1. Architectural Pattern of an Animal
CHAPTER 9
Architectural Pattern of an Animal
Powerpoints revised by Franklyn Tan Te
9-1
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2. Cnidarian polyps have radial symmetry and cell-tissue grade of organization (Dendronephthya sp .).

3. Zoologists recognize 34 major phyla of living multicellular animals
New Designs for Living
Zoologists recognize 34 major phyla of living multicellular animals
Survivors of about 100 phyla that appeared 600 million years ago during Cambrian explosion which was the most important evolutionary event in geological history.
All major body plans evolved within a few million years due to extensive selection and adaptation processes.
Basic uniformity of all life derives from common ancestry and similar cellular construction

4. Hierarchical Organization of Animal Complexity
Life is organized from simple to complex
Each group is arranged to be more complex than the preceding one
Five Grades of Organization
Protoplasmic Grade of Organization
Unicellular groups are the simplest eukaryotic organisms
Perform all basic functions of life within the confines of a single cell like the Paramecium
Protoplasm contains organelles with specialized functions and diversity among groups is due to varying subcellular components and structures

5. Hierarchical Organization of Animal Complexity
Cellular Grade of Organization
Form metazoans—multicellular organisms like Volvox
Have greater structural complexity by combining cells into larger aggregates.
Cells are specialized parts of the whole organism but cannot live alone
Cells demonstrate division of labor and perform specialized tasks earlier accomplished by subcellular components of unicellular organisms.

6. Hierarchical Organization of Animal Complexity
Cell-Tissue Grade of Organization
Cells grouped together into definite patterns or layers to perform a common function as a coordinated unit called tissue.
Most cells can still be scattered all around the body.
Animals are called eumetazoans like sponges and jellyfishes that represent this group.
Due to the unique structure of sponges, some scientists still classify them at the cellular level rather than the cell-tissue level.

7. Hierarchical Organization of Animal Complexity
Tissue –Organ grade of Organization
Aggregated tissues now assembled into larger functional units called organs
Organs can be composed of more than one kind of tissue and have specialized functions
The heart is surrounded by connective tissues
Represented by flatworms
Organ-System Grade of Organization
Several organs work together to perform a common function for the survival of the animal
Considered the highest level of organization and associated with most complex animal phyla like nemerteans, crabs, and chordates

9. Animal body plans are different in:
Grade of organization
Body symmetry
Number of embryonic layers
Number of body cavities
Symmetry is balance of proportions and the correspondence of size and shape of parts on opposite sides of a median plane
Types of Animal Symmetry
Spherical: ball shaped
Radial: tube- or vase-like
Bilateral: right and left sides

10. Figure 9.1 Different types of animal symmetry.

11. Animal Body Plans Spherical symmetry Radial symmetry
Any plane passing through the center and divides the body into mirrored halves
Best suited for floating and rolling
Found in unicellular forms but rare in large animals
Radial symmetry
Body divided into similar halves by more than two planes passing through longitudinal axis
Found in sponges, jellyfishes, sea urchins, and related groups
End of tubular body forms mouth called oral surface while the opposite end forms basal attachment disc called aboral surface

12. Animal Body Plans Biradial symmetry Variant form radial symmetry
Have part that is single or paired rather than radial
Only two planes passing through the longitudinal axis that produces mirrored halves
Usually sessile, freely floating, or weakly swimming animals like ctenophores
No anterior or posterior end
Can interact with the environment in all directions

13. Animal Body Plans Bilateral Symmetry
Organism divided along a sagittal plane into two mirror portions forming right and left halves
Much better fitted for directional (forward) movement which is advantageous to an animal moving through its environment head first
Associated with cephalization which is the differentiation of a head region and the concentration of nervous tissues and sense organs in the front area
Also has mouth in front to allow for more efficient feeding and detection of prey

14. Animal Body Plans Regions of bilaterally symmetrical animals:
Anterior- head end; Posterior-tail end
Dorsal- back side; Ventral- bottom or belly side
Medial- midline of body
Lateral- right and left sides
Distal- parts farther from the middle of body
Proximal- parts are nearer the middle of body
Frontal plane (coronal plane)- divides body into dorsal and ventral halves
Sagittal plane- divides body to right and left
Transverse plane (cross section)- divides body into anterior and posterior halves

15. Figure 9.2 The planes of symmetry as illustrated by a bilaterally symmetrical animal.

16. Body Cavities and Germ Layers
Body cavity
Internal space represented by gut cavity and fluid-filled body coelom that cushions and protects internal organs
Body cavity is dependent on mesodermal pouch formation during gastrulation
Types of body cavities
Acoelomate: no body cavity
Pseudocoelomate: partial body cavity
Coelomate: true body cavity

17. Body Cavities and Germ Layers
Variations in body cavity formation
In Sponges
Cellular grade of organization and have no real body cavity- Acoelomate
After blastula formation, cells reorganize to form adult body and does not form gastrula
Cells grow and surround a chamber called spongocoel
Blastula has no external opening so no gut cavity forms

18. Body Cavities and Germ Layers
In other animal phyla
Development proceeds from blastula to gastrula
Invagination of surface cells form the archenteron or primitive gut
Opening to archenteron is the blastocoel and becomes the mouth or the anus
Embryo now has two cavities- gut and blastocoel
Inside gut is lined by endoderm
Outer layer of cells is ectoderm
Middle area lined with mesoderm

19. Body Cavities and Germ Layers
In Protostomes
Mesoderm forms as endodermal cells near blastopore migrate into the blastocoel
Three body plans are possible
Acoelomate plan
Mesodermal cells completely fill the blastocoel so no body space is formed
Gut is only body cavity
Region between ectoderm and endoderm is filled with spongy mass of parenchyma cells that are from embryonic connective tissue and are important for transport and disposal of metabolic wastes

20. Body Cavities and Germ Layers
Pseudocoelomate plan
Mesodermal cells line the outer edge of the blastocoel only partially lined with mesoderm
Pseudocoelom is a false body cavity
Two body cavities formed where persistent blastocoel forms pseudocoelom and a gut cavity

21. Body Cavities and Germ Layers
Schizocoelous coelomate plan
Mesodermal cells fill blastocoel and then splits to form a space called a coelom
A true body cavity that is completely lined by mesoderm
Two body cavities are formed: gut and coelom

22. Body Cavities and Germ Layers
In Deuterostomes
Mesoderm forms by an enterocoelous plan where cells from the central gut lining form pouches and expand into blastocoel
Pouch wall forms mesodermal ring and pouches enclose a space, the coelom cavity
Pouches pinch off from gut lining completely enclosing the coelom bounded by mesoderm.
Forms two body cavities- gut and coelom
Mesodermal mesenteries suspend organs in the coelom

23. Schizocoelous plan
Enterocoelous plan
Figure 9.3 Mesoderm resides in different parts of the gastrula.

24. Figure 9.4 Acoelomate, pseudocoelomate, and eucoelomate body plans are shown as cross sections of representative animals.

25. Developmental Origins in Triploblasts Body Plans
Triploblastic animals follow one of several major developmental pathways
Most common pathways are by spiral or radial cleavage
Radial cleavage
Typically accompanied by three traits
Blastopore becomes the anus and new opening becomes the mouth
Coelom formation is by enterocoely
Cleavage is regulative
Animals with these features are called deuterostomes

26. Developmental Origins in Triploblasts Body Plans
Spiral cleavage
Produces embryos whose developmental pattern contrast with those of deuterostomes
Blastopore becomes the mouth
Cleavage is mosaic
May be acoelomate, pseudocoelomate, or coelomate via schizocoely
Animals with these features are called lophotrochozoan protostomes
Ecdysozoan protostomes
Exhibit a range of cleavage patterns including spiral and superficial cleavage
Can be coelomate or pseudocoelomate

27. Figure 9.5 Different developmental
sequences produce diploblastic
versus triploblastic animals.

28. A Complete Gut Design and Segmentation
Types of gut design
Few diploblasts and triploblasts form blind or incomplete gut cavity
Same opening for entrance of food and exit of wastes
Most common animal groups form a complete gut
Allows for one-way flow of food from mouth to anus
Tube-within-a-tube design is very adaptive to the various types of food

29. A Complete Gut Design and Segmentation
Metamerism (Segmentation)
Serial repetition of similar body segments along longitudinal axis of body
Each segment is a metamere or somite that contains internal and external structures of several vital organ systems
Segments can be seen during early development and also appear as superficial ectodermal and body wall features in adults
Permits greater body mobility and complexity of structure and function
Found in annelids, arthropods, and chordates

30. Figure 9.6 Phyla with segmentation.