04Class 11 Biology
Animal Kingdom short notes
Short notes on how animals are classified and the main features of each phylum, from Porifera to Chordata.
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Basis of classification
- Levels of organisation run from cellular, to tissue, organ, and organ system.
- Symmetry is radial or bilateral. Germ layers are diploblastic or triploblastic.
- A true coelom is lined by mesoderm. Pseudocoelomates have a false coelom, and acoelomates have none.
Non-chordates
- Porifera: sponges with canals and collar cells. Examples: Sycon, Spongilla.
- Coelenterata: cnidoblasts and a polyp or medusa form. Examples: Hydra, Obelia.
- Ctenophora: comb plates, and bioluminescent. Example: Pleurobrachia.
- Platyhelminthes: flatworms with flame cells, and acoelomate. Examples: Taenia, Fasciola.
- Aschelminthes: roundworms with a pseudocoelom. Examples: Ascaris, Wuchereria.
- Annelida: metameric segmentation, with nephridia. Examples: Nereis, earthworm, leech.
- Arthropoda: the largest phylum, with jointed legs and a chitin exoskeleton.
- Mollusca: soft body with a mantle, usually a shell, and a radula. Examples: Pila, Octopus.
- Echinodermata: a water vascular system and spiny skin, with radial symmetry in adults. Examples: starfish, sea urchin.
- Hemichordata: a proboscis, collar and trunk. Example: Balanoglossus.
Chordates
- All have a notochord, a dorsal hollow nerve cord and pharyngeal gill slits at some stage.
- Fish have gills. Cartilaginous fish include sharks, and bony fish include Labeo.
- Amphibians have moist skin and a three-chambered heart. Example: frog.
- Reptiles have dry scaly skin and usually a three-chambered heart, while crocodiles have four chambers.
- Birds have feathers and a four-chambered heart, and they're warm-blooded.
- Mammals have hair and mammary glands, and most give birth to live young.
Where students slip up
- Saying sea stars are bilaterally symmetrical as adults. Their larvae are, but the adults are radial.
- Mixing up flame cells (flatworms) with nephridia (annelids).
- Forgetting crocodiles have a four-chambered heart, unlike most reptiles.
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