**Refer to handout and make jot notes**
Unit 2 Reproduction: The Cell
The History of Cell Discovery:
Hans & Zacharias Janssen – 1590 – father and son Dutch spectacle-makers are sometimes
credited for inventing the first truly compound microscope.
However, the origin of the microscope - just like the origin of the
telescope - is a matter of debate.
Robert Hook - 1665 – improved on the compound microscope and illumination system
- observed slices of cork through a microscope and compared cork’s tiny
cavities to “small rooms” such as in a monastery and called them
“cella”, which is Latin for cell
- “Father of Microscopy" and published 'Micrographia'
Anton van Leeuwenhoek - 1680's – produced over 500 single lens microscopes
- discovered bacteria, protozoa, human blood cells & spermatozoa
Matthias Schleiden - 1838 - proposed that all plants are made up of cells
Theodor Schwann - 1839 - proposed that all animals are made up of cells
Rudolph Virchow - 1855 - proposed that cells can come only from other cells
- "Father of Pathology" cited as the first to recognize leukemia cells
The last three scientists are cofounders of the Cell Theory.
Discovering the Origins of Cells: A TimelIne
What was Needham’s experiments &
conclusions?
Redi Tested what theory:
What was Pasteur’s experiments &
conclusions?
What was Redi’s experiment and
conclusions?
Stated
living
cells
come
from
other
living
cells
Needham
4th C BC
1665
Aristotle
Hooke
1668
Redi
Rejection to
what hypothesis:
His Theory is :
- First
scientist
to call
spaces
in cork
“cells”
1680
A. van
Leeuwenhoek
- Observed living
cells such as
bacteria,
protozoa, human
blood cells &
spermatozoa
through a simple
microscope
Mid 1700’s
Spallanzani
Mid 1800’s
1838
Pasteur
1839
1855
Virchow
What was Spallanzani’s experiment
& conclusions?
Schleiden
- Discovered
that plants are
made of cells
Schwann
- Discovered
that animals
are made of
cells
What is a Cell?
- the basic structural unit of life
Technological advancements such as improved microscopes have helped to
study living things in detail
• Cell Theory: - the idea that cells are the fundamental units of life
1. All organisms are composed of one or more cells.
2. Cells are the basic units of structure and
function in all organisms.
3. All cells come from the division of previously existing cells
therefore they must contain genetic information.
The activity of an entire organism depends on total activity of its independent
cells.
Characteristics of Living Things
• It is not always an easy thing to tell the difference between living, dead, and non-living
things. Prior to the 1600's many people believed that nonliving things could
spontaneously turn into living things. For example, it was believed that piles of straw
could turn into mice. That is obviously not the case. There are some very general rules
to follow when trying to decide if something is living, dead, or non-living. Listed here are
the six rules used by scientists:
• Living things:
- are made of cells.
- obtain and use energy.
- grow and develop.
- reproduce.
- respond to their environment.
- adapt to their environment.
• If something follows one or just a few of the rules listed above, it does not
necessarily mean that it is living. To be considered alive, an object must exhibit all
of the characteristics of living things. Sugar crystals growing on the bottom of a
syrup container is a good example of a nonliving object that displays at least one
criteria for living organisms.
• Can you think of some other examples of nonliving objects displaying living
characteristics?
III. Two Basic Cell Types:
1. Prokaryotic Cells - means “without nucleus”
- single-celled organisms
- lack internal membrane bound organelles (ie. no nucleus)
- ex. bacteria - range in size from 1 to 10 micrometers (µm)
2. Eukaryotic Cells - means “true nucleus”`
- multi-cellular organisms
- contain many membrane-bound organelles (ie. nucleus)
- all living organisms other than bacteria, ranging in size
from 10 to 100 micrometers (µm)
**Both prokaryotic and
eukaryotic cells possess a
cell membrane &/or cell wall,
genetic material (DNA or
RNA), ribosomes and
cytoplasm.
Robert Hooke (1635-1703)
Anton Van Leeuwenhoek (1632-1723)
M. Schleiden (1804 – 1881)
T. Schwann - 1810 – 1882
Rudolf Ludwig Carl Virchow (1821-1902)
Redi
F. Redi (1626 – 1697)
Spallanzani (1729 - 1799
Louis Pasteur (1822 - 1895)