echinoderms and invertebrate chordates. phylum echinodermata name means spiny skin include organisms...
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Phylum Echinodermata
Name means spiny skin Include organisms such as
Asteroidea sea stars sea urchins, sand dollars sea lilies brittle stars sea cucumbers.
All inhabit marine environments
Characteristics
Five-part radial symmetry as adults, bilateral symmetry as larvae Radial symmetry helps slow or fixed animals sense food or
predators from all directions Endoskeleton
For support and protection Water-vascular system
Movement, exchange of gases, capture food, and excrete wastes
Endoskeleton
calcium carbonate (calcite) plates, ossicles, and spines that are covered with a thin layer of skin
Some spines on sea stars are modified to into pincer like appendages- protect and clean the surface of a sea star
Can contract muscles to tighten their skin to make the calcite plates rigid, or relax the muscles to enable flexibility
Varied methods of nutrition
Sea stars are carnivorous, prey on clams Sea urchins are herbivores, graze on algae Brittle stars, sea lilies, sea cucumbers feed
on dead and decaying matter
Invertebrate Chordate
Phylum Chordata Chordate criteria
Notochord Dorsal hollow nerve cord Gill slits Post anal tail Muscle blocks
Notochord
Rodlike structure located between digestive system and dorsal hollow nerve cord. Retained until adulthood in invertebrate chordates Replaced by backbone in vertebrates Develops from mesoderm Provides support so that side to side movement
can propel the animal forward
Dorsal hollow nerve cord
Develops from ectoderm that forms a tube composed of cells surrounding a fluid filled canal that lies above the notochord. These cells develop into the spinal cord.
Cells in anterior portion of cord develop into brain
Nerves connect the nerve cord to each block of muscles.
Gill Slits
Paired openings located in the pharynx behind mouth.
Many chordates only have gill slits during embryonic development
Those that have gill slits as adults, strain food from water – the fishes have internal gills that exchange gases during respiration