NCERT-Invertebrates -Phylum Porifera to Echinodermata Characteristics

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Porifera Characteristics

Characteristic	Description
Phylum	Porifera
Common Name	Sponges
Environment	Generally marine
Symmetry	Mostly asymmetrical
Cell Organization	Cellular level of organization
Water or Canal Transport System	Through minute pores (ostia) in the body wall into a central cavity (spongocoel), then out through the osculum. Helpful in feeding, respiratory exchange, and waste removal.
Cell Types	Choanocytes or collar cells line the spongocoel and the canals
Digestion	Intracellular digestion
Support Structure	Body supported by a skeleton made up of spicules or spongin fibers
Reproduction (Sexual)	Hermaphroditic: eggs and sperms are produced by the same individual
Reproduction (Asexual)	Fragmentation
Fertilization	Internal
Development	Indirect: larval stage morphologically distinct from the adult
Examples	Sycon (Scypha), Spongilla (Fresh water sponge) and Euspongia (Bath sponge).

Porifera Characteristics

Coelenterata (Cnidaria) Characteristics

Characteristic	Description
Phylum	Coelenterata (Cnidaria)
Environment	Aquatic, mostly marine
Symmetry	Radially symmetrical
Specialized Cells	Cnidoblasts or cnidocytes containing stinging capsules or nematocysts on tentacles and body
Function of Cnidoblasts	Anchorage, defense, and prey capture
Cell Organization	Tissue level of organization, diploblastic
Gastrovascular Cavity	Central cavity with a single opening, mouth on hypostome
Digestion	Extracellular and intracellular
Skeletal Structure	Some have a skeleton composed of calcium carbonate
Body Forms	Polyp (sessile and cylindrical) and medusa (umbrella-shaped and free-swimming)
Reproduction	Alternation of generation (Metagenesis): polyps produce medusae asexually and medusae form the polyps sexually
Examples	Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan), Meandrina (Brain coral)

Porifera Characteristics

Ctenophora Characteristics

Characteristic	Description
Phylum	Ctenophora
Common Name	Sea walnuts or comb jellies
Environment	Exclusively marine
Symmetry	Radially symmetrical
Cell Organization	Tissue level of organisation, diploblastic
Ciliated Comb Plates	Body bears eight external rows of ciliated comb plates for locomotion
Digestion	Both extracellular and intracellular
Bioluminescence	Well-marked
Reproduction	Sexes not separate, reproduction occurs only sexually. Fertilisation is external with indirect development
Examples	Pleurobrachia and Ctenoplana

Platyhelminthes Characteristics

Characteristic	Description
Phylum	Platyhelminthes
Common Name	Flatworms
Body Shape	Dorso-ventrally flattened
Symmetry	Bilaterally symmetrical
Cell Organization	Triploblastic, acoelomate with organ level of organisation
Special Features	Hooks and suckers in parasitic forms, some absorb nutrients directly through body surface, flame cells for osmoregulation and excretion
Reproduction	Sexes not separate, internal fertilisation, development through many larval stages
Regeneration Capacity	Some possess high regeneration capacity
Examples	Taenia (Tapeworm), Fasciola (Liver fluke)

Aschelminthes Characteristics

Characteristic	Description
Phylum	Aschelminthes
Body Shape	Circular in cross-section, hence roundworms
Environment	Freeliving, aquatic, terrestrial, or parasitic in plants and animals
Body Organization	Organ-system level of organization
Symmetry	Bilaterally symmetrical
Cavities	Pseudocoelomate
Alimentary Canal	Complete with a muscular pharynx
Excretion	Through excretory pore by an excretory tube
Reproduction	Sexes are separate (dioecious), fertilization internal, development may be direct or indirect
Examples	Ascaris (Roundworm), Wuchereria (Filaria worm), Ancylostoma (Hookworm)

Annelida Characteristics

Characteristic	Description
Phylum	Annelida
Environment	Aquatic (marine and freshwater) or terrestrial; free-living or parasitic
Body Organization	Organ-system level of body organization
Symmetry	Bilaterally symmetrical
Segments	Metamerically segmented
Coelom	Coelomate animals
Locomotion	Longitudinal and circular muscles; some possess lateral appendages called parapodia
Circulatory System	Closed circulatory system
Excretion	Nephridia for osmoregulation and excretion
Neural System	Paired ganglia connected by lateral nerves to a double ventral nerve cord
Reproduction	Sexual, mostly dioecious
Examples	Nereis, Pheretima (Earthworm), Hirudinaria (Bloodsucking leech)
NCERT⁺	The word protostome comes from the Greek word meaning “mouth first, ”The mouth or anus develops from a structure called the blastopore. The blastopore is the indentation formed during the initial stages of gastrulation. In later stages, a second opening forms, and these two openings will eventually give rise to the mouth and anus. It has long been believed that the blastopore develops into the mouth of protostomes
Protostome	Spiral cleavage and determinate cleavage
schizocoely	The coelom of most protostomes is formed through a process called schizocoely, meaning that during development, a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom.

Arthropoda Characteristics

Characteristic	Description
Phylum	Arthropoda – Largest phylum of Animalia, Over two-thirds of all named species on earth are arthropods
Body Organization	Organ-system level of organisation
Symmetry	Bilaterally symmetrical
Segments	Segmented body
Coelom	Coelomate animals
Exoskeleton	Chitinous exoskeleton covering the body, The body consists of head, thorax and abdomen.
Appendages	Jointed appendages for movement and feeding
Respiration	Gills, book gills, book lungs, or tracheal system
Circulatory System	Open circulatory system
Sensory Organs	Antennae, compound and simple eyes, statocysts
Excretion	Through malpighian tubules
Reproduction	Mostly dioecious, fertilisation usually internal, mostly oviparous
Examples	Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect), Anopheles, Culex, Aedes (Mosquitoes), Gregarious pest-Locusta (Locust), Living fossil – Limulus (King crab)
NCERT⁺	The word protostome comes from the Greek word meaning “mouth first, ”The mouth or anus develops from a structure called the blastopore. The blastopore is the indentation formed during the initial stages of gastrulation. In later stages, a second opening forms, and these two openings will eventually give rise to the mouth and anus. It has long been believed that the blastopore develops into the mouth of protostomes
Protostome	Spiral cleavage and determinate cleavage
schizocoely	The coelom of most protostomes is formed through a process called schizocoely, meaning that during development, a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom.

Mollusca Characteristics

Characteristic	Description
Phylum	Mollusca – Second largest animal phylum
Environment	Terrestrial or aquatic (marine or fresh water)
Body Organization	Organ-system level of organisation
Symmetry	Bilaterally symmetrical
Coelom	Coelomate animals
Shell	Calcareous shell covering the body
Segments	Unsegmented body
Body Parts	With Distinct head, muscular foot, visceral hump
Mantle	A soft and spongy layer of skin forms a mantle over the visceral hump, The space between the hump and the mantle is called the mantle cavity
Respiration and Excretory	Feather like Gills in the mantle cavity
Sensory tentacles	in anterior head region
Radula	File-like rasping organ in the mouth for feeding
Reproduction	Usually dioecious, mostly oviparous with indirect development
Examples	Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish), Aplysia (Seahare), Dentalium (Tusk shell) and Chaetopleura (Chiton).
NCERT⁺	The word protostome comes from the Greek word meaning “mouth first, ”The mouth or anus develops from a structure called the blastopore. The blastopore is the indentation formed during the initial stages of gastrulation. In later stages, a second opening forms, and these two openings will eventually give rise to the mouth and anus. It has long been believed that the blastopore develops into the mouth of protostomes
Protostome	Spiral cleavage and determinate cleavage, This means that even at this early stage, the developmental fate of each embryonic cell is already determined. A cell does not have the ability to develop into any cell type.
schizocoely	The coelom of most protostomes is formed through a process called schizocoely, meaning that during development, a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom.

Echinodermata Characteristics

Characteristic	Description
Phylum	Echinodermata (Spiny bodied)
Endoskeleton	Composed of calcareous ossicles
Environment	All are marine
Symmetry	Adults: Radially symmetrical, Larvae: Bilaterally symmetrical
Body Organization	Organ-system level of organisation
Coelom	Enterocoelomate animals
Digestive System	Complete with mouth on lower or ventral side and anus on dorsal or upper side
Water Vascular System	Aids in locomotion, food capture and transport, and respiration
Excretory System	Absent
Reproduction	Sexes are separate, sexual reproduction, external fertilisation
Development	Indirect with free-swimming larva
Examples	Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber), Ophiura (Brittle star)
NCERT⁺	The word deuterostome originates from the word meaning “mouth second” (in this case, the anus develops first). blastopore develops into the mouth of protostomes, with the second opening developing into the anus; the opposite is true for deuterostomes.
Deuterostomes	Radial cleavage and indeterminate cleavage, in which cells are not yet pre-determined at this early stage to develop into specific cell types.
Enterocoely	Deuterostomes differ in that their coelom forms through a process called enterocoely. Here, the mesoderm develops as pouches that are pinched off from the endoderm tissue. These pouches eventually fuse to form the mesoderm, which then gives rise to the coelom..

Hemichordata Characteristics

Characteristic	Description
Phylum	Hemichordata – was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata.
Collar Structure	Rudimentary structure called stomochord, similar to notochord
Environment	Small group of worm-like marine animals
Body Symmetry	Bilaterally symmetrical
Body Organization	Organ-system level of organisation
Coelom	Coelomate animals
Body Shape	Cylindrical body with anterior proboscis, collar, and trunk
Circulatory System	Open circulatory system
Respiration	Through gills
Excretory Organ	Proboscis gland
Reproduction	Sexes are separate, external fertilisation, indirect development
Examples	Balanoglossus and Saccoglossus