CH-4 (ANIMAL KINGDOM) BIOLOGY CLASS -XI, CBSE NCERT EXAM NOTES

Chapter-4
Animal Kingdom

Table of Contents []

• Animal Kingdom Structure
• Classification
  • Levels of Ogranisation
  • Symmetry
  • Germinal Layers
  • Coelm
  • Segmentation
  • Notochord
• Phylum Porifera
• Phylum Coelenterata
• Classes of Fungi
• Phylum Ctenophora
• Phylum Aschelminthes
• Phylum Annelida
• Phylum Arthropoda
• Phylum Mollusca
• Phylum Echinodermata
• Phylum Hemichordata
• Phylum Chordata
• Vertebrata have two Division
• Super-class : Pisces
  • Class:Chondrichthyes
  • Class:Osteichthyes
• Super Class : Tetrapoda
  • Class:Amphibia
  • Class:Reptilia
  • Class:Aves
  • Class:Mammalia

Points to Remember

Basis Of Classification :

Animals are classified on the basis of follwing few fundamental features :-

1. Levels of Ogranisation :

(1) Cellular level : Cell are aranged as loose cell aggregtes, e.g., sponges.

(2) Tissue level : The cells performing the same function are arranged into tissue, e.g., Coelenterates.

(3) Organ level : Tissue are grouped together to form organs, each specialized for a particular function. e.g., platyhelminthes.

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

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

Closed types : Blood is circulated through blood vessels (arteries, veins and caplillaries).

2. Symmetry :

• Asymmetical : Cannot be divided into equal halves through median plane e.g, Sponges.
• Radial Symmetry : Any plane through central axis can divide organism into identical halves. e.g., Coelenterates, Ctenophores and Echinoderms.
• Bilateral Symmetry : Only one plane can divide the organism into two identical left and right halves e.g., Annelids and Arthropods.

3. 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., porifers and Coelenterates. (Cnidarians)
• Triploblastic : Three layers present in developing embryo i.e., ectoderm, mesoderm and endoderm. e.g., platyhelminthes to Chordates.

4. Coelm : (Body cavity which is lined by mesoderm)

• Coelomates : Have coelom e.g, Annelids, Arthropods, Molluscs, Echinoderms, Chordates etc.
• Pseudocoelomates : No true coelem as mesoderm is present in scattered pouches between ectoderm and endoderm. e.g., Aschelminthes.
• Acoelomates : Body cavity is absent e.g., Aschelminthes.

5. Segmentation : (A) True Metamerism : Found Annelids, 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 (meta members) with serial repetition of atleast some organs, then phenomenono is called metamerism e.g., Earhworm. (B) Pseudocoelomates : Found in tapeworm. The proglottids (segments of tapeworm) budded of from neck not embryonic in origin.

6. Notochord :

• Rod-like structure formed during embryonic development on the dorsal side. It is mesodermally derived e.g., Chordates.
• Non-chordates do not have notochord e.g., porifera to echinoderms.

Phylum Porifera :

• Also called sponges.
• Are usually marine and asymmetrical.
• Have cellular level of orgaisation and diploblastic animals.
• Food gathering, respiratory exchange and removal of wastes occurs through water canal system. Digestion intracelluar.
• Ostia (minute pores on body), spongocoel (body cavity) and osculum help in water transport. They ar 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 larval stage distinct from adult stage) e.g., 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 orgaisation.
• Are diploblastic (with mesogloea)
• Capature of prey, anchorage and defence occurs through cnidoblasts/ cnidocytes (have stinging capsules nematocytes) present on tentacles.
• Digestion exteracelluar and intracelluar.
• Have a central gastro-vascular cavity and an opening, hypostome.
• Body wall of some composed of calcium carbonate. e.g., corals.
• Exhibit two body forms : polyp and medusa e.g., Hydra, Aurelia.
• Altenation of generation between body form called Metagenesis ocurs in Obelia where:

  
           Medusa        sexually  Polyp. (Sessile and cylinderical)
       (free swimming & Asexually
       umbrella shaped)
          

• e.g., 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 intracelluar.
• 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 reproductionn occurs. External fertilisation. Indirect development. e.g., Ctenoplana, Pleurobrachia.

Phylum Platyhelminthes :

• Alos called as 'flat worms'.
• Have dorsoventrally flattened body. Are mostly endoparasites in animals.
• Are bilaterally symmetrical, triploblastic, acoelomate, with organ level of organisation.
• Absorb nutrients through body surface.
• Parasitic forms have hooks and suckers.
• 'Flame cells' helps in osmoregulation and excertion.
• Sexes not separate.
• Fertilisation internal. Many larval stages present. 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, pseudocoelomate.
• Alimentary canal complete (has musucla pharynx), waste removed through excertory pore.
• Sexes separate. (dioecious)
• Females longer than males.
• Fertilisation internal. Development direct or indirect. e.g., Ascaris, Wuchereria, Amcylostoma.

Phylum Annelida :

• Are aquatic or terrestrial. free-living or parasitic.
• Are bilaterally symmetrical, triploblastic, organ-system level of orgaisation and metamerically segmented body.
• Are coelomate animals.
• Have longitudinal and circular musucles for locomotion.
• Have closed circulartory system.
• Nereis (dioecious and aquatic annelida) has lateral appendages called parapodia for swimming.
• Have nephridia for osmoregulation and excertion.
• Neural system consists of paired gangila connected by lateral nerves to a double ventral nerve cord.
• Reproduction is sexual.
• e.g., Eathworm (Pheretima) and Leech (Hirudinaria) which ar hermaph rodites (i.e., monoecious).

Phylum Arthropoda :

• Largest phylum of Animalia.
• Are bilaterally symmetrical, triploblastic, 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. Excertion through malpighian tubules.
• Sensory organs : Antennae, eyes; Organs of balance : Statocysts.
• Fertilisation usually internal. Development is indirect or direct. Are mostly oviparous.
  
• e.g., Apis, Bombyx, Laccifer, Anopheles, Culex, Aedes, Locusta, Limulus.

Phylum Mollusca :

• Second largest phylum of Animalia.
• Terrestrial or aquatic.
• Are bilaterally symmetrical, triploblastic and organ system level of organisation, coelomate.
• Body vidisble into head, muscular foot and visceraal hump and is covered by calcareous shell and is unsegemented.
• Mantle : Soft and spongy layer of skin; Mantle cavity : Space between visceral hump and mantle.
• Respiration and excertion by feather like gills in mantle cavity.
• Head has sensory tentacles. Radula a rasping organ for feeding in mouth.
• Are oviparous, dioecious, have indirect development.
• e.g., 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 sytem level of orgaisation.
• Triploblastic and coelomate.
• Digestive system complete. Mouth ventral, Anus on dorsa side.
• Food gathering, respetition, locomotion carried out by water vasuclar system.
• Excretory system is absent.
• Reproduction-sexual, sexes ar separate.
• Fertilisation external. Development indirect (free swimming larva)
• e.g., Asteria, Cucumaria, Antedon, Echimus, Ophiura.

Phylum 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 cylinderical, has proboscis, collar and trunk.
• Circulatory Sytem-open.
• Respiration by gills, excertion by proboscis gland.
• Sexes separate, external fertilisation, indirect development.
• e.g., Balanoglossus, Saccoglossus.

Phylum Chordata :

• Presence of Notochord.
• Have dorsal holloww nerve cord.
• Have paired pharyngeal gill slits.
• Bilaterally symmetrical, triploblastic, coelomate, organ system level of organisation.
• Heart is ventral.
• Post anal tail present, closed circulartory system.

(i) Sub-Phyla Urochordata/ Tunicata
• Notochord present only in larval tail.
  e.g., Ascidia, Salpa, Doliolum

(ii) Sub-phyla Cephalochordata
• Notochord extends from head to tail (Persistent)
  e.g., Amphibians.

(iii) Sub-phyla Vertebrata
• Have notochord only during embryonic period.
• Notochord gets replaced by bony or cartilaginous vertebral column.
• Have ventral muscular, kidneys for excertion and osmoregulation, paired appendages (fins or limbs)

Vertebrata have two Division :

(a) Agnatha (Lacks Jaw) : Class : Cyclostomata

• Live as ectoparasites on some fishes.
• Have sucking and circular mouth without jaws.
• Have 6-15 paris of gill slits for respiration.
• No scales, no paired fins.
• Cranium and vertebral column is cartilaginous.
• Marine, Migrate to fresh water for spawing and die after spawing.
• Larva returns to oceans after metamorphosis.
• e.g., Petromyzon, Myxine

(b) Gnathostomata (Bear Jaws)- divides into two super classes :

Super-class : Pisces

1. Class : Chondrichthyes :
• Have cartilaginous endoskeleton, are marine with streamlined body.
• Mouth ventral.
• Gill slits without 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.
• e.g., Torpedo, Trygon, Scoliodon, Pristis, Carcharodan

2. 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.
• Skin has cycloid/ ctenoid scales.
• Have air bladder which regulates buoyancy.
• Sexes separate.
• Usually oviparous, fertilisation external.
• Development direct.
• e.g., Hippocampus, Labeo, Catla, Betla, Clarias, Exocoetus


Sub-Phylum Vertebrata : Gnathostomata

Super Class : Tetrapoda

1. 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 in 3-chambered; Cold-blooded; Sexes separate; Fertilisation external.
• Oviparous Indirect development.
• e.g., Bufo, Rana, Hyla, Salamandra, Ichthyophis

2. Class : Reptilia :
• Creep or crawl to locomote. mostly terrestrial.
• Body has dry and cornifed skin and epideremal scales or scutes.
• Tympanum, when present, are two pairs.
• Snakes and lizards shed scales as skin cast.
• Heat 3-chambered but 4-chambered in crocodiles.
• Sexes Separate; fertilisation internal.
• Oviparous. Direct development.
• e.g., Testudo, Naja, Vipera, Calotes, Crocodilus, Hemidactylas

3. Class : Aves :
• Presence of feather except flightless birds and beak (modified jaws) without teeth.
• Forelimbs are modified inot wings.
• Hind limbs have scales, modified for walking, swimming or clasping.
• Skin is dry as no glands on skin except oil gland at base of tail.
• Endoskelton 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
• Sexes separate, fertilization internal.
• Oviparous. Direct development.
• e.g., Columba, Struthio, Pavo, Corvus, Neophron, Psittacula, Aptenodytes.

4. 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.
• e.g., Rattus, Canis, Elephas, Equus. Oviparous mammal is Ornithorhynchus.