Unit 8 Chapter 25 What is an animal?

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Unit 8Chapter 25What is an animal?
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Characteristics of Animals

• 1) They are multicellular
• 2) They are heterotrophs (consumers)
• Motility most animals use locomotion to find
  their food sources
• Sessile organisms that
  are permanently attached
  (dont spend much
  energy to obtain
  food)

Sponges are sessile animals
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Characteristics of Animals

• 3) They injest their food
• 4) They have specialized cells, tissues, organs,
  systems
• Ex the complex digestive tract of the earthworm

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Characteristics of Animals

• 5) They have similar stages of development
• Blastula
• Fluid-filled ball formed
  from many cell divisions
• Gastrula
• Blastula folds inward to
  form two layers

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Gastrulation

• Formation of a cavity of two or more layers with
  an opening at one end
• 1) Ectoderm outermost layer
• 2) Endoderm innermost layer
• Higher animals have a third, middle layer
• 3) Mesoderm develops into muscles, etc

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Symmetry

• the arrangement of body structures
• 1) Radial symmetry
• Can be divided along any
  plane, through a central
  axis, into
  roughly equal halves

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• 2) Bilateral symmetry
• Can be divided down its length into similar right
  left halves
• Has a definite
  front (anterior,)
  rear
  (posterior),
  top (dorsal,) and
  belly side (ventral)

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Body plans

• Acoelomates
• Develop from 3 cell layers, but have NO body
  cavity
• Ex flatworms

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Body plans

• Pseudocoelomates
• A fluidfilled body cavity only partially lined
  with mesoderm
• Ex Roundworms

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Body plans

• Coelomates
• Has a fluid-filled body cavity completely
  surrounded by mesoderm
• Ex segmented worms all higher animals

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Animal Diversity

• Invertebrates
• Animals without backbones
• Often having exoskeletons outside their body for
  framework support

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Animal Diversity

• Vertebrates
• An animal with an endoskeleton a backbone
• Endoskeletons are internal frameworks that
  provide protection, support, muscle attachment
• Ex fishes, amphibians,
  reptiles, birds mammals