CBSE CLASS 11 CHAPTER 4 NOTES

 

CHAPTER 4

CBSE BIOLOGY
CLASS 11

CHAPTER 4

ANIMAL KINGDOM

INTRODUCTION

·        When we look around – we find different animals – with different structures & forms

·        Over a million animal species – described till now

·        Need for classification – important

·        Classification – helps in assigning systematic position – to newly described species

BASIS OF CLASSIFICATION

·        Through structure & forms are different – in different animals

·        Fundamental features like – arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems – common to various individuals

·        These features – used as basis – for animal classification

LEVEL OF ORGANISATION

·        All members of Animalia – multicellular

·        But they donot have – same pattern of organisation of cells

·        Examples

·        (i) Sponges – cells are arranged loosely – as cell aggregates – exhibit cellular level of organisation

o   Division of labour – among cells

·        (ii) Coelenterates – arrangement of cells is complex

o   Cell – performing same function – arranged into tissues

o   Exhibit – tissue level of organisation

·         (iii) Platyhelminthes & other higher phyla – tissues grouped to form organs

o   Each organ – perform specialised function

o   Exhibition – organ level of organisation

·        (iv) Animals like – Annelids, Arthropods, Molluscs, Echinoderms & Chordates – organs associate to form functional systems

o   Each system – perform specific physiological function

o   Exhibit – organ system level of organisation

o   Organ system – differ in complexities – in different animal groups

o   Eg: Platyhelminthes – single opening outside the body – serves as both mouth & anus – incomplete digestive system

o   Higher animals – has 2 openings – mouth & anus – complete digestive system

CIRCULATORY SYSTEM

·        Circulatory system – 2 types

o   OPEN TYPE

§  Blood pumped out of heart

§  Cells & tissues – directly bathed in it

o   CLOSED TYPE

§  Blood circulated through blood vessels of varying diameters

§  Arteries, veins & capillaries

SYMMETRY

·        Animals – categorised based on symmetry

·        3 types

·        (i) ASSYMETRY

o   Any plane that passes through the centre – does not divide them into equal halves

o   Eg: Sponges

·        (ii) RADIAL SYMMETRY

o   Any plane – passing through central axis of the body – divides the organism into 2 equal halves – called radial symmetry

o   Eg: Coelenterates, Etenophores & Echinoderms

·        (iii) BILATERAL SYMMETRY

o   Animal body – can be divided into 2 identical left & right halves – only through one plane – Bilateral symmetry

o   Eg: Annelids, Arthropods, etc.,

DIPLOBLASTIC & TRIPLOBLASTIC ORGANISATION

·        (i) DIPLOBLASTIC

o   Animals in which – cells are arranged – in 2 embryonic layers – (i) ectoderm (external layer) (ii) endoderm (internal layer) – called diplomatic animals

o   Eg: Coelentrates

o   An undifferentiated layer – Mesoglea – present between ectoderm & endoderm

·        (ii) TRIPLOBLASTIC

o   Animals in which – developing embryo has – 3 germinal layers – called triphoblastic animals

o   3 germinal layers – ectoderm, mesoderm & endoderm

o   Eg: Platyhelminthes to chordates – triploblastic animals

COELOM

·        Presence or absence of cavity – between body wall & gut wall – very important for classification

·        Body cavity – lined by mesoderm – called coelom

·        (i) Coelomates

o   Animals having coelom

o   Eg: Annelids, molluscs, arthropods, echinoderms, hemichordates & chordates

·        (ii) Pseudo coelomates

o   Animals in which body cavity – not lined by mesoderm

o   Instead, mesoderm present as scattered pouches – between ectoderm & endoderm – called pseudocoelom

o   Eg: Aschelminthes

·        (iii) Acoelomates

o   Animals in which – body cavity is absent – called acoelomates

o   Eg: Platyhelminthes

SEGMENTATION

·        In some animals – body externally & internally – divided into segments

·        Some organs – repeat serially

·        Eg: Earthworm – body shows metameric segmentation – phenomenon called metamerism

NOTOCHORD

·        Notochord – mesodermally derived rod-like structure

·        Formed on dorsal side – during embryonic development – in some animals

·        Animals with notochord – chordates

·        Animals without notochord – non-chordates

·        Eg: Porifera to Echinoderms

CLASSIFICATION OF ANIMALIA

 

PHYLUM – PORIFERA

·        Members – commonly known – sponges

·        Marine animals

·        Asymmetrical

·        Primitive multicellular; cellular level of organisation

·        Sponges – water transport or canal system – present

·        Water enters – minute pores (Ostia) in body wall – into central cavity (spongocoel) – then goes to osculum

·        Pathway of water – helps in food gathering, respiratory exchange & waste removal

·        Choanocytes or collor cells – line spongocoel & canals

·        Digestion – intracellular

·        Body supported by – skeleton – made up of spicules or spongin fibres

·        Sexes – not separate (Hermophrodite)

·        I.e., Eggs& sperms – produced by same individuals

·        Asexual reproduction – by fragmentation

·        Sexual reproduction – by gamete formation

·        Fertilisation – internal; development – indirect – have larval stage – distinct from adult

·        Eg: Sycon (Scypha), Spongilla (Fresh water sponge) & Euspongia (Bath sponge)

 

PHYLUM – COELENTERATA (CNIDARIA)

·        Aquatic, mostly marine, sessile or free-swimming

·        Radially symmetrical

·        Name Cnidaria – derived from – Cnidoblasts or cnidocytes – contains stinging capsules or nematocytes – on tentacles & the body

·        Cnidoblasts – used for Anchorage, defence & capturing prey

·        Exhibit – tissue level organisation

·        Diploblastic

·        Have central gastro-vascular cavity – with single opening (hypostome)

·        Digestion – extracellular & intracellular

·        Some cnidarians (Eg: Corals) – skeleton composed of – calcium carbonate

·        Have 2 basic body forms

·        (i) Polyp – sessile, cylindrical – Eg: Hydra, Adamsia, etc.,

·        (ii) Medusa – umbrella shaped & free-swimming  - Eg: Aurelia or jelly fish

·        Some Cnidarians – exist in both forms – shows alternation of generation (Metagenesis)

·        I.e., Polyps – produce Medusa’s asexually; Medusa’s – form polyps sexually. Eg: Obelia

·        Example for Coelenterates – Physalia (Portuguese mon-of-war), Adamsia (Sea Anemone), Pennatula (Sea-pen), Gorgonia (Sea fan) & Meandrina (Brain Coral)

 

PHYLUM - CTENOPHORA

·        Commonly called – Sea walnuts or comb jellies

·        Exclusively marine

·        Radially symmetrical

·        Diploblastic

·        Tissue level of organisation

·        Body bears – 8 external rows of ciliated Comb plates  - helps in locomotion

·         Digestion – extracellular & intracellular

·        Bioluminescence – property of living organism to emit light – seen in Ctenophores

·        Sexes – separate

·        Reproduction – only sexual

·        Fertlilization – external ; devolopment – indirect

·        Eg: Pleurobrachia & Ctenoplana

 

PHYLUM - PLATYHELMINTHES

·        Dorso-ventrally flat body – called flat worms

·        Mostly endoparasites – found in animals including human being

·        Bilaterally symmetrical

·        Triploblastic

·        Acoelomate

·        Organ level of organisation

·        Hooks & suckers – present in parasitic forms

·        Some parasites – absorb nutrition directly from host – through body surface

·        Specialised cells – flame cells – helps in Osmoregulation & excretion

·        Sexes – not separate

·        Fertilization – internal

·        Development – through many larval stages

·        Some members – Eg: Planaria – possess high regeneration capacity

·        Eg: Taenia (Tapeworm), Fasciola (Liver fluke)

 

PHYLUM – ASCHELMINTHES

·        Body – circular in cross-section – called round worm

·        May be free living, aquatic & terrestrial – or parasitic in plants & animals

·        Organ-system level of organisation

·        Bilaterally symmetrical

·        Triploblastic

·        Pseudocoelomate

·        Alimentary canal – complete – with well developed muscular pharynx

·        Excretory tube – removes body waste – from body cavity – through excretory pore

·        Sexes – separate (Dioecious) – male & female – distinct

·        Females – often longer than males

·        Fertilisation – internal; development – may be direct (young ones resemble adult) or indirect

·        Eg: Ascaris (Round worm), Wuchereria (Filaria worm), Ancylostoma (Hook worm)

 

PHYLUM - ANNELIDA

·        May be aquatic (marine & fresh water) or terrestrial

·        Free living; sometimes parasitic

·        Organ-system level of organisation

·        Bilateral symmetry

·        Triploblastic

·        Metamerically segmented

·        Coelomate animals

·        Body surface – has distinct segments or metamers

·        Latin, annulus: little ring – hence the name Annelida

·        Have longitudinal & circular muscles – helps in locomotion

·        Aquatic Annelids (Nereis) – have lateral appendages – parapodia – helps in swimming

·        Closed circulatory system – present

·        Nephridia (sing. Nephridium) – helps in osmoregulation & excretion

·        Neural system – paired ganglia (sing. Ganglion) – connected by lateral nerves – to a double ventral nerve cord

·        Nereis (aquatic form) – dioecious

·        But Earthworm & leeches – monoecious

·        Reproduction – sexual

·        Eg: Nereis, Pheretima (Earthworm) & Hirudinaria (blood sucking leech)

 

PHYLUM - ARTHROPODA

·        Largest phylum of Animalia

·        Includes insects

·        Over 2/3^rd of all named species on earth – Arthropods

·        Organ-system level of organisation

·        Bilaterally symmetrical

·        Triploblastic

·        Segmented & coelomate  

·        Body – covered by chitinous exoskeleton

·        Body – head, thorax & abdomen

·        Have jointed appendages

·        Anthros – joint; poda – appendages

·        Respiratory organs – gills, book gills, book lungs or tracheal system

·        Circulatory system – open type

·        Sensory organs – antennae, eyes (compound & simple), statocysts or balance organs – present

·        Excretion – through malphighian tubules

·        Mostly dioecious

·        Fertilisation – usually internal

·        Mostly oviparous

·        Development – may be direct or indirect

·        Eg: Economically important insects – Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect)

·        Vectors – Anopheles, Culex & Aedes (Mosquitoes)

·        Gregarious pest – Locusia (Locust)

·        Living fossil – Limulus (King Crab)

 

PHYLUM - MOLLUSCA

·        Second largest animal phylum

·        Terrestrial or aquatic (marine or fresh water)

·        Organ-system level of organisation

·        Bilaterally symmetrical

·        Triploblastic & coelomate

·        Body – covered by – calcareous shell

·        Unsegmented body – have distinct head, muscular foot & visceral hump

·        Soft & spongy layer of skin – forms mantle over visceral hump

·        Space between hump & mantle – called mantle cavity – in which feather-like gills are present

·        Have respiratory & excretory functions

·        Anterior head – has sensory tentacles

·        Mouth – file-like rasping organ (Radula) – helps feeding

·        Usually dioecious & oviparous

·        Development – indirect

·        Eg: Pila (Apple snail), Pintada (Pearl Oyster), Sepia (Cuttle fish), Loligo (Squid), Octopus (Devi fish), Aplysia (Sea Hare), etc.,

 

PHYLUM - ECHINODERMATA

·        Have exoskeleton – made of calcareous ossicles – hence named Echinodermata (spiny bodied)

·        All are marine

·        Organ-system level of organisation

·        Adult Echinoderms – radially symmetrical

·        Larvae – bilaterally symmetrical

·        Triploblastic & Coelomate

·        Digestive system – complete – with mouth on lower side (ventral) – Anus on upper side (Dorsal)

·        Most distinctive feature – presence of water vascular system – helps in locomotion, capture & transport of food & respiration

·        Excretory system – absent

·        Sexes – separate

·        Reproduction – sexual

·        Fertilisation – usual external

·        Development – indirect – with free-swimming larva

·        Eg: Asterias (Star fish), Echinus (Sea Urchin), Antedon (Sea Lily), Cucumaria (Sea cucumber) & Ophiuna (Bottle star) 

 

PHYLUM - HEMICHORDATA

·        Hemichordata – earlier considered as a sub-phylum – under phylum chordata

·        Now – placed as a separate phylum – under non-chordata

·        Phylum consists of – small group of worm-like marine animals

·        Organ-system level of organisation

·        Coelomate animals

·        Body – cylindrical

·        Body has – anterior proboscis, a collor & a long trunk

·        Circulatory system – open type

·        Respiration – through gills

·        Excretory organ – proboscis gland

·        Sexes – separate

·        Fertilisation – external

·        Development – indirect

·        Eg: Balanoglossus & Saccoglossus

 

PHYLUM - CHORDATA

·        Characterised by – presence of notochord, a dorsal hollow nerve cord & paired pharyngeal gill slits

·        Bilaterally symmetrical

·        Triploblastic & Coelomate

·        Organ-system level of organisation

·         posses post anal tail

·        Circulatory system – closed

·        Phylum Chordata – divided into 3 sub phyla – Urochordata or Tunicata, Cephalochordata and Vertebrata

·        Subphyla Urochordata & Cephalochordata – often referred to as protochordata – exclusively marine

·        In Urochordata – notochord present – only in larval tail

·        Cephalochordata – notochord – extends from head to tail – persistent throughout their life

·        Eg: Urochordata – Ascidia, Salpa, Doliolum

·        Cephalochordata – Branchiostoma (Amphioxus or Lancelet)

 

SUB PHYLUM – VERTEBRATA

·        Possess notochord – during embryonic period

·        In adult – notochord replaced by – cartilaginous or bony vertebral column

·        Thus vertebrates are chordates – but all chordates are not Vertebrata

·        Vertebrates – also have muscular heart – with 2,3 or 4 chambers

·        Kidneys – excretion & osmoregulation

·        Have paired appendages – may be fins or limbs

 

CLASS - CYCLOSTOMATA

·        Members – ectoparasites on some fishes

·        Have an elongated body – bearing 6-15 pairs of gill slits – for respiration

·        Have sucking & circular mouth – without jaws

·        Body – devoid of scales & paired fins

·        Cranium & vertebral column – cartilaginous

·        Circulation – closed type

·        Generally marine – but migrate to fresh water for spawning

·        After spawning – within few days – die

·        Larvae – after metamorphosis – return to ocean

·        Eg: Petromyzon (Lamprey) & Myxine  (Hagfish)

 

CLASS - CHONDRICHTHYES

·        Marine animals

·        Body – streamlined

·        Have cartilaginous endoskeleton

·        Mouth – ventral side

·        Notochord – persistent throughout life

·        Gill slits – separate, without operculum (gill cover)

·        Skin – tough containing placoid scales

·        Teeth – modified placoid scales – backwardly directed

·        Jaws – very powerful; predacious

·        Air bladder – absent; so they swim constantly – to avoid sinking

·        Heart – 2 chambered – one auricle, one ventricle

·        Some have – electric organs (Eg: Torpedo)

·        Some have poison sting (Eg: Trygon)

·        Poikilothermous animals – cold blood – i.e., lack capacity to regulate body temperature

·        Sexes – separate

·        Males – pelvic fins bears claspers

·        Fertilisation – internal; viviparous

·        Eg: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (great white shark), Trygon (String ray)

 

CLASS - OSTEICHTHYES

·        Includes – marine & fresh water fishes with bony endoskeleton

·        Body – streamlined

·        Mouth – mostly terminal

·        4 pairs of gills – covered by operculum on each side

·        Skin – covered by – cycloid / ctenoid Scales

·        Air bladder present – regulates buoyancy

·        Heart – 2 chambered (one auricle, one ventricle)

·        Cold-blooded animals

·        Sexes – separate

·        Fertilisation – usually external

·        Mostly oviparous

·        Development – direct

·        Eg: Marine – Exocoetus (Flying fish), Hippocampus (Sea horse)

·        Fresh water – Labeo (Rohit), Catla (Katla), Clarias (Magur)

·        Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish)

CLASS - AMPHIBIA

·        Amphi – dual; bios – life

·        Amphibians – can live in aquatic as well as terrestrial habitats

·        Most of them have – 2 pairs of limbs

·        Body – divisible into head & trunk

·        Some – have tail

·        Skin – moist, without scales

·        Eyes – have eyelids

·        Tympanum – represents ear

·        Alimentary canal, urinary & reproductive tract – open into common chamber – Cloaca – opens to exterior

·        Respiration by – gills, lungs & through skin

·        Heart – 3 chambered (2 auricles, 1 ventricle)

·        Cold blooded animals

·        Fertilisation – external

·        Oviparous; development – direct or indirect

·        Eg: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless Amphibia)

 

CLASS - REPTILIA

·        Reptilia – refers to creeping or crawling mode of locomotion

·        Latin, repere or reptum – to creep or crawl

·        Mostly terrestrial

·        Body covered by – dry & cornified skin, epidermal scales or scutes

·        No external ear openings

·        Tympanum – represents ear

·        Limbs – if present – 2 pairs

·        Heart – usually 3 chambered, but 4 chambered in crocodiles

·        Poikilothermic

·        Snakes & lizards – shed their scales as skin cast

·        Sexes – separate

·        Fertilisation – internal

·        Oviparous; development – direct

·        Eg: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodiles), Alligator (Alligator), Hemidactylus (wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper)

 

CLASS – AVES

·        Aves (birds) – feathers are present

·        Most of them fly; except flightless birds (Eg: Ostrich)

·        Possess beak

·        Forelimbs – modified into wings

·        Hindlimbs – generally have scales – modified for walking, swimming or clasping tree branches

·        Skin – dry without glands – except oil glands at tail base

·        Endoskeleton – fully ossified (bony) – long bones are hollow – with air cavities (pneumatic)

·        Digestive tract – has additional chambers, crop & gizzard

·        Heart – completely 4 chambered

·        Warm blooded – Homoiothermous – i.e., able to maintain constant body temperature

·        Respiration – by lungs – air sacs connected to lungs – supplement respiration

·        Sexes – separate

·        Fertilisation – internal

·        Oviparous; development – direct

·        Eg: Corvus (crow), Columba (Pigeon), Psittacula (Parrot), Siruthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture)

 

CLASS – MAMMALIA

·        Found in various habitat – Polarice caps, deserts, mountains, forests, grasslands & dark caves

·        Some – adapted to fly or live in water

·        Most unique character – presence of milk producing glands – mammary glands – by which they nourish young ones

·        Have 2 pairs of limbs – adapted for – walking, running, climbing, burrowing, swimming & flying

·        Skin is unique – have hair

·        External ear or pinnae – present

·        Different types of teeth – in jaws

·        Heart – 4 chambered

·        Homoiothermous

·        Respiration – by lungs

·        Sexes – separate

·        Fertilisation – internal

·        Viviparous – with few exceptions

·        Development – direct

·        Eg: Oviparous: Ornithorhynchus (Platypus),

·        Viviparous: Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphirus (common dolphin), Balaenoptera (Blue Whale), Panthera tigris (Tiger), Panthera leo (Lion)