Cells – The Basic Unit of Life

The Characteristics of Living Things §All living things have these six characteristics. §Anything without one of these six characteristics is nonliving. §Living things are called organisms.

1. Made of Cells §Organisms are made up of one or more cells. §A cell is the basic unit of structure and function in living things. l Cells = the of life.

2. Use and Need Energy §All organisms need and use energy to live. §Energy is the ability to do work.  Sunlight is the source of energy for most living things. l Plants use the energy in sunlight to make food, and animals get energy by eating plants or other animals that have eaten plants.

3. Adapted to Their Surroundings §Organisms are adapted, or suited, to their surroundings.  All organisms have features that help them survive in their surroundings. l For example: fish have gills

4. React to Changes  Organisms react to change in their surroundings.  Any reaction to change is called a response. l For example: A bright light may cause you to blink.

5. Reproduce §Organisms produce more organisms of their own kind. §Reproduction allows organisms to continue living on the earth.

6. Grow and Develop  Living things change, or develop, during their lifetimes. l One way organisms change is by growing. Living things may also change in appearance. For example: tadpoles and frogs §All organisms grow and develop.

Summary  Biologists use six characteristics to classify something as a living thing. 1. Made of Cells 2. Use and Need Energy 3. Adapted to Their Surroundings 4. React to Changes 5. Reproduce 6. Grow and Develop §All living things display all of the above characteristics.

Hairy T- cell

Cell Theory Three part theory about cells 1. All living things are made of cells.

Part 2 of the Theory 2. The cell is the basic structural and functional unit of life.

Part 3 of the Theory 3. All cells come from pre-existing cells. yeast cells dividing

Who came up with this theory? 1. Schleiden (circa 1838) All plants are made of cells! Onion skin cells

2. Schwann Who came up with this theory? All animals are made of cells! Human red blood cells

Who came up with this theory? 3. Virchow All cells come from pre- existing cells!