Ppt, Ch 24, section 2
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Chapter 24 Introduction to Animals
Section 1: Animal Characteristics
Section 2: Animal Body Plans
Section 3: Sponges and Cnidarians
Click on a lesson name to select.
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Evolution of Animal Body Plans
Anatomical
features in
animals’ body
plans mark the
branching
points on the
evolutionary
tree.
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Evolution of Animal Body Plans
Relationships on
this tree are
inferred by
studying
similarities in
embryological
development and
shared anatomical
features.
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Symmetry
Similarity or balance among body structures of organisms
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Symmetry
TYPES OF SYMMETRY
Asymmetry – No tissue and irregular in shape
Radial symmetry –
Has a top and a bottom but no sides
Can be divided on multiple planes
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Symmetry
TYPES OF SYMMETRY
Bilateral symmetry –
Can be divided on one plane to show a mirror image
on each side.
Has a top, bottom and sides.
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Cephalization
Animals with bilateral symmetry tend to
have a posterior (tail-end) and anterior
(head-end).
They also have a tendency to concentrate
nervous tissue and sensory organs at the
anterior end of the animal
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Body Cavities
Coelomates
Have a fluidfilled cavity with
tissue formed
from mesoderm
that lines and encloses the organs in the
coelom
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Body Cavities
Pseudocoelomates
Have a fluid-filled
body cavity that
develops between
the mesoderm and
the endoderm rather than developing
entirely within the mesoderm
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Body Cavities
Acoelomates
Have solid bodies
without a fluid-filled
body cavity
between the gut
and the body wall
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Development in Coelomate Animals
Protostomes
The mouth develops from the first opening in
the gastrula.
Deuterostomes
The anus develops from the first opening in
the gastrula.
Chapter 24 Introduction to Animals
Chapter 24 Introduction to Animals
24.2 Animal Body Plans
Segmentation
Segmented animals can be “put together”
from a succession of similar parts.
Can survive damage to one segment
Movement is more effective