CBSE Class 11 Biology Animal Kingdom Notes

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Animal Kingdom Class 11 Biology Revision Notes

Class 11 Biology students should refer to the following concepts and notes for Animal Kingdom in standard 11. These exam notes for Grade 11 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Animal Kingdom Notes Class 11 Biology

4. Animal Kingdom


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.


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.


• 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.

• Development is indirect, with larval stage which metamorphoses to adult. e.g., Sycon, Euspongia.


• 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.


• 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


• 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.


• 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.


• 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.


• 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.


• 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 calledmantle.
• 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.

• 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.

• 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

• 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.


• Notochord present only in tail of larval stage. e.g., Ascidia, Salpa, Doliolium.

• Notochord extends from head to tail. e.g., Amphioxus.
• 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) -

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.

Important Questions for NCERT Class 11 Biology Animal Kingdom


Ques. One of the special characters of coelenterata only is the occurrence of
(a) polymorphism             (b) flame cells
(c) hermaphroditism        (d) nematocysts. 

Answer: D


Ques. Radial symmetry is, usually, exhibited in animals which
(a) are attached to the substratum
(b) have one opening of alimentary canal
(c) live in water
(d) have ciliary mode of feeding. 

Answer: A


Ques. Which of the following is an example of platyhelminthes?
(a) Plasmodium          (b) Schistosoma
(c) Trypanosoma        (d) Wuchereria

Answer: B


Ques. Among the following organisms point out a completely non-parasitic form
(a) Tapeworm              (b) Mosquito
(c) Sea anemone         (d) Leech.

Answer: C


Ques. Tube feet are the characteristic structures of
(a) starfish     (b) jellyfish
(c) crayfish    (d) cuttlefish. 

Answer: A


Ques. Which of the following does not have an open circulatory system?
(a) Frog’s tadpole          (b) Prawn
(c) Chelifer                   (d) Cockroach

Answer: A


Ques. Which is common between ostrich, penguin and kiwi?
(a) Running birds          (b) Migratory birds
(c) Flightless birds        (d) Four toed birds

Answer: C


Ques. Which one assists in locomotion?
(a) Trichocysts in Paramecium
(b) Pedicellariae of starfish
(c) Clitellum in Pheretima
(d) Posterior sucker in Hirudinaria 

Answer: D


Ques. What is true about Taenia saginata?
(a) Life history has pig as intermediate host.
(b) There are two large suckers on scolex.
(c) Rostellar hooks are absent.
(d) Rostellum has double circle of hooks. 

Answer: C


Ques. Which one of the following animals possesses nerve cells but no nerves?
(a) Hydra                     (b) Tapeworm
(c) Earthworm             (d) Frog’s tadpole 

Answer: A


Ques. Budding is a normal mode of asexual reproduction in
(a) starfish and Hydra            (b) Hydra and sponges
(c) tapeworm and Hydra        (d) sponge and starfish.

Answer: B


Ques. Tracheae of cockroach and mammal are similar in having
(a) paired nature                (b) noncollapsible walls
(c) ciliated inner lining        (d) origin from head.

Answer: B


Ques. A larval stage occurs in the life history of all members of the group
(a) frog, lizard and cockroach
(b) Ascaris, housefly and frog
(c) housefly, earthworm and mosquito
(d) butterfly, frog and mosquito. 

Answer: D


Ques. Gorilla, chimpanzee, monkeys and humans belong to the same
(a) species        (b) genus
(c) family          (d) order. 

Answer: D


Ques. What is common in whale, bat and rat?
(a) Absence of neck
(b) Muscular diaphragm between thorax and abdomen
(c) Extra-abdominal testes to avoid high temperature of body
(d) Presence of external ears 

Answer: B


Ques. Aristotle’s lantern occurs in Class
(a) Echinoidea           (b) Asteroidea
(c) Holothuroidea      (d) Ophiuroidea. 

Answer: A


Ques. Starfish belongs to
(a) asteriodea           (b) ophiuroidea
(c) holothuroidea      (d) crinoidea.

Answer: A


Ques. Eye of the molluscan group that resembles vertebrate eye is
(a) bivalvia           (b) gastropoda
(c) pelecypoda      (d) cephalopoda. 

Answer: D


Ques. Adult Culex and Anopheles can be distinguished with the help of
(a) mouth parts/colour     (b) sitting posture
(c) antennae/wings          (d) feeding habits. 

Answer: B


Ques. Sound box of birds is called
(a) pygostyle        (b) larynx
(c) syrinx             (d) synsacrum. 

Answer: C


Ques. Ascaris larva is called
(a) cysticercus     (b) rhabditiform
(c) hexacanth      (d) onchosphere. 

Answer: B


Ques. What is correct about Taenia?
(a) Male organs occur in posterior proglottides.
(b) Male organs occur in anterior proglottides.
(c) Female organs occur in anterior proglottides.
(d) Mature proglottides contain both male and female organs. 

Answer: D


Ques. The simplest type of canal system in porifera is
(a) ascon type      (b) leucon type
(c) sycon type      (d) radial type. 

Answer: A


Ques. An egg laying mammal is
(a) kangaroo     (b) platypus
(c) koala           (d) whale. 

Answer: B


Ques. Kidney of adult rabbit is
(a) pronephros       (b) metanephros
(c) mesonephros    (d) opisthonephros.

Answer: B


Ques. Which one occurs in echinodermata?
(a) Bilateral symmetry      (b) Radial symmetry
(c) Porous body                (d) Soft skin 

Answer: B


Ques. An insect regarded as greatest mechanical carrier of diseases is
(a) Pediculus     (b) Cimex
(c) Musca         (d) Xenopsylla.

Answer: C

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