1. SC.912.L.14.1 The Cell Theory

2. What you need to know
You need to know the cell theory and how continuous investigations and/or new scientific information influenced the development of cell theory.
You need to know how scientific claims are evaluated through scientific argumentation, critical and logical thinking and consideration of alternative explanations, in the context of cell theory.
You need to know the difference between theories and laws and be able to explain how a theory is developed.  

3. The cell theory
All living things are composed of cells. They may be unicellular or multicellular.
Cells are the basic units of structure and function in living things
Cells arise from pre-existing cells

4. All living things are composed of cells.
They may be unicellular (single cell)
or multicellular (multiple cells)

5. The cell is the basic unit of life

6. Prokaryotic Cells Eukaryotic Cells
Cells arise from pre-existing cells (result from replication of pre existing cells).
Prokaryotic Cells Eukaryotic Cells
(reproduce by binary fission) (reproduce by mitosis and meiosis)
Cells replicate the genetic information before dividing to form new cells.

7. The invention of the microscope made the discovery of the cells possible It was not until the mid-1600s that scientists began to use microscopes to observe living things

8. Robert Hooke’s Work English scientists
In 1665 he used a compound microscope he built.
Looked at tree bark
Called the structures “cells”
He observed dead cells

9. Anton van Leeuwenhoek’s Work
Dutch scientist
Used a simple microscope
Looked at pond water
He saw single cells “animals” swimming in the water and called them “animalcules” (tiny animals)
He observed live cells

10. Matthias Schleiden’s work
German botanist
In 1838 used a microscope to study plants
He concluded that plants are made up of cells
Became the first person to propose the idea that cells are the basic unit of life and that plants grow by making new cells

11. Theodor Schwann’s Work
German biologist
In 1839 used a microscope to study animals
He concluded that animals are made up of cells

12. Rudolph Virchow’s work
German physician
In 1850 proposed that cells come from pre-existing cells and not spontaneously from non living matter
He based his ideas on his own research as well as that done by other scientists

13. Prokaryotes and Eukaryotes
Cells fall into two broad categories, depending on whether they contain a nucleus.
The nucleus is a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA. The nucleus controls many of the cell’s activities.

14. Prokaryotes and Eukaryotes
Eukaryotes are cells that enclose their DNA in nuclei.
Prokaryotes are cells that do not enclose DNA in nuclei.

15. Prokaryotes
Prokaryotic cells are generally smaller and simpler than eukaryotic cells.
Despite their simplicity, prokaryotes grow, reproduce, and respond to the environment, and some can even move by gliding along surfaces or swimming through liquids.
The organisms we call bacteria are prokaryotes.

16. Eukaryotes
Eukaryotic cells are generally larger and more complex than prokaryotic cells.
Most eukaryotic cells contain dozens of structures and internal membranes. Many eukaryotes are highly specialized.
There are many types of eukaryotes: plants, animals, fungi, and organisms commonly called “protists.”

17. Prokaryotic and Eukaryotic Cells
PROKARYOTIC CELL
BOTH
EUKARYOTIC CELL
No nucleus
DNA of prokaryotes floats freely around the cell
DNA
Nucleus present
DNA is held within its nucleus
No membrane bound organelles
Plasma membrane
(cell membrane)
Membrane bound organelles
Smaller and simpler
Cytoplasm
Larger and more complex
Divide by binary fission
Ribosomes
Cells divide by mitosis
Usually a single circular chromosome
DNA is replicated before cell division
Multiple linear chromosomes
Have organelles that secrete proteins.