This document discusses cells and their organization in living organisms. It explains that all complex organisms are composed of systems, which are made up of organs, which are made of tissues, which are in turn made up of cells. The development of the microscope allowed scientists to study cells directly by making microscopic objects visible. The document then provides examples of typical cell sizes measured in micrometers and nanometers, which are too small to be seen with the naked eye. An activity example shows how to calculate the actual size of an object viewed under a microscope.

1. THE UNIT OF LIFE The cell

2. How big is a cell?

3. Levels of biological
organization

4. FROM CELLS TO
ORGANISMS
All complex organisms are
made up of a group of
systems.
All systems are composed
of a group of organs.
All organs are made of
tissues.
All tissues are made up of
cells.

5. MICROSCOPE
In order to view and study
cells, we had to move
further in technology.
The development of the
microscope allowed us to
study and learn more
about the smallest forms
of life.
Everything that cannot be
seen with the naked eye is
considered microscopic.

6. CELL SIZE
Microscopic objects
are meassured in:
◦ μm = 10-3 mm
◦ nm = 10-6 mm
These are not visible
with a naked eye.
Eye resolution is 0.2
mm
◦ If two objects are
separated by a
smaller distance, we
will see them as one.
Exercise:
If an object meassures 1
mm, how many
micrometers does it
meassure? And how
many nanometers?

7. ACTIVITY
5 cm
Image magnified: 1500 times
How large is
the
Paramecium
in reality?
5cm
1500
= 0,0033 cm
How many μm is
that?
33
μm

8. ASSIGNMENT
Do homework assignment.
Google: Cell size and scale (University of Utah)
Use this animation available on-line to answer these
questions.
1. A human egg is ________ than an amoeba.
2. A red blood cell is ____________ than a yeast.
3. A skin cell is 30 ____ wide.
4. A sperm is _____ micrometers long.
5. An E. coli bacteria is _____ times larger than the hepatitis virus.
6. The smallest organelle is the ___________