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Important Notes For NEET Biology - Animal Kingdom

Find below the important notes for the chapter, Animal Kingdom as per the NEET Biology syllabus. This is helpful for aspirants of NEET and other exams during their last-minute revision. Important notes for NEET Biology- Animal Kingdom covers all the important topics and concepts useful for the exam. Check BYJU’S for the full set of important notes and study material for NEET Biology and solve the NEET Biology MCQs to check your understanding of the subject.

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Animal Kingdom

Animals are classified on the basis of common fundamental features like the cellular arrangement, symmetry of the body, presence or absence of the coelom, specific features of the digestive, circulatory and reproductive system

Cellular level of organisation: cells arranged as loose aggregates, present in Porifera (sponges)

Tissue level of organisation: cells performing the same function form tissues, present in coelenterates

Organ level of organisation: tissues grouped together to form an organ, which performs particular function, e.g. Platyhelminthes

Organ system level of organisation: afew organs coordinatively perform a certain physiological function, e.g. Annelids, Arthropods, Molluscs, Echinoderms and Chordates

Open circulatory system: cells and tissue directly receive the blood pumping out of the heart

Closed circulatory system: blood is circulated through arteries, veins and capillaries

Diploblastic: embryo with two germinal layers called external ectoderm and internal endoderm, e.g. Porifera, Cnidaria

Triploblastic: embryo with three germinal layers, mesoderm between ectoderm and endoderm, e.g. Platyhelminthes to Chordates

Asymmetrical: no line of symmetry in the body, e.g. sponges

Radial symmetry: any plane passing through centre divides the body in two symmetrical halves, e.g. coelenterates, ctenophores

Bilateral symmetry: a plane divides the body in symmetrical left and right halves, e.g. annelids, arthropods, etc.

Echinoderms exhibit radial as well as bilateral symmetry at different stages of their life

Body cavity between the body wall and gut wall, lined by mesoderm is called coelom

Acoelomates: body cavity is absent, e.g. Platyhelminthes

Pseudocoelomates: mesoderm is present as scattered pouches, e.g. Aschelminthes

Coelomates: having coelom (body cavity) e.g. from Annelida to Chordata

Earthworm’s body shows metameric segmentation

Animals with notochord are called chordates, animals without notochord are called non-chordates, e.g. Porifera to Echinodermata

Also see: Biology syllabus for NEET

Classification of Animals

Classification of animal kingdom

Classification of the Animal Kingdom based on common fundamental features

Phylum – Porifera (Sponges)

Marine, asymmetrical with the cellular level of organisation

Food intake, gaseous exchange and excretion occurs through the water transport system

Water enters through pores called Ostia and goes out through osculum via central cavity known as spongocoel

Spongocoel is lined by collar cells or choanocytes

Intracellular digestion

Body skeleton is made up of spongin fibres or spicules

Sponges are hermaphrodite

Reproduce asexually by fragmentation and sexually by the formation of gametes

Fertilisation is internal and the development of zygote goes through a distinct larval stage

Examples: Spongilla (freshwater sponge), Euspongia (bath sponge), Sycon,

Phylum – Coelenterata (cnidaria)

Aquatic, sessile or free-swimming, tissue level of organisation, diploblastic and radially symmetrical and acoelomate

The central gastro-vascular cavity has a single opening called hypostome, which is surrounded by sensory tentacles

Cnidoblasts are present on the tentacles, which contain nematocysts

Digestion is extracellular and intracellular

Corals have calcium carbonate skeleton

A polyp is a sessile and cylindrical form, e.g Hydra, Adamsia

Medusa is an umbrella-shaped free-swimming form, e.g. Aurelia (jellyfish)

In some coelenterates, e.g. Obelia alternation of generation (metagenesis) exist. Polyp form produces medusae asexually and medusae produce polyp sexually

Examples: Meandrina (Brain coral), Adamsia (Sea anemone), Gorgonia (Sea-fan), Physalia (Portuguese man of war)

Phylum – Ctenophora (sea walnuts or comb jellies)

Marine, tissue level of organisation, diploblastic and radially symmetrical and acoelomate

Eight rows of ciliated comb plates present externally

Digestion is extracellular and intracellular

Bioluminescence is present

Hermaphrodite

Sexual reproduction, fertilisation is external with indirect development

Examples: Ctenoplana, Pleurobrachia

Phylum – Platyhelminthes (flatworms)

Mostly endoparasites, dorsoventrally flattened body, triploblastic, bilaterally symmetrical, acoelomate with organ level of organisation

Hooks and suckers are present in parasites

Flame cells are present, which help in osmoregulation and excretion

Hermaphrodite or monoecious

Internal fertilisation and indirect development through many larval stages

Planaria can regenerate

Examples: Fasciola (Liver fluke), Taenia (tapeworm)

Phylum – Aschelminthes

Free-living or parasitic, aquatic or terrestrial

Round body in cross-section, bilaterally symmetrical, triploblastic, pseudocoelomate with organ system organisation

The alimentary canal is complete and has a muscular pharynx

Dioecious, females are longer than males

Internal fertilisation with direct or indirect development

Examples: Ascaris (roundworm), Wuchereria (Filarial worm), Ancylostoma (hookworm)

Phylum – Annelida

Bilaterally symmetrical, triploblastic, coelomate, organ system organisation

Metamerically segmented

Longitudinal and circular muscles help in locomotion

Nereis, an aquatic animal has appendages called parapodia, which help in swimming

Closed circulatory system

Nephridia is present for osmoregulation and excretion

Paired ganglia are present, which are connected to double ventral nerve cord by lateral nerves

Reproduction is sexual. Nereis is dioecious, earthworm and leeches are monoecious

Examples: Pheretima (earthworm), Nereis, Hirudinaria (bloodsucking leech)

Phylum – Arthropoda

Largest phylum with two-thirds of all known animals

It contains insects

Bilaterally symmetrical, triploblastic, coelomate, organ system organisation

Their body is covered by chitinous exoskeleton

The characteristic property of the group is jointed legs

Their body can be divided into three regions; head, thorax and abdomen

Respiration is by trachea, gills, book gills, book lungs

The circulatory system is open type

Statocyst or balancing organs are present

Eyes are simple or compound

Malpighian tubules help in excretion

Mostly dioecious, oviparous and fertilisation is internal

Examples: economically important species- Bombyx (silkworm), Apis (honey bee) Vector for diseases- mosquitoes like Anopheles, Aedes, Culex.Living fossil- Limulus (King crab)

Phylum – Mollusca

Bilaterally symmetrical, triploblastic, coelomate, organ system organisation

Unsegmented body covered with a calcareous shell

Distinct head, muscular foot and the visceral hump is present

Respiratory and excretory functions are executed by feather-like gills

The radula is a rasping organ for feeding

They are dioecious, oviparous with indirect development

Examples: Pila (apple snail), Octopus (devilfish), Loligo (squid), Sepia (cuttlefish), Pinctada (pearl oyster)

Phylum – Echinodermata

Adult- radially symmetrical, larvae- bilaterally symmetrical

Triploblastic and coelomate

Endoskeleton of calcareous ossicles

The mouth is present on the ventral side and anus on the dorsal side

The characteristic feature is the presence of Water vascular system, which helps in feeding, locomotion and respiration

Dioecious, external fertilisation with indirect development

Examples: Asterias (starfish), Ophiura (brittle star), Antedon (sea lily), Echinus (sea urchin)

Phylum – Hemichordata

Presence of stomochord, a structure similar to the notochord

Bilaterally symmetrical, triploblastic, coelomate, organ system organisation

Cylindrical body with a proboscis, a collar and a long trunk

Gills are present and circulation is open type

Proboscis gland works as an excretory organ

Dioecious, external fertilisation with indirect development

Examples: Balanoglossus, Saccoglossus

Phylum – Chordata

Characteristic features are a dorsal hollow nerve cord, a notochord and paired gill slits

Bilaterally symmetrical, triploblastic, coelomate, organ system organisation

The circulatory system is closed and the post-anal tail is present

Three subphylums come under Chordata:

Urochordata– notochord present only in the larval tail, e.g. Ascidia, Salpa, Doliolum

Cephalochordata– notochord present throughout life from head to tail, e.g. Branchiostoma (Lancelet or amphioxus)

Vertebrata– Notochord is present in the embryonic stage, it gets replaced by Vertebral Column

Vertebrata is further divided into two divisions

Agnatha (without jaws): Class Cyclostomata

Gnathostomata (with jaws): has two Super Class:

Pisces (bear fins): two Classes- Chondrichthyes, Osteichthyes

Tetrapoda (bear limbs): four classes- Amphibia, Reptilia, Aves and mammals

Watch the below video to know more about Chordates.

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Class I – Cyclostomata (Circular Mouthed Fishes)

Characterised by circular and sucking mouth without jaws

Ectoparasites on fishes

6-15 pairs of gill slits

Scales and fins are absent

Cartilaginous vertebral column and cranium

Closed type circulation

Marine but migrate to freshwater for spawning where they die, larvae after metamorphosis come back to the ocean

Examples: Petromyzon (Lamprey), Myxine (Hagfish)

Class II – Chondrichthyes (Cartilaginous fishes)

Cartilaginous endoskeleton, the mouth is on the ventral side

Gill is without operculum

The notochord is present throughout life

Placoid scales are present on the skin which makes it tough

It swims constantly to avoid sinking as air bladders are absent

Two chambered heart and poikilothermous (cold-blooded)

Separate sexes, internal fertilisation and many are viviparous

Claspers are present on male’s pelvic fin

Electric organs are present in Torpedo and Trygon has poison sting

Examples: Scoliodon (Dogfish), Trygon (Stingray), Pristis (Sawfish), Carcharodon (Great white shark)

Class III – Osteichthyes (Bony fishes)

Streamlined body, bony endoskeleton, 4 pairs of gills with operculum

Skin is covered by cycloid scales

Two chambered heart and air bladder for buoyancy, poikilothermous

Sexes are separate, oviparous, external fertilisation with direct development

Examples: Marine- Hippocampus (Sea horse), Exocoetus (Flying fish)

Freshwater- Labeo (Rohu), Clarias (Magur), Catla (Katla)

Aquarium- Betta (Fighting Fish), Pterophyllum (Angelfish)

Super Class: Tetrapoda

Class IV – Amphibia Class V – Reptilia Class VI – Aves Class VII – Mammalia

Aquatic as well as terrestrial Mostly terrestrial Feathers for flying Mostly terrestrial but few can fly or live in water

Two pair of limbs Limbs are absent or two pairs Forelimb modified into wings, hindlimbs modified for walking, swimming, clasping etc. Two pair of limbs

Skin is moist and scales are absent Dry cornified skin with scales or scute Dry skin with only oil glands at the base of the tail, pneumatic bones Skin is hairy, mammary glands to feed the young one

Respiration by gills, skin or lungs The respiratory organ is lungs The respiratory organ is lungs The respiratory organ is lungs

3 chambered heart, poikilotherms 3 chambered heart, Poikilotherms

4 chambered heart in crocodiles

4 chambered heart, homeotherms (warm-blooded) 4 chambered heart, homeotherms (warm-blooded)

Oviparous Oviparous Oviparous VIviparous

Platypus- Oviparous

Sexes are separate, external fertilisation with indirect development Sexes are separate, internal fertilisation with direct development Sexes are separate, internal fertilisation with direct development Sexes are separate, internal fertilisation with direct development

Frog, Salamander, Ichtthyophis (limbless salamander) Crocodile, Alligator, Chameleon, Naja, Viper Birds (crow, pigeon, parrot, etc.), ostrich (flightless bird) Kangaroo, cat, lion, Blue whale, Dolphin