Cells Essential Question How does your body repair a wound like a cut or broken bone?

Cells In the 1660’s, Robert Hooke began using microscopes to look at different materials.

Cells When he looked at a piece of cork, he saw many compartments, which he called cells. The cells were empty because they were dead.

Cells In the 1670’s, Anton van Leeuwenhoek looked at a drop of pond water under microscope. He saw many tiny single celled organisms moving around.

Cells The work of Hooke and Leewenhoek and many, many others over a long time are summarized in 3 concepts, together called cell theory.

Cell Theory Theory: a widely accepted scientific explanation. When an idea becomes SO well tested and has SO much evidence that it is accepted by the scientific community, it is called a theory. Saying something is “just a theory” in science makes no sense!!

Cell Theory Every living thing is made of one or more cells.

Cell Theory Unicellular: made of only one cell Too small to see directly

Cell Theory Multicellular: made up of many cells

Cell Theory There are about 37.2 trillion cells in the human body

Cell Theory 2) Cells carry out all the functions needed to support life.

Cell Theory Growth and development Use of energy Reproduction Getting rid of waste Responding to the environment

Cell Theory Different types of cells carry out different functions. In your body, you have… Muscle cells Blood cells Brain cells Skin cells Bone cells and many more!

Cell Theory 3) Cells only come from other living cells.

Cell Theory By the 1850’s, many people had observed the same thing-cells dividing under a microscope. One living cell divides into two identical cells.

Cell Theory The process of cells dividing is called mitosis. Mitosis allows living things to grow and repair themselves by creating new cells.

Eukaryotic Cells Two main categories of cells Prokaryotic: no nucleus and the genetic material is loose in the cell. Most unicellular organisms are prokaryotic

Eukaryotic Cells Eukaryotic: DNA is in a nucleus inside the cell. Almost all multicellular organisms (like plants and animals) are eukaryotic. (YOU are eukaryotic)