Notes of Ch 4 Animal Kingdom| Class 11th Biology

Study Material and Notes of Ch 4 Animal Kingdom Class 11th Biology

Topics in the Chapter


  • Basis of Classification
  • Phylum Porifera
  • Phylum Coelenterata
  • Phylum Ctenophora
  • Phylum Plathyhelminthes
  • Phylum Aschelminthes
  • Phylum Annelida
  • Phylum Arthropoda
  • Phulum Mollusca
  • Phylum Echinodermata
  • Phyum Hemichordata
  • Phylum Chordata
  • Division of Vertebrata
  • Super-class: Pisces
  • Super Class: Tetrapoda

Basis of Classification

→ Animals are classified on the basis of following few fundamental features:

(i) Levels of Organisation:

(a) Cellular level : Cells are arranged as loose cell aggregates.
Example: sponges.

(b) Tissue level : The cells performing the same function are arranged into tissues.
Example: Coelenterates.

(c) Organ level : Tissues are grouped together to form organs, each specialised for a particular function.
Example: platyhelminthes.

(d) Organ system level : Organs are associated to form functional systems like Annelids, Arthropods, Molluscs, Echinoderms and Chordates.
→ Example: Circulatory System.

• Open type: Blood pumped out through heart. Not confined to blood vessels. Cells and tissues aredirectly bathed in it.

• Closed types: Blood is circulated through blood vessels (arteries,veins and capillaries)

(ii) Symmetry

• Asymmetrical: Cannot be divided into equal halves through median plane.
Example: Sponges.

• Radial symmetry: Any plane passing through central axis can divide organism into identical halves. Example: coelentrates,Ctenophores and echinoderms.

• Bilateral symmetry: Only one plane can divide the organism into two identical left and right halves
Example: Annelids and Arthropods.

(iii) 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)
Example: porifers and Coelentrates. (Cnidarians)

• Triploblastic: Three layers present in developing embryo i.e., ectoderm, mesoderm and endoderm.
Example: Platyhelminthes to Chordates.

(iv) Coelom (Body cavity which is lined by mesoderm)

• Coelomates: Have coelom
Example: Annelids, Arthropods, molluscs, Echinoderms, Chordates etc.

• Pseudocoelomates: No true coelem as mesoderm is present in scattered pouches between ectoderm and endoderm.
Example: Aschelminthes.

Acoelomates : Body cavity is absent
Example: Platyhelminthes.

(v) Segmentation 

(A) True Metamerism

→ Found in Annelida,Arthropoda, Chordata.

→ Segmentation is external as well as a internal in Annelids.

→ Segmentation is external in Arthropods.

→ Segmentation is internal in chordates.

• Metamerism: If body is externally and internally divided into segments (metameres) with serial repetition of atleast some organs, then phenomenon is called metamerism.
Example: Earthworm.

(B) Pseudometamerism

→ Found in tapeworm.

→ The proglottids (segments of tapeworm) budded off from neck not emryonic in origin.

(vi) Notochord

→  Rod-like structure formed during embryonic development on the dorsal side.

→ It is mesodermally derived.
Example: Chordates.

→ Non-chordates do not have notochord. Example: porifera to echinoderms.

Phylum Porifera

→ Also called sponges.

→ Are usually marine and asymmetrical.

→ Have cellular level of organisation and diploblastic animals.

→ Food gathering, respiratory exchange and removal of wastes occurs 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 skeleton of spicules or spongin fibres.

→ Animals are hermaphrodite. Fertilisation internal. Development is indirect (i.e., has a larval stage distinct from adult stage)
Example: Sycon, Euspongia.

→ Spongilla (Fresh water sponge)

Phylum Coelenterata

→ Also called Cnidarians.

→ Are usually marine and radially symmetrical.

→ Sessile or free swimming.

→ Have tissue level of organisation.

→ Are diploblastic (with mesogloea)

→ Capture of prey, anchorage and defence occurs through cnidoblasts/cnidocytes (have stinging capsules nematocytes) present on tentacles.

→ Digestion extracellular and intracellular.

→ Have a contral gastro-vascular cavity and an opening, hypostome.

→ Body wall of some composed of calcium carbonate. Example: corals.

→ Exhibit two body forms : polyp and medusa Example: Hydra, Aurelia.

→ Alternation of generation between body forms called metagenesis ocurs in Obelia where :
→ Example: Physalia, Adamsia, Pennatula, Gorgonia,Meandrina.

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 (Property of living organisms to emit light).

→ Hermaphrodite (sexes are not separate).

→ Only sexual reproduction occurs. Exernal fertilization. Indirect development.
Example: Ctenoplana, Pleurobrachia.

Phylum Plathyhelminthes

→ Also called as ‘flat worms’.

→ Have dorsoventrally flattened body. Are mostly endoparasites in animals.

→ Are bilaterally symmetrical, triploblastic, acoelomate,with organ level of orgnisation.

→ Absorb nutrients through body surface.

→ Parasitic forms have hooks and suckers.

→ ‘Flame cells’ help in osmoregulation and excretion.

→ Sexes not separate.

→ Fertilisation internal. Many larval stages present. Planaria has high regeneration capacity. 
Example: Taenia, Fasciola.

Phylum Aschelminthes

→ Also called ‘round worms’.

→ May be free living, parasitic, aquatic or terrestrial.

→ Are bilaterally symmetrical, triploblastic, pseudocoelomate.

→ Alimentary canal complete (has muscular pharynx), wastes removed through excretory pore.

→ Sexes separate. (dioecious)

→ Females longer than males.

→ Fertilisation internal. Development direct or indirect. Example: Ascaris,Wuchereria, Ancylostoma.

Phylum Annelida

→ Are aquatic or terrestrial, free-living or parasitic.

→ Are bilaterally symmetrical, triploblastic, organ-system level of organisation and metamerically segmented body.

→ Are coelomate animals.

→ Have longitudinal and circular muscles for locomation.

→ Have closed circulatory system.

→ Nereis (dioecious and aquatic annelid) has lateral appendages called parapodia for swimming.

→Have nephridia for osmoregulation and excretion.

→ Neural system consists of paired gangila connected by lateral nerves to a double ventral nerve cord.

→ Reproduction is sexual.

→ Example: Earthworm (Pheretima) and Leech (Hirudinaria) which are hermaph
rodites (i.e., monoecious).

Phylum Arthropoda

→ Largest phylum of Animalia.

→ Are bilaterally symmetrical, triplobastic, segmented externally and organ system level of organisation, coelomate.

→ Body divisible into head, thorax, abdomen and has a chitinous exoskeleton. Jointed appendages are present.

→ Respiration by gills, book gills, book lungs or tracheal system. Excretion through malpighian tubules.

Sensory organs: Antennae, eyes; Organs of balance : Statocysts.

→ Fertilisation usaully internal. Development is indirect or direct. Are mostly oviparous.

→ Example: Apis, Bombyx, Laccifer, Anopheles, Culex, Aedes, Locusta, Limulus.

Phulum Mollusca

→ Second largest phylum of Animalia.

→ Terrestrial or aquatic

→ Are bilaterally symmetrical, triplobastic and organ system level of organisation, coelomate.

→ Body vidisble into head, muscular foot and visceral hump and is covered by calcareous shell and is unsegmented.

Mantle: Soft and spongy layer of skin.
Mantle cavity: Space between visceral hump and mantle.

→ Respiration and excretion by feather like gills in mantle cavity.

→ Head has sensory tentacles. Radula-file like rasping organ for feeding in mouth.

→ Are oviparous, dioecious, have indirect development.

→ Example: Plia, Pinctada, Octopus,Sepia, Loligo, Aplysia, Dentalium, Chaetopleura.

Phylum Echinodermata

→ Are spiny bodied organisms with endoskeleton of calcareous ossicles.

→ Are exclusively marine, radially symmetrical in adult but bilaterally symmetrical in larval stage. Organ system level of organisation.

→ Triploblastic and coelomate.

→ Digestive system complete. Mouth ventral, Anus on dorsal side.

→ Food gathering, respiration, locomotion carried out by water vascular system.

→ Excretory system is absent.

→ Reproduction–sexual, sexes are separate.

→ Fertilisation external. Development indirect (free swimming larva)

→ Example: Asterias, Cucumaria, Antedon, Echinus, ophiura.

Phyum Hemichordata

→ Represents small group of worm-like organisms.

→ Was earlier placed as sub-phylum of Phyum Chordata.

→ Bilaterally symmetrical, triploblastic and coelomate with organ system level of organisation.

→ Body cylindrical, has proboscis, collar and trunk.

→ Circulatory System–open.

→ Respiration by gills, excretion by proboscis gland.

→ Sexes separate, external fertiliastion, indrect development.

→ Example: Balanoglossus, saccoglossus.

Phylum Chordata

→ Presence of Notochord.

→ Have dorsal hollow nerve chord.

→ Have paired pharyngeal gill slits.

→ Bilaterally symmetrical, triploblastic, coelomate, organ system level of organisation.

→ Heart is ventral.

→ Post anal tail present, closed circulatory system.

(i) Sub-Phyla Urochordata /Tunicata

→ Notocohord present only in larval tail.
Example: Ascidia, Salpa, Doliolum

(ii) Sub-phyla Cephalochordata

→ Notochord extends from head to tail (Persistent)
Example: Amphioxus.

(iii) Sub-Phyla Vertebrata

→ Have notochord only during embryonic period.

→ Notochord gets replaced by bony or cartilaginous vertebral column.

→ Have ventral muscular heart, kidneys for excretion and osmoregulation, paired appendages (fins or limbs)

Vertebrata have two Division

(i) Agnatha (Lacks Jaw): 

→ Class : Cyclostomata

→ Live as ectoparasites on some fishes.

→ Have sucking and circular mouth withut jaws.

→ Have 6-15 paris of gill slits for respiration.

→ No scales, no paried fins.

→ Cranium and vertebral column is cartilagenous.

→ Marine, Migrate to fresh water for spawning and die after spawning.

→ Larva returns to ocean after metamorphosis.

→ Example: Petromyzon, Myxine

(ii) Gnathostomata (Bear Jaws)

→ Divides into two super classes:
(a) Super Class: Pisces
(b) Super Class: Tetrapoda

(a) Super-class: Pisces

(i) Class: Chondrichthyes 

→ Have cartilagenous endoskeleton, are marine with streamlined body.

→ Mouth ventral.

→ Gill slits withut operculum (gill cover).

→ Skin has placoid scales; jaws–very powerful.

→ No air bladder, so swim constantly to avoid sinking.

→ Teeth are backwardly directed, modified placoid scales.

→ Notochord is persistent throughout life.

→ Two chambered heart; poikilotherms (cold-blooded)

→ Sexes separate; males have claspers on pelvic fins.

→ Internal fertilisation; viviparous.

→ Example: Tarpedo, Trygon, Scoliodon, Pristis, Carcharodon

(ii) Class: Osteichthyes

→ Have bony endoskeleton, Aquatic

→ Mouth is usually terminal. Body-Streamlined

→ Four pairs of gill slits covered by operculum, heart two chambered, cold blooded.

→ Sking has cycloid/ctenoid scales.

→ Have air bladder which regulates buoyancy.

→ Sexes separate.

→ Usually oviparous, fertilisation external.

→ Development direct.

→ Example: Hippocampus, Labeo, Catia, Betla, Clarias, Exocoetus

Sub-Phylum Vertebrata : Gnathostomata

(b) Super Class: Tetrapoda

(i) Class: Amphibia

→ Can live in aquatic as well as terrestrial habitats.

→ Body divisible into head and trunk, paired limbs.

→ Skin moist. No scales.

→ Tympanum represents ear. Eyes have eyelids.

→ Cloaca is the common chamber where alimentary canal, urinary and reproductive tracts open.

→ Respiration by gills, lungs or skin.

→ Heart is 3-chambered; cold-blooded; Sexes separate; fertilisation external.

→ Oviparous. Indirect development.

→ Example: Bufo, Rana, Hyla, Salamandra, Ichthyophis

(ii) Class: Reptilla

→ Creep or crawl to locomote. Mostly terrestrial.

→ Body has dry and cornified skin and epideremal scales or scutes.

→ Tympanum represents ear.

→ Limbs, when present, are two pairs

→ Snakes and lizards shed, scales as skin cast.

→ Heart 3-chambered but 4-chambered in crocodiles.

→ Sexes Separate; fertilisation internal.

→ Oviparous. Direct development.

→ Example: Testudo, Naja, Vipera, Calotes, Crocodilus, Hemidactylus

(iii) Class: Aves

→ Presence of feathers except flihtless birds and beak (modified jaws) without teeth.

→ Forelimbs are modified into wings.

→ Hind limbs have scales, mofidied for walking, swimmng or clasping.

→ Skin is dry as no glands on skin except oil gland (preen gland) at base of tail.

→ Endoskeleton bony with air cavities (pneumatic) and hollow bones to assist in flight.

→ Crop and Gizzard—Additional chamber in digestive tract.

→ Air sacs are connected to lungs to supplement respiration.

→ Warm blooded (homoiothermous), Heart–Four chambered.

→ Oviparous. Direct development.

→ Example: Columba, Struthio, Pavo, Corvus, Neophron, Pstittacula Aptenodytes.

(iv) Class: Mammalia

→ Have mammary glands to nourish young ones.

→ Have two pairs of limbs, adapted to perform special work.

→ Skin has hairs.

→ External ears or, pinna present.

→ Different types of teeth in jaw.

→ Homoiothermous; Heart–Four chambered, Lungs for respiration.

→ Sexes are separate, fertilisation internal.
→ Viviparous. Direct development.

→ Example: Rattus, Canis, Elephas, Equus. Oviparous mammal is Ornithorhynchus.

NCERT Solutions of Class 11 Animal Kingdom

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