Fossil is hard to interpret because the animals' or plants' are at least 10,000 years ago, so it is very hard to tell the shape or species or the animals' or plants' fossils. In addition, the paleontologists always break the fossils to take the main shape out, so a lot of fossils do not have enough parts on them. Getting a fossil also is hard since the paleontologists are getting the fossils under the heating sun and inside the ground. On the other hand, interpreting the fossils also can become easier because some ants are helpers who collect the tiny pieces of fossils under the ground. To sum up these reasons, interpreting the fossils is a hard job, and we need to appreciate the hard works of the paleontologists.
Directional selection is one kind of natural selection that a single phenotype is favored, which cause the alleles' frequency change in one direction. The greyhound dog can be a perfect example of directional selection because the breeders choose the ancestors of these dogs whose speeds are fast. Therefore, their offsprings are the fastest dogs. Stabilizing selection is a type of natural selections in which genetic diversity decreases as the population stabilizes on a particular trait. An example of stabilizing selection is Siberian Husky, a dog lives in the snow, because they have heavy muscles in their bodies, so these dogs will not sink into the snow. Disruptive selection is the changes in population genetics, which extreme values for a trait is more favorable than a intermediate values. The examples of disruptive selections can be based on the different large animals, such as an elephant because the larger animals need more food and oxygen, so these animals can live in a new enviroment even the change is extreme.
