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Biology 320 Invertebrate Zoology Fall 2005


Biology 320 Invertebrate Zoology Fall 2005 Highlights from Chapter 6 Introduction to Eumetazoa What Defines an Animal? Irritability responds to external stimuli ... – PowerPoint PPT presentation

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Title: Biology 320 Invertebrate Zoology Fall 2005

Biology 320Invertebrate ZoologyFall 2005
  • Highlights from Chapter 6
  • Introduction to Eumetazoa

What Defines an Animal?
  • Irritability responds to external stimuli
  • Locomotion
  • Sense of direction
  • Polarized distribution of organs
  • Sponges are classified as Parazoa (near
    animals) by some, and animals by others
  • Clearly metazoan
  • Have unified distribution of cells

Eumetazoan Tissues
  • All eumetazoans posses the four PRIMARY tissue
    types, to some extent
  • Epithelium
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
  • Epithelia that are more developed and diverse
    than in parazoans
  • Has allowed organisms to colonize habitats that
    are more physiologically challenging (i.e.
    freshwater and terrestrial)
  • Increases compartmentalization in organisms
  • Two main types (generally speaking)
  • Epidermis barrier to external environment
    which allows for homeostasis of internal
  • Gastrodermis lines mouth and gut, and allows
    for extracellular digestion

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  • Posses connective tissues
  • Bind other tissues together
  • Offer structural support - skeleton
  • Types of skeletons
  • Exoskeleton example insect cuticle
  • Endoskeleton example sea urchin test
  • Hydrostatic skeleton animal has a water-filled
    cavity (i.e. gastrovascular cavity, coelom,
    etc.). Muscle contractions displace water,
    generating force that can be used to do work

  • Eumetozoans posses musculature that allows them
    to bend / turn while moving
  • Muscle types
  • Smooth
  • Cross-striated
  • Obliquely striated
  • Muscles are usually arranged in antagonistic sets
  • One muscle moves body part one way, while the
    other restores its original position
  • Human example biceps and triceps
  • Tubular invertebrates longitudinal and circular

  • Eumetozoans posses nervous systems
  • Neurons evolved with muscle tissue
  • Regulate muscle contraction so that animals can
    respond to stimuli
  • Nerve impulses travel along membranes of axons
    to effectors (target cells)
  • Important terms
  • Motor unit
  • Synapse
  • Neurotransmitter
  • Action potential

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Sense Organs
  • Animals must respond to stimuli in order to
  • Three main classes of stimuli
  • Electromagnetic energy mainly light
  • Mechanical energy sound vibrations, touch,
    pressure, gravity
  • Chemical stimuli taste, smell
  • Animals must posses the appropriate receptors to
    respond to these stimuli
  • Photoreceptors
  • Mechanoreceptors
  • Chemoreceptors

  • Basic reflex arc
  • Receptor
  • Afferent signal
  • Integration center (ganglion, CNS, etc.)
  • Efferent signal
  • Effector (target cell, organ, etc.)
  • Many types of receptors throughout the animal
    kingdom some are very simple and not considered
    to be organs
  • Ocelli simple eyes that serve as photoreceptors
  • Statocysts gravity / orientation receptors

Movement Vs. Body Size
  • Smaller animals
  • Often move using cilia
  • Dont coast after stopping in water
  • Friction overcomes momentum due to large SAVol
  • Large animals
  • Typically move using musculature
  • Continue to move after stopping
  • Smaller SAVol
  • Surface area is correlated with drag, while
    volume is correlated with musculature
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