Wednesday, Oct. 22- Cells - Introduction to Cellular Theory

Objective: You will understand that cells are the basic unit of life and know the three principles of cell theory.

Cells are the smallest living unit.

1665 – Robert Hooke creates simple microscope and looks at a slice of cork (dead cells of oak bark); sees cavities that look like the cells of a monastery. Called them Cellulae (small rooms.)

By mid 1800s, scientists have learned a lot about cells, but not where they came from. Believed in spontaneous generations (come from nonliving things)

Major People

Francesco Redi – 1668, questions spontaneous generation. Maggots on rotting meat. Some jars sealed, cheesecloth, open. Maggots only in open jars

John Needham – 1745, boiled chicken broth to kill microorganisms, sealed in flask. Microorganisms grew – thought it proved spontaneous generation. Others thought it came from microorganisms in the air.

Louis Pasteur – 1859, puts broth in S shaped flask so air can get in but microorganisms would get stuck. Upright, flasks were sterile. Tilted, microorganisms could enter flask.

Cell Theory

Rudolf Virchow studying cells at same times as Pasteur. In 1855, produces hypothesis that cells are produced by other cells.

Three principles

• All living organisms are made up of one or more cells.
• Cells are the basic unit of all living things
• New cells are produced from existing cells.

Cellular Organization

Specialized cells do a particular job, For example, cells form tissue. Four types of tissues: muscle (heart beat), nerve (carry messages to brain), epithelial (linings and covers body – skin), and connective (cartilage, ligaments).

Tissues then make up organs and organs make up busy systems. For example, there are several organs in the digestive system.