Sunday, December 7, 2014

9th Animal kingdom- Diversity of living organism

Animal kingdom: It consists of organisms which are eukaryotic, multicellular and heterotrophic. Their ells do not have cell-walls. Most animals are mobile.

Animal kingdom classified on the basis of the following points: Arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems


Animalia  are further classified as Non- Chordates( Porifera, Coelenterata, Platyhelminthes , Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata) and Chordates { Protochordata, Vertebrata ( Pisces, Amphibians, Reptilia, Aves, Mammalia)}

Non- Chordates 

Porifera: Organisms of this group have holes or ‘pores’, all over the body and therefore known as sponges. They are mainly found in marine habitats Pores helps in circulating water throughout the body to bring in food oxygen and removal of waste. They are hermaphrodite i.e., eggs and sperms are produced by the same individual. Sponges reproduce asexually by fragmentation and sexually by formation of gametes. Fertilisation is internal . They are primitive multicellular animals and have cellular level of organisation. Sponges have a water .

Examples of Porifera : (a) Sycon (b) Euspongia (c) Spongilla

Coelenterata: They are aquatic, mostly marine and radically symmetrical. They have tissue level of organisation. They are diploblastic i.e he body is made of two layers of cells: one makes up cells on the outside of the body (ectoderm) , and the other makes the inner lining of the body(endoderm). They exhibit tissue level of organization.

Some of these species live in colonies (corals), while others have a solitary like–span (Hydra). Jellyfish and sea anemones are common examples.

Platyhelminthes: The body is bilaterally symmetrical, meaning that the left and the right halves of the body have the same design. There are three layers of cells from which differentiated tissues can be made (triploblastic).

There is no true internal body cavity or coelom, in which welldeveloped organs can be accommodated. The body is flattened dorsiventrally, meaning from top to bottom, which is why these animals are called flatworms. They are either freeliving or parasitic. Some examples are freeliving animals like planarians, or parasitic animals like liverflukes. Fertilisation is internal.

Nematoda: They bilaterally symmetrical and triploblastic. The body is cylindrical rather than flattened. There are tissues, but no real organs, although a sort of body cavity or a pseudocoelom, is present. some of them are parasitic like round worms or pin worm and other are living in soil and water like rhabditis.

Annelid animals : are bilaterally symmetrical and  segmented. There is an open circulatory  system, and so the blood does not flow in well defined  blood vessels. The coelomic cavity is blood-filled. They have jointed legs (the word ‘arthropod’ means ‘jointed legs’). Some familiar examples are prawns, butterflies, houseflies, spiders, scorpions and crabs

Arthropoda: The word Arthropoda “means organisms with jointed legs” They are bilaterally symmetrical Triploblastic(three layers of cells ), familiar with cockroaches. The Coelom is blood filled called as Haemo Coelom. Ex. Prawn, Scorpion, Housefly

 MolluscaThe word Mollusca “means organisms with soft body” They are bilaterally symmetrical, Triploblastic(three layers of cells), familiar with Octopus, Pila. Foot is for moving, kidney like organ for excretion, with open circulatory system. Ex. Unio, chiton

Echinodermata: The word Echinodermata “means organisms with spiny skinned”. Exoskeleton is with calcium carbonate. They are radially symmetrical Triploblastic ( three layers of cells ) with coelomic cavity, familiar with Star fish. They are exclusively free-living marine animals. Ex. Sea Cucumber, Feather Star

Chordates: They are further classified as two major groups such as Protochordata& Vertebrata

(A).Protochordata: Notochord present in at least larval forms, but very rudimentary. It is a rod like supporting structure, runs along with nervous tissue from the gut of animal. They  are bilaterally symmetrical, triploblastc(three layers of cells) with a Coelom, familiar with Amphioxus. Ex. Balanoglossus

(B).Vertebrata: Notochord is replaced by vertebral column and internal skeleton. They are bilaterally symmetrical, triploblastic, coelomic and segmented having paired gill pouches.

Vertebrates are grouped into five classes.

Pisces: These are commonly called as “fishes”, exclusively aquatic. Body is streamlined and a tail for locomotion. Gills for respiration, heart is two chambered, cold blooded, skin is covered with scales, plates. They are cold-blooded animals. Skeleton of bone ( Rohu) / cartilage( Shark). They lay eggs. Ex. Lion Fish, Dog Fish

Amphibians: These are commonly called as “Amphibians” because they can live on land and in water”. Body is streamlined and a webbed foot/ foot for locomotion. Gills or lungs or skin for respiration, heart is three chambered, cold blooded, skin is lack of scales, plates. They are cold-blooded animals. They lay eggs. Ex. Rana, Hyla

Reptilia: These are commonly called as “Reptilians”. A lung for respiration, heart is three chambered (Crocodile heart is four chambered), skin have scales. They are cold-blooded animals. They lay eggs. Ex. Snakes, Turtles (Please refer Fig. 7.23, NCERT Text Book Page- 93).

Aves :These are commonly called as “Birds”. A lung for respiration, heart is four chambered, fore limbs are modified for flight, skin has feathers. They are warm-blooded animals. They lay eggs. Ex. Ostrich (Flightless Bird), Pigeon, Sparrow

Mammalia: These are commonly called as “animals with mammary glands for producing milk to nourish their young ones”. A lung for respiration, heart is four chambered, skin has hairs, sweat or oil glands. They are warm-blooded animals. They lay eggs (Platypus, Echidna), give birth to young ones poorly developed (Kangaroo) & give birth to developed  young ones (Human beings). Ex. Lion, Whale,


NOMENCLATURE: The system of scientific naming or nomenclature was introduced by Carolus Linnaeus. It is unique to identify in the world. We limit ourselves to writing the names of the Genus and Species of that particular organism. The world over, it has been agreed that both these names will be used in Latin forms.When printed is given in italics and when written by hand, the Genus and Species name have to be underlined separately.

Ex. Ostrich (Common name): Struthiocamelus(scientific name with two parts namely the Genus and Species).

Key terms:

Any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry.

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

Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals.

Animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals

The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates.

The body cavity which is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes. 

The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes. 

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