Transcript 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
 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
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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 environment
 Gastrodermis – lines mouth and gut, and allows for extracellular
digestion
 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
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Motor unit
Synapse
Neurotransmitter
Action potential
Sense Organs
 Animals must respond to stimuli in order to survive
 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
 Don’t coast after stopping in
water
 Friction overcomes momentum
due to large SA:Vol
 Large animals
 Typically move using
musculature
 Continue to move after stopping
 Smaller SA:Vol
 Surface area is correlated with
drag, while volume is correlated
with musculature