1. INTRODUCTION

Multicellular organisms with holozoic mode of nutrition are called the metazoans Based on the complexity of organization, meta- zoans are divided into subkingdoms. Parazoa (Sponges) and Eumetazoa

Metazoa: 

1.Parazoa (Sponges)

2.Eumetazoa (Rest all animals)

Animal Kingdom BASIS OF CLASSIFICATION

Though there are differences in structure and form of different animals, there are several fundamental features common to various animals in relation to the arrangement of cells, body symmetry, and nature of coelom patterns of digestive, circulatory, or reproduc- tive systems So, these features are used as the basis of classification EP

Labels Of Organization 

Though all members of Animalia are multicellular, all of them do got exhibit the same pattern of organization of cells, For example, in sponges, the cells are arranged as loose cell aggregates, ie, they exhibit cellular level of organization. Some division of labour occurs among the cells. In coelenterates and clenophores, the cells performing the same function are arranged into tissues. It is called tissue level of organization. A still higher level of organization, ie, organ level of organization is exhibited by members of

Platyhelminthes In Aschelminthes. Annelids, Arthropods, Molluscs, Echinoderms, and Chordates, organ system level of organi zation is seen. Here, organs have been associated to form functional system. Organ systems in different group of animals exhibit various patterns of complexities. For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth as well as anus, and hence is called incomplete-digestive tract A complete digestive tract has

In Aschelminthes, Annelids, Arthropods, and Molluses, mouth develops from blastopore during embryonic life, so, they have pro-

tostomous development In Echinoderms and Chordates, anus develops first, so it is called deuterostomous development

Similarly, the circulatory system may be of two types:

(1) Open type of circulatory system in which blood is pumped out of the heart and the cells and tissues are directly bathed in it

This is found in arthropods, molluscs, hemichordates, and urochordates (tunicates) (1) Closed type of circulatory system in which the blood is circulated through a series of vessels of varying diameters (arteries veins, and capillaries), it is found in annelids and vertebrates

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Multicellular organisms with holozoic mode of nutrition are called the metazoans Based on the complexity of organization, meta- zoans are divided into subkingdoms. Parazoa (Sponges) and Eumetazoa

Metazoa: 

1.Parazoa (Sponges)

2.Eumetazoa (Rest all animals)

Animal Kingdom BASIS OF CLASSIFICATION

Though there are differences in structure and form of different animals, there are several fundamental features common to various animals in relation to the arrangement of cells, body symmetry, and nature of coelom patterns of digestive, circulatory, or reproduc- tive systems So, these features are used as the basis of classification EP

Labels Of Organization 

Though all members of Animalia are multicellular, all of them do got exhibit the same pattern of organization of cells, For example, in sponges, the cells are arranged as loose cell aggregates, ie, they exhibit cellular level of organization. Some division of labour occurs among the cells. In coelenterates and clenophores, the cells performing the same function are arranged into tissues. It is called tissue level of organization. A still higher level of organization, ie, organ level of organization is exhibited by members of

Platyhelminthes In Aschelminthes. Annelids, Arthropods, Molluscs, Echinoderms, and Chordates, organ system level of organi zation is seen. Here, organs have been associated to form functional system. Organ systems in different group of animals exhibit various patterns of complexities. For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth as well as anus, and hence is called incomplete-digestive tract A complete digestive tract has

In Aschelminthes, Annelids, Arthropods, and Molluses, mouth develops from blastopore during embryonic life, so, they have pro-

tostomous development In Echinoderms and Chordates, anus develops first, so it is called deuterostomous development

Similarly, the circulatory system may be of two types:

(1) Open type of circulatory system in which blood is pumped out of the heart and the cells and tissues are directly bathed in it

This is found in arthropods, molluscs, hemichordates, and urochordates (tunicates) (1) Closed type of circulatory system in which the blood is circulated through a series of vessels of varying diameters (arteries veins, and capillaries), it is found in annelids and vertebrates

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Multicellular organisms with holozoic mode of nutrition are called the metazoans Based on the complexity of organization, meta- zoans are divided into subkingdoms. Parazoa (Sponges) and Eumetazoa

Metazoa: 

1.Parazoa (Sponges)

2.Eumetazoa (Rest all animals)

Animal Kingdom BASIS OF CLASSIFICATION

Though there are differences in structure and form of different animals, there are several fundamental features common to various animals in relation to the arrangement of cells, body symmetry, and nature of coelom patterns of digestive, circulatory, or reproduc- tive systems So, these features are used as the basis of classification EP

Labels Of Organization 

Though all members of Animalia are multicellular, all of them do got exhibit the same pattern of organization of cells, For example, in sponges, the cells are arranged as loose cell aggregates, ie, they exhibit cellular level of organization. Some division of labour occurs among the cells. In coelenterates and clenophores, the cells performing the same function are arranged into tissues. It is called tissue level of organization. A still higher level of organization, ie, organ level of organization is exhibited by members of

Platyhelminthes In Aschelminthes. Annelids, Arthropods, Molluscs, Echinoderms, and Chordates, organ system level of organi zation is seen. Here, organs have been associated to form functional system. Organ systems in different group of animals exhibit various patterns of complexities. For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth as well as anus, and hence is called incomplete-digestive tract A complete digestive tract has

In Aschelminthes, Annelids, Arthropods, and Molluses, mouth develops from blastopore during embryonic life, so, they have pro-

tostomous development In Echinoderms and Chordates, anus develops first, so it is called deuterostomous development

Similarly, the circulatory system may be of two types:

(1) Open type of circulatory system in which blood is pumped out of the heart and the cells and tissues are directly bathed in it

This is found in arthropods, molluscs, hemichordates, and urochordates (tunicates) (1) Closed type of circulatory system in which the blood is circulated through a series of vessels of varying diameters (arteries veins, and capillaries), it is found in annelids and vertebrates

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