Hairy T-cell

An idea that has been proposed, repeatedly tested, and found to be true-so far.

•  A scientific hypothesis that survives experimental testing becomes a scientific theory

Theory Definition:

Cells

• The basic units of a living system or organism

Further explaining the CELL THEORY

Unicellular

Unicellular

Multicellular

Multicellular

PART 1

unicellular

multicellular

If an organism is unicellular (made of only ONE cell), such as a paramecium, is it

considered living?

YES, according to the first part of the cell theory: All living things are composed of cells,

If an organism has cells, even if it only has 1 cell, it is a living (biotic) organism.

Unicellular organisms

•  Some organisms only consist of a single cell

•  But these do usually have the components of cells (nucleus, membrane etc)

Image Credit Paramecium

2 Types of Cells:

•  Prokaryotic - Cells that don’t have a membrane-covered nucleus for example: bacteria

•  Eukaryotic – Cells with a nucleus covered by a membrane for example: plant and animal cells

Prokaryote Eukaryote

YES, even though prokaryotic CELLS do not have a nucleus, it is still a living thing because it is a

type of CELL.

If an organism is prokaryotic,

is it considered living?

Form Fits Function Cell have different

shapes (structure) to enable them to

perform different tasks (function)

READ ONLY:

How do we know cells exist?

•  Invention of the microscope made it possible for people to discover and learn about cells

•  Robert Hooke looked at cork cells

•  Anton van Leuenhock used a simple microscope and was the first person to see microorganisms.

Not ALL cells are microscopic

Ostrich eggs are the largest unicelluar organism

Who was…Robert Hooke? (1665)

- used a compound microscope to look at cork (from bark of a tree) & he saw empty boxlike structures that he named “cells”.

What he saw?

Who was…Antonie van Leewenhooke? (mid 1600’s)

- used a simple microscope to look at pond water.

- was the first to observe microorganisms in pond water.

Anton van Leeuwenhoek • First

compound light microscope

What did van Leeuwenhoek’s microscope look like?

Cell Theory –

• developed by 3 German scientists:

•  Matthias Schleiden, • Theodor Schwann, • and Rudolf Virchow

Definition

= Three part theory about cells

1. All living things are made of cells.

Part 2 of the Theory

2. The cell is the building block and basic unit of life.

Who came up with this theory?

1. Schleiden (circa 1838)

All plants are made of cells!

Onion skin cells

Who was…Matthias Schleiden? (1830’s)

Onion cells Elodea cells Cork cells

-  studied numerous plant parts under the microscope and declared “ALL PLANTS ARE MADE OF CELLS!”

2. Schwann

Who came up with this theory? All animals are made of cells!

Human red blood cells

Who was… Theodor Scwhann? (mid 1830’s)

-  Cheek cells Amphibian Blood

- Used a microscope to observe numerous animal tissues and declared “ALL ANIMALS ARE MADE OF CELLS!”

Part 3 of the Theory

3. All cells come from pre-existing cells.

yeast cells dividing

Who came up with this theory?

3. Virchow

All cells come from pre-existing

cells!

Who was… Rudolf Virchow? (Mid 1830’s)

- observed living cells dividing and declared “ALL CELLS COME FROM OTHER LIVING CELLS!”

These scientists discoveries led to the cell theory…

What is the CELL THEORY??? Theory that states… 1.  All organisms are made of one or

more cells. 2. The cell is the basic unit of life

which can perform life processes. 3. All cells come from other living

cells.

REVIEW Cell

Theory: 1.  All living things

are made of CELLS.

2.  The CELL is the basic structural and functional unit of life.

3.  All CELLS come from pre-existing cells.

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Some Random Cell Facts

•  The average human being is composed of around 100 Trillion individual cells!!!

•  It would take as many as 50 cells to cover the area of a dot on the letter “i”

WOW!!!

Organelles

• -Tiny cell structures that are specialized parts of a cell that have specific functions – a cell “organ.”

If Cells could be really big ……

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