24.2 Animal Body Plans
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PRESENTATIONS
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24.3 Sponges and Cnidarians – T.J. (Thur, May 29)
25.1 Flatworms - Jimmy (Thur, May 29)
25.2 Roundworms and Rotifers - Joe (Fri, May 30)
25.4 Segmented Worms (Annelids) - Crisanta (Fri, May 30)
25.3 Molluscs - Larissa (Tuesday, June 3)
26.1 Arthropod Characteristics - Jack (Tuesday, June 3)
26.2 Arthropod Diversity - Chinzorig (Wednesday, June 4)
26.3 Insects + Their Relatives - Lauryn (Wednesday, June 4)
27.1 Echinoderms Characteristics (Monday, June 9)
28.1 and 28.2 Fishes - (Tuesday + Wednesday, June 10 + 11)
28.3 Amphibians – (Thursday, June 12)
DISSECTIONS
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25.2 Roundworms and Rotifers - Monday, June 2 (Ascaris)
25.4 Segmented Worms (Annelids) - Monday, June 2 (Earthworm)
25.3 Molluscs - Friday, June 6 (Clam, Squid)
26.1 – 26.3 Arthropod Characteristics - Monday, June 9
(grashopper, crayfish)
27.3 Echinoderms Characteristics – Tuesday, June 10 (sea star)
28.1 - 28.2 Fishes - Thursday, June 12 (perch)
28.3 Amphibians - Thursday, June 12 (frog) maybe
Evolution of Animal Body Plans
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Anatomical features in
animals’ body plans mark the
branching points on the
evolutionary tree.
For example, animals without
tissues are grouped
separately from animals with
tissues, and animals without
segments are grouped
separately from animals with
segments.
Recall the relationships among
animals on this tree are
inferred by studying
similarities in embryological
development and shared
anatomical features.
However, molecular data (DNA,
ribosomal RNA, and proteins)
suggest other relationships
among animals
Development of Tissues
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Tissues mark the first
branching point on the
evolutionary tree
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Sponges are the only
animals without tissues
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They are on the notrue-tissues branch.
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All other phyla branch
off from the tissues
branch of the tree.
Body Symmetry
• The first branching point off the tissues branch
• Symmetry describes the similarity, or balance, among body structures
• The type of symmetry defines the kind of movements the animals can make
A. Asymmetry
B. Radial Symmetry
C. Bilateral Symmetry
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ASSYMETRY
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NO SYMMETRY at all = their shapes are not regular
Examples: ??
Sponges, corals
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RADIAL SYMETRY
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Some animals have two halves that look almost the same when the animal is
divided along any plane through its central line
• This is radial symmetry.
Examples: ??
• Jellies, sea anemones…
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Crown Jellyfish
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Soft Coral Polyps
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BILATERAL SYMETRY
Animals with bilateral symmetry have two halves that look like mirror images
when the animal is divided along only one plane through its central axis.
Examples: ??
• birds, dogs, humans…
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Candy striped Annelid
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Blue Spotted Sting Ray
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Marine Flatworm
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BILATERAL ASSYMETRY
African Elephants
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BILATERAL ASSYMETRY
Which cell layers are involved in development?
• Most animals with radial symmetry develop from two cell layers—the
ectoderm and the endoderm
• All animals with bilateral symmetry develop from three cell layers—the
ectoderm, the endoderm, and the mesoderm
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What is the body plan called CEPHALIZATION?
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An animal with bilateral symmetry has a head end and a tail end.
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What is the body plan called CEPHALIZATION?
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An animal with bilateral symmetry has a head end and a tail end.
The head end is called the anterior end.
The tail end is called the posterior end.
When the nervous tissue and sensory organs are located at the anterior end, the
body plan is called CEPHALIZATION
Most animals with cephalization move with their anterior ends first
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What is the body plan called CEPHALIZATION?
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An animal with bilateral symmetry also has a backside and an underside.
The backside is the dorsal surface.
The underside, or belly, is the ventral surface
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Body Cavities
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An animal with bilateral symmetry also has a gut where food is digested.
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The gut is either a sac inside the body or
A tube that runs through the body
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Body Cavities
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A saclike gut has one opening: the mouth
 The mouth takes in food and disposes of wastes
Examples: sponges, jellyfish, flatworms
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Body Cavities
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A tubelike gut has an opening at each end
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Food is taken in at the mouth and digested, nutrients are absorbed, and
waste is then excreted through the anus.
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Body Cavities
Acoelomate
Pseudocoelomate
Coelomate
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Acoelomate
Pseudocoelomate
Coelomate
Acoelomates
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An acoelomate (ay SEE lum ate) is an animal that does not have a fluid
filled body cavity (it has only digestive cavity)
This animal has a solid body with no circulatory system.
Nutrients and wastes spread from one cell to another.
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Pseudocoelomates
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The pseudocoelom (soo duh SEE lum) is a fluid filled cavity that forms
between the mesoderm and the endoderm.
This position limits tissue, organ, and system development
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Coelomates
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Most animals with bilateral symmetry have a fluid filled cavity between
the gut and the outside body wall called a coelom (SEE lum).
The coelom and the organs within it form from the mesoderm.
The coelom was an adaptation that enabled coelomates to develop larger
and more specialized body structures for increased nutrient and waste
transport.
Development in Coelomate Animals
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Coelomates branch into two lines of
development:
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Protostomes
Deuterostomes
Biologists compare how embryos
develop to decide if animals are
closely related.
PROTOSTOME Development
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The mouth of a protostome develops from the first opening in the gastrula.
Also, during development, the mesoderm splits down the middle, forming a coelom between the
pieces.
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Deuterostome Development
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In a deuterostome, the anus develops from the first opening in the gastrula.
The mouth forms from another part of the gastrula
Also, during development, the coelom forms from two pouches of mesoderm.
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Segmentation
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A segmented animal has a series of sections that are exactly alike
Segmentation
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A segmented animal has a series of sections that are exactly alike
Segmentation has two advantages:
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Other sections might be able to perform the function of a damaged section, enabling
the animal to survive.
Segments can move independently. This enables flexible and complex movement.
HOMEWORK/CLASSWORK
• 24.2 Reading Notes
• 24.2 Study Guide