Chapter 04 Kingdom Animalia

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        Kingdom Animalia

Classification also helps in Assigning a systematic position.

Basis of Classification :-

Arrangement of cells , body symmetry , nature of coelom, pattern of digestive , circulatory or

reproductive systems.

Levels of Organisation :-

Through all members of Animalia are multicellular all of them do not exhibit the same pattern

of organization of cells. For example , in sponges,. They exhibit cellular levels of organization.

In coelenterates , the arrangements of cells is more complex.

The cells performing the same functions are arranged into tissues, hence is called tissue level .

Organ level is exhibit by members of Platyhelmanthes.

Annelids , Arthropods, Molluscs, Echinoderms and Chordates. 

The digestive system in Platyhalmanthes has only a single opening to the outside of the body

that serves as both mouth and anus, and hence is called incomplete. A complete digestive

systems has two openings, mouth and anus.

(i) Open type :- in which the blood is pumped out of the heart and the cells and tissues

are directly bathed in it and.

(ii) Closed type :- in which the blood is circulated through a series of vessels of

varying diameters ( arteries, veins and capillaries).

Symmetry :-

Sponges are mostly Asymmetrical. Radial symmetry Coelonterates , ctenophores and

echinoderms.

Annelids, Arthropods

The body can be divided into identical left and right halves in only one plane, exhibit bilateral

Symmetry.

Diploblastic and Triploblastic Organisation :-

Animals in which the cells are arranged in tw0 embryonic layers, an external ectoderms and

an endoderm are called diploblastic animal eg Coelonterates. An undifferentiated layer,

mesogiea.

Those animals in which the develops the developing embryo has a third germinal layers,

mesoderm.

Triploblastic animals (platyhelmanthes to chordates ).

Coelom :-

The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are

called coelomates. Eg, annelids, molluscs , arthropods , echinoderms . hemichordates and

chordates. Scattered pouches in between the ectoderm and endoderm.

Such a body cavity is called pseudocoelom and the animals possenssing them are called

pseudocoelomates. Eg. Ascheminthes.

The animals in which the body cavity is absent are called Acoelomates, eg Platyhelmanthes.

Segmentation :-

In some animals , the body is externally and internally divided into segments with a serial

repletion o fat least some organs. For example. In earthworm, the body shows the pattern

called metameric segmentation and the phenomenon is known as metamerism.

Notochord :-

Notchord is a mesodermally derived rod-like structure formed on the dorsal side during

embryonic development in some animals. Animals notochord are called chordates . non-

chordates eg, porifera or echinoderms.

Classification of animals :-

Phylum – Porifera

Members of this are commonly known as sponges.

They are generally marine and mostly asymmetrical animals.

Sponges have a water transport or canal systems. Central cavity , spongocoel from where it

goes out trough the osculum. This pathway of water transport is helpful in food gathering ,

respiratory exchanges and removal of waste. Choanocytes or collar cells line the spongocoel.

The body is supported by a skeleton made up of spicules or spongia fibres. Sexes are not

separate hermaphrodite.

Fertilisation is internal and development is indirect.

Example :- Sycon (Scyphal) , Spongilla (fresh water sponges) and Euspongia (bath sponge).

Phylum – Coelonterata (Cnidaria) :-

They are aquatic marine, sessile or free swimming, radially symmetrical animals .

The name cnidaria is derived from the cnidoblasts or cnidocytes (which capsules or

nemanocysts) present on the tentacles and the body.

Cnidoblasts are used for anchorage, defense and for the capture of prey. Tissue level of

organization and diploblastic. They have a central gastro-vascular cavity with a single opening,

mouth on hypostome.

Digestion is extracellular and intracellular.

Eg:- Corals have a skeleton composed of calcium carbonate.

Cnidarians exhibit two basic body forms called polyp and medusa. The former is a sessile and

cylindrical form like Hydra. Adamsia, etc. whereas , the latter is umbrella shaped and free –

swimming like Aurelia or jelly fish.

Alternation of generation ( Metagenesis). Ie. Polyps produce medusae asexually and medusa

form the polyps sexually (eg Obelia).

Example :- Physalia ( Portuguese man of war) , Ademsia (Sea anemone), Pennatula (Sea-pen),

Gorgonia (Sea-fan) and Meandrina (Brain corall).

Phylum – Ctenophora :-

Ctenophore , commonly known as sea walnuts or comb jellies are exclusively marine, radially

symmetrical, diploblastic organisms with tissue level of organization.

The body bears eight external rows of ciliated comb plates, which help in locomotion.

 Digestion is both extracellular and intracellular Bioluminance.

 Sexes are not separate.

 Fertilisation is external with indirect development. Example ;- Pleurobrachia &

Ctenophora.

Phylum – Platyhelminthes :-

They have dorso-ventrally flattered body , hence are called Flateworm. These are mostly

ecdoparasite found in animals including human beings.

 Hooks & suckers are present in the parasite forms.

 Some of them absorb nutrients from the host directly through their body surface.

 Specialised cells called flame cells helps in Osmoregulation & excretion.

 Fertilisation is internal & development is through many through many larval stages.

 Planaria posses high regeneration capacity.

Example : Tania (Tapeworm) , Fasciola (liver fluke).

Phylum – Aschelminthes :-

The body of the aschelminthes is circular in cross-section. Hence, the roundworm.

 Parasite in potato and animals

 Roundworm have organ-system level of body.

They are bilaterally symmetrical, triploblastic & pseudocoelomate animals.

Alimentary canal is complete with a well-developed muscular pharaynx.

 Male & female are distinct.

 Often female are longer than males. Fertilisation is internal & development may be

direct or indirect.

Example :- Ascaris (Roundworm) , Wuchereria (Filaria worm) , Ancylostoma

(Hookworm).

Phylum - Annelida :-

They may be aquatic (marine & fresh water) or terrestrial : free – living. They exhibit organ-

system level of body organization & bilateral symmetry.

 They are triploblastic, metamerically segmented.

 Body surface is distinctly marked out into segments or metamers.

 Annelida (latin; annulus, little ring).

 They possess longitudinal & circular muscles. Which help in locomotion.

 Nereis possess lateral appendages.

 Parapodia which help in swimming. A closed circulatory is present.

 Nephridia ( sing, nephridium) help in osmoregulation & excetrion.

 Nereis , an aquatic form, is dioecious , but earthworms & leeches are monoecious.

Reproduction is sexual.

Example :- Nereis , pheretima ( Earthworm) & Hirudinaria ( blood sucking leech).

Phylum- Arthropoda :-

This is the largest phylum of animals which includes insects.

Over two-thirds of all named species on earth are arthropoda.

 The body of arthropoda is covered by chitinous exoskeleton.

 The body consists of head, ,thorax & abdomen.

They have jointed appendages (arthrox-joint, poda-appendages).

Respiratory organs are gills, book-gills, book, lungs or tracheal system.

 Sensory organs like antennae , eyes (compound & simple), statocysts or balancing

organs are present.

 Excretion takes place through malphigians tubules. They are mostly oviparous,

development may be direct & indirect.

Example :-

Economically important insects Apts (Honey bees), bombyx ( silkworm), Lacifers

( lac-insect).

Vectors – Anopheles, culex & Aedes (Mosquitos) , Gregarious pest – Locusia ( Locust).

Livina Fossile - Limules ( king crab).

Phylum – Mollusca –

This is the second largest animals phylum.

 Molluses are terrestrial or aquatic (marine of fresh water).

Body is covered by a calcareous shell & is unsegmented with a distinct head, muscular

foot & visceral hump.

 The space between the hump & the mentic is called the mantic cavity. They have

respiratory & excretotry functions.

 File-like rasping organ for feeding, called radula.

 They are usually dioecious & oviparous with indirect development.

Example -

Pila (Apple snall), Pinctoda (Pearl oyster), Spia (Cuttlefish) , Loligo

(Squid) , Octopus (Devil fish) , Aplysia (sea-hare), Dentalium (Task shell) &

Chaetopleura (Chiton).

Phylum – Echinodermata –

These animals have an endoskeleton of calcareous ossicles.

Echinodermata ( spiny bodied).

 The adult Echinodermata are radially symmetrical larve are bilaterally

symmetrical.

 Digestive system is complete with mouth on the lower (ventral) side and anus on the

upper (dorsal) side.

 The distinctive features of Echinodermata is the presence of water vascular

system, which helps in locomotion , capture & transport of food & respiration.

 Fertilisation is usually external development is indirect with free-swimming larva.

Example , Asterias (star fish) , Echinus (sea urchin), Antedon (sea lily), Cucumaria (sea

cucumber) & Ophitura ( Brittle star ).

Phylum – Hemichordata :- 

Hemichordata was earlier considered as a sub-phylum under

phylum chordata.

Hemichordate have a rudimentary structure in the collar region

called stomochord, a structure similar to notochord.

The phylum consists of a small group of worm-like marine animals.

 The body is cylindrical.

 Anteriior proboscis , a collar & a long trunk. Circulatory system is of open type.

 Excretory organs is proboseois gland.

Phylum – Chordata :-

Animals belonging to phylum chordata are fundamentally characterized

by the presence of notochord, a dorsal hollow nerve cord & paired pharyngeal gill slits.

[ comparision of chordates & non-chordates]

Chordates :-

 Notochord present.

 Central nervous system is dorsal, hollow & single.

 Pharynx perforated by gills sites.

 Heart is ventral.

 A post and part ( tail) is present.

Non-Chordates :-

 Notochord absent.

 Central nervous system is ventral , solid, & double.

 Gills sites are absent.

 Heart is dorsal of present.

 Post and tail is absent.

Phylum chordata is divided into three subphyla. Urochordata or Tunicala, cephalochordata &

Vertebrate.

Protochordartes & are exclusively marine.

 In urochordata, notochord is present only in larval tail.

Cephalochordata, it extends from head to tail region & is persistant throughout their

life.

Example /-

Urochordata – Ascidia , Salpa , Doliolum, cephalochordta –

Branchiostoma ( Amphioxus or Lancelt).

Comparison of Chordates and Non-chordates :- 

The notochord is replaced by a cartilaginous or bony vertebral column in the adult. Thus all

vertebrates are chordates but all chordates are not vertbrates.