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In what animals do two major patterns of embryological development occur?
Coelomate animals
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What do the embryos of the animals begin as?
Hallow balls of cells that indent to form a ball two cell layers thick with an opening called blastopore
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In flatworms, annelids, mollusks, and arthropods, the mouth develops from or near the blastopore and are called what?
Protostones
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In what two groups of animals does the anus develop ffrom or near the blastopore and the mouth forms later.
Echinoderms and chordates
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What represents a revolution in embryonic development?
Dueterostomes
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In protostomes the development fate of each embryonic cell is _________________?
Fixed meaning each cell is destined to develop into a particular part of the animal and no other (determined development)
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In deuterostomes embryo if the cells are ____________ at an early, each cell can develop into a complete organism
Separated (Indeterminate development)
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Echinoderms were the first _____________
deuterostome animals
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Echinoderms evolved more than __________ years ago
650 million
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Echinoderms were the first to develop a __________
Exoskeleton or internal skeleton
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What does echinoderm mean?
Spiny Skin
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What is the Spine composed of?
Hard calcium-rich plates called ___________
ossicles that are just beneath the delicate skin
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When ossicles first formed they were ___________ in living tissue and so are truly an endoskeleton
enclosed
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In adults the ossicles ___________
fuse
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About how species are there for echinoderms?
6000 most are marine
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What do echinoderms include?
sea stars, sea urchins, sand dollars, brittle stars, and sea cucumbers
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What does the nervous system consist of?
a central ring of nerves from which five branches arise but there is no centralization of nerve function "brain"
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What are echinoderms characterized by?
pentamerous radial symmetry - five appendages each containing a duplicate set of various internal organs
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Echinoderms do not have what?
heart, brain, nor eyes, but some stars have light sensitive parts on their arms.
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Where is the mouth situated?
On the underside and their anus on top except feather stars, seacuccumbers, and some urchins
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What are the tentacle structures iof echinoderms called?
tube feet
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What do tube feet have?
Suction pads situated at their extremities which they use for locomotion.
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What are the tube feet controlled by?
Water Vascular System
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