3.1 Discovering Cells7.1 All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope

An Overview of Cells• Key concept: Cells are the basic units of structure and

function in living things.• Examples of function: obtaining oxygen, getting rid of

waste, obtaining food, growing, and more…• Cells function similarly in all organisms, they carry out

the basic processes of life similarly• Cells are so small they are measured in micrometers• One square centimeter of Skin is more than 100,000 cells• Cells are visible only through microscope

First Observations of Cells• 1590ish invention of the microscope• Key concept: The invention of the

microscope made it possible for people to discover and learn about cells.

Robert Hooke•one of first people to observe cells•built his own microscope- one of the best of his time•observed cork which looked like small rectangular rooms they called cells

First Observations of CellsAnton van Leeuwenhook•Dutch businessman•Built simple microscopes in his spare time•Looked at drops of lake water, scrapings from teeth and gums, water from rain gutters

Animalcules- means “little animals,” small organisms that moved that he found in things like lake water

Development of the Cell Theory

• Schleiden- all plants are made of cells• Schwann- all animals are made of

cells• Virchow- new cells are formed only

from cells that already exist• Until these men’s time people

believed that cells can come from non-living matter

Cell TheoryAn explanation of the relationship between cells and living thingsi. All living things are made of cells. ii. Cells are the basic units of structure and functioniii. All cells are produced from other cells

Unicellular and Multicellular• Unicellular- single celled• Multicellular- many cells• Key concept: “In multicellular

organisms, cells are often organized into tissues, organs, and organ systems.

• Tissue- a group of singular cells that work together

• Organs- is made up of different kinds of tissue

• Organ system- a group of organs wanted to what those