Levels of Organization
Mrs. McCabe
04/08
Adapted from Joe Krupens, Standley Middle School
Division of Labor &
The First Level
Within multi-cellular organisms there is division of labor.
Division of labor means that the work (labor) of keeping the
organism alive is divided (division) among the different parts
of the body. Each part has a job to do and as each part does its
special job, it works in harmony with all the other parts.
The arrangement of specialized parts within a living thing is
sometimes referred to as levels of organization. Cells of course,
are the first level of organization.
Cells: LOTS of Different Kinds!
Here are two examples. Can you guess what kind?
Nerve Cells
Skin Cells
Second Level: Tissues
In any multi-cellular organism, cells rarely work alone. Cells that
are similar in structure and function are usually joined
together to form tissues. Tissues are the second level of
organization.
There are four basic/major types of tissues in the human body:
Muscle tissue, nerve tissue, connective tissue, and epithelial
tissue. (There are other kinds of tissues besides these.) Other kinds of tissue
include bone tissue (a strong solid tissue that gives you shape and support)
made of bone cells in your body form bone tissue. Blood cells in your body are
part of blood tissue, a liquid tissue responsible for transporting food and
oxygen throughout the body.
Let’s Look Again…
Here are the cells we saw before, but if you look closely, you can
see that they all look similar. Nerve cells working together make
nerve tissue, and skin cells make up a special type of epithelial
tissue.
Taken One At A Time….
Connective tissue connects
and supports parts of the
body. Blood, fat, ligaments,
cartilage, bones, and
tendons are all connective
tissues.
Nerve tissue carries messages
back and forth between the
brain and every other part of
the body. The brain, spinal
cord, and nerves are made up
of nerve tissue.
Epithelial tissue covers and lines
the surfaces of your body and
organs, inside and out. They
primarily serve as protective
barriers. Skin is one example.
Muscle tissue can contract, or
shorten. Because of this,
muscle tissue makes parts of
your body move.
Level Three: Organs
When a bunch of different types of tissues work together,
they form an organ. There are many organs in the body.
How many can you name??
GET IT????
Level Four: Organ Systems
Each organ in your body is
part of an organ system, a
group of organs that work
together to perform a major
function.
For example, your heart is
part of your circulatory
system, which carries oxygen
and other materials
throughout your body.
Besides the heart, blood
vessels are organs that work
in your circulatory system.
The nervous system detects and
interprets information from the
environment outside the body and
from within the body; controls
most body functions.
The immune system fights
disease.
The excretory system removes
wastes.
The endocrine system
controls many body processes
by means of chemicals, like
hormones.
The muscular system enables the
body to move; moves food
through the digestive system, and
keeps the heart beating.
The skeletal system supports and
protects the body, and works with
the muscular system to allow
movement; makes and stores
blood cells and stores some other
materials.
The digestive system takes food
into the body, breaks the food
down into smaller particles, and
absorbs the digested materials.
The respiratory system takes
oxygen into the body and
eliminates carbon dioxide.
The reproductive system
produces sex cells that can
unite with other sex cells to
create offspring; controls male
and female characteristics.
Let’s Review….
• 1st Level: Cells working together form
• 2nd Level: Tissues, which can form
• 3rd Level: Organs, which work together to
form
• 4th Level: Organ Systems, which work
together to form
• 5th Level: Organisms!