuals with that trait reproducing more. Change is connected to environment, so if the environment changes then the species must also change or go extinct. Lastly, evolution affects not merely skin, claws, or feathers but also part of the brain and thought processes of a species.
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Back To CourseHigh School Biology: Help and Review
36 chapters | 570 lessons
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