4. 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
bychoanocytes (collar cells).
• Body wall has spicules and spongin fibers.
• Animals are hermaphrodite.
• Fertilization internal.
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, • 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
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.
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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
bychoanocytes (collar cells).
• Body wall has spicules and spongin fibers.
• Animals are hermaphrodite.
• Fertilization internal.
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, • 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
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.
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