KINGDOM ANIMALIA
Characteristics of Animals
January 16th, 2007
Characteristics of Life
1. Living things are organized.
2. Living things are made up of cells.
3. Living things metabolize.
4. Living things maintain an internal
environment.
5. Living things grow.
6. Living things respond.
7. Living things reproduce.
8. Living things evolve.
Seven Levels
of Taxonomic
Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Kingdom Animalia
All animals are multicellular,
mitochondrial heterotrophs—they have
multiple cells with mitochondria and they
rely on other organisms for their
nourishment.
Most animals ingest their food and then
digest it in some kind of internal cavity.
Animal Species
Somewhere around 9 or 10 million
species of animals inhabit the earth.
About 800,000 species have been
identified.
Animal Phyla
Biologists recognize about 36 separate
phyla within the Kingdom Animalia.
Animal Phyla Web Page
Major Animal Phyla
Mollusca
5%
Arthropoda
87%
Other
12%
Chordata
2%
Cnidaria
1%
Platyhelminthes
1%
Nematoda
1%
Annelida
1%
Porifera
1%
Echinodermata
1%
Animal Movement
Most animals are capable of complex
and relatively rapid movement
compared to plants and other
organisms.
Animal Reproduction
Most animals reproduce sexually, by
means of differentiated haploid cells (eggs
and sperm).
Most animals are diploid, meaning that
the cells of adults contain two copies of the
genetic material.
Animal Sizes
Animals range in size from no more
than a few cells (like the mesozoans) to
organisms weighing many tons (like the
blue whale).
a mesozoan
blue whale
Animal Habitats
Most animals inhabit the seas, with
fewer in fresh water and even fewer on
land.
Animal Cells
Animal cells, like all eukaryotic cells,
have internal structures called
organelles that serve specific functions
for the cell.
Animal cells lack the rigid cell walls
that characterize plant cells.
Animal Cell Diagram
Animal Bodies
The bodies of most animals (all except
sponges) are made up of cells organized
into tissues.
Each tissue is specialized to perform
specific functions.
In most animals, tissues are organized
into even more specialized organs.
Animal Symmetry
The most primitive animals are
asymmetrical.
Cnidarians and echinoderms are
radially symmetrical.
Most animals are bilaterally
symmetrical.
Radial Symmetry
…applies to forms that can be divided
into similar halves by more than two
planes passing through it.
Animals with radial symmetry are
usually sessile, free-floating, or weakly
swimming.
Bilateral Symmetry
Animals with bilateral symmetery are
most well-suited for directional
movement.
Radial vs. Bilateral Symmetry
Cephalization
Bilateral Symmetry usually has led to
cephalization—the process by which
sensory organs and appendages became
localized in the head end of animals.
Evolutionary Trends
If we analyze the basic body plans of
animals, we find that they illustrate
evolutionary trends.
Four major “advances” (in order):
1.
2.
3.
4.
Multicellular body plan
Bilaterally symmetrical body plan
“Tube-within-a-tube” body plan
Coelomate body plan
3 Major Bilateral Body Plans
 Acoelomates
 Pseudocoelomates
 Coelomates
Each plan consists of 3 cell layers:
endoderm, mesoderm, ectoderm
Acoelomates
These animals
have no other cavity
than the gut.
They are often
called the “solid
worms.”
Pseudocoelomates
These animals have a
body cavity (the
pseudocoelom) which is not
completely lined with
mesoderm.
The “tube within a tube”
body plan.
This category is also
composed of mostly
worms.
Coelomates
These animals have a
“true coelom” lined with
mesodermal peritoneum.
Most animals are
coelomate.