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  • Animal kingdom

    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
    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.
    PHYLUM HEMICHORDATA :
    • Have small worm-like marine animals.
    • Was earlier placed as sub-phylum of Phylum Chordata.
    • Bilaterally symmetrical, triploblastic and coelomate.
    • Body cylindrical, has proboscis, collar and trunk.
    • Circulation is open type.
    • Respiration by gills
    • Excretion by proboscis gland.
    • Sexes separate, external fertilization, indirect development.
    e.g., Balanoglossus

  • #2
    PHYLUM CHORDATA :
    • Presence of Notochord (between gut and nerve cord)
    • Have dorsal hollow nerve chord.
    • Have paired pharyngeal gill slits.
    • Heart is ventral.
    • Post anal tail present.
    • Bilaterally symmetrical, triploblastic, and coelomate with organ system level of organization.
    • Circulation is closed type.
    SUB-PHYLA UROCHORDATA :
    • Notochord present only in tail of larval stage. e.g., Ascidia, Salpa, Doliolium.
    SUB-PHYLA CEPHALOCHORDATA :
    • Notochord extends from head to tail. e.g., Amphioxus.
    SUB-PHYLA VERTEBRATA :
    • Have notochord only during embryonic period.
    • Notochord gets replaced by bony or cartilaginous vertebral column.
    • Have ventral muscular heart with two, three or four chambered.
    • Paired appendages which may be fins or limbs.
    • Kidneys for excretion and osmoregulation.
    Division Agnatha (lack jaws) -
    Class: Cyclostomata :
    • Have sucking and circular mouth without jaws.
    • Live as ectoparasites on some fishes.
    • Devoid of scales, no paired fins.
    • Cranium and vertebral column is cartilaginous.
    • Marine habit but migrates to fresh water for spawning and die after spawning.
    • Larva returns to ocean after metamorphosis.
    e.g., Petromyzon.
    Division Gnathostomata (Bear Jaws) -
    SUPER-CLASS: PISCES -
    Class 1: Chondrichthyes :
    • Have cartilaginous endoskeleton.
    • Mouth ventrally located.
    • Notochord persists throughout life.
    • Gill slits are separate and without operculum.
    • Skin has placoid scales.
    • Jaw contains teeth, which are modified placoid scales.
    • Mostly predaceous.
    • Swim bladder absent.
    • Heart is two chambered. (one auricle and one ventricle)
    • Some of them contain electric organs ( e.g. Torpedo)
    • Some possesses poison sting. ( e.g. Trygon)
    • Poikilotherm or cold blooded.
    • Dioecious.
    • Sexually dimorphic, male’s pelvic fin bears claspers.
    • Fertilization internal.
    • Many of them viviparous.
    e.g., Torpedo, Trygon, Scoliodon.
    Class 2 : Osteichthyes :
    • Includes both marine and fresh water fishes.
    • Bony endoskeleton.
    • Mouth is usually terminal.
    • Four pairs of gill slits covered by operculum.
    • Skin has cycloid/ctenoid scales.
    • Air bladder is present for buoyancy.
    • Heart is two chambered.
    • Cold blooded animals.
    • Dioecious.
    • Sexually monomorphic.
    • Fertilization external.
    • Mostly oviparous
    • Development is indirect.
    e.g., Hippocampus, Labeo, Catla, Betta.

    SUPER CLASS: TETRAPODA -
    Class-1: Amphibia
    • Can live in aquatic as well as terrestrial habitats.
    • Most of them have two pairs of limbs.
    • Body divisible into head and trunk.
    • Skin moist, without scales.
    • Tympanum represents ear.
    • Cloaca is the common chamber where alimentary, urinary and reproductive tracts open.
    • Respiration by gills, lungs or skin.
    • Heart is 3-chambered.( two auricle and one ventricle)
    • Cold blooded animals.
    • Sexes separate.
    • Fertilization is external and requires water.
    • Oviparous. Indirect development.
    • e.g., Bufo, Rana, Hyla.
    Class - 2: Reptilia
    • Creeping or crawling mode of locomotion.
    • Body has dry and cornified skin and epidermal scales or scutes.
    • Tympanum represents ear.
    • Limbs when present are two pairs.
    • Mostly three chambered heart but 4-chambered in crocodiles.
    • Snakes and lizards shed scales as skin cast.
    • Poikilotherm.
    • Sexes are separate.
    • Fertilization internal.
    • Oviparous. Direct development.
    • e.g., Testudo, Naja, Vipera, Calotes.
    Class - 3: Aves
    • Presence of feathers and most cay fly except flightless bird like ostrich.
    • Jaw modified to beak without teeth.
    • Forelimbs are modified into wings.
    • Hind limbs have scales.
    • No glands on skin except oil gland at base of tail.
    • Endoskeleton bony with air cavities (pneumatic) and hollow bones to assist in flight.
    • Digestive tract has additional chambers like crop and gizzard.
    • Heart is four chambered.
    • Homoiothermous or warm blooded, able to maintain constant temperature.
    • Air sacs are connected to lungs to supplement respiration.
    • Oviparous. Direct development.
    • e.g., Columba, Struthio, Corvus.
    Class- 4: Mammalia
    • Have mammary glands to nourish young ones by secreting milk.
    • Have two pairs of limbs.
    • Skin has hairs.
    • External ears or pinna present.
    • Different types of teeth in jaw.
    • Heart is four chambered.
    • Homoiothermous.
    • Respiration by lungs.
    • Sexes separate, fertilization internal.
    • Viviparous or oviparous. Direct development.
    e.g., Rattus, Canis Elephas, Equus. Oviparous mammal is Ornithorhynchus.'

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