Evolution: Change In Allele Frequency
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Evolution, defined as either change over time or a change in allele frequency, is how species can develop or adapt over a length of time, creating new/better traits to better fit their environment. They key evolutionary steps are as follows: from single celled organisms to multicell, movement of the multicellular out of water, the growth of mammals from small to large, and the development of primates into humans.
There are four different ways adaptions - any trait that an organism has evolved - can occur: mutation, genetic drift, migration, and natural selection. Mutation is the way all new alleles are created, and can be either harmful or helpful. Mutation is the random change in a sequence of DNA, and can effect anything from the organism's color, to size, to amount of limbs. A mutation must be heritable (able to pass down), for it to really change a species, because one member of the species' mutation doesn't help/harm the reproductive success of the species as a whole. The mutation may or may not help the first individual reproduce; if it doesn't, the mutation will die off with the first organism to have it. If it is reproductively successful, it will be passed on. 
Genetic drift is the random change in allele frequency; when a group is taken from the population and forced to only reproduce with each other, there is only a specific amount of alleles that will be shown in the group's offspring. There are two examples of this: founder effect and bottleneck. The founder effect is where the breeding happens within a certain population, and the frequencies in alleles are changed, and bottleneck is more forced, when extreme and rapid environmental change kills off certain alleles, leaving only certain left to reproduce.
Thirdly, migration, also known as gene flow, occurs when a group of individuals move from one environment to another. The moving of these few individuals changes the whole allele frequency of the population - as there are new alleles being introduced. Lastly, there is natural selection, or, famously, survival of the fittest. The individuals with the most reproductively successful traits are allowed to pass down those traits, while individuals with badly suited traits are less apt to reproduce. The individuals best suited to the environment are the ones that survive long enough to reproduce and pass on their DNA. |
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Types of Natural Selection
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There are three different types of natural selection: stabilizing selection, directional selection.
In all species, there are three different types of each allele. This can be for anything - fur color (dark, medium, light), size (small, medium, large), speed (fast, medium, slow), etc. Directional selection is when the environment only supports one extreme. This can either be the low extreme or the high extreme; for example, a tall giraffe is guaranteed more success in an environment than a medium-sized or short giraffe is; because of its long neck, the availability of food makes it easier for the animal to feed, and therefore live long enough to reproduce. Stabilizing selection is when an environment supports the average, or middle. For instance, a frog might survive in an environment best with medium-sized and medium-strength legs, as legs too powerful and big require to much energy and food, and slow the frog down, and small legs have no power, not allowing the frog to jump and escape predators. Lastly, there is disruptive selection, where the environment supports the two extremes, but not the middle. An example of this is rabbits in certain environments - big rabbits are large enough to not be eaten by predators, while small rabbits are small enough to hide and remain hidden. Medium-sized rabbits would make a meal for predators, easy to be spotted and not too large to be eaten. |
Examples of Evolution
There are a couple examples of evolution. The most famous and well-known example is probably fossils - ancient organisms made immortal by rock. Today, we are able to tell how old each layer of rock is, and, by association, how old the creature buried in it is. By comparing the dead animal to animals similar to it today, scientists can tell how the organism has evolved to become the species it is today. In some cases, the animal hasn't changed at all.
Another example is geography: thousands of years ago, all continents on earth were one giant land mass called Pangea. There are creatures miles away from each other today on different corners of the world that evolved from similar ancestors in Pangea.
It is also clear when you study the physicalities of different animals - for example, humans have the appendix, a vestigial organ, that may be a remnant from when we were primates; humans and fish look similar in early forms of embryos; whales, humans, and bats all have the same type of bone structures that make up their "arms", an example of homologous structures.
Another example is geography: thousands of years ago, all continents on earth were one giant land mass called Pangea. There are creatures miles away from each other today on different corners of the world that evolved from similar ancestors in Pangea.
It is also clear when you study the physicalities of different animals - for example, humans have the appendix, a vestigial organ, that may be a remnant from when we were primates; humans and fish look similar in early forms of embryos; whales, humans, and bats all have the same type of bone structures that make up their "arms", an example of homologous structures.
Special Adaptations
- Jewel anemones reproduce by longitudinal fission (splitting in half), which allows them to reproduce easily without needing to find a mate.
- Sea anemones use their tentacles to sting other animals (ie shrimp, small fish), using minimal energy to acquire food.
- Live in groups on rocky overhangs/in caves to prevent being swept away by current and where they can be shaded by light.
- Unlike similar anemones such as Caryophyllia smithii and Caryophyllia inornata, the jewel anemone doesn't have a calcareous skeleton (which would contain both exterior protection and interior muscles).
