Animals are the multicellular eukaryotic organisms which belong to the kingdom Animalia.
Criteria for classification
Animals are classified on the basis of different features.
• Cellular or tissue level of body organization
• Body symmetry
• Type of body cavity called as coelom
• Presence or absence of segmentation
• Presence or absence of a backbone.
Classification of animal kingdom
Classification of the kingdom Animalia includes Invertebrata and Vertebrata.
Invertebrata: It includes group of animals that do not possess a vertebral column. Invertebrata is classified into different phyla such as Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca and Echinodermata.
a) Porifera are multicellular organisms exhibiting minimal level of tissue organization. They lack nervous system. Porifera get their name from two words, “pori,” meaning “holes,” and “fera,” meaning “bearing”. Porifera includes Sycon, Spongilla and Euplectella. e.g. Sponges.
b) Coelenterates are radially symmetrical organisms which live in marine habitat except for hydra. Some are solitude and some are colonial. Coelenterates get their name from two Greek words - “koilos,” meaning “hollow,” and “enteron,” meaning “intestine”. e.g. Corals, Hydra.
c) Platyhelminthes are either free living or parasitic. They are triploblastic animals. Platyhelminthes get their name from two Greek words - “platy,” meaning “flat,” and “helminthes,” meaning “worms”. e.g. Planaria.
d) Nematoda are bilaterally symmetrical, triploblastic parasitic worms. Nematoda get their name from two Greek words - “nema,” which means “thread,” and “ode,” which means “like”. Nematodes can be free living or parasitic.
e) Annelida are bilaterally symmetrical, triploblastic, schizocoelomates with segmented body. Annelida get their name from the Latin word “anellus,” which means "little ring". Annelids are characterised by the presence of a circulatory system. e.g. Earthworm.
f) Arthropoda are bilaterally symmetrical, triploblastic animals with true coelom. Arthropoda means “joint legs”. This phylum gets its name from the Greek words arthron, meaning “joint”, and podos, meaning “foot”.
g) Molluscs are bilaterally symmetrical, triploblastic gastropods with reduced coelom. Mollusca is derived from a Latin word, which means “thin-shelled and soft”.
h) Echinodermata are triploblastic animals with true coelomic cavity. Echinodermata are spiny skinned organisms which get their name from the Greek words “echinos,” meaning protective “spines,” and “derma,” meaning “skin”. Skeletons of echinoderms are hard calcium carbonates. They exhibit radial symmetry.
Protochordata: These are the organisms belonging to the phylum Chordata, and are primitive chordates. Protochordates possess a notochord during their early stage of development. The notochord is a long rod-like support that runs all along the back of the animal separating the nervous tissue from the gut. e.g.Balanoglossus, Herdmania.
Vertebrata: These are the most advanced group of animals with true vertebral column and strong endoskeleton. Vertebrates are grouped into different classes based on bilateral symmetry, notochord, dorsal nerve cord, paired gill pouches, triploblastic, and coelomate. These classes are Pisces, Amphibia, Reptilia, Aves and Mammalia.
a) Pisces includes all fish. These are aquatic cold blooded organisms with a spindle-shaped body covered by scales.
b) Amphibians are cold-blooded animals. Amphibians can live both on land and in water. They are the first vertebrates to have four limbs, each with five digits and are called tetrapods.
c) Reptilia are cold-blooded animals. They have four limbs with five fingers or toes each, and hence, are called pentadactyle tetrapods.
d) Aves are warm-blooded animals. Birds bear three clawless digits.
Animals are the multicellular eukaryotic organisms which belong to the kingdom Animalia.
Criteria for classification
Animals are classified on the basis of different features.
• Cellular or tissue level of body organization
• Body symmetry
• Type of body cavity called as coelom
• Presence or absence of segmentation
• Presence or absence of a backbone.
Classification of animal kingdom
Classification of the kingdom Animalia includes Invertebrata and Vertebrata.
Invertebrata: It includes group of animals that do not possess a vertebral column. Invertebrata is classified into different phyla such as Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca and Echinodermata.
a) Porifera are multicellular organisms exhibiting minimal level of tissue organization. They lack nervous system. Porifera get their name from two words, “pori,” meaning “holes,” and “fera,” meaning “bearing”. Porifera includes Sycon, Spongilla and Euplectella. e.g. Sponges.
b) Coelenterates are radially symmetrical organisms which live in marine habitat except for hydra. Some are solitude and some are colonial. Coelenterates get their name from two Greek words - “koilos,” meaning “hollow,” and “enteron,” meaning “intestine”. e.g. Corals, Hydra.
c) Platyhelminthes are either free living or parasitic. They are triploblastic animals. Platyhelminthes get their name from two Greek words - “platy,” meaning “flat,” and “helminthes,” meaning “worms”. e.g. Planaria.
d) Nematoda are bilaterally symmetrical, triploblastic parasitic worms. Nematoda get their name from two Greek words - “nema,” which means “thread,” and “ode,” which means “like”. Nematodes can be free living or parasitic.
e) Annelida are bilaterally symmetrical, triploblastic, schizocoelomates with segmented body. Annelida get their name from the Latin word “anellus,” which means "little ring". Annelids are characterised by the presence of a circulatory system. e.g. Earthworm.
f) Arthropoda are bilaterally symmetrical, triploblastic animals with true coelom. Arthropoda means “joint legs”. This phylum gets its name from the Greek words arthron, meaning “joint”, and podos, meaning “foot”.
g) Molluscs are bilaterally symmetrical, triploblastic gastropods with reduced coelom. Mollusca is derived from a Latin word, which means “thin-shelled and soft”.
h) Echinodermata are triploblastic animals with true coelomic cavity. Echinodermata are spiny skinned organisms which get their name from the Greek words “echinos,” meaning protective “spines,” and “derma,” meaning “skin”. Skeletons of echinoderms are hard calcium carbonates. They exhibit radial symmetry.
Protochordata: These are the organisms belonging to the phylum Chordata, and are primitive chordates. Protochordates possess a notochord during their early stage of development. The notochord is a long rod-like support that runs all along the back of the animal separating the nervous tissue from the gut. e.g.Balanoglossus, Herdmania.
Vertebrata: These are the most advanced group of animals with true vertebral column and strong endoskeleton. Vertebrates are grouped into different classes based on bilateral symmetry, notochord, dorsal nerve cord, paired gill pouches, triploblastic, and coelomate. These classes are Pisces, Amphibia, Reptilia, Aves and Mammalia.
a) Pisces includes all fish. These are aquatic cold blooded organisms with a spindle-shaped body covered by scales.
b) Amphibians are cold-blooded animals. Amphibians can live both on land and in water. They are the first vertebrates to have four limbs, each with five digits and are called tetrapods.
c) Reptilia are cold-blooded animals. They have four limbs with five fingers or toes each, and hence, are called pentadactyle tetrapods.
d) Aves are warm-blooded animals. Birds bear three clawless digits.