• On the Earth, there are many different living things.
Each living thing has something in common. They are all
made of cells.
• What is the name for a living thing?
• An organism
• All organisms, no matter how large or how small are
made of cells.
• The cell is the smallest unit of living things that can
carry out the basic processes of life.
• Cells divide and split into two new cells. Every cell in
every living thing on Earth originally came from another
What are all living things made of?
• Cells
• What do you think the term unicellular
• One-celled
• An organism that is unicellular is made up of
one cell that carries out all its life processes
such as growing, reproducing, responding to
its environment, and getting food.
• Examples are: amoebas and euglena
• That’s one busy little cell !
• What do you think the term
multicellular means?
• Many-celled
• A multicellular organism is made of
more than one cell.
• Can you think of some examples of
multicellular organisms?
• Frogs, trees, YOU!
How many cells does an
organism have?
Some have only one cell. These are called
unicellular organisms.
Others have many cells. These are called
multicellular organisms.
Where do cells come from?
•Other cells
Can you name examples of
Robert Hooke
• Robert Hooke was an English scientist. In
1665, he looked at a slice of cork in his
microscope and saw many little boxed and he
called them cells.
How are unicellular and multicellular
organisms similar and different?
• They are similar because they are both
made of cells.
• They are different because unicellular
organisms are made of just one cell
while multicellular organisms are made
of many cells that work together to take
care of different functions.
Why do you think there are more unicellular
organisms than multicellular organisms?
• Most unicellular organisms are much
smaller than multicellular organisms
and have simpler structures. They do
not require as many resources or as
much space.
Why do organisms need cells?
• Cells are able to perform
all the activities that keep
organisms alive.
• What is inside an animal
cell? (brainstorm as a
• Organelles are basic structures that help cells
perform life processes. They have functions
that keep the cell alive.
• Some important organelles are:
• Nucleus
• Mitochondria
• Vacuoles
• And more…
Which organelle controls the cell’s
•The nucleus
What do mitochondria do?
• They supply energy for the cell
by breaking down food.
Where are wastes stored in cells?
• Wastes are stored in the
• Where are an animal cell’s organelles found?
• They are found in the cytoplasm (gel like liquid).
• What is the function of the cell membrane shown in
the diagram of an animal cell?
• It protects the cell and its organelles, gives the cell
shape, and controls what materials move in and out
of the cell.
How are mitochondria similar to tiny
power plants?
• Mitochondria are similar to power plants
because they provide energy for the cell.
Talk time!
Do you think a cell could
function without a nucleus?
Explain your answer.
• Do plants need to eat food?
• No, they make food.
• What helps plants get energy
and make food?
• Sunlight
Plant Cell
• What is the shape of the plant cell?
• What are the parts of the plant cell?
• Does the plant cell have parts that the animal cell
does not have?
• Yes, the plant cell has a cell wall and chloroplasts
which the animal cell does not have.
• Cell wall- provides strength and support
• Chloroplasts- a green structure where the energy
from sunlight is used to produce food for the plant.
They contain chlorophyll that causes the chloroplasts
and some plants to be green.
• What parts do both the plant and animal cell contain?
• Nucleus, cytoplasm, vacuoles, a cell membrane, and
Which cells have a stronger outer covering- a
plant cell or an animal cell?
• A plant cell has a stronger outer covering. A
stiff cell wall surrounds the plant cell. An
animal cell does not have a cell wall
surrounding it.
• As the number of cells in an
organism increases, cells must
specialize in one or a few activities
in order for the organism to
function well.
In complex organisms, organization
starts at the cell level.
• Cells are building block of the body.
• Similar cells working together at the same
job form a tissue.
• A group of tissues that work together to
perform a specific function form an organ.
• Organs that work together to perform a
certain function make up an organ system.
• Organ systems that work together form an
Cell Organization
This is an animal cell.
The tissue is a muscle tissue.
The organ is a heart.
The organ system is the circulatory
• The organism is a salamander.
How does the complexity change as
you move from a cell to an organism?
• Each level becomes more complex. Cells
form tissues, tissues form organs,
organs form organ systems, and organ
systems form organisms.
Organ Systems work together to bring
food, oxygen, and other materials to cells.
• Think of two systems that would work
together in a salamander. Which organ
system sends food to which other
organ system in the salamander?
• The digestive system sends food to the
circulatory system. Then the blood
vessels in the circulatory system take
this food to the cells.
How do organs compare to organ
• Organs are made of tissues and make organ
systems. In organs systems, organs work
together to carry out a function of an organ
system such as digestion.
How are complex organisms
• Complex organisms are made
up of cells that form tissues,
tissues that form organs, and
organs that form organ
Think about it!
Why is it important for us to learn
about cells?
Take 2 minutes to think about this
question. You will share your
answer with your group.