Introduction to the Invertebrates

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Introduction to the Invertebrates
Lecture 3 Chapter 3 082908 II
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Components of Animal Structure

• Body Symmetry
• Body Architecture Complexity Body Type
• Locomotion and Support
• Feeding Mechanisms
• Excretion and Osmoregulation
• Circulation and Gas Exchange
• Nervous Systems and Sense Organs
• Reproduction

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VI. Circulation and Gas Exchange

• Internal transport materials (nutrients, gases,
  and metabolic waste products) transported by way
  of rudimentary circulatory mechanisms.

Fig 3.24 Sponges (Ph. Porifera) and Cnidarians
(Ph. Cnidaria) use environmental water as their
circulatory fluid.
Fig 3.24 Blastocoelomates (e.g. nematodes) use
fluids of body cavity for circulation. most of
these animals are small, or are long and thin,
and adequate circulation is achieved by body
movements.
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VI. Circulation and Gas Exchange

• Internal transport materials (nutrients, gases,
  and metabolic waste products) transported by way
  of rudimentary circulatory mechanisms
• Circulatory systems open and closed circulatory
  systems move materials through body using a
  circulatory fluid (blood).

Fig 3.24 Closed circulatory system in an
earthworm (Ph. Annelida). Blood stays in
distinct vessels or lined chambers.Blood
carries nutrients and gases.Coelomic fluid
carries wastes.
Fig 3.24 Open circulatory system in an insect
(Ph. Arthropoda). Blood (hemolymph) empties
from vessels into the body cavity and directly
bathes organs.
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VI. Circulation and Gas Exchange

• Internal transport materials (nutrients, gases,
  and metabolic waste products) transported by way
  of rudimentary circulatory mechanisms
• Circulatory systems open and closed circulatory
  systems move materials through
• Gas exchange and transport one of the principal
  functions of circulatory fluids is to carry
  oxygen and carbon dioxide through the body
  exchange them with the environment.

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VI. Circulation and Gas Exchange
Gas exchange
(air or water)
(blood or body cavity fluid)

• Gases diffuse across a wet membrane, (they must
  be in solution to dissolve across the membrane)
  at the exchange site.
• The gasses will move down a concentration
  gradient, which is maintained by the circulation
  of internal fluids to and away from these areas.

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VI. Circulation and Gas Exchange

• Internal transport
• Circulatory systems
• Gas exchange and transport
• Gas exchange surfaces
• Across body surface - Protists, tiny soft
  bodied inverts (also vertebrate amphibians).
  Restricted to aquatic or damp terrestrial
  environments.

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VI. Circulation and Gas Exchange

• Internal transport
• Circulatory systems
• Gas exchange and transport
• Gas exchange surfaces
• Across body surface
• Specialized organs Gills in many marine
  freshwater invertebrates Hindgut irrigation in
  sea cucumbers and trachea in insects,
  centipedes and millipedes.

Fig 3.26 Tracheal system of an insect
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VI. Circulation and Gas Exchange

• Internal transport
• Circulatory systems
• Gas exchange and transport
• Gas exchange surfaces
• Across body surface
• Specialized organs
• Modifications to increase surface area for
  increased gas exchange.

Fig 3.26 Polychaete (Ph. Annelida) tentacles
Sea slug (Ph. Mollusca) branchial plume chiton
with gills (Ph. Mollusca).
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Components of Animal Structure

• Body Symmetry
• Body Architecture Complexity Body Type
• Locomotion and Support
• Feeding Mechanisms
• Excretion and Osmoregulation
• Circulation and Gas Exchange
• Nervous Systems and Sense Organs
• Reproduction

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VII. Nervous Systems Sense Organs

• Nervous system and body plan the structure of
  the nervous system of any animal is related to
  its bauplan and its mode of life.
• Nerve net nervous system is a non-centralized,
  diffuse meshwork
• major receptors are regularly and radially
  distributed
• in radially symmetrical animals (i.e. jelly fish
  or sessile anemone)

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VII. Nervous Systems Sense Organs

• Nervous system and body plan
• Nerve net
• Central nervous system centralize and
  concentrate major coordinating elements
• made up of an anteriorly located neuronal mass
  (ganglion)
• one or more longitudinal nerve cords that often
  bear additional ganglion.

The primitive ladder-like arrangement of nerve
chords is seen today in free-living flatworms
(Ph. Platyhelminthes).
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VII. Nervous Systems Sense Organs

• Nervous system and body plan
• Sense organs
• Cephalization the concentration of major sense
  organs anteriorly, forming a head region, in
  bilaterally symmetrical animals.
• Information about the environment is gathered by
  the leading end of the motile animal.

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Components of Animal Structure

• Body Symmetry
• Body Architecture Complexity Body Type
• Locomotion and Support
• Feeding Mechanisms
• Excretion and Osmoregulation
• Circulation and Gas Exchange
• Nervous Systems and Sense Organs
• Reproduction

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VIII. Reproduction
The biological success of any species depends
upon its members staying alive long enough to
reproduce itself.
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VIII. Reproduction

• Asexual reproduction vegetative growth through
  mitosis.

ADVANTAGES rapid asexual reproduction can
take advantage of favorable environmental
conditions, especially in disturbed habitats. -
overwintering periods of harsh environments.
Fig 3.33 (a) simple mitotic binary fission
(protists) (b) fragmentation followed by
regeneration of lost parts (vermiform
invertebrates). (c) budding (Hydra)
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VIII. Reproduction

• Asexual reproduction
• Sexual reproduction fusion of gametes to form
  zygotes.

ADVANTAGES recombination allows for
maintenance of high genetic heterozygosity in
individuals high polymorphisms in populations.
Fig 3.35 Formation of haploid cells (gametes
sperm and eggs) through meiosis and the
subsequent fusion of pairs (fertilization) of
those cells to produce a diploid zygote.
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VIII. Reproduction

• Asexual reproduction
• Sexual reproduction
• Parthenogenesis unfertilized eggs develop into
  viable individuals. (i.e. gastrotrichs, rotifers,
  tardigrades, nematodes, gastropods, certain
  insects, and various crustaceans).

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Take-home Messages

• The nature of the circulatory system is directly
  related to the size, complexity, and lifestyle of
  the organism in question.
• The structure of the nervous system of any animal
  is related to its bauplan and its mode of life.
• The biological success of any species depends
  upon its members staying alive long enough to
  reproduce itself.

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Study Questions - 090308

• Gas must diffuse across a moist gas exchange
  surface. What are two adaptations in terrestrial
  invertebrates that enable them to exchange gas
  without loosing moisture to the environment?
• Differentiate nerve net and ladder-like
  nervous systems.
• Define cephalization and explain how it relates
  to bilateral symmetry and motility.
• Name one advantage and one disadvantage to
  asexual reproduction and sexual reproduction in
  invertebrates.