Animal Kingdom XI Biology/Notes C4

Revision Notes on Animal Kingdom

Animal kingdom comprises of multicellular eukaryotic animals and is one of the kingdoms among five kingdom scheme of classification (by Whittaker).

Classification of animal kingdom is based on different important characteristic features like habitat, level of organization, symmetry etc.

(i) Characters of Non Chordata (Invertebrates): The animals which lack a notochord are called invertebrates. e.g. Amoeba, sponges, Hydra, worms, insects, etc., Invertebrates are characterised by the following salient features –

(1) The vertebral column is absent.

(2) the nerve cord is solid in nature.

(3) The nerve cord is present on the ventral side and never on the dorsal side.

(4) When alimentary canal is present, it lies dorsal to the nerve cord.

(5) Invertebrates may be acoelomate or pseudocoelomate or true coelomate.

(6) They have either asymmetry or radial symmetry or bilateral symmetry.

(7) The circulatory system is open type or closed type.

(8) They exhibit all possible type of reproduction.                                                                                 

Revision Notes on Phylum Protozoa and Porifera

The name “Protozoa” was coined by Goldfuss (1817). The branch of their study is called Protozoology.

(i) Salient Features

(1) Protozoans are the simple and primitive organisms

(2) free living or parasitic

(3) All the free living forms are aquatic

(4) asymmetrical or radially symmetrical or bilaterally symmetrical

(5) They are unicellular (acellular)

(6) They have protoplasmic grade of organization.

(7) Locomotion is affected by flagella, cilia or pseudopodia.

(8) Nutrition is holophytic, holozoic, saprozoic or parasitic.

(9) Digestion is intracellular

(10) Excretion & Respiration occurs by diffusion

(11) In fresh water protozoans osmoregulation is carried out by the contractile vacuoles.

(12) Encystment is a common phenomenon

(13) Reproduction occurs by asexual and sexual methods.

(ii) Classification of Protozoa

(a) Class 1. Flagellata or Mastigophora

(1) The body is covered by a thin pellicle or cuticle.

(2) The locomotory organs are flagella.

(3) The contractile vacuoles are present in fresh water forms with accessory vacuoles.

(4) Chloroplast is found in some forms.

(5) They may be free-living or parasitic.

(6) The class flagellata has been divided into eight orders.

(7) Examples: Chrysamoeba, Cryptomonas, Euglena, Volvox, etc.

(8) Euglena is a connecting link between Animal & Plant.

(9) Trychonymph (symbiotic) live in alimentary canal of termite that is digest to cellulose.

(b) Class 2. Rhizopoda

(1) There is no definite cell wall or pellicle

(2) There is no definite shape

(3) The locomotory organs are pseudopodia

(4) There is no permanent mouth or anus.

(5) The contractile vacuoles are present in the fresh water forms.

(c) Class 3. Ciliophora

(1) The body is covered by thin pellicle

(2) They have a fixed permanent shape

(3) The locomotory organs are cilia

(4) Tentacles are present

(5) The class ciliophora is divided into two sub-classes, namely Ciliata and Suctoria.

Sub-class 1 - Ciliata

(1) Cilia are present throughout life.

(2) Tentacles are absent

(3) Mouth and cytopharynx are usually present.

(4) Contractile vacuoles are present.

(5) Trichocysts, organs of offense and defense are present in certain forms.

(6) Examples: Paramecium, Stylonchia Vorticella, etc., Paramecium is filter feeder

(7)  In a paramecium two contractile vacuoles are present. Posterior contractile vacuole is highly active.

Sub-class 2 - Suctoria

(1) Cilia are present only in the young conditions and adults are devoid of them.

(2) Tentacles are present in the adult

(3) One to many contractile vacuoles are present

(4) Examples: Acineta, Dendrocometes, Dendrosoma, etc.

(d) Class 4 - Sporozoa

(1) They are exclusively endoparasitic

(2) The body is covered by pellicle.

(3) Reproduction takes place by spore formation

(4) The class is divided into two sub-classes, namely, Telosporidia and Neosporidia

Sub-class 1 - Telosporidia

(1) The spores do not contain polar capsules or filaments

(2) The life history ends with the formation of spores.

(3) The spore cases are simple and contain many spores

(4) Examples: Monocystis, Gregarina, Isopora, Eimeria, Plasmodium, Babesia, etc.

Sub class 2 - Neosporidia

(1) The trophozoite is amoeboid multinucleated

(2) Spore cases are complex usually having a single germ

(3) Examples: Nosema, Myxidium, Globidium, etc.

Phylum Porifera 

(i) The word “Porifera” means pore bearers (Gr., porus = pore; ferre = to bear); their body wall has numerous minute pores, called ostia, through which a continuous current of outside water is drawn into the body.

(ii) Phylum porifera has the following salient features:

(1) All the sponges are Aquatic, Sedentary, Asymmetrical or Radially,

(2) They are diploblastic.

(3) The body is perforated by numerous minute pores called ostia.

(4) The ostia open into a large cavity called spongocoel.

(5) The spongocoel opens to the outside by a large opening called osculum.

(6) The sponges possess an endoskeleton in the form of calcareous spicules.

(7) Excretion and respiration occur by diffusion.

(8) They have greater power of regeneration.

(9) Reproduction takes place by asexual or sexual methods.

(10) Development is indirect or direct. The common larval are parenchymula, amphiblastula, etc.



Phylum Cnidaria (or Coelenterata)

(i) ‘Tissue grade’ eumetazoans with a radial symmetry.

(ii) The term “Coelenterata” signifies the presence of a single internal cavity called coelenteron, or gastrovascular cavity, combining functions of both digestive and body cavities. The term “Cnidaria” indicates the presence of stinging cells (Gr., knide = nittle or stinging cells).

(iii) Phylum coelenterata has the following salient features –

         (1) Coelenterates are multicellular organisms

         (2) They have tissue-grade of organization

         (3) The body is radially symmetrical. Radial symmetry is the symmetry of a wheel

         (4) All the members of this phylum are aquatic

         (5) They are solitary or colonial

         (6) polyps and medusa occur in the life cycle.

         (7) The body wall is diploblastic.

         (8) Nematocysts or stinging cells are present.

         (9) Coelom is absent; hence coelenterates are acoelomate animals

         (10) A gastrovascular cavity or coelenteron is present.

         (11) Mouth is present; but anus is absent

         (12) Digestion is extracellular as well as intracellular

         (13) Respiratory, excretory and circulatory system are absent

         (14) Nervous system is diffuse-type, formed or nerve-nets.

         (15) Reproduction is by asexual and sexual methods

         (16) Development is indirect as there are one or two larval forms

         (17) Life history has alternation of generations or metagenesis.

Phylum Ctenophora

(i) Ctenophora is a small phylum. These animals exhibit the characters of Coelenterata and platyhelminthes.

(ii) Phylum Ctenophora shows the following salient features

         (1) All the ctenophores are marine.

         (2) They are solitary and pelagic.

         (3) They are transparent.

         (4) They have tissue-grade of organization.

         (5) They have biradial symmetry.

         (6) They are acoelomate animals.

         (7) They are non-segmented.

         (8) Their body-wall is diploblastic.

         (9) The mesogloea contains cells.

         (10) Nematocysts are absent.

         (11) Special adhesive cells called colloblasts are present in all ctenophores.

         (12) The gastrovascular system is well developed.

         (13) Two anal openings are present.

         (14) Skeletal system is absent.

         (15) Excretion and respiration are carried out by diffusion.

         (16) The nervous system is in the form of nerve net.

         (17) An aboral sense organ in present in the form of statocyst.

         (18) Cilia are used for locomation.

         (19) They are hermaphrodites.

         (20) Development is indirect. It includes a cydippid larva.

Phylum Platyhelmithes

(i) “Platyhelminthes” means flatworms (Gr., platys = flat; helmins = worms); their body is dorsoventrally flattened. 

(ii) Salient features:

(1) They are dorsoventrally flattened like a leaf

(2) They show organ grade of organization

(3) They are acoelomate animals

(4) They are triploblastic animals.

(5) They are bilaterally symmetrical animals.

(6) Some members have segmented body.

(7) Many of the parenchyma cells give rise to muscle fibres.

(8) The digestive system is completely absent from Cestoda and Acoela.

(9) The respiratory organs are absent. In parasites respiration is anaerobic

(10) There is no circulatory system

(11) The excretory system is formed of protonephridia (flame cells)

(12) The nervous system is well developed.

(13) They are hermaphrodites, i.e., both male and female reproductive organs are present in the same animal

(14) Fertilization is internal in them.

(15) They are free-living or parasitic.


Phylum Nematoda (or Nemanthelminthes)

(i) The term “Nematoda” literally means “threadworms” or “roundworms” (Gr., nema = thread + eidos = form).

(ii) Salient features

(1) Many endoparasites of various animals and plants.

(2) Mostly minute or small; some large (1 mm to 25 cm); some upto several metres long.

(3) Slender, cylindrical, elongated body usually tapering towards both ends, and non-segmented.

(4) Body wall formed of a thick, tough and shiny cuticle.

(5) The false body cavity, or pseudocoel is spacious, with a fluid but no free cells

(6) Straight alimentary tract with terminal mouth and anus

(7) Circulatory system and respiratory organs absent.

(8) They are usually unisexual with sexual dimorphism.

(iii) Classification of Nematoda: On basis of the presence of absence of some specialized sense organs and caudal glands, and characteristics of excretory system,

Phylum Mollusca

(i) Basically bilateral and protostomial eucoelomate eumetazoans whose soft body (L., mollis or molluscum = soft)

is non-segmented and enclosed within a skin–fold (mantle) which usually secretes a calcareous shell.

(ii) Salient Features:

(1) Molluscs are multicellular organisms

(2) They have a bilateral symmetry, but snails are asymmetrical

(3) They are triploblastic animals.

(4) They are coelomate animals.

(5) They have organ system grade of organization.

(6) The body is soft and non-segmented.

(7) The soft body is covered by a fleshy fold of the body wall. It is called mantle.

(8) The molluscs are provided with one or two calcareous shells.

(9) Respiration is carried out by the gills or pulmonary chambers.

(10) The digestive system is well developed.

(11) The circulatory system is of an open type.

(12) The excretory organ is the kidney.

(13) The nervous system is well developed.

(14) The sensory organs are eyes, statocysts and osphradia.

(15) Sexes are separate in them, or they are hermaphrodites.

(16) The development in their case in either direct or indirect


Phylum Echinodermata

(i) The term “Echinodermata” means spiny skin (Gr., echinos = spiny + dermatos = skin).

(ii) Salient features:

(1) Echinoderms are exclusively marine beings.

(2) They are triplobalstic and coelomate animals.

(3) They have radially symmetrical body.

(4) They have organ system grade of organization.

(5) They have well developed

(6) They have a water–vascular system with tube–feet for locomotion, feeding and respiration.

(7) Circulatory system is of the open–type.

(8) The sensory organs are poorly developed.

(9) The excretory organs are absent.

(10) They have pedicellariae.

(11) Development is indirect.

(12) The larval forms are bilaterally symmetrical.

(ii) Characters of Chordata (Vertebrates): The animals which possess a notochord are called vertebrates.

(1) Aquatic, aerial or terrestrial.

(2) Body small to large, bilaterally symmetrical and metamerically segmented.

(3) A post anal tail usually projects beyond the anus at some stage and may or may not persist in the adult.

(4) Exoskeleton often present; well developed in most vertebrates.

(5) Body wall triploblastic with 3 germinal layers : ectoderm, mesoderm and endoderm.

(6) Coelomate animals having a true coelom, enterocoelic or schizocoelic in origin.

(7) A skeletal rod, the notochord, present at some stage in life cycle.

(8) A cartilaginous or bony, living and jointed endoskeleton present in the majority of members (vertebrates).

(9) Pharyngeal gill slits present at some stage; may or may not be functional.

(10) Digestive system complete with digestive glands.

(11) Blood vascular system closed.

(12) Excretory system comprising proto-or meso- or meta-nephric kidneys.

(13) Nerve cord dorsal and tubular. Anterior end usually enlarged to form brain.

(14) Sexes separate with rare exceptions.

Phylum Chordata

Superclass Pisces

Class 1 - Chondrichthyes (Cartilaginous Fishes)

General characters:-

(1) Mostly marine and predaceous.

(2) Body fusiform or spindle shaped.

(3) Fins both median and paired, all supported by fin rays.

(4) Skin tough containing minute placoid scales and mucous glands.

(5) Endoskeleton entirely cartilaginous, without true bones

(6) Notochord persistent.

(7) Respiration by 5 to 7 pairs of gills.

(8) Heart 2–chambered (1 auricle and 1 ventricle).

(9) Kidneys opisthonephric. Excretion is ureotelic.

(10) Brain with large olfactory lobes and cerebellum. Cranial nerves 10 pairs.

Class 2 - Osteichthyes (Bony fishes)

General Characters:-

(1) Inhabit all sorts of water-fresh, brackish or salt; warm or cold.

(2) Body spindle-shaped and streamlined.

(3) Fins both median and paired, supported by fin rays of cartilage or bone.

(4) Skin with many mucous glands, usually with embedded dermal scales of 3 types; ganoid, cycloid or ctenoid.

(5) Endoskeleton chiefly of bone

(6) Respiration by 4 pairs of gills on body gill arches

(7) Ventral heart 2-chambered (1 auricle + 1 ventricle).

(8) Adult kidneys mesonephric. Excretion is ureotelic.

(9) Brain with very small olfactory lobes, small cerebrum and well developed optic lobes and cerebellum.

(10) Well developed lateral line system.      

Class Amphibia

General characters:-

(1) Aquatic or semi aquatic (freshwater), air and water breathing, carnivorous, cold–blooded, oviparous, tetrapod vertebrates.

(2) Head distinct, trunk elongated. Neck and tail may be present or absent.

(3) Pigment cells (chromatophores) present.

(4) Exoskeleton absent.

(5) Endoskeleton mostly bony. Notochord does not persist. Skull with 2 occipital condyles.

(6) Respiration by lungs, skin and mouth lining.

(7) Heart 3–chambered (2 auricles + 1 ventricle).

(8) Kidneys mesonephric. Excretion is ureotelic.

(9) Brain poorly developed. Cranial nerves 10 pairs.

 (10) Nostrils connected to buccal cavity.      

Class Reptilia

General characters:-

(1) Predominantly terrestrial, creeping or burrowing.

(2) Body bilaterally symmetrical and divisible into 4 regions-head, neck, trunk and tail.

(3) Limbs 2 pairs, pentadactyle.

(4) Exoskeleton of horny epidermal scales, shields, plates and scutes.

(5) Skin dry, cornified and devoid of glands.

(6) Alimentary canal terminates into a cloacal aperture.

(7) Endoskeleton bony. Skull is with one occipital condyle (monocondylar).

(8) Heart usually 3–chambered, 4–chambered in crocodiles.

(9) Respiration by lungs throughout life.

(10) Kidney metanephric. Excretion is uricotelic.

Class Aves

General characters:-

(1) Feather-clad, air-breathing, warm-blooded, oviparous, bipedal flying vertebrates.

(2) Limbs are two pairs.  

(3) Exoskeleton is epidermal and horny.

(4) Skin is dry and devoid of glands except the oil or preen gland at the root of tail.

(5) Pectoral muscles of flight are well developed.

(6) Skull smooth and monocondylic, bearing a single occipital condyle. Cranium large and dome-like. Sutures indistinct.

(7) Vertebral column short. Centra of vertebrae heterocoelous (saddle-shaped).

(8) Sternum large, usually with a vertical, mid ventral keel for attachment of large flight muscles.

(9) Ribs double-headed (bicephalous) and bear posteriorly directed uncinate processes.

(10) Both clavicles and single inter clavicle fused to form a V–shaped bone, called furcula wishbone.

(11) Heart completely 4–chambered. There are neither sinus venosus or truncus arteriosus. Only right aortic (systemic) arch persists adult. Renal portal system vestigial. Blood corpuscles nucleated.

(12) Birds are the first vertebrates to have was blood. Body temperature is regular (homoiothermous).

(13) Respiration by compact, spongy, distensible lungs continuous with thin air-sacs.

(14) Larynx without vocal cords. A sound box or syrinx, producing voice, lies at or near the junction of trachea and bronchi.

(15) Kidneys metanephric and 3–lobed.

Class Mammalia

General characters:-

(1) Hair-clad, mostly terrestrial, air-breathing, warm blooded, viviparous, tetrapod vertebrates.

(2) Limbs 2 pairs, pentadactyle, each with 5 or fewer digits. Hind limbs absent in cetaceans and sirenians.

(3) Exoskeleton includes lifeless, horny, epidermal hairs, spines, scales, claws, nails, hoofs, horns, bony dermal plates, etc.

(4) Skin richly glandular containing sweat, sebaceous (oil) and sometimes scent glands in both the sexes. Females also have mammary glands with teats producing milk for suckling the young.

(5) Endoskeleton thoroughly ossified. Skull dicondylic having 2 occipital condyles. Cranium large. A single zygonmatic arch present. Pterygoids msall, scale-like. Otic bones fused into periotic which forms tympanic bulla with tympanic. Each half of lower jaw made of a single bone, the dentary, articulating with squamosal of skull Vertebrae with terminal epiphyses and flat centra (acoelous). Cervical vertebrae usually 7. Ribs bicephalous. Coracoid vestigial.

(6) Teeth are of several types (heterodont), borne is sockets (thecodont) and represented by two sets (diphyodont).

(7) Respiration always by lungs (pulmonary). Glottis protected by a fleshy and cartilaginous epiglottis. Larynx contains vocal cords.

(8) Heart 4-chambered with double circulation.

(9) Kidneys metanephric.

(10) Brain highly evolved. Both cerebrum and cerebellum large and convoluted. Optic lobes small and 4 in number called corpora quadrigemina. Corpus callosum present connecting both cerebral hemispheres. Cranial nerves 12 pairs.

(11) Senses well developed. Eyes protected by lids, the upper of which is movable. External ear opening protected by a large fleshy and cartilaginous flap called pinna. Middle ear cavity with 3 ear ossicles–malleus, incus and stapes. Cochlea of internal ear spirally coiled.

(12)  Sexes separate.

(13) Fertilization internal preceded by copulation.

(14) Except egg-lying monotremes, mammals are viviparous, giving birth to living young ones.