Evolution of animals

1. An Introduction to Animal
Diversity
Ch. 32

2. The Animal Kingdom
Animals are:
Multicellular
Heterotrophic
Eukaryotic
Composed of
tissues that develop
from embryonic
layers

3. Bacteria &
archaea
Protists Plants Fungi Animals
Cells Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic
Nutritional
mode
Photoautotroph
Chemoautotroph
Photoheterotroph
chemoheterotroph
Photoauto-
trophs
Hetero-
trophs
Mixotrophs
Photoauto-
trophs
Hetero-
trophs,
Exo-
enzymes,
absorbtion
Heterotrophic
Reproduction Binary fission -
asexual
Some
sexual,
some
asexual
Sexual,
alternation
of
generations
Asexual
budding
Sexual and
asexual
Sexual, few
asexual

4. Reproduction & Development
Usually a small, flagellated sperm
fertilizes a larger egg to form a diploid
zygote
Zygote goes through cleavage
Cell division by mitosis without cell growth

5. Reproduction & Development
 cleavage leads to the formation of a
hollow ball of cells called a blastula

6. Reproduction & Development
After blastula comes gastrulation (to
form a gastrula)
Layers of embryonic tissues form
These layers will become the various parts of
the body

7. Reproduction & Development
Many animals have a larval
stage
Larva is a sexually
immature form
Morphologically distinct
Eats different food than adult
May live in different habitat
than adult
Larvae undergo
metamorphosis and
transform into adults

8. Quick Think
Complex early developmental
patterns such as the formation of
a blastula and a gastrula are
shared by diverse animals ranging
from grasshoppers to clams to
humans. What does thisWhat does this
observation imply about theobservation imply about the
timing of the origins of thesetiming of the origins of these
processes in animal evolution?processes in animal evolution?

9. The history of animals may
span more than a billion years
Huge diversity of fossil species

10. Neoproterozoic Era
1 billion to 542 million years ago
Earliest known fossils
Most animal phyla began to evolve
during this period

11. Paleozoic Era
542-251 mya
During the Cambrian period of this era, animal
diversification took off
This is referred to as the Cambrian Explosion
Paleontologists have found the oldest known fossils
relatives of ~ 1/2 of all extant animal phyla
The first animals with hard, mineralized skeletons
appear
Extant -
still in
existence

12. Mesozoic Era
251-65.5 mya
No new body plans, but
diversification of
Cambrian organisms
New niches occupied
First coral reefs
Wings appear
Large dinosaurs appear
First mammals (tiny,
nocturnal, insectivores)
appear

13. Cenozoic Era
65.5 mya to present
Huge diversification of
insects and
angiosperms
Mass extinctions of
large, non-flying
dinosaurs
Large mammals begin
to appear

14. Quick Think
Put the following milestones in animal evolution
in chronological order, from least recent to
most recent:
a. Origin of mammals
b. Earliest evidence of terrestrial arthropods
c. First fossil animals
d. Extinction of large, non-flying dinosaurs
C, B, A, D

15. Animals can be characterized
by “body plans”
Symmetry -
animals can be
classified
according to the
symmetry (or lack
of it) of their
bodies

16. Symmetry
Radial symmetry - the parts of the
animal radiate from the center

17. Symmetry
Bilateral symmetry - two-sided
symmetry
Animal has a left and right side

18. Cephalization
Many animals with
bilateral symmetry
have sensory
equipment
concentrated at
one end of the
body - this is known
as cephalization

19. Quick Think
Name an organism with radialName an organism with radial
symmetry:symmetry:
Name an organism withName an organism with
bilateral symmetry:bilateral symmetry:

20. Body Plans -
Tissues
Tissue - collection of
specialized cells
isolated from other
tissues by membranous
layers
Sponges do not have
true tissues
All other animals derive
tissues from the layers of
cells present in the
gastrula

21. Body Plans - Tissues
Animals with 2 layers in the
gastrula (called germ layers) are
said to be diploblastic
Diploblastic animals include
jellyfish and corals
Endoderm
Ectoderm

22. Body Plans - Tissues
Other animals have a
third germ layer - the
mesoderm (between
the endoderm and the
ectoderm)
These animals are
triploblastic
All bilaterally
symmetrical animals
are triploblastic

23. Body Plans - Body Cavities
Some triploblastic animals have a fluid-filled
body cavity called a coelom
This space separates the digestive tract from
the outer body wall
A true coelom forms from the mesoderm
Animals with a true coelom are called
coelomates

24. Body Plans - Body Cavities
Pseudocoelomates - triploblastic animals with a
cavity formed from the blastocoel, not the
mesoderm

25. Body Plans - Body Cavities
Acoelomates - triploblastic animals that
lack a coelom
Flatworms are acoelomates

26. Body Plans - Body Cavities
Functions -
Cushions organs
Allows internal
organs to grow and
move independently
from the outer body
wall

27. Quick Think
Among the characteristics
unique to animals is
A gastrulation.
B multicellularity
E heterotrophic
nutrition
D flagellated
sperm.
C sexual
reproduction
Why are
the other
choices
incorrect?