1. An Introduction to Cells
Indicator B – 2.1:
Recall the three major tenets of cell theory
Indicator B – 2.3:
Compare the structures and organelles of prokaryotic and eukaryotic cells.

2. Key Concepts Cell Theory Unicellular vs. Multicellular Organisms
Prokaryotes vs. Eukaryotes

3. It is essential for you to know:
All living things are composed of one or more cells.
Cells are the basic unit of structure of all living things.
All presently existing cells arose from previously existing cells.

4. Objectives Recall the major tenets of the Cell theory.
Compare unicellular organisms and multicellular organisms.
Differentiate between prokaryotic cells and eukaryotic cells.

5. The History of Cell Biology

6. The History of Cell Biology
A person who studies cells is called a cytologist.

7. Robert Hooke English physicist 1665 Saw a slice of cork tree tissue
Tiny chambers
Termed them “cells”
(looked like monks’ cells in monastery)

8. Robert Hooke Published his book Micrographia
Contained drawings of cork cells
Used early microscope

9. Anton Van Leeuwenhoek Dutch businessman 1674 Perfected microscope
(about 300x)
Saw living things in pond water
“Animalcules”
Observed bacteria (on wood teeth) and protozoa

10. Matthias Schleiden German botanist 1838
Concludes that all plants are made up of cells

11. Theodor Schwann German zoologist 1839
Concluded that all animals are made up of cells

12. Rudolph Virchow German physician/pathologist 1855
Worked with eggs from various organisms
Proposes that all cells come from existing cells

13. The Cell Theory A cell is the basic unit of life.
All of the scientists’ work contributed to what is now called the cell theory:
All living things are composed of one or more cells.
Cells are the basic units of structure and function in an organism.
Cells come only from the reproduction of existing cells.

14. Prokaryotes & Eukaryotes
Biologists divide
cells into two
categories:
Prokaryotes
Eukaryotes

15. Prokaryotes & Eukaryotes
No nuclei
Have cell membrane, cell wall, plasmid, ribosomes, cytoplasm
Smaller and simpler
Most bacteria and archae
Divide by binary fission

16. Prokaryotes & Eukaryotes
Have a nucleus
Usually bigger and more complex
Cell membrane, cytoplasm, & organelles.
Plants, animals, fungi, and many microorganisms.

17. Unicellular Organisms
Sometimes the cell is the organism.
Do everything that you would expect a living thing to do.
Include both prokaryotes and eukaryotes.
Prokaryotes: bacteria and archae
Eukaryotes: some types of algae, protists, fungi.

19. Multicellular Organisms
Made up of more than one cell.
Cells in multicellular organisms are specialized to perform particular functions within the organism.
This is cell specialization.
Think:
blood cells, hair cells, digestive cells, etc.

21. Levels of Organization
The levels of organization in a multi-cellular organism are:
individual cells
tissues
organs
organ systems

22. Levels of Organization
Cell: nerve cell
Tissue: nerve tissue
Organ: the brain
Organ System: Nervous System