Introduction to the Animal Kingdom

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Introduction to the Animal Kingdom
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What IS an Animal?

• Coral
• sessile (rooted?)
• stem, branches,
• greenish.
• Resembles plant
• but this IS an animal! Why?

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What IS an Animal?

• Definition of "Animal"
• Multicellular (so are plants, fungi)
• Eukaryotic (so are plants, fungi)
• Diploid (usually) (sporophytes are, too)
• Meiosis produces gametes
• Sperm, egg are the only haploid cells
• Heterotrophic by ingestion
• Cells lack cell walls.

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What IS an Animal?

• Basic structure (not definition) Tube-in-tube
• Body wall outer tube
• gut (GI tract) inside tube
• mouth
• anus

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Embryological Development in Animals

• Every animal begins as ZYGOTE
• How do animals develop tube-in-tube body form?
• Important in understanding relationships,
  classification of Phyla.

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Three fundamental processes

• 1. Morphogenesis
• (morph- shape, genesis origin)
• Origin of shape, form
• 2. Differentiation
• Process of cells becoming different, and
  specializing for different functions
• 3. Growth
• Increase in size, requires input of matter, food

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Sequence of Events

• 1. Fertilization
• 2. Activation
• 3. Cleavage
• 4. Gastrulation
• 5. Mesoderm formation
• 6. Organogenesis

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Sequence of Events(frog or sea urchin model)

• 1. Fertilization
• Fusion of sperm nucleus with egg nucleus
• Produces zygote (diploid)
• 2. Activation
• Increase in metabolism
• Egg metabolically inert, zygote active
• Movement of cytoplasm
• Synthesis of materials needed for cleavage

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Sequence of Events

• 3. Cleavage
• from Zygote
• Division by mitosis
• 2 blastomeres ? 4 blastomeres ? 8 blastomeres ?
  16 ? 32 ? 64 ? 128 ? 256 ? 512
• ? Blastula

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Sequence of Events

• 4. Gastrulation formation of a gut
• Major MORPHOGENIC event !!!
• Location of cells after GASTRULATION determines
  further development

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Sequence of Events

• 4. Gastrulation
• Invagination movement of cells to inside
• yields 2 tissue layers
• Ectoderm
• Endoderm
• yields Archenteron
• ancient gut first formation of "inside tube."

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Sequence of Events
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Sequence of Events

• 5. Mesoderm Formation
• 3rd "germ layer"
• Ectoderm outside skin
• Mesoderm "middle skin"
• Endoderm inside skin
•  
• Details of mesoderm formation vary among phyla !!
• to be studied with those phyla.

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Sequence of Events

• 6. Organogenesis
• Formation of organs from three germ layers
• Differentiation continued Morphogenesis

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Organogenesis

• Ectoderm
• Epidermis
• Lining of mouth rectum
• Cornea of eye
• Lens of eye
• Nervous system

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Organogenesis

• Endoderm forms thin linings (mostly)
• linings of gut branches
• lining of excretory ducts, bladder
• " " lungs, trachea
• " " reproductive ducts,
• uterus, vas deferens
• liver
• pancreas

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Organogenesis

• Mesoderm
• Skeleton,
• Muscles (skeletal, smooth, cardiac)
• Dermis of skin
• Heart, blood, blood vessels
• Kidneys,
• Ovaries/testes, etc.

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Organogenesis

• Ectoderm
• How Nervous system gets inside
• Dorsal surface of embryo forms Neural plate
• Plate sinks inward forming Neural groove
• Edges of groove fuse to separate Neural tube from
  epidermis