Levels of Cellular Organization

TEKS: 7.12C living systems at all levels of organization

demonstrate the complementary nature of structure and function .

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 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

There are four basic/major types of tissues in the human body:

Muscle tissue, nerve tissue, connective tissue, and epithelial

tissue.

• Other kinds of tissue include bone tissue

• Blood cells in your body are part of blood tissue

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.

Let’s Look Again…

Here are the cells we saw before, but if you look closely, you can

see that they all look similar to each other. Nerve cells working

together make nerve tissue, and skin cells make up a special type

of epithelial tissue.

Different types of tissueConnective 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: OrgansWhen 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??

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.

Let’s Review….

• ONLY Level: Cells unicellular organisms

working individually

• 4th Level: Organ Systems, which work

together to form

• 2nd Level: Tissues, which can form

• 3rd Level: Organs, which work together to

form

• 5th Level: Organisms!

• 1st Level: Cells working together form

Atom

Molecule

Macromolecule

Organelle

Cells

Tissues

Organs

Organ

Systems

Organisms

Population

Community

Ecosystem

Biome

Biosphere

Write this on your page:

And now…

Computer search: http://www.ck12.org/biology/Organization-of-the-Human-

Body/lesson/Organization-of-the-Human-Body/