Introduction to Animals
Characteristics
Multicellular
Organization
 Heterotrophic
 Sexual
reproduction and
development
 Movement

Multicellular Organization

Most animals contain large numbers of
cells.


Humans contain 50 trillion cells.
In most animals, there is a division of
labor.
Specialization is the adaptation of a cell for a
particular function.
 Tissues are the organization of cells. Cell are
able to organize by the joining of cells by cell
junctions.
 Cell specialization has allowed organisms

Animals are Heterotrophic



They must obtain
complex organic
material from other
sources.
Most accomplish this
through ingestion.
Digestion is
accomplished within
the animal. This
process extracts the
carbohydrates, protein
and lipids from the
food eaten.
Sexual Reproduction and
Development



Sexual reproduction restores the diploid
number and increases genetic variation.
During the developmental process, the zygote
undergoes many mitotic divisions. These
identical cells must undergo differentiation.
Differentiation is process of cell becoming
different from each other and being specialized.
Movement



Most animal are able to
move.
The ability to move
results from the
interrelations of two
types of tissues found
only in animals: nervous
tissue and muscular
tissue.
There are a few animals
that are sessile.
Origin and Classification



The first animals probably
arose from the sea.
Taxonomists have grouped
animals into several phyla
based on evolutionary
relationships.
Many taxonomist recognize
30 or more animal phyla. We
will investigate 11 phyla. Ten
of the phyla include
invertebrates and only
Chordata includes the
vertebrates.
Animal Body Structure
Symmetry
Germ
layers
Body Cavities
Symmetry


Asymmetry refers to the consistent overall
pattern of structure of an animal.
Animals have three patterns of symmetry.
 Asymmetry – no symmetry
 Radial Symmetry – similar parts branch in
all directions from a central point
 Bilateral Symmetry- similar halves on
either side of a central plane.
Patterns of Symmetry
Identify the Type of Symmetry

Most animals have a dorsal, ventral,
anterior and posterior side or
orientation.
Dorsal – top
 Ventral – bottom
 Anterior – head
 Posterior - tail


Most animals exhibit cephalization, the
concentration of sensory and brain
structures in the anterior. Animals
with cephalization have a head!
Germ Layers

Germ layers are
fundamental tissue
types found in all
animals except
sponges (no true
tissues).
Ectoderm
 Mesoderm
 Endoderm

Body Cavities

Most animals have a
fluid filled space that
forms between the
digestive tract and the
outer wall of the body
during development.
This space is known as
a COELOM.

Acoelomate (without a coelom)

2 germ layers





not separated by a cavity
least complex body plan
sponges and cnidarians
3 layer acoelomate

3 germ layers




endoderm, mesoderm and ectoderm
not separated by a cavity
flatworms
Pseudocoelomate




ectoderm and endoderm
pseudocoelom
cavity formed between mesoderm and endoderm
roundworms and rotifers
Coelomate



cavity developed within the mesoderm
most complex body plan
mollusks, annelids, arthropods, echinoderms, and chordates
Animal Diversity

Invertebrates
10 phyla
 95% of animals


Chordates
Notochord
 Dorsal nerve cord
 Pharyngeal pouches
 Postanal tail


Vertebrates

Include fishes, birds and
mammals
Kingdom Animalia
Invertebrates
Chordates
Vertebrates
What is the difference in
a vertebrate and an
invertebrate?
A vertebrate is an animal with a
backbone and invertebrates do not
have a backbone.
Comparison of Invertebrates and Vertebrates
Invertebrate
symmetry
germ layers
Body cavities
Segmentation
support
Respiratory/
circulatory
Digestive/excretory
Nervous
reproduction
Vertebrate