Sunday, February 25, 2007

Meiosis

Meiosis is the process of cell division where sex cells are produced, also when chromosomes split and form sex cells in the end. The male sex cell is called sperm and the female sex cell is called an egg. This division occurs in all eukaryotes. There are three basic steps:
1) the chromosome doubles
2) the 1st division
3) the 2nd division


Here’s an example of meiosis. A human body cell has 46 chromosomes.
Female:
46
I
92
/ \
46 46
/ \ / \
23 23 23 23
I \ I /
1 egg & 3 polar bodies
or
\ I I /
4 sperm
Interesting facts that I learned were:
1) There are four stages in a nuclear division: prophase, metaphase, anaphase, and telophase.
2) Meiosis comes from the Greek work meioun, which means “to make smaller.”
3) Some eukaryotes lost the ability to carry out meiosis and got the ability to reproduce by parthenogensis.
In my opinion, I think that meiosis is an important part of life. Without the process of meiosis, any living organism wouldn't be able to reproduce. If our parents didn't reproduce, we all wouldn't be here today.
Here are the links to the articles I got my information from:

Thursday, February 22, 2007

Cells

Cells. Such a tiny word can mean so much. A cell is the basic unit of life. Every single living organism has cells. Cells are everywhere, because they are microscopic. There are unicellular and multicellular organisms. Organisms that are unicellular, for example, are bacteria, yeasts, and amoebas. Other multicellular organisms are plants, animals, and humans.

Interesting facts that I learned from these articles are:

1) It takes millions of cells to make up the skin on the palm of your hand.

2) Animals have a skeleton because of a unique structure, the cell wall, which is why plants droop.

3) The human body has over ten trillion cells. (10,000,000,000,000)

In my opinion, I think that cells are the most important subject in science and life. Every living organism has cells, which I think, is extremely interesting. There would be no life if there weren’t any cells. Cells make everything come to life because it is the basic unit of life. If it weren’t for cells, we wouldn’t have most of the supplies we need today.

Here are the links to the article:

http://www.worldbookonline.com/wb/Article?id=ar102240&st=cell
username: xroads
password: vikings

http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm

Thursday, February 1, 2007

Europe's first stegosaurus was discovered.

What dinosaur do you know of that is an herbivore, 20 feet long and is studded with spikes on its tail? If you guessed a stegosaurus, you are correct. After the Jurassic period ended, about 150 million years ago, all dinosaurs became extinct. Because of this, there are fossils from these dinosaurs. Europe found their first stegosaurus fossil. Dinosaur fossils are usually found in North America, but not commonly in other continents. Surprisingly this happened. When the continents were still connected, Pangaea, dinosaurs would cross land bridges to other parts of land, which in this case is now known as Europe.

I think that this extremely fascinating to find fossils in other continents. Before reading this article, I thought that dinosaurs fossils were only found in North America and not in other coninents.

Finding dinosaur fossils can relate to science because when you discover something new you want to research about it and know more about it. By resarching about the fossil it can tell you what kind of dinosaur it cane from and learn more about that dinosaur. This can also relate to life because dinosaurs were once living, just like humans, but then became extinct.

This article can be found at cnn.com. Here's the link
http://www.msnbc.msn.com/id/16926228/