Download What is a Theory?

Guess who’s coming to dinner?
“Plant growth comes about
through the production of
new cells…propagated
from the cytoblasts [nuclei]
of old cells”
Matthias Schleiden
“Once when he was dining with
Scheliden in 1837, the conversation
turned on the nuclei of vegetable
cells. Schwann remembered having
seen similar structures in the cells of
the notochord and instantly realized
the importance of connecting the
two phenomena.”
Theodor Schwann
The Cell Theory

All organisms are composed of cells

Cells are the smallest living unit of living things
The Cell Theory

All organisms are composed of cells

Cells are the smallest living unit of living things
“Omnis cellula e cellula.” *
(1855)xxx
Rudolf Virchow
* “All cells arise from cells”
The Cell Theory

All organisms are composed of cells

Cells are the smallest living unit of living things

All cells come from cells
Spontaneous
generation
What is a Theory?
Important Scientific Theories

Cell theory

Germ theory of disease

Theory of evolution

Atomic theory

Heliocentric theory of the solar system

Universal gravitation

Theory of relativity

Quantum theory

String theory
Linnaeus believed every
living thing could be
classified as a plant or an
animal.
What do we believe
today is the most
fundamental division
among living things?
Tree of Life
The Eukaryotic Cell
Nucleus
•
•
•
•
Genetic material (DNA)
Chromatin (chromosomes)
Nuclear envelope (with pores)
Nucleolus
The Prokaryotic Cell
Archaea

First believed to be bacteria

Live in Extreme environments
Halobacteria
Tree of Life
A Survey of Cell types

Plasma Cell

Makes and secretes
antibodies.
A Survey of Cell types

Paramecium

Single cell motile organisms
A Survey of Cell types

Sperm Cell

Need large amounts of energy
for tail movement
A Survey of Cell types

Neuron and Neuronal
synapse
A Survey of Cell types

Intestinal epithelium

Absorb nutrients from
gut.
A Survey of Cell types

Is this a cell? If so, what kind of cell?

What is the arrrow pointing to?
Bonus Cell(s)?:

What are the green sphere’s?

What is their role for the organism they reside in?
What do mitochondria and chloroplasts
have in common?
The Endosymbiosis Theory

Similar in size to prokaryotic cells

Two membranes

Own DNA

Own ribosomes, prokaryote-like

Divide independently

DNA sequence like prokaryotic genes
ancestral cell
membrane infolding
creates nucleus, ER
endosymbiosis
results in mitochondria
endosymbiosis
results in chloroplasts
ancestral
animal cell
ancestral
plant cell
Why are prokaryotes small and
eukaryotes large?
Which are more successful:
prokaryotes or eukaryotes?