COMPARATIVE STUDY OF KINGDOM ANIMALIA

Features	Porifera (Sponges)	Cnidaria (Coelenterata)	Ctenophora (Comb jellies or Sea walnuts)
Grades of organization	Cellular	Tissue	Tissue
Symmetry	Asymmetrical/radial	Radial	Radial
Germ layers	Diploblastic	Diploblastic	Diploblastic
Coelom	Acoelomate	Acoelomate	Acoelomate
Habit and habitat	Aquatic (mostly marine). Sedentary. Solitary or colonial.	Aquatic (mostly marine). Sessile/free swimming. Solitary/colonial.	Exclusively marine. Solitary & pelagic
Digestive system	Absent. Water transport (canal system) to gather food. Intracellular digestion.	Incomplete. Intracellular & extracellular digestion.	Incomplete. Intracellular and extracellular digestion.
Respiratory system	Absent. Respiration by canal system	Absent	Absent
Circulatory system	Absent. Circulation by canal system	Absent	Absent
Excretory system	Absent. Excretion by canal system.	Body surface.	Body surface.
Neural system	Absent.	Only a network of neurons.	Only a network of neurons.
Reproductive system	Asexual (fragmentation) and Sexual. Hermaphrodite. Internal fertilization. Development is indirect.	Polyp reproduces asexually (budding) and medusa sexually. Most are separate sexes. External fertilization. Development is indirect.	Only Sexual. Hermaphrodite. External fertilization. Development is indirect.
Unique features	Millions of minute pores (ostia). Spongocoel (body cavity) and canals are lined with choanocytes (collar cells). Body is supported by spicules and spongin fibres.	Tentacles with cnidoblasts. A gastro-vascular cavity (coelenteron) with a single opening (mouth) on hypostome. Polyp & Medusa forms are seen. Some shows alternation of generation. Corals have skeleton (CaCO3).	Locomotion is by 8 vertical external rows of ciliated comb plates. Tentacles present. Shows Bioluminescence
Examples	Sycon (Scypha), Spongilla (fresh water sponge), Euspongia (Bath sponge)	Hydra, Obelia, Aurelia, Physalia (Portugese man of war), Adamsia (Sea- anemone), Pennatula (Sea pen)), Gorgonia (Sea fan), Meandrina (Brain coral) etc.	Ctenoplana, Pleurobrachia

1.      Canal system (water transport): A system in sponges. Here, water enters through minute pores (ostia) in the body wall into a central cavity (spongocoel), from where it goes out through osculum. Canal system is used for food gathering, gas exchange and removal of wastes.

2.      Hermaphrodite: Male and female sex organs are seen in same individual.

3.      Tentacles: Finger-like structures which surrounds the mouth of coelenterates. Used for food capture & defense.

4.     Cnidoblasts (Cnidocytes): These are stinging cells (present on the tentacles and the body) with a poison-filled capsule  called nematocyst. Cnidoblast is used for anchorage, defense and to capture prey.

5.      Polyp & Medusa: 2 types of body forms in cnidarians.

Polyp is tubular attached asexual form, with upwardly directed mouth & tentacles. E.g. Hydra, Adamsia.

Medusa is umbrella like, free-swimming sexual form, with downwardly directed mouth & tentacles. E.g. Aurelia (Jelly fish).

6.      Alternation of generation (Metagenesis): The phenomenon in which polyps produce medusae asexually and medusae form the polyps sexually. E.g. Obelia.

7.      Bioluminescence: It is the property of some animals to emit light from the body.

Features	Platyhelminthes (Flatworms)	Aschelminthes (Nemathelminthes or Roundworms)	Annelida (Segmented or Ringed worms)	Arthropoda (Joint-legged animals)
Grades of organization	Organ & Organ system	Organ system	Organ system	Organ system
Symmetry	Bilateral	Bilateral	Bilateral	Bilateral
Germ layers	Triploblastic	Triploblastic	Triploblastic	Triploblastic
Coelom	Acoelomate	Pseudocoelomate	Eucoelomate	Eucoelomate
Habit and habitat	Mainly aquatic. Endoparasites. Some are free-living.	Aquatic and terrestrial. Free living or parasitic in plants & animals.	Terrestrial, fresh water or marine. Free living or parasitic.	Cosmopolitan
Digestive system	Incomplete	Complete. Tubular alimentary canal with well-developed muscular pharynx.	Complete	Complete and well developed.
Respiratory system	Absent	Absent	Cutaneous respiration. Some have branchial (gill) respiration	Gills/ book gills/ trachea/book lungs
Circulatory system	Absent	Absent	Closed type	Open type
Excretory system	Flame cells	An excretory tube to remove body waste through excretory pore.	Nephridia	Antennary glands/ Malpighian tubules/ coxal glands
Neural system	Present	Present	Paired ganglia connected by lateral nerves to a double ventral nerve cord.	A nerve ring followed by a double ventral ganglionated nerve cord.
Reproductive system	Asexual (fragmentation) and Sexual. Hermaphrodite. Internal Fertilization. Development is indirect (many larval stages).	Sexes are separate (Dioecious). Sexual reproduction. Internal fertilization. Development is direct or indirect.	Sexual. Earthworms & leeches are hermaphrodites. Neries is dioecious. Development is indirect.	Sexes are separate. External fertilization in aquatic forms. Internal fertilization in land forms. Mostly oviparous. Development is direct or indirect.
Unique features	Unsegmented, dorso-ventrally flattened body (except tape worms). Hooks & suckers in parasitic forms. Some absorb nutrients from the host through their body surface.	Syncitial epidermis. Thick cuticle. Sexual dimorphism (females are longer than males).	True segmentation. Longitudinal and circular muscles help in locomotion. Locomotory organs are setae (in earthworm) or parapodia (in Neries).	Jointed appendages. Body has 3 regions: head, thorax & abdomen. Body is covered by chitinous cuticle (exoskeleton). Sensory organs are antennae, compound & simple eyes, statocysts (balance organs).
Examples	Taenia solium (Tape worm), Fasciola (Liver fluke), Planaria (shows high regeneration capacity).	Ascaris (Roundworm), Ancylostoma (Hookworm), Wuchereria (Filarial worm).	Pheretima (Earthworm), Hirudinaria (Blood sucking Leech), Neries.	Spider, Scorpion, Crab, Prawn, Insects etc. Economically important insects: Apis, Bombyx, Laccifer. Vectors: Mosquitoes (Anopheles, Culex & Aedes), Housefly etc. Gregarious pest: Locusta. Living fossil: Limulus (King crab)