This document summarizes key characteristics of the Kingdom Animalia. It describes how animals are multicellular, eukaryotic organisms that ingest food and digest it internally. It notes there are over 9 million identified animal species across 36 phyla, with arthropods being the largest phylum at 87% of species. The document outlines animal traits like movement, reproduction, size, habitats, cells, tissues, organs, symmetry, and evolutionary trends in body plans.

1. KINGDOM ANIMALIA
Characteristics of Animals
January 16th, 2007

2. 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.

3. Seven Levels Kingdom
of Taxonomic Phylum
Classification Class
Order
Family
Genus
Species

4. 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.

5. Animal Species
Somewhere around 9 or 10
million species of animals
inhabit the earth.
About 800,000 species have
been identified.

6. Animal Phyla
Biologists recognize about 36
separate phyla within the
Kingdom Animalia.
Animal Phyla Web Page

7. Major Animal Phyla
Mollusca
5%
Chordata
Arthropoda Other
2%
87% 12%
Cnidaria
1%
Platyhelminthes
1%
Nematoda
1%
Annelida
1%
Porifera
1%
Echinodermata
1%

8. Animal Movement
Most animals are capable of
complex and relatively rapid
movement compared to plants
and other organisms.

9. 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.

10. 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

11. Animal Habitats
Most animals inhabit the seas,
with fewer in fresh water and
even fewer on land.

12. 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.

13. Animal Cell Diagram

14. 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.

15. Animal Symmetry
The most primitive animals are
asymmetrical.
Cnidarians and echinoderms
are radially symmetrical.
Most animals are bilaterally
symmetrical.

16. 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.

17. Bilateral Symmetry
Animals with bilateral
symmetery are most well-suited
for directional movement.

18. Radial vs. Bilateral
Symmetry

19. Cephalization
Bilateral Symmetry usually has
led to cephalization—the
process by which sensory
organs and appendages became
localized in the head end of
animals.

20. Evolutionary Trends
If we analyze the basic body plans
of animals, we find that they
illustrate evolutionary trends.
Four major “advances” (in order):
1. Multicellular body plan
2. Bilaterally symmetrical body plan
3. “Tube-within-a-tube” body plan
4. Coelomate body plan

21. 3 Major Bilateral Body Plans
 Acoelomates
 Pseudocoelomates
 Coelomates
Each plan consists of 3 cell
layers: endoderm, mesoderm,
ectoderm

23. Acoelomates
These animals
have no other
cavity than the
gut.
They are often
called the “solid
worms.”

24. 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.

25. Coelomates
These animals have
a “true coelom”
lined with
mesodermal
peritoneum.
Most animals are
coelomate.