ANIMAL KINGDOM
Animals are classified on the basis of common fundamental features like the cellular
arrangement, symmetry of the body, presence or absence of the coelom, specific features of
the digestive, circulatory and reproductive system
Cellular level of organization: cells arranged as loose aggregates, present in Peripheral
(sponges)
Tissue level of organization: cells performing the same function form tissues, present in
coelenterates
Organ level of organization: tissues grouped together to form an organ, which performs
particular function, e.g. Platyhelminthes
Organ system level of organization: few organs coordinative perform a certain
physiological function, e.g. Annelids, Arthropods, Mollusks, Echinoderms and Chordates
Open circulatory system: cells and tissue directly receive the blood pumping out of the
heart
Closed circulatory system: blood is circulated through arteries, veins and capillaries
Diploblastic: embryo with two germinal layers called external ectoderm and internal
endoderm, e.g. Peripheral, Cnidarian
Triploblastic: embryo with three germinal layers, mesoderm between ectoderm and
endoderm, e.g. Platyhelminthes to Chordates
Asymmetrical: no line of symmetry in the body, e.g. sponges
Radial symmetry: any plane passing through center divides the body in two symmetrical
halves, e.g. coelenterates, ctenophores
Bilateral symmetry: a plane divides the body in symmetrical left and right halves, e.g.
annelids, arthropods, etc.
Echinoderms exhibit radial as well as bilateral symmetry at different stages of their life
Body cavity between the body wall and gut wall, lined by mesoderm is called coelom
Acoelomates: body cavity is absent, e.g. Platyhelminthes
Pseudo coelomates: mesoderm is present as scattered pouches, e.g. As helminthes
Coelomates: having coelom (body cavity) e.g. from Annelida to Chordata
Earthworm’s body shows metameric segmentation
Animals with notochord are called chordates, animals without notochord are called non-
chordates, e.g. Peripheral to Echinodermata
Also see: Biology syllabus for NEET
Classification of Animals
, Classification of the Animal Kingdom based on common
fundamental features
1.
1. Phylum – Peripheral (Sponges)
Marine, asymmetrical with the cellular level of organization
Food intake, gaseous exchange and excretion occurs through the water
transport system
Water enters through pores called Ostia and goes out through osculum via
central cavity known as spongocoel
Spongocoel is lined by collar cells or choanocytes
Intracellular digestion
Body skeleton is made up of spongin fibres or spicules
Sponges are hermaphrodite
Reproduce asexually by fragmentation and sexually by the formation of
gametes
Fertilization is internal and the development of zygote goes through a distinct
larval stage
Examples: Spoonbill (freshwater sponge), Euspongia (bath sponge), Sicyon,
1.
Animals are classified on the basis of common fundamental features like the cellular
arrangement, symmetry of the body, presence or absence of the coelom, specific features of
the digestive, circulatory and reproductive system
Cellular level of organization: cells arranged as loose aggregates, present in Peripheral
(sponges)
Tissue level of organization: cells performing the same function form tissues, present in
coelenterates
Organ level of organization: tissues grouped together to form an organ, which performs
particular function, e.g. Platyhelminthes
Organ system level of organization: few organs coordinative perform a certain
physiological function, e.g. Annelids, Arthropods, Mollusks, Echinoderms and Chordates
Open circulatory system: cells and tissue directly receive the blood pumping out of the
heart
Closed circulatory system: blood is circulated through arteries, veins and capillaries
Diploblastic: embryo with two germinal layers called external ectoderm and internal
endoderm, e.g. Peripheral, Cnidarian
Triploblastic: embryo with three germinal layers, mesoderm between ectoderm and
endoderm, e.g. Platyhelminthes to Chordates
Asymmetrical: no line of symmetry in the body, e.g. sponges
Radial symmetry: any plane passing through center divides the body in two symmetrical
halves, e.g. coelenterates, ctenophores
Bilateral symmetry: a plane divides the body in symmetrical left and right halves, e.g.
annelids, arthropods, etc.
Echinoderms exhibit radial as well as bilateral symmetry at different stages of their life
Body cavity between the body wall and gut wall, lined by mesoderm is called coelom
Acoelomates: body cavity is absent, e.g. Platyhelminthes
Pseudo coelomates: mesoderm is present as scattered pouches, e.g. As helminthes
Coelomates: having coelom (body cavity) e.g. from Annelida to Chordata
Earthworm’s body shows metameric segmentation
Animals with notochord are called chordates, animals without notochord are called non-
chordates, e.g. Peripheral to Echinodermata
Also see: Biology syllabus for NEET
Classification of Animals
, Classification of the Animal Kingdom based on common
fundamental features
1.
1. Phylum – Peripheral (Sponges)
Marine, asymmetrical with the cellular level of organization
Food intake, gaseous exchange and excretion occurs through the water
transport system
Water enters through pores called Ostia and goes out through osculum via
central cavity known as spongocoel
Spongocoel is lined by collar cells or choanocytes
Intracellular digestion
Body skeleton is made up of spongin fibres or spicules
Sponges are hermaphrodite
Reproduce asexually by fragmentation and sexually by the formation of
gametes
Fertilization is internal and the development of zygote goes through a distinct
larval stage
Examples: Spoonbill (freshwater sponge), Euspongia (bath sponge), Sicyon,
1.
