What is a cell?

DEFINITION

A cell is the basic unit of any organism or living thing. This means that it is the smallest “part” that is able to carry out life processes.

It is what all living things are made of.

THE DISCOVERY OF CELLS:

In 1655, Robert Hooke observed dead cork cells using a very basic

microscope.

By 1650, Anton van Leeuwenhoek and other scientists wereusing simple microscopes to examine many different materials.

Van Leeuwenhoek discovered protozoa in 1674 and bacteria in 1683.From discoveries like these came the formation of the cell theory.

In 1590, the microscope was invented by Zacharias Janssen At almost the same time, Galileo invented the telescope!

The Cell Theory

When Schleiden and Schwann proposed the cell theory in 1838,

cell biology research was forever changed.

The cell theory and three parts and states that:

All life forms are made from one or more cells.

Cells only arise from pre-existing cells.

The cell is the smallest form of life.

THE DEVELOPMENT OF THE CELL THEORY:

Cell Theory

Types of Microscopes

Arm

EyepieceBody Tube

NosepieceObjective

Lenses

Stage ClipsStage

DiaphragmIlluminator

Base

Coarse Adjustment Knob

Fine Adjustment Knob

Viewing cells and organisms

THE COMMON HOUSE FLY

http://www.pbrc.hawaii.edu/bemf/microangela/

• Wet Mount• Wet Mount

• Dry Mount• Dry Mount

Life Processes

Life processes are characteristics of living things. These are activities or processes carried out by the cells of all living things. Whether an organism is only one cell or made up of many cells, all living things:produce organisms of the same kind, obtain energy from the environment (the chemical activities involved in this are called metabolism and include processes such as respiration and excretion), move, grow and develop at some point during their life spans, and respond to stimuli in their environments.

How Big Are Cells?

So what about viruses?

Cell Shapes

Red blood cell

amoeba

Nerve cell

Green algae

White blood cell

Cell Function

In multicellularorganisms, each kind of cell does its own special job.This is known as specialization.

Classification of Organisms based on type of cells

5 Kingdoms of Organismswith cells that differ in their characteristics:Protists; Fungi; Monera; Plants; Animals

Green algae

Mouse cellsPlant cells from a leaf

Fungus cell

Rod-shaped bacteria

Parts of Cells

QUESTION:How does a cell, especially an organism that isonly made up of a single cell, carry out all of theactivities and the life processes and survive ?

ANSWER:The cells have even smaller partscalled organelles (tiny organs).

� Golgi body

� nucleus

� cell membrane

� cell wall

� ribosomes

� endoplasmic reticulum� lysosomes

� cytoplasm

� mitochondria

� vacuoles

Bibliography

http://www.neosoft.com/~uthman/blood_cells.html

http://library.thinkquest.org/3564/

http://megasun.bch.umontreal.ca/protists/protists.html

http://www.plantbio.ohiou.edu/pbc/plasmos/home.htm#contents

http://www.pbrc.hawaii.edu/bemf/microangela/

http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells2.html

http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells3.html

http://www.ucmp.berkeley.edu/history/hooke.html

http://www.cellsalive.com/