Integrated Principles of Zoology, 11e

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Pseudocoelomates
Echinodermata
Mollusca
PORIFERA
Arthropoda
Acoelomates
Chordata
Annelida
Cnidaria
Protozoa
Triploblastic (Bilateria)
Diploblastic (Eumetazoa)
Multicellular animals (Metazoa)
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Protoplasmic grade
All activities occur within organelles and
cytoplasm of a singe cell, as in protozoa
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Cellular grade --
Colonies of cells, some with the same functions
that differ from others. examples Volvox,
sponges
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Cell - tissue grade --
cells that perform a specific function are
concentrated into layers, but no distinct organs
are developed. Example -- Cnidaria.
Polyp and Medusa of Cnidaria (Radiate Animals)
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Pseudocoelomates
Echinodermata
Mollusca
Arthropoda
Acoelomates
Chordata
PORIFERA
Annelida
Cnidaria
Placozoa
Protozoa
Bilateria (three germ layers)
Eumetazoa (two germ layers) diploblasts
Metazoa (multicellular animals, blastula present)
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Characteristics of sponges
1) cellular grade of organization
For example all digestion is intracellular
2) sessile (one recently described exception)
3) marine and freshwater filter feeders with
elaborate filter feeding apparatus
4) they rival reef-building corals in their
contribution to coral reefs
5) Classification based on skeleton
construction
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Basic Sponge Structure
Two epithelial layers
1-- pinacocytes form the outside layer,
the pinacoderm
2-- Choanocytes line the internal chambers to
set up water flow through the sponge.
3-- archeocytes form the skeletal structure and
can differentiate into other cell types.
Mesohyal (yellow) is the intracellular matrix
of the sponge where pinacocytes and archeocytes
are found.
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(Amoeboid cells)
(Individual cells capture and digest food)