Chapters 29 and 30 – Intro to Invertebrates Notes Sheet
Name:________________ (in case you lose it)
What makes an animal?
How can you tell if something is an animal or not?
What are some examples of animals?
Evolution of Animals (intro)
All animals are multicellular heterotrophic organisms that must take in preformed food.
mulitcellular: made of more than one cell
heterotrophic: take in food from other organisms; non-photosynthetic
food: complex organic molecules; often glucose related compounds
Criteria for the Evolution of Animals
 1. Multicellularity
 2. True Tissues
 3. Bilateral
Symmetry
 4. Body Cavities
 5. The Coelom
 6. Segmentation
 7. Development
Classification Criteria
 Level of organization
Cellular, tissue, organ
 Body Plan
Sac, tube-within-a-tube
 Segmentation
Segmentation leads to specialization
 Symmetry
Radial - Two identical halves
Bilateral - Definite right and left halves
 Type of Coelom
Pseudocoelom
Coelom
 Early Developmental Pattern
Protostome - First embryonic opening becomes the mouth
Dueterostome - Second embryonic opening becomes the mouth
In order to be considered an
animal, what must be true about
this organism?
Multicellularity - Sponges
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Only level of animal to have cellular organization
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Saclike bodies perforated by many pores
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Beating of flagella produces water currents that flow through pores into central cavity
and out osculum
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Sessile filter feeders
 Asexual reproduction by fragmentation or budding
True Tissue Layers
Many animals have a total of three possible germ layers
 ____________: _______________________________________________
 ____________: _______________________________________________
 ____________: _______________________________________________
phlya Ctenophora and Cnidaria develop only ectoderm and endoderm
 Diploblasts – animals derived from only 2 embryonic layers
 Radially symmetrical
So what is in the middle if these organisms (the first with true tissue layers) ?
What are Ctenophora called again?
Comb Jellies – Ctenophora
Characteristics:
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Cnidarians
Tubular animals that most often reside in shallow marine waters
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Hydra
_______________ cnidarian
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Obelia
A colony of polyps enclosed by a hard, chitinous covering. Polyps? Chitin?
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Also has ____________________________________________________________
Where are we now?
How are cnidarians and
ctenophora different from
sponges?
What new “feature” do
they possess that sponges
did not have?
Bilateral Symmetry – Flatworms and Nematodes
Bilateral Symmetry
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Cephalization
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Pseudocoelomates
Both phyla today will be considered pseudocoelomates
What is the difference between acoelomates, pseudocoelomates and
coelomates (or eucoelomates?)
_______________________________have a fluid filled body cavity called a coelom
with a complete lining called peritoneum derived from mesoderm (one of the
three primary tissue layers).
_______________________________, which is a fully functional body cavity. Tissue
derived from mesoderm only partly lines the fluid filled body cavity of these animals.
Thus, although organs are held in place loosely, they are not as well organized as in a
coelomate.
_______________________________ animals, like flatworms, have no body cavity at
all. Organs have direct contact with the epithelium. Semi-solid mesodermal tissues
between the gut and body wall hold their organs in place.
Flatworms (phylum Platyhelminthes)
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Ribbon worms (phylum Nemertea)
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Flatworms
Belong to the phylum platyhelminthes. (Plat = flat)
There are three classes:
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Characteristics of Flatworms
Planarians (genus Dugesia)
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 Three kinds of muscle layers:
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Planarians, cont.
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Excretory organ functions in osmotic regulation and water excretion
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Can reproduce asexually
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Hermaphroditic
Practice cross-fertilization
Parasitic flatworms are flukes (trematodes) and tapeworms (cestodes)
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Well-developed nerves and gastrovascular cavity are unnecessary
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Reproductive system well developed
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Usually hermaphroditic
Flukes
Parasitic Flatworms
Tapeworms
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Have anterior region with modifications for attachment to intestinal wall of host
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Behind head region, scolex, a long series of proglottids are found
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Segments each containing a full set of both male and female sex organs
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Complicated life cycles
Class Trematoda
Class Cestoda
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Phylum Nemertea - (Rhynchocoela) Ribbonworms
 The nemerteans (ribbon worms) are _______________________________________________
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 Unlike members of the Platyhelminthes nemerteans have a____________________________
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 Prey is captured using a ____________________________________________________.
 The proboscis lies in an interior cavity called the rhynchocoel and muscular pressure on fluid in
the rhynchocoel causes the proboscis to be quickly everted.
 The prey is wrapped in the sticky, slime-covered, proboscis and stabbed repeatedly with the
stylet. ________________ in the slime incapacitate the prey.
What is different about the
animals we discussed
today?
How are flatworms
(Platyhelminthes) different
from cnidarians?
How are nematodes
different from flatworms?