BI256 Study Guide - Siphonophorae, Filter Feeder, Obelia

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9 Sep 2014
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01/22/2013
Porifera  the simples metazoans
Belong to the cellular level of organization
There are no organs, no systems, no mouths or digestive tract, but have a rudimentary nervous
integration
Adult sponges have no germ layers and therefore are not diploblastic or triploblastic
Adult sponges are in the sessile form and can be either solitary or colonial
Some can have characteristic shape and radial symmetry, while majority have no regular form or
symmetry
Body Plans
Asconoid  the basic sponge
A simple sac with the spongocoel (atrium) lined by flagellates choanoctyes and the outside
covered by flattened pinacocytes
Between these two layers is a mesohyl containing wandering amoebocytes
The wall is strengthened by a skeleton composed of inorganic compounds forming spicules
and/or organic sponging fibers
Class Calcarea:
Calcerous carbonate spicules
A three grades of structure are found in this class:
Asconoid Forms: represent a stage through which the more complex syconoid and leuconoid
sponges pass during their development
Syconoid Forms: (Grantia)
Common solitary form
Found in shallow, coastal waters to a depth of 200m
Reproduction:
Asexual = Budding
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Sexually = form stomoblastula from the ovum
Class Hexactinellida:
Spicules are siliceous and six-pointed or hexaxon
Spicules are fused to form a glass-like skeleton
Occur in deep or abyssal waters
Class Demospongiae:
Largest number of parazoan species
Contain siliceous spicules and/or spongin fibers
If siliceous spicules are present they are often monaxon, never hexaxon
All species are Leuconoid and are of irregular shape (no symmetry)
Spongillidae are the only fresh-water sponges
They are cosmopolitan
Their shape depends on their age, shape of substrate, and water currents
Reproduction:
Sexually during the spring and summer
Develop free, motile larvae
Asexually during late summer and fall
Gemmules are produced which contain a central mass of archaeocytes (full of food reserves)
Euspongia live in warm, sub-tropical seas to a depth of about 300m
They reproduce sexually
Leuconoid is the principal body plan for these sponges because it promotes larger size and more
efficient water circulation
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