I bet you didn't know that there have been fossils of tropical plants found deep within the ice of Australia. Well there have, and this has caused scientists to do a lot of thinking about the history of Earth and what it might have been like before humans were here. Now we have a whole new idea about what Earth was like, and have come up with the theory that all of the continents were in one large mass called Pangaea.
Pangaea was a landmass that consisted of all of the continents and other land masses. The theory of continental drift explains how Pangaea broke up and was separated into the continents as we now know them. This explains why Antarctica has tropical fossils on in. It was once part of Pangaea, and was closer to the equator so it would have had a warmer climate. Then it moved to the South Pole and became much colder, which preserved those plants.
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.
A punnett square is what you use in science when trying to find out what percent chance a child has of receiving a certain trait from its parents. It is just a type of chart that you can use to do this. Here is an example of how you would use a punnett square...
For example, if the father is hybrid for dark hair (dominant trait) and the mother has light hair (recessive trait) then you can use a punnett square to find out what percent chance their child has of receiving either trait. You put the mother's genotype on top represented by two little "a"s, and the fathers genotype on the side represented by a big "D" and a little "d". Then you bring the two cross and down the punnett square, and if there is a big letter you always put it first. So when you do this with those two genotypes you get "Dd" in the upper left quadrant, "Dd" in the upper right, and "dd" in the lower left and the lower right quadrants. that way you know that it is a fifty-fifty chance that the child of those two parents is going to have dark or light hair. The example on the right is not of the exact cross that I explained, but it does show how a punnett square works. So now you should understand how to use a punnett square.
In science class we are working on a group project where everyone has a specific animal, and we have to demonstrate that animals' adaptations using puppets. Each group does their own show that includes all four animals from that group. So my group includes a field cricket played by me, then a red-tailed hawk, Mexican free-tailed bat, and a puffin which are played by the other members of my group. In the puppet show we have the choice to entertain our audience with either a song, poem, dance or something else creative and interesting.
My animal is the field cricket. I have done some research on them and found that even though they are very common, simple insects, they are still pretty interesting. I found out that it is only the males that make the humming sounds with their legs, and it is their mating call. Also, every different species of cricket has its own call so the females can recognize a male of their own species. This is just one interesting fact about the field cricket. I think this project is going to be pretty fun.
This past quarter science was pretty tough for me because I did really bad on one test early on, so I spent the rest of the quarter trying to get my grade up. The test I didn't do well on was about photosynthesis and respiration. It wasn't really that I didn't understand the topic, but that I didn't study. The part that I really should have studied better were the chemical formulas for those two processes. That test really taught me that I do actually need to study for tests even though in elementary school I could ace them without studying. Luckily for me though, I was able to get my grade up by the end of the quarter by studying for all the other tests and trying my hardest in that class.
Interphase is basically the beginning of mitosis, or you could think of it as preparing the cell for mitosis or meiosis. Many people think that interphase actually is the first stage of mitosis, but it actually is not. Prophase is the first stage of mitosis because mitosis is the division of the cell, and once again interphase is what prepares the cell for mitosis. During interphase the main thing that happens is that the DNA strands thicken into chromatin. Then the chromatin thickens into a certain amount of chromosomes depending on the animal or plant. A cell spends most of its time in this stage, and is mainly just performing normal cell processes during this time. So this is basically what interphase is.
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