Plant fossils are one very important thing that scientists use to find out how the environments of different areas of the world have changed over time. The fossils of plants can be useful in this because certain plants can only survive in certain environments. Usually you can tell about what kind of plant the fossil is just by looking at it, or at least be able to tell what kind of environment it would have lived in because of features such as its leaves.
One example of how plant fossils have been helpful in finding out about the past environments of the Earth, is the fossils that were found in Antarctica. Deep into the ice of Antarctica preserved fossils were found of plants. The plants were actually tropical! This shows that Antarctica was most likely much warmer than it is now, which also means that is must have been much closer to the equator. This is also evidence for continental drift. As you can see, plant fossils can be used to understand what our Earth was once like, and can be used for a lot of other things in science as well.
Th Grand Canyon is a good example of both superposition and cross cutting relationships. The way it shows superposition is simple. It is made of sedimentary rock that is arranged in very obvious layers. The rocks on top are younger than the rocks on the bottom. This makes sense because you can't stack something from the top. It just isn't possible. It is like stacking photos. The ones at the bottom of the stack are older because you stacked them before the other photos. That is how superposition is shown in the Grand Canyon.
The Grand Canyon also shows cross cutting. The principle of cross-cutting relationships states that when one geologic feature cuts through another, the one that is cutting through is the younger of the two. This can be found in many places throughout the Grand Canyon. One example of this is a type of intrusion called a dike. A dike is just a band of igneous rock that cuts through another pre-existing geologic feature. That is one way that cross-cutting relationships is found in the Grand Canyon, but there are many others throughout its vastness.
Peppered moths in England used to be mostly all white, and only a fraction of the population was black. This was the case until the industrial revolution began. During the industrial revolution there were a lot of black fumes and gases being emitted from factories and such. The smoke would cover trees and make the bark turn black. This caused a major change in the peppered moth species.
Because the trees had turned black due to the fumes from factories, white peppered moths were less camouflaged and therefore much easier for predators to see. The lack of protection via camouflage caused most white moths to die off, but the black moths began to flourish where their white relatives had before. Since the trees were now black, they provided the black peppered moths with camouflage. Less of them were constantly being preyed upon, so they had a chance to grow in population, and soon outnumbered the white moths. When something like that happens it is called natural selection. Natural selection is a type of evolution. The peppered moth in England is a perfect example of natural selection.
A population is a group of any size of plants or animals. In most populations there is competition. This can be caused by numerous things and can eventually cause various parts of evolution to take place such as extinction or speciation. One main thing that can cause competition is a limited amount of resources available to the population. Another main factor in competition is overpopulation. Rats are a good example of overpopulation. Two parents may have twelve babies in one litter. They can have many litters in their lifetime. Then all their babies grow up and have their own babies. So each rat could be responsible for thousands of rats after it. That is overpopulation.
Overpopulation and limit resources kind of work together to create competition. If there are not enough resources in the first place, plus a population is growing extremely rapidly, there is a problem. The total population is growing faster than the amount of resources is. Members of that population will have to compete for the small amount of resources available to them. There won't be enough for everyone though, so some of them will die off. This is how competition begins in a population.
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