The Cell Theory
The Cell Theory
• All living things are composed of cells
• Cells are the basic unit of structure and
function of living things
• All cells are produced from other cells
The Cell Theory
• All living things are composed of cells
– Plants and Animals are alive, therefore they are
made up of cells
– Unicellular organisms are one celled organisms
• Ameoba (animal)
• Algae (plant)
– Multicellular organisms are organisms with many
cells
• Cats (animal)
• Oak Tree (plant)
The Cell Theory
• Cells are the basic unit of structure and
function of living things
– Cells are organized into tissues
– Tissues are organized into organs
– Organs are organized into organ
systems
– Organ systems are organized into the
organism
Cells>Tissue>Organ>Organ
System>Organism
The Cell Theory
• All cells are produced from other cells
– One cells grows and divides
• Now you have 2 cells
– 2 cells grow and divide
• Now you have 4 cells
– 4 cells grow and divide
• Now you have 8 cells
– New cells are needed for an organism to
grow and also to replace cells that die
Closure Question
• What are the 3 statements made by
The Cell Theory?
– 1. All living things are made of cells.
– 2. Cells are the basic unit of structure and
function in living things.
– 3. Cells come from other cells.
Diversity of Cellular Life
Cells
• Are the simplest form of life
• Chemical elements organized into cells
become living matter.
• All organisms are
made-up of cells
• All the substances
of an organism are
the products of its cells
Life is Cellular
–
–
Some things are
only one cell
(unicellular)
Some have many
cells (multicellular)
Unicellular or Multicellular
• SINGLE CELL
ORGANISM
• MULTI-CELL
ORGANISM
Cells are small for 2 Reasons
Reason 1:

Limited in size by the RATIO between their Outer
Surface Area and Their Volume.
A small cell has more SURFACE AREA than a
large cell for a GIVEN VOLUME OF CYTOPLASM.
Unicellular Organisms may be
Prokaryotic
Eukaryotic
Remember? What does the Eukaryotic Cell
have that Prokaryotic Cells does not?
No nucleus
No organelles
Has a nucleus
Has organelles
Colonial Organisms
Video:
• A colony of single-celled organisms
is a colonial organism. It's likely that
early colonial organisms were the first
evolutionary step from single celled
life to multicellular species.
Synura (above) and rotifer egg.
Synura: Three individual colonies. Ref: synura01.
Three Scenedesmus. Ref: scened00
Volvox releasing daughter colonies. Ref: volvox01
Colonial Organisms
• The difference between a multicellular
organism and a colonial organism is
that individual cells from a colony can,
if separated,
survive on their own,
while cells from a
multicellular life form
(e.g., liver cells)
cannot.
Filamentous Algae
Colonial Organisms
• In a multicellular organism the cells
have become specialized and taken on
specific jobs to help out the whole
organism
• In a colonial organism,
there is little difference
between cells.
Volvox carteri, a colonial freshwater alga.
The small dots are regular cells and the
large ones are asexual reproductive cells
Cell Differentiation
• Cell differentiation- When cells take
on a different shape, size, and
chemistry, suitable for a certain
function during development.
• Cells vary in size, shape, and internal
components
• The variety of cell shapes include
round, flat, long, rectangle, etc.
• Some cells have different extensions
from the cell membrane
Cell Specialization
• cell specialization- The characteristic
of having separate roles for each type
of cell in a multicellular organism; the
cells is specifically designed for a
certain function; it has a certain
purpose or job.
• The size and shape of a cell is related to
its function
Division of Labor
• division of labor- A more efficient way of
getting jobs done in a multicellular organism
because the different tasks are dispersed to
different cells, each of which is specialized to
do that job.
• The organelles that make up a certain cell are
also determined by the specific functions
carried out by the cell
Levels of Organization
• levels of organization- A system of
hierarchy in which a group of things
are arranged in order of rank,
complexity, or size. Each group is
made up of smaller parts and/or are a
part of a larger group. (example- cells
form tissues, which form organs, etc.)
Levels of Organization
•
•
•
•
Cell
Tissue
Organ
Organ system
Cells
Many
different types
of cells are
formed during
embryonic
development.
Cells Continued
• Cells occur in many
different shapes
and sizes so they
can perform many
different functions.
Tissue
Many different cells work together to form a tissue.
Cartilage
Fat
Muscle
Skin
Nerves
Bone
Organ
Many tissues working together form an organ
Organ System
Each organ
system is made up
of several different
organs that work
together and
enable the system
to do its job.
Eleven Organ Systems
•
•
•
•
•
•
Circulatory
Digestive
Endocrine
Excretory
Integumentary
Lymphatic
•
•
•
•
•
Muscular
Nervous
Reproductive
Respiratory
Skeletal
Review of Organization
1. Cells – have a special job to do
(i.e. cell from intestine)
Review of Organization
2. Tissues – a group of similar
cells that work together to carry
out a special job (i.e. group of
lining cells in intestine)
Review of Organization
3. Organ – a group of tissues that
work together to do a job (i.e. small
intestine)
Review of Organization
4. Organ system – a group
of organs that work
together to do a certain
job (i.e. digestive system)
Review of Organization
5. Organism – all organ
systems working together
(i.e. digestive, respiratory,
circulatory, etc.)
Review of Organization
Review of Organization
• Some organisms are made up of only
one cell but they have all the features
of living things
– The parts of their cell
still work together
• Other organisms have organs and organ
systems like humans
– Systems work together to keep us alive