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24.2 Animal Body Plans

PRESENTATIONS• 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• 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

• 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

Evolution of Animal Body Plans

• Tissues mark the first branching point on the evolutionary tree

• Sponges are the only animals without tissues

• They are on the no-true-tissues branch.

• All other phyla branch off from the tissues branch of the tree.

Development of Tissues

Which animals have no tissues?

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Body Symmetry

A. AsymmetryB. Radial SymmetryC. Bilateral 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

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ASSYMETRY• NO SYMMETRY at all = their shapes are not regular• Examples: ??• Sponges, corals

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RADIAL SYMETRY• 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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10Crown Jellyfish

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Soft Coral Polyps

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BILATERAL SYMETRYAnimals 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

15Blue Spotted Sting Ray

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Marine Flatworm

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African Elephants

BILATERAL ASSYMETRY

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BILATERAL ASSYMETRYWhich 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?• An animal with bilateral symmetry has a head end and a tail end.

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What is the body plan called CEPHALIZATION?• 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?• 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• An animal with bilateral symmetry also has a gut where food

is digested. The gut is either a sac inside the body or A tube that runs through the body

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Body Cavities• A saclike gut has one opening: the mouth

The mouth takes in food and disposes of wastesExamples: sponges, jellyfish, flatworms

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Body Cavities• A tubelike gut has an opening at each end

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

Acoelomate

Pseudocoelomate

Coelomate

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Acoelomates• 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• 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

Coelomates• 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

• Coelomates branch into two lines of development:

Protostomes Deuterostomes

• Biologists compare how embryos develop to decide if animals are closely related.

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PROTOSTOME Development• 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• 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.

• A segmented animal has a series of sections that are exactly alike

Segmentation

• A segmented animal has a series of sections that are exactly alike

• Segmentation has two advantages:• 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.

Segmentation

HOMEWORK/CLASSWORK• 24.2 Reading Notes

• 24.2 Study Guide