Cell theory
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Cell theory is a way to describe the biology of living things. Cell theory says that the cell is the basic unit of life. Cells by themselves are alive, but they can also be part of a larger living thing. The smallest living organisms (like bacteria but not viruses) and the biggest ones (like humans and whales) are all made of cells. Very small organisms like bacteria and amoebas are only made of one cell each, so they are called unicellular organisms ("uni" means "one"). Larger organisms are made of many cells, and they are called multicellular organisms.
These cells were born from older cells, in a process called cell division. Cells contain information that is passed from the parent cell to the daughter cells, so that the daughter cells can do what they need to do. This information is carried on molecules called DNA.
Because cells are alive, they must be able to eat and do other things to stay alive. All cells have chemical ways of consuming food. These are part of its metabolism.
Even though there are many kinds of cells, they have some similarities too. Many of the chemicals inside of them are the same.
[change] History
Robert Hooke discovered cells in 1663. He used a microscope to look at a piece of cork cambium. What he saw through the microscope reminded him of the small rooms that monks lived in. These rooms were called cellula in Latin, so Hooke called his discovery "cells". Hooke did not know that he was looking at dead cell walls and not living cells.[needs proving]. These cell walls did not have the nucleus and other organelles found in most living cells.
The first man to look at a live cell under a microscope was Anton van Leeuwenhoek. In 1674, he described the algae Spirogyra.[needs proving] He also described bacteria, which he called "animacules".[needs proving]
