MULTICELLULAR ORGANISMS
Cellular Differentiation
Tissues
Organs
Organ Systems
CELLULAR DIFFERENTIATION – RECAP!
 Cell
specialization takes place early in
the development of multicellular
organisms
 Each cell undergoes changes and develops
characteristics to make it unique from
other cells
 Once a cell has differentiated it can
perform a very specific function within the
organism.

Examples of differentiated cells in our bodies:
Muscle Cells
Fat Cells
Epithelial Cells
Nerve Cells
What happens next?
Tissues
Organs
Organ Systems
Tissues
A
group of cells that are similar in shape and
function are called a TISSUE
 In animals, there are 4 basic types of tissues;
epithelial tissue, muscle tissue,
connective tissue and nervous tissue.
 E.g. Blood – connective tissue
External covering and lining for mouth,
heart, liver, eyes – epithelial tissue
 In plants – tissues made from thick walled
plant cells are used for structure
Organs
 Organs
are different tissues that group
together to form larger structures that work
together to achieve one or more functions
within the organism.
 Skin is the largest human organ and it is made
up of connective, epithelial, nervous and fat
tissues
 Skins provides structural support and barrier
that protects our insides from our outside!
 Other animal organs are:
Organ Systems
 Organs
never work alone
 2 or more organs working together to perform
a related function are a organ system.
 Organ systems often overlap and share organs
 Organ systems are interdependent – they need
contact with the brain in order to function
properly.
 Plants have 2 major organ systems: the root
system and the shoot system
 How many different animal systems can you
think of?
HUMAN ORGAN SYSTEMS
CHECK YOUR LEARNING
1.
2.
In your own words, write a definition for cell,
tissue, organ, and organ system. Give an
example of each of these in your body.
Name the 5 organ systems in your body that
you learned about in this section.
a)
b)
What is the major function or each of these
systems?
What are the 4 types of tissues found in most organ
systems?