27 terms

Chapter 26 - Sponges and Cnidarians

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dorsal side
back of an animal - the spine side, away from the abdomen
ventral side
The underside, belly, or the lower body surface
anterior end
the end of an animal that contains its head
posterior end
the end of an animal that contains its tail
asymmetry
an animal with no symmetry (ex. sea sponges)
radial symmetry
body plan in which body parts repeat around the center of the body - like a sea anemone, jellyfish, sea star
bilateral symmetry
body plan with left and right halves; ex: worms, arthropods, and chordates
ectoderm
in animals, the outer layer of embryonic tissue from which the skin and nervous system develop
mesoderm
middle layer of embryonic tissue in animals from which the skeleton and muscles develop
endoderm
inner layer of embryonic tissue from which the digestive organs develop in animals
coelom
A body cavity that contains the internal organs
aceolomate
an animal that has no true coelom - body cavity. (ie. flatworms)
pseudocoelomate
An animal whose body cavity is not completely lined by mesoderm.
coelomate
an animal that has a body cavity completely lined with mosoderm - the body cavity holds the internal organs are located
protostome
means first mouth - the blastopore (first hole that develops in the embryo) becomes the mouth, anus open opposite the mouth later on
deuterostome
means second mouth - the blastopore becomes the anus, mouth opens opposite the anus later on
hermaphrodite
An individual that functions as both male and female in sexual reproduction by producing both sperm and eggs.
choanocytes
specialized cell in sponges that uses a flagellum to move a steady current of water through the sponge
spongin
the network of protein fibers making up the simple skeleton of some sponges
budding
asexual reproduction in which a part of the parent organism pinches off and forms a new organism
gastrovascular cavity
a digestive cavity with only one opening; found in simple animals
gastroderm
inner lining of the gastrovascular cavity in a cnidarian
nematocyst
stinging structure within each cnidocyte of a cnidarian that is used to poison or kill prey
nerve net
a loose web of interconnected nerve cells that control nervous responses in cnidarians
statocysts
nerve cells that sense gravity in a cnidarian
ocelli
light-sensitive eyespots
hydrostatic skeleton
support structure that consists of water contained under pressure in a closed cavity

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