Animal Body Systems:
Organization
levels of organization, body cavities, cephalization
Animal Cells
 All animal cells have a nucleus, cell
membrane, cytoplasm, ribosomes, and
lack a cell wall, but are they all alike?
Red & white blood cells
 Specialization of cells – designed for a specific
function
 Think about it: How does their structure
fit their function?
Epithelial cell (skin)
Neuron (brain)
Cells
Tissues
 Similar cells are grouped together into units called tissues
 These cells work together to perform a particular
function or task
 Cell types in the body are grouped into four basic kinds of
tissue.
1. Epithelial
2. Nervous
3. Connective
4. Muscle
1. Epithelial Tissue
 Covers most internal and external
body surfaces
 Protects other tissues from dehydration and physical
damage
 Also produce secretions
such as sweat and mucus
 Cells are flat and thin
and usually only a few
cells thick
Back to Tissues
2. Nervous Tissue
 Transmits nerve impulses (information)
throughout the body
 Consists of neurons (nerve cells) and their supporting cells
Back to Tissues
3. Connective Tissue
 Supports, protects, and insulates the body
 What structures in the
body do you think are
made of connective
tissue?
 Fat
 Bone
 Cartilage
 Blood
Back to Tissues
4. Muscle Tissue
 Cells that are able to contract in
response to stimulation
 They make you move! 
 Three types:
 Skeletal muscle-
called voluntary muscle because you
can control contractions
 Smooth musclecalled involuntary muscle because you cannot
consciously control its slow, long-lasting
contractions
 Cardiac musclefound in the heart
Back to Tissues
Tissues
Organs
 A group of different types of tissues that
work together to perform a single
function
 EXAMPLE: The heart contains cardiac muscle tissue and
connective tissue, is surrounded by epithelial tissues, and is
stimulated by nervous tissue. As different as each of these tissues
are, they all work together to make your heart work!
Organs
Systems
 An organ system is a group of
organs that works together to
carry out major activities or
processes of the body
 Each organ belongs to at least one organ
system (but may belong to several!)
 EXAMPLE: the stomach is just one organ
in the digestive system – it works with
many other organs (the mouth, intestines,
and more) to make the process of digestion
possible.
 What organ systems make up a human?
(hint, there are 11!)
Our organs are protected and supported
SKULL
in body cavities!
In humans, our internal organs are housed
in one of four major body cavities, large
fluid-filled spaces.
• What are our four body cavities?
• What are the advantages of body
cavities?
• Allows us to move without harming
or deforming the organs
• Each cavity is protected by muscle
and/or bone.
RIB CAGE
SPINE
Vertebrae
PELVIS
and ABS
Internal Body Cavities
 Body cavities are fluid-
filled spaces that provide
a space for internal
organs.
 Why?
Animal with a body cavity (coelom)
 Because now there was a
place to put them and
protect them!!! If
animals do not have a
cavity, they cannot
become as complex.
Animal without a body cavity
Internal Body Cavities
Coelomates
 Have a body cavity, a fluid-filled space found between the
body wall and the digestive tract.
 The internal organs of coelomates are suspended within the
coelom.
 Why is this important?
 This protects the
organs from the
movement of the
surrounding muscles.
Internal Body Cavities
Acoelomates
 Animals with no body cavity or no fluid-filled space.
 The space between an acoelomate’s body wall and gut is
completely filled with tissues.
Cephalization
 A process through which most bilaterally
symmetrical animals have evolved an anterior
concentration of sensory structures and nerves.
 Where is your concentration of sensory structures and
nerves?
 Animals with cephalic ends (aka heads) are often active and
mobile.
 Did you notice that cephalization occurred only in bilaterally
symmetrical animals? What does that term mean?
Symmetry in Animals
Most animals are…
 Bilateral Symmetry: can be divided into
right and left halves
or they are…
 Radial Symmetry: body parts arranged
around a central axis
Although a few (sponges) are
asymmetrical.
Let’s Review…
organs
tissues
cells
organ
systems
organism
 What are the four type of tissues in humans?
 Where are organs stored and protected?
 What is the term for an organism that does
not have a body cavity?
 What is cephalization?
 What type of body symmetry do humans
have?
Closing
Activity
Grape A
Grape B
Initial Mass
Description of Grape
Mass after 24 hours
1.
2.
3.
4.
5.
6.
Draw a data table in your notebook similar to the one
above.
Obtain two grapes and two small beakers.
Place each grape in one of the small beakers. Label them
Grape A and Grape B.
Measure the mass of each grape and record it in your data
table in the appropriate column.
Using forceps, peel the skin off of Grape A and place the
grape back into its container. Discard the skin.
Set the containers in the designated location for 24 hours.