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The Characteristics of Cells
Transcript of The Characteristics of Cells
In this section we will discuss:
1. What is a cell?
2. Why are most cells small?
3. What is the cell theory?
4. What do all cells have in common?
5. What are the two types of cells?
Seeing the First Cells
In 1665 a British scientist named Robert Hooke was looking at a piece of cork from the bark of a tree using his homemade microscope. He said it looked like honeycomb or lots of little boxes. He named those boxes cells. He later found these cells in plants, feathers, fish scales, and fly eyes.
Seeing Cells in other Life-forms
In 1673, Anton van Leeuwenhoek used his own homemade microscope to look at microorganisms in pond scum. He also compared blood from different animals and looked at tartar from his teeth and from other animals. He was the first to discover bacteria and discovered that yeast are alive.
The Cell Theory
Cell Theory has 3 parts that explain cells.
: All organisms are composed of one or more cells.
: The cell is the basic unit of life in all living things.
The first two parts were written by Theodor Schwann in 1839.
: All cells come from existing cells.
The last part was written 20 years later by Rudolf Virchow.
- a protective barrier between the inside of the cell and the outside that controls the passage of materials into and out of the cell.
Hereditary material - all cells contain DNA that controls the activities of the cell as well as contains the information needed to make new cells.
- the structures that all cells contain that enable them to live, grow, and reproduce.
- the fluid that fills the inside of cells and surrounds organelles.
We are made of many tiny cells instead of one large cell because of surface-to-volume ratio. A cell as large as us would not have a large enough membrane to allow in the needed materials to stay alive, so we are made of many small cells instead.
The Benefits of being Multicellular
Many kinds of cells
We are also made of many different types of cells which allows us to have specialized parts made of specialized cells.
Does an elephant have larger cells than a human?
Two types of cells
- a membrane covered organelle that contains the cells' DNA.
There are two types of cells: cells with a nucleus and cells without a nucleus.
- cells without a nucleus, also known as bacteria.
- cells that have a nucleus
Every living thing that is not bacteria is made of one or more eukaryotic cells. These cells are about ten times larger that prokaryotes and are much more complex (they have more specialized parts)
What is a Cell?
is the smallest functional and structural unit of all living organisms.
is any living thing that carries out its own life processes.
Robert Hooke was the first to describe cells. He looked at the bark of a cork tree under a microscope.