04 Oktober 2009

Prokaryotes – Bacteria

Prokaryotes – Bacteria

Prokaryotes, which includes, bacteria are the simplest of all the cells. There are two major groups of prokaryotic organisms --- the Kingdom Eubacteria and the Kingdom Archaebacteria. Eubacteria are known as true bacteria. They are the most common type of prokaryote. They are found everywhere, on surfaces and in the soil. Archaebacteria or the ancient bacteria are found in extreme environments, like hot sulfur springs and thermal vents in the ocean floor. Archaebacteria are thought to be some of the oldest life forms on earth.

Most bacteria are heterotrophic and don't make their own food. That means they have to rely on other organisms to provide them with food. These bacteria have to break down, or decompose, other living things to obtain energy. Very few bacteria cause illness. Some bacteria are used to make food, such as cheese and yogurt. Scientists have genetically engineered a type of bacteria that breaks down oil from oil spills. Some bacteria, like E.coli, live inside the guts of animals and help them to digest food.

Bacteria are unicellular and are covered with a thick outer cell wall. Color and label the cell wall purple. Just within the cell wall is the cell membrane. Color and label the cell membrane pink. Along the surface of some bacteria are structures called pili (pilus-singular) that help bacteria adhere to surfaces. Color and label all the pili light green. Some bacteria are motile (can move). Many of these bacteria have long, whip like structures called flagella (flagellum-singular). Color and label the flagella dark green. Since bacteria are prokaryotes, they do NOT have a nucleus. They do have a single strand of DNA (double helix) in the nucleoid region (center of the cell). This single strand of DNA contains all the instructions for making more bacterial cells. Locate the DNA and color and label it yellow. Bacterial cells reproduce by a process called binary fission. The inside of the bacterial cell is filled with cytoplasm. Color and label the cytoplasm light blue. Sprinkled throughout the cytoplasm of the cell are small, round structures called ribosomes. Ribosomes make proteins for the cell. Label and Color all of the ribosomes red.

1. What kingdom of bacteria are known as true bacteria?
2. What are the oldest life forms on earth?
3. Name some uses for bacteria.

4. What part of the bacteria cell helps it stick to surfaces?
5. What part of the bacterial cell aids in movement?

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