Activity-3: Write the special character of the phyla of the animal kingdom, with the help
of given diagrams
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Echinodermata
Mollusca
Platyhelminthes
Arthropoda
Annelida
Triploblastic
animals
Answers
Explanation:
Table of Contents
Basis for Animal Kingdom Classification
Levels of Organisation
Symmetry
Diploblastic and Triploblastic Organisation
Coelom
Segmentation
Notochord
Classification of Animal Kingdom
Phylum – Porifera
Phylum – Coelenterata (Cnidaria)
Phylum – Ctenophora
Phylum – Platyhelminthes
Phylum – Aschelminthes (Nemotoda)
Phylum – Annelida
Phylum – Arthropoda
Arachnids
Crustaceans
Insects
Phylum – Mollusca
Phylum – Echinodermata
Phylum – Hemichordata
Phylum – Chordata
Classification of Animal Kingdom – Porifera, Coelenterata, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Chordata.]
Basis for Animal Kingdom Classification
Classification of Animal Kingdom is based on various fundamental features like –
Levels of Organisation,
Symmetry,
Diploblastic and Triploblastic Organisation,
Coelom development,
Segmentation of the body and
Presense or absence of Notochord.
The broad classification of Animalia based on common fundamental features:
Levels of Organisation
Though all members of Animalia are multicellular, all of them do not exhibit the same pattern of organisation of cells.
For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit cellular level of organisation. Some division of labour (activities) occur among the cells.
In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues, hence is called tissue level of organisation.
A still higher level of organisation, i.e., organ level [organ level of organisation] is exhibited by members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialised for a particular function.
In animals like Annelids, Arthropods, Molluscs, Echinoderms and Chordates, organs have associated to form functional systems, each system concerned with a specific physiological function. This pattern is called organ system level of organisation.
Organ systems in different groups of animals exhibit various patterns of complexities.
For example, the digestive system in Platyhelminthes (incomplete digestive system) has only a single opening to the outside of the body that serves as both mouth and anus, and is hence called incomplete. A complete digestive system has two openings, mouth and anus.
Similarly, the circulatory system may be of two types: open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it and closed type in which the blood is circulated through a series of vessels of varying diameters (arteries, veins and capillaries).
Symmetry
Animals can be categorised on the basis of their symmetry.
Sponges are mostly asymmetrical, i.e., any plane that passes through the centre does not divide them into equal halves.
When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry. Coelenterates, Ctenophores and Echinoderms have this kind of body plan.
Animals like Annelids, Arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry.