PHYLUM PLATYHELMINTHES :
- Also called as ‘flat worms’.
- Have dorsoventrally flattened body.
- Mostly endoparasites in animals including human.
- Bilaterally symmetrical,
- Triploblastic
- Acoelomate
- Organ level organization.
- Absorb nutrients through body surface.
- Parasite forms have hooks and suckers.
- ‘Flame cells’ help in osmoregulation and excretion.
- Fertilization internal. Many larval stages.
- Planaria has high regeneration capacity.
e.g., Taenia, Fasciola.
PHYLUM ASCHELMINTHES :
- Also called ‘round worms’.
- May be free living, parasitic, aquatic or terrestrial.
- Are bilaterally symmetrical, triploblastic, Pseudocoelomates.
- Alimentary canal complete (has muscular pharynx), wastes removed through excretory pore.
- Organ system level of organization.
- Sexes separate i.e. dioecious.
- Shows sexual dimorphism.
- Females longer than males.
- Fertilisation internal.
- Development direct or indirect.
e.g., Ascaris, Wuchereria.
PHYLUM ANNELIDA :
- Are aquatic or terrestrial, free-living or parasitic.
- Are bilaterally symmetrical, triploblastic,
- Organ-system level of organization
- Metamerically segmented body.
- Have longitudinal and circular muscles in body wall for locomotion.
- Aquatic annelid like Nereis has oar shaped parapodia for movement.
- Have nephridia for osmoregulation and excretion.
- Nervous system consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
- Circulatory system is closed type.
- Earthworm (Pheretima) and Leech (Hirudinaria) which are hermaphrodites (i.e., monoecious).
- Nereis an aquatic form is dioecious.
- Fertilization is external
- Development is direct or indirect.
PHYLUM ARTHROPODA :
- Largest phylum of Animalia includes insects.
- Are bilaterally symmetrical, triploblastic and organ system level of organization, coelomate and segmented body.
- Body divisible into head, thorax, abdomen.
- Body covered by a chitinous exoskeleton.
- They have jointed appendages.
- Respiration by gills, book gills, lungs or tracheal system.
- Circulation is open type.
- Excretion through malpighian tubules.
- Sensory organs: Antennae, eyes; Organs of balance: Statocysts.
- Mostly dioecious.
- Fertilisation internal.
- Are mostly oviparous.
- Development is indirect or direct. e.g., Apis, Bombyx, Anopheles, Locusta, Limulus.
PHYLUM MOLLUSCA :
- Second largest phylum of Animalia.
- Terrestrial or aquatic.
- Are bilaterally symmetrical, triploblastic and organ system level of organization, coelomate.
- Body divisible into head, muscular foot and visceral hump and is covered by a soft and spongy layer of skin called mantle.
- Unsegmented body.
- Body is covered by calcareous shell.
- Respiration and excretion by feather like gills (ctenedium) in mantle cavity.
- Head has sensory tentacles. Radula-file like rasping organ for feeding.
- Usually dioecious, dioecious, have indirect development.
e.g., Pila, Pinctada, Octopus.
PHYLUM ECHINODERMATA :
- Are spiny bodied organisms.
- Endoskeleton of calcareous ossicles.
- Are exclusively marine.
- Radially symmetrical in adult but bilaterally symmetrical in larval stage.
- Organ system level of organization.
- Triploblastic and eucoelomate.
- Digestive system complete. Mouth ventral, Anus on dorsal side.
- Food gathering, respiration, locomotion carried out by water vascular system.
- Excretory system is absent.
- Dioecious i.e. sexes are separate.
- Fertilization external. Development indirect (free swimming larva)
e.g., Asterias, Cucumaria.
