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Biology, animal kingdom


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Main groups of Animal Kingdom are : Porifera (sponges) Cnidaria or Coelenterata (jellyfish, hydras, sea anemones, Portuguese man-of-wars, and corals) Ctenophora (pleurobrachia and ctenoplana) Platyhelminthes (flatworms, including planaria, flukes, and tapeworms) Nematoda or Aschelminthes (roundworms, including rotifers and nematodes)


6 . Annelida (segmented worms, including earthworms, leeches, and marine worms ) 7. Arthropoda (including arachnids, crustaceans, millipedes, centipedes, and insects ) 8. Mollusca (mollusks, including bivalves, snails and slugs, and octopuses and squids ) 9.Echinodermata (including sea stars, sea cucumbers, sand dollars, and sea urchins) Hemichordata (balanoglossus and saccoglossus) Chordata (animals with nerve chords - this group includes the vertebrates)


PORIFERA Porifera – (having pores) Commonly known as sponges. Most primitive group 5000 species. Most are marine to remain attached to the rocks. Range from 1cm to 1m in length. Larger ones are asymmetric (few are radially symmetrical). Body consists of a layer of cells lining a non-living matrix.


5. Pores “ostia” connect outside to a central chamber “spongocoel” from where water goes out to “osculum”. 6. “Choanocytes” or collar cells are flagellated and line the canal while flagellated cells line the outer and inner surfaces and Amoeboid cells wander through the matrix carrying food between cells. 7. Sponges have ‘water transport’ or canal system. 8. The body is supported by a skeleton made up of spicules or spongin fibres .


They are hermaphrodite. Asexual reproduction by fragmentation and sexual is through the gametes (some cells become egg cells or spum cells). Fertilization is internal. Sponge is a republic of cells which identify one another aggregate and grow together. Sponge cells separated by straining pieces of sponge through a fine net, can reaggregate and grow into a sponge.


Sponges Porifera Aphrocallistes vastus


COELENTERATA (CNIDARIA) Cnidaria term is derived from the cnidoblasts, cnidoblasts which contain the stinging capsules or nematocytes present on the tentacles and the body. Includes 9000 species. They are aquatic, mostly marine (hydra fresh water), sessile or free swimming and radially symmetrical. Tissue level of organisation.


Diploblastic and body consists of 2 layers: (i) Ectoderm. (ii) Endoderm. Ectodermal cells, lining the blind sac or Gastro vascular are specialized for secreting digestive enzymes. Gastro vascular cavity has single opening, mouth on hypostome. Digestion is extracellular and intracellular. Some have, eg. Corals have skeleton composed of CaCo 3. Cnidaria exhibit 2 basic forms the Polyp and Medusa.


Polyp : Polyp is sessile and the body is hydra like that is a cylindrical stock with mouth and tentacles facing upwards. Medusa : Medusa is the free floating or swimming structure like the jelly fish, it is like a bell or an umbrella with mouth and tentacles facing downwards. The medusa can be regarded as an upside- down polyp, the reduced stock which can swim away. Example -> Physalia,. Adamisa, Pennatula, Gorgonia, Meandrina.


Acropora millepora Gorgonians snailfur Hydractinia echinata


CTENOPHORA Commonly known as Sea walnuts or Comb jellies. They are generally marine, radially symmetrical, diploblastic organisms with tissue level of organisation. Body bears 8 external rows of ciliated comb plates, which help in locomotion. Digestion is both extracellular and intracellular .


Biolumiescence (the property of a living organism to emit light) is well marked in ctenophores. Sexes are not separate. Reproduction takes place only by sexual means. Fertilisation is external with indirect develpoment. Example- Pleurobrachia and Ctenoplana.


PLATYHELMINTHES The phylum Platyhelminthes (meaning flatworms in greek) contains about 13000 species mostly parasites that live in other animals, including man. They are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation. Hooks and Suckers are present in the parasite forms.


They don’t have (parasite tapeworms) their own digestive sac. They absorb nutrients through their body wall, while living the hosts intestine. Planaria and the parasitic flatworms have specialized cells called “Flame cells” for excretion and osmoregulation. Planaria have primitive sensory organs consisting of 2 eye spots on the dorsal side for light perception. Their body is coordinated by a pair of nerve cords running along the ventral side.


Flatworms can regenerate and reproduce asexually from a part of the body. They also reproduce sexually. They are hermaphrodite, but the anatomy encourages cross-fertilization rather than self-fertilization. The fertilization is internal. Indirect development is through many larval stages. Example- Tapeworm – upto 4m in length


Human liver fluke Clonorchis sinensis broad fish tapeworm Diphyllobothrium latum common liver fluke Fasciola hepatica


ASCHELMINTHES The body of the aschelminthes is circular in cross-section, hence the name is roundworms . They may be free living, aquatic and terrestrial or parasitic in plants and animals. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals having organ system level of organisation. They have tube–within -a tube – body plan with mouth, pharynx, intestine and anus.


The mouth may be arrived with teeth to cut and pierce plant tissue. An organised nerve ganglionis present around the pharynx with dorsal and ventral nerves to coordinate movement. An excretory tube removes body wastes from the body cavity. They are unisexual, often with small and larger female individuals. The fertilization is internal.


Development may be direct or indirect. They are also known as Nematodes. (Nemathelminthes – phylum) Example- Ascaris (Round worm) Wuchereria (Filaria worm) Ancyclostomata (Hook worms)


ANNELIDA Their body surface is distinctly marked out into segments or metameres and hence the name is Annelida. [ Latin, annulus : little ring] They may be aquatic (marine and fresh water) or terrestrial, free living and sometimes parasitic. They are bilaterally symmetrical, triploblastic, metamerically segmented,coelomate animals having organ system level of organisation .


They possess longitudinal and circular muscles which help in locomotion as in earthworm. In earthworm bristles or chaetae are present on the lower side to help to grip the ground during locomotion. The polychaetes have numerous bristles on lateral appendages called parapodia. They consist of a muscular pharynx to swallow food, an oesophagus to carry it to the stomach where it is churned and digested and a long intestine to absorb the nutrients.


A closed circulatory system of blood vessels, a ‘heart’ to move the blood is found. Oxygenation of blood occurs through the moist skin. Excretory organs are paired Nephridia in each segment. Sexes are separate in polychaetes but earthworms and leeches are hermaphrodite. Reproduction is sexual. Example- Nerieis, Pheretima.


Haementeria ghilianii Nephtys hombergii Lumbricidae


ARTHROPODA Animals which have joint legs and appendages. It has about 9,00,000 species, thus the phylum arthropoda costitutes the largest group of animals. It includes four major classes- : Arachnida (scorpion and spiders) : Crustacea (crabs and prawns) : Myriapoda (millipedes and centipedes) : Insecta (all insects)


The body is covered by chitinous exoskeleton. They have a segmented body but not separated by septa as in annelids. They are bilaterally symmetrical, triploblastic and coelomate animals. Respiratory organs are gills, book gills, book lungs or tracheal system. Circulatory system is of open type. Sensory organs are like antennae, eyes (compound and simple), statocyst or balance organs are present.


The body consists of head, thorax and abdomen. In arachnids the head and thorax are fused as a cephalothorax. The head consists of severak fused segments with appendages modified top serve as antennae mouth parts. Thorax segments carry legs and wings; the abdomen has no legs in insects. Excretion takes place through ‘Malpighian-tubule’. They are mostly dioecious/unisexual .


13. Fertilization is usually internal. 14. They are mostly oviparous. (scorpion-viviparous) 15. Development may be direct or indirect. Example- Economically important insects- Apis (Honey bee), Bombyx (silkworm) Vectors :– Anepheles, Acedes (mosquitoes) Gregarious pest :- Locusta (locust) Living Fossil :- Limulus (king crab)


Honey bee Apis mellifera silk moth Bombyx mori


MOLLUSCA The soft bodied and shelled animals. Latin: Molluscus = soft bodied Second largest animal phylum. The anterior head region has sensory tentacles. The mouth contains a file like rasping organs for feeding. The three major molluscan groups are gastropods, trivalves and cephalopods .


4. Gastropods have a single coated shell. The group includes snails and the shell less slug. Their larvae are bilaterally symmetric but this symmetry is lost in adults because of the twisting of the viseera as the shell is formed. 5. Bivalves have 2 hinged shells and include aysters and clams, they are pieter feeders. 6. The Cephalopods include octopuses and squids. The foot and head regions are combined and modified into a structure bearing eyes and eight or ten tentacles with numerous suction cups.


Octopodidae common or european cuttlefish Sepia officinalis Sepia latimanus

ECHINODERMATA (spiny/skinned):

ECHINODERMATA (spiny/skinned) Only marine animals such as star fishes, brittle stars, sea urchins, sea ciumber, sand dollars and sea lillies. These animals have an endoskeleton of calcareous ossicles and hence the name Echinodermata. All echinoderms are radially symmetrical with body parts occuring in fives.


The star fish h five arms radiating from a centre. But, their larvae are bilaterally symmetrical they become radially symmetrical they become radially symmetrical as they mature. Their most distinctive feature is the “water vascular system”. It consists of an array of radiating canals and tube like appendages called tube-feet. Their main function is locomotion and the capture of food. They have organ system level of organization, triploblastic and coelomate animals.


Digestive system is complete with mouth on the lower(ventral) side and anus on the upper (dorsal) side. An excretory system is absent. Sexes are separate and reproduction is asexual. Fertilization is usually internal. Development is indirect with free swimming larvae.


crown-of-thorns starfish Acanthaster planci Asterias amurensis fire urchin Asthenosoma varium


HEMICHORDATA Hemichordata was earlier cosidered as a sub phylum under phylum chordata. But now it is placed as a separate phylum under non-chordata. Worm like marine animals with organ system level of organization. They are bilaterally symmetrical, triploblastic and coelomate animals. Body is cylindrical and is composed of anterior proboseis, a collar and a long trunk.


It has open circulatory system. It respirates through gills. Its excretory organ is proboseis gland. Their sexes are separate. Fertilization is external. Developmet is indirect. Example - Balanoglossus


CHORDATA 1. 3 main characters of chordates :- (i) notochord (ii) a dorsal hollow nerve cord (iii) a paired pharyngeal gill slits 2. These are bilaterally symmetrical, triploblastic, coelomate which have organ system level of organization.


They possess a post anal tail and a closed circulatory system. Chordates are divided into 3 sub-types – (i) Urochordata (ii) Cephalochordata (iii) Vertebrata


Ablabys taenianotus rifleman Acanthisitta chloris Bolivian chinchilla rat Abrocoma boliviensis Ablepharus pannonicus northern goshawk Accipiter gentilis cheetah Acinonyx jubatus



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