Biology (level 2)

Differential Reproductive Success        Differential reproductive success  has to do with natural selection. Natural Selection is a gradual process by which certain traits of a species become either more or less common. The traits can determine the survival of the population of a certain species. Differential reproduction is that the organisms that are best adapted to the environment will be able to survive and reproduce offspring.   

Evidence for EvolutionThere are 3 different things that are evidence for evolution. These 3 things are DNA, fossils, and homologous and analogous.DNA       DNA is a molecule with a genetic code where all organisms store the complex information they need to live, grow, and reproduce. This information is copied and passed from parent to offspring. Scientist have figured out that DNA is very similar in many organisms. Sometimes the DNA gets changed because of a it gets copied wrong and passed on to the offspring. So when certain organisms' DNA are very similar that means that they are closer related. Scientists compare different organisms' DNA to figure out their recent ancestors. For example, scientists have figured out that Fossils       Fossils are another evidence of evolution. Scientists are able to tell by the bone structure of the organisms how closely related they are. Since scientists are not able to go back in time and look at older organisms DNA, they can use fossils to determine how closely related they are. Due to changes in the environment, organisms have to adapt which sometimes causes their bone structure to change slightly. Scientists look at the amount and shape of the bones to determine which organisms they are more closely related to.Homologous/Analogous       Homologous structures are structures that are similar in different species of common ancestry. For example, a dog, whale, and a bird are closely related to a human. We know this because the flipper of the whale, the wing of the bird, and the leg of the dog are similar to the arm of a human. They all have a bone called a humerus, a radius and ulna bones, carpals bones, and phalanges bones.       Analogous structures are body parts that share a common function but not structure. For example, the wind of a bee and the wing of a bird are analogous structures. They are analogous structures because they both share a common function, allowing the animal to fly, but do not have the same structure. In the example with the flipper of a whale, wing of a bird, leg of a dog, and arm of a human, They have a similar bone structure but they serve as different purposes.

Mass Extinction       It is an event during which many species become extinct over a relatively short period of time. It isn't a small increase in background extinction ("business as usual" extinction). In mass extinction, ecosystems vanish and whole food webs collapse. Species become extinct because their environment breaks down and the ordinary process of natural selection can't compensate quickly enough.       Many mass extinctions were probably caused by several factors. For example, one mass extinctions could have been caused by an asteroid crashing into Earth. Other examples that could cause mass extinction are volcanic eruptions, moving continents, sharp climate change, and changing sea levels. 

SpeciationSpeciation is the formation of a new species. This usually happens in response of isolation from the main population. For example, some turtles swam from mainland to a group of islands. The turtles on one of the islands developed long necks and have a "saddleback" shaped shells. A group of turtles on another island have short necks and "domed" shaped shells. 

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