What are the Characteristics of the Kingdom Animalia

What are the Characteristics of the Kingdom Animalia

Kingdom : Animalia or Animal Kingdom 

•  These organisms are multicellular, eukaryotic and without chlorophyll.
• The cells possess no cell walls and plastids.
• Central vacuoles are absent but small vacuoles may occur.
• Most of them are free moving (except sponges and some coelentrates)
• Nutrition is primarily ingestive.
• Reproduction is generally sexual and the haploid stage is represented only by gametes.
• Growth of organisms stops when the adult stage is reached.

Phylum – Porifera :

• Sessile (stalk-less) and marine except one group that lives in fresh water.
• Simplest multicellular, diploblastic animals.
• Have organisation at cellular colony level. Thus, cells are loosely held together and do not form tissues.
• Asymmetrical or radially symmetrical. Sponges may be vase-like, rounded, sac-like branched.
• Body is perforated by numerous pores, the ostia that open into a canal system having canals and chambers lined with collared flagellated cells or choanocytes.
• Examples – Sycon, Euplectella, (Venus flower basket) Spongilla (Fresh water sponge).

Phylum – Cnidaria (Coelenterata) :

• Aquatic, mostly marine, a few such as Hydra are fresh water solitary or colonial forms.
• Body shows radial symmetry.
• Possese specialized cells (cnidoblasts) bearing stinging organoids called nematocysts. Nematocysts serve the functions of paralysing the prey by injecting poison or to hold the prey.
• Exhibit the phenomenon of polymorphism
  (Ex- Physalia).
• Body shows two main forms, the polyps and the medusae.
• Examples – Hydra, Obelia (sea fur) , Aurelia(jelly fish), Metridium (sea anemone).

Phylum – Platyhelminthes :

• Bilaterally symmetrical and dorsoventrally flattended animals.
• Body thin, soft, leaf-like or ribbon-like.
• Digestive cavity (when present) with a single opening, the mouth (anus is absent).
• Suckers and hooks are usually present.
• Circulatory and respiratory system and skeleton are absent.
• Excretory system consists of blind tubules called protonephridia.
• Examples : Dugesia (Planaria), Fasciola (liver fluke), Schistosoma (Blood fluke), Taenia solium (Pork Tape worm).

Phylum – Aschelminthes or nematoda

• They are parasitic or free-living.
• They are triploblastic, unsegmented and show bilateral symmetry.
• Body cavity is not a true coelom.
• Alimentary canal is complete.
• Sexes are separate.
• Examples : Ascaris (Round worm), Enterobius (Pin worm), Wuchereria (filaria worm)

Phylum – Annelida :

• They occur in moist soil, fresh water and sea.
• They are elongated, with segmented body and bilateral symmetry.
• First animals with true body cavity (coelom).
• Body bears lateral appendages for locomotion in the form of chitinous setae or parapodia.
• Examples : Nereis (sand worm) Aphrodite (sea mouse), Pheretima (earthworm), Hirudinaria (Cattle leech)

Phylum – Arthropoda :

• Body is covered with a thick chitinous covering.
• Respiration through general body surface, by gills, air tubes (tracheae) or book-lungs.
• Body segments are grouped into two regions-cephalothorax (head and thorax together and abdomen, or three regions-head, thorax and abdomen.
• Triploblastic, bilaterally symmetrical and metamerically segmented animals.
• Each body segment usually bears paired lateral and jointed legs or appendages.
• Example : Palemon (Prawn), Daphnia (water flea), Limulus (King crab), Palamnaeus (Scorpion)

Phylum – Mollusca :

• They have soft, unsegmented body.
• Body is divided into three regions  (head  visceral mass and ventral foot).
• Outer surface is covered by a hard calcareous shell.
• Respiration is by gills called ctenidia.
• The sexes are usually separate.
• Examples : Chiton, Pila (Snail), Unio (Fresh water mussel), Octopus (Devil fish).

Phylum – Echinodermata :

• They are marine, gregarious (live in groups) and free-living animals.
• Shape may be star-like, spherical or elongate.
• Body surface is covered all over by calcareous spines.
• Aristotle’s lantern for mastication.
• Their symmetry is radial in adults but bilateral in larvae.
• Tube feet for locomotion.
• These are unsegmented.
• Body cavity is modified into a water-vascular system or ambulacral system with tube like outward extension for locomotion, called tube feet.
• Examples : Asterias (Star fish), Echinus (Sea urchin), Holothuria (Sea cucumber), Antedon (Feather star)

Phylum – Chordata

• Chordata are characterized by following basic features :
• A dorsal, hollow, tubular nerve cord.
• Notochord present.
• Gill slits in the pharynx.
• Tail behind the anal opening.
• Ventral heart.

Sub-phylum : Protochordata

• The sub-phylum protochordata includes animals which are bilaterally symmetrical, unsegmented, tripolblastic and have a body cavity or coelom.
• The animals belonging to protochordata possess a notochord at some stage in the life history. This is flexible rod that lies between the dorsal nerve tube and the gut.
• The notochord provides a place for muscles to attach. It increases internal support and locomotory power.
• Protochordates are usually marine, soft, have worm-like or vase-like forms.
• Examples : Balanoglossus (a corn worm or tongue worm), Herdmania and Amphioxus, etc.

Sub-phylum : Vertebrata

• The sub-phylum vertebrata includes animals which are bilaterally symmetrical, triploblastic, coelomic and segmented.
• The animal body typically consists of four regions : head, neck , trunk and tail.
• The notochord is replaced partly or fully by a jointed vertebral column (back bone) in the adult. The body of vertebrates is characterized by the presence of a well developed skeletal system that allows a special distribution of muscle attachment points to be used for movement.
• Besides vertebral column and internal skeleton the vertebrates have a well developed nervous system (brain) and sense organs (eyes, ears and nose).
• The vertebrates have a complex differentiation of body tissues or organs.
• There are two pairs of appendages (fins or limbs)
• Respiration is by gills in lower aquatic vertebrates. Higher land forms have lungs for gaseous exchange.
• Sexes are separate.

Subphylum Vertebrata is divided into seven classes :

• Class : Pisces
• Class : Amphibia
• Class : Reptilia
• Class : Aves
• Class : Mammalia

Pisces

• The animals belonging to class-Pisces are commonly called fishes. They exclusively live in water
• The skin of fishes is covered with scales/plates, which helps these animals to live in water
• The body may be long, laterally compressed and spindle shaped or dorsiventrally flattened and disc shped. It usually consists of head, trunk and a musclular tail.
• The muscular tail and fins help them to swim in water and move from one places to another.
• Fishes are cold-blooded animals and their hearts have only two chambers – one auricle and one ventricle.
• Fishes obtain oxygen dissolved in water and breathe through gills.
• They are egg laying animals. Fertilization is external.

There are many kinds of fishes. They have been broadly grouped under three categories.

• Cyclostoma : The round mouthed fishes. Examples, The hag fish, the lamprey.
• Chondrichthyes : The cartilaginous fishes. Examples Scoliodon (dog fish or the Indian Shark), sting ray, electric ray (Torpedo) (figure).
• Osteichthyes : The bony fishes. Examples, Labio rohita (Rohu), Hippocampus (Sea horse), Tuna, etc.

Class – Amphibia :

• In evolutionary terms, amphibians form the first group among the chordates to live out of water and to comprise first four-legged (tetrapod) land vertebrates. They live on land but lay their eggs in water. Amphibians are vertebrates leading two lives.
• These cold blooded animals live partly in fresh water and partly on land (moist places).
• Skin is smooth or rough, moist, slimy, glandular and mostly without scales.
• Heart 3 chambered.
• Body with distinct head and trunk, no neck.
• Two pairs of pentadactyl (five digit) limbs are present. Digits or toes without claws. Limbs may be absent in some cases.
• Example : Ichthyophis, Amphiuma (congo ell), Salamandra, Ambystoma, Necturus, Rana (bull frog), Bufo (toad), Hyla (tree-frog).

Class – Reptilia :

• Cold-blooded, terrestrial or aquatic vertebrates with body covered with dry water-proof skin having horny scales or scute plates.
• Heart 3½ chambered. Crocodyles have 4 chambered heart.
• Body varies in form and is usually divided into head, neck, trunk and tail.
• Limbs tetrapodous pentadacytle (five-toed) type with clawed digits (limbs are absent snakes and some lizards).
• Tympanum small and depressed.
• Teeth are present in all reptiles except in tortoises and turtles.
• Example : Kachuga (roofed-terrapin), Testudo (land-tortoise), Uromastix (sand-lizard), Hemidactylus (wall lizard), Calotes (garden-lizard), Draco (flying-lizard) Chamaeleon, Cobra etc.

Class – Aves :

• Warm-blooded, tetrapodous vertebrates (birds) with various flight adaptations.
• Size ranges from smallest humming bird to largest ostrich.
• Heart 4 chambered.
• Horny scales persist on the feet but feathers cover most of the body. Cutaneous glands are absent.
• Boat-shaped body is divisible into head, neck, trunk and tail.
• Fore-limbs modified into wings for flight. Kiwis have vestigial wings.
• Example : Gallus (chicken), Passer (house sparrow), Corvus (crow), Columba (pigeon), Psittacula (parrot), Pavo (peafowl peacock), Eudynamys (koel), Bubo (owl)

Class – Mammalia  :

• Mammals are primarily terrestrial vertebrates. They occur in all sorts of habitats from the polar regions to the tropics.
• The body is variously shaped and generally divisble into head, neck, trunk and tail.
• The skin is glandular and mostly covered by a horny epidermal exoskeleton of hair.
• There are two pairs of pentadactyl limbs. These are variously adapted for various purposes.
• Respiration occurs only by lungs.
• The heart is four chambered, having two auricles and two ventricles.
• Sexs are usually distinguishable externally.
• Mammals are mostly viviparous (alive-bearing). However, some are oviparous and lay eggs (e.g., platypus and echidna. Kangaroos give brith to very poorly developed young ones). They are characterized by having milk-secreting mammary glands in the females for sucking the young for some time after birth.
• Examples : Macropus (Kangaroo), Bat, Ratuus (rat), Oryctolagus (rabit), Felis (cat), Panthera (lion, tiger, leopard), Canis (dog) Elephas (elephant), Balaena (whale), Macaca (monkey), Hamo (man), Pan (chimpanzee)