Monday, September 3, 2012
Thursday, July 12, 2012
Chapter 1 Plant and Animal Cells and Functions
Lesson 1
What is a Cell?
A cell is the building block of life. A cell is the smallest unit of a living thing that
can perform all life processes. All living things are made of cells. Some living things are made of just one cell. But most
living things are made of many cells. Examples of multicelled organisms are plants and animals.
Cells play many different
roles. Some cells help the living thing get energy and it uses to grow,
develop, and reproduce. Other cells help it get rid of what it doesn’t need. Others
help it move or react to its environment. Other cells may protect the living
thing or help it stay healthy. All cells come from other living cells.
The Parts of a Cell
Each part of the cell helps it to carry out its life processes.
The
nucleus is the control center for the cell. The instructions for
the cells activities are stored in the nucleus.
The cell membrane is the cells outer border. It
separates the cell from its environment.
It also controls what substances move in or out of the cell.
The cytoplasm contains the things that the
cell needs to carry out its life processes.
Cells Working Together
In a many-celled plant or animal, cells are organized to work together. Different types of cells do differnt types of work. Groups of the same type of cell form a tissue. Groups of tissues that work together form an organ. Groups of organs that work together form systems.
An organism is the highest level of cell organization. It is a complete living thing that is made from all parts in all the systems working together.
Like animal cells, plant cells have a cell membrane, cytoplasm, and a nucleus. But plant cells also have parts that animal cells do not have. Plants make their own food. They need special parts to do this. Chloroplasts are the special parts in the plant cells that trap the Sun's energy. The plant needs this energy to make food. Animal cells do not have chloroplasts.
The cell wall is another part of the plant cell that an animal cell does not have. The cell wall is outside the cell membrane. It helps to support and protect the cell.
Review for the Section:
1. The smallest unit of a living thing that can perform all life processes is a____________.
2. What are two roles of cells?
3. This structure contains things needed to carry out life processes?
4. A group of tissues that work together is an _______________.
5. Name two structures that a plant cell has that an animal cell does not have.
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