Intro to Animals

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Intro to Animals Development

• Beth Walker
• AP Biology

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Characteristics of Animals

• Multicellular
• Heterotrophic
• Eukaryotic
• Ingest their food
• Lack cell walls (cell membranes only)
• Collagen for support
• Intercellular junctions tight junctions,
  desmosomes, gap junctions
• Tissue nervous muscular
• Most reproduce sexually w/ motile sperm
  non-motile egg
• Development egg sperm ? zygote ? blastula ?
  gastrula

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Early Embryonic Development
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Development

• Cleavage ? successive mitotic cell divisions
• Blastula ?
• hollow ball of cells formed from cleavage
• multicellular
• Gastrula ?
• Blastula folds inward
• Embryonic tisses are formed
• Ectoderm
• Endoderm
• Mesoderm

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Tissues

• Parazoa no true tissues
• Sponges Phylum Porifera
• Eumetazoa true tissues
• Radiata
• diploblastic ? only having 2 tissue/germ layers
• Jellyfish, coral, anemones, comb jellies
• Bilateria
• triploblastic ? having 3 tissue layers
• All other animals

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Tissue Layers

• Ectoderm ? outer body coverings nervous system
• Endoderm ? lining of the digestive system
  organs that arise from the digestive tract (liver
  lungs)
• Mesoderm ? muscles other organs

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Tissue Layers
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Symmetry

• Asymmetry no symmetry
• Radial Symmetry
• No left or right side
• Top bottom surface only
• Symmetrical around a central axis
• Bilateral Symmetry
• Left and right side only
• Divided into left right mirror images
• cephalization

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Symmetry
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Coelom Body Cavity

• Must be triploblastic 3 germ layers
• Acoelomate
• No body cavity
• Flatworms/ Phylum Platyhelminthes
• Pseudocoelomate
• False body cavity
• Partially lined with mesoderm
• Roundworms/Phylum Nematoda Phylum Rotifera
• Coelomate
• True body cavity
• Completely lined with mesoderm
• Mollusks, segmented worms (Annelida), arthropods,
  echinoderms, chordates

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Protostomes vs. Deuterostomes

• Protostomes
• Spiral cleavage
• Determinate cleavage (each embryo is determined
  early on)
• Schizocoelous (coelom forms from splits in the
  mesoderm)
• Mouth develops from blastopore
• Deuterostomes
• Radial cleavage
• Indeterminate cleavage (each embryo cell can
  still develop into an entire embryo)
• Enterocoelous (coelom forms from mesodermal
  outpocketings)
• Mouth develops from anus

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