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). |
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) |
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 |