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Porifera

Porifera. With pores, sessile, asymetric, diploblastic Cells- outer pinacoderm, middle- amoebocytes and inner-choanocytes Skeleton- spicules and spongin fibres Water canal system Eg: Sycon, Spongilla ( Fresh Water sponge), Euplectella ( Glass sponge). Phylum Cnidaria.

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Porifera

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  1. Porifera • With pores, sessile, asymetric, diploblastic • Cells- outer pinacoderm, middle- amoebocytes and inner-choanocytes • Skeleton- spicules and spongin fibres • Water canal system • Eg: Sycon, Spongilla ( Fresh Water sponge), Euplectella ( Glass sponge)

  2. Phylum Cnidaria

  3. General Characteristics • They are radially symmetrical; oral end terminates in a mouth surrounded by tentacles. • They have 2 tissue layers • Outer layer of cells - the epidermis • Inner gastrodermis, which lines the gut cavity or gastrovascular cavity (gastrodermis secretes digestive juices into the gastrovascular cavity) • In between these tissue layers is a noncellular jelly-like material called mesoglea

  4. Cnidarian Body Plans • Polyp form • Tubular body, with the mouth directed upward. • Around the mouth are a whorl of feeding tentacles. • Only have a small amount of mesoglea • Sessile • Medusa form • Bell-shaped or umbrella shaped body, with the mouth is directed downward. • Small tentacles, directed downward. • Possess a large amount of mesoglea • Motile, move by weak contractions of body

  5. Nutrition • Cnidarians are carnivores with hydras and corals consuming plankton and some of the sea anenomes consuming small fishes • They use they tentacles to capture prey and direct it toward the mouth so that it can be digested in the gastrovascular cavity via secretions from gland cells (extracellular digestion); some food is phagocytized by special cells and digestion occurs intracellularly • The gastrovascular cavity exists as 1 opening for food intake and the elimination of waste • There is no system of internal transport, gas exchange or excretion; all these processes take place via diffusion

  6. Alternation of generation • Mouth or hypotostome present • Ctenophora: Comb jellies • diploblastic, tissue level organisation • An outer epidermis, mesoglea with amoebocytes, and • An inner gastrodermis • Colloblasts- on epidermis of tentacles- for prey capture • locomotion- cilia with comb plates for nutrition • Eg: CtenoplanaHormephora

  7. Platyhelminthes: Flat worms • unsegmented, bilateral symmetry, triploblastic • Acoelomate, organ system level of organisation • Suckers and hooks for holding the intestine of host • Incomplete gun – only mouth present, no anus • Excretion- Flame cells • Regeneration capacity high in Planarians • Eg; Taeniasolium, Fasciola hepatica

  8. NEMATHELMINTHES - Round worms / thread worms • Bilateral symmetry, Triploblastic , pseudo coelomate • Alimentary canal- complete with muscular pharynx • No respiratory and circulatory system • muscles- Circular and longitudinal • Sex- seperates; male shorter than female • Fertilisation – internal • Ascaris, Wuchereria, Ancylostoma ( Hook worm)

  9. Annilida : Annullus: little ring • Triploblastic, bilateral symmetry, coelomate • Metamerism • Muscles- longitudinal and circular • Digestion – complete • Excretion- nephridia; circulation- closed • Some are bisexual • Development- indirect through Trocophore larva • Eg; Pheritima, Tubifex ( blood worm), Neries

  10. Arthropoda • Body – Head, thorax and abdomen • Jointed appendages, antennae, eyes ( ommatidia) and statocysts • Digestive system is complete • Chitin ; undergoes Ecdysis/ moulting • Respiration- Gills/ trachea/ Book lungs/ / Book Gills • Excretion- Malphigian tubules/ nephridia • Fertilisation- internal , oviparous • Apis , Bombyx, Laccifer, Anopheles, culex, locusts, Limulus

  11. Mollusca ( soft body) • Body- Head, Visceral mass , muscular foot • Radula- rasping organ • Body wall – with mantle- secretes shell • Digestion – complete; excretion- nephridia • Unisexual, external fertilisation, oviparous • Indirect development- Veliger, trocophore and Golchidium larvae

  12. Echinodermata • Endoskeleton- calcarious plates with spines • larvae- bilateral sym and adults- radial sym • Water vascular system with tube feet, radial canals– excretion, circulation • High regeneration capacity • development- indirect: Plateus, bipinnaria and auricularia

  13. Hemichordata • Body- Proboscis, collar and trunk • proboscis- Ciliated for collecting food • Mouth- between proboscis and collar • Stomochord- similar to notochord • Excretion- proboscis gland • Reproduction- sexual, dev- indirect ( tornaria)

  14. Chordata • Protochordata • Includes tunicates ( urochordates) and Cephalochordates • Tunicates- notochord and nerve chord present only in larva • Cephalochordates- nerve chord and notochord persistant • Vertebrata • Notochord replaced by vertebral column • Respiration – gills/lungs • Circulation – closed • -Includes Agnatha and Gnathosomata

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