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features of important phyla

Features of Important Phyla


Cnidaria: Platyhelminth: Nematode: Echinoderm: Annelid: Mollusc: Arthropod: Chordate:
Body layers: Diploblastic. Triploblastic. Triploblastic. Triploblastic. Triploblastic. Triploblastic. Triploblastic. Triploblastic.
Coelom: No. No. Pseudocoelom. Yes. Yes. Yes. Yes. Yes.
Symmetry: Radial. Bilateral. Bilateral. Pentamerous (5 lines). Bilateral. Bilateral. Bilateral. Bilateral.
Segmentation: No. No. No. No. Metameric segments separated by septae. No. Head = 6 segments. Thorax = 3 segments. Abdomen = 11 segments. Segmental muscle blocks on either side of the body.
Lifestyle: Sedentary or free swimming. Free living or parasitic. Free living or parasitic. Free living. Free living. Free living or occasionally parasitic. Free living or parasitic. Free living or parasitic.
Body form: Polyp and medusa stages (polymorphic). Dorso-ventrally flattened (large surface area : volume ratio). Parasites have a cuticle. Cylindrical tapering at ends. Have a cuticle. Variable. Cylindrical. Ridged due to segmentation. Outer tough cuticle. Non-parasitic worms have chaetae (bristles). Some have parapodia (like paddles). Muscular foot, visceral mass and mantle membrane which may secrete a shell. 3 sections – head, thorax and abdomen. Exoskeleton. Paired, jointed appendages (may be legs, antennae, wings). Obvious head. Hair / feathers / scales on body surface. Paired limbs formed from more than one body segment. Post anal tail. Notochord present at some stage.
Gut: Single opening (no separate mouth and anus). Simple central cavity. Tubular with side passages. Single opening. Tubular with mouth and anus. Mouth ventral, anus dorsal. Rasping jaw or eversible stomach! Straight, differentiated tube with mouth and anus. Simple tube with mouth and anus. Digestive gland produces enzymes. Tubular coiled gut with distinct regions. Tubular coiled gut with distinct regions. Associated organs produce digestive secretions.
Feeding: Tentacles around the mouth. Stinging cells (nematocysts) paralyse prey. Predatory, if free living. Absorptive if parasitic. Some have a spike-like tooth to stab prey or a stylet to suck body fluids. Some evert stomach onto prey. Others grind algae off surfaces. Scavenge on decaying matter. Food and soil taken in. Soil egested as cast. Marine worms can be filter feeders. Many mechanisms in this phylum; herbivores, carnivores, scavengers, filter feeders, parasites. Herbivores, carnivores, scavengers, filter feeders, parasites. Specialised mouth parts. Herbivores, carnivores, scavengers, parasites. Mouth with specialised jaws and teeth.
Gas exchange: Diffusion from water over whole body surface. Diffusion through damp body surface. Diffusion through damp body surface. Diffusion. Diffusion through damp body wall. Aquatic - gills. Terrestrial - simple lung. Most have spiracles and tracheal tubes that take air directly to the muscles. Often have active ventilation. Complex lungs or gills. Active ventilation.
Circulation None (done by diffusion). None. None. Coelomic fluid. No proper blood. Closed blood system. Open blood system and heart. Open blood system and heart. Closed blood system and complex heart.
Asexual reproduction: Budding. Fission. c Regeneration. Bilateral division. If present then by longitudinal division. Shows ability to regenerate. No. No. No.
Sexual reproduction Simple gonads. Hermaphrodite. Sometimes hermaphrodite. Mainly separate sexes in separate individuals. Hermaphrodite. Either hermaphrodite or separate sexes in separate bodies. Either hermaphrodite or separate sexes in separate bodies. Internal fertilisation. Lay eggs. Separate sexes in separate bodies. Lay eggs. Separate sexes in separate bodies. Complex reproductive structures. Lay eggs, or give birth to live young.
Example of species: Hydra oligactis (brown hydra). Class = Hydrozoa. Fasciola hepatica (sheep liver fluke). Class = Trematoda. Ascaris lumbricoides (parasitic roundworm). Class = Ascaridae. Oreasta reticulatus (starfish). Class = Asteroidea. Lumbricus terrestris (earthworm). Class = Oligochaeta. Helix (snail). Class = Gastropoda. Locusta (locust). Class = Insecta. Homo sapiens (human). Class: Mammalia / Bufo Bufo (common toad). Class = Amphibia.







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