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Basic Characteristics
1. Eukaryotic
2. Multicellular
3. Heterotrophic
If mobile, get food by moving
If sessile, get food
by filter feeding
4. intracellular digestion
Symmetry
= is the arrangement of body
structures
Asymmetry= no symmetry
Example: Sea Sponge
Symmetry
Radial Symmetry= can be divided
evenly along many different planes
Example: Hydra, Jellyfish
Symmetry
Bilateral Symmetry= can be divided
equally only along length into Left
and Right sides
Example: Human, Dog
Cephalization
Cephalization: sense organs are
concentrated at the head end of
the body
Can process info
from environment
much faster
Directional Terminology
Anterior - head end
Posterior - tail end
Directional Terminology
Dorsal - back side
Ventral - belly side
Development
Fertilization of egg cell by sperm
cell produces a zygote
Development
1. Zygote divides by mitosis to form
a blastula (hollow ball of cells)
Development
The blastula is made of identical,
unspecialized cells
These are embryonic stem cells
 Scientists would like to harvest
these to do research because they
can turn into any type of cell
Stem Cells
Development
2. One side folds
inward, forming
a gastrula
Germ Layers
3. The layers of the gastrula start
to differentiate into different
germ layers:
Cells on outer layer
are the ectoderm
Produce the skin
and nervous tissue
Germ Layers
 Cells on inner layer are endoderm
 Produce the digestive system
Germ Layers
 A 3rd layer forming between the
endo- and ectoderm is called the
mesoderm
Produces the muscular,
respiratory,
circulatory, &
excretory systems
Skeletons
All skeletons allow movement and
provide support & protection
1. Exoskeleton
= Hard outer
covering
Skeletons
2. Endoskeleton
= Internal structure made of bone
and/or cartilage