ANIMAL KINGDOM

POINTS TO REMEMBER :


Levels of organization :

  • Cellular level
  • Tissue level
  • Organ level
  • Organ system level

Circulatory System :

Open type: Blood pumped out through heart. Cells and tissues are directly bathed in it.

Closed type: Blood is circulated through vessels.

Symmetry :

  • Asymmetrical: Cannot be divided into equal halves through median plane. e.g., Sponges.
  • Radial symmetry: Any plane passing through central axis can divide organism into equal halves. e.g., Hydra.
  • Bilateral symmetry: Only one plane can divide the organism into equal halves. e.g., Annelids and Arthropods.

CLASSIFICATION ON BASIS OF GERMINAL LAYERS :

  • Diploblastic: Cells arranged in two embryonic layers i.e. external ectoderm and internal endoderm. (Mesoglea may be present in between ectoderm and endoderm) e.g., Coelenterates. (Cnidarians)
  • Triploblastic: Three layers present in developing embryo i.e., ectoderm, endoderm and mesoderm. e.g., Chordates.
  • Coelom (Body cavity which is lined by mesoderm)
  • Coelomates: Have coelom e.g., Annelids, Chordates etc.
  • Pseudocoelomates: No true coelom as mesoderm is present in scattered pouches between ectoderm and endoderm. e.g., Aschelminthes.
  • Acoelomates: Body cavity is absent. E.g. Platyhelminthes.
  • Metamerism: If body is externally and internally divided into segments with serial repetition of at least some organs then phenomenon is called metamerism.        e.g., Earthworm.
  • Notochord: Rod-like structure of mesodermal origin, formed during embryonic development on the dorsal side.  e.g., Chordates.

PHYLUM PORIFERA :

  • Also called sponges.
  • Are usually marine and asymmetrical.
  • Have cellular level of organization.
  • Food gathering, respiratory exchange and removal of wastes occur through water canal system.
  • Digestion intracellular.
  • Ostia (minute pores on body), spongocoel (body cavity) and osculum help in water transport. They are lined by choanocytes (collar cells).
  • Body wall has spicules and spongin fibers.
  • Animals are hermaphrodite.
  • Fertilization internal.
  • Development is indirect, with larval stage which metamorphoses to adult. e.g., Sycon, Euspongia.

PHYLUM COELENTERATA :

  • Also called Cnidarians.
  • Are usually marine and radially symmetrical.
  • Sessile or free-swimming.
  • Have tissue level of organization
  • Diploblastic.
  • Presence of cnidoblast, for anchorage, defense and capture of prey.
  • Central body cavity called gastro-vascular cavity or coelenterone.
  • Digestion extracellular and intracellular.
  • Blind sac type body plan, with one opening called hypostome.
  • Body wall composed of calcium carbonate.
  • Exhibit two body forms: polyp and medusa e.g., Hydra, Aurelia.
  • Alternation of generation between body forms called Metagenesis occurs in Obelia where Medusa sexually   reproduced and polyp asexually reproduced. •e.g., Physalia, Adamsia.

PHYLUM CTENOPHORA :

  • Also called as sea walnuts or comb jellies.
  • Are exclusively marine, radially symmetrical.
  • Have tissue level organisation, are diploblastic.
  • Digestion both extra and intracellular.
  • Body has eight external rows of ciliated comb plates for locomotion.
  • Show Bioluminescence (living organism emit light).
  • Sexes are not separate i.e. hermaphrodite.
  • Reproduce only by sexual methods.
  • External fertilization.
  • Indirect development

e.g., Ctenoplana. Pleurobranchia

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
Email Id : [email protected]