Animal Kingdom

• The phylum Arthropoda is the largest animal group, with over one million species.
• They also have an exoskeleton made up of chitin, which provides protection and support to their bodies.
• Insects, crustaceans, arachnids, and myriapods belong to the phylum Arthropoda.
• The exoskeleton is made up of chitin, which provides protection against predators and environmental stressors.
• Fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems are used as the basis of animal classification
• Levels of Organisation:

  • Cellular level: e.g., sponges
  • Tissue level: e.g., coelenterates
  • Organ level: e.g., Platyhelminthes
  • Organ system level: e.g., Annelids, Arthropods, Molluscs, Echinoderms, Chordates
• Symmetry:

  • Asymmetrical: e.g., sponges
  • Radial symmetry: e.g., Coelenterates, Ctenophores, Echinoderms
  • Bilateral symmetry: e.g., Annelids, Arthropods
• Diploblastic and Triploblastic Organisation:

  • Diploblastic: e.g., coelenterates
  • Triploblastic: e.g., Platyhelminthes to Chordates
• Coelom:

  • Coelomate: e.g., Annelids, Molluscs, Arthropods, Echinoderms, Chordates
  • Pseudocoelomate: e.g., Aschelminthes
  • Acoelomates: e.g., Platyhelminthes
• Segmentation:

  • Some animals exhibit metameric segmentation with serial repetition of organs
• Notochord:

  • Animals with notochord are called chordates
  • Animals without notochord are called non-chordates
• Phylum Annelida:

  • Organ-system level of body organisation
  • Bilateral symmetry
  • Triploblastic, metamerically segmented, and coelomate animals
  • Body surface marked into segments or metameres
  • Longitudinal and circular muscles aid in locomotion
  • Aquatic annelids like Nereis have lateral appendages called parapodia for swimming
  • Closed circulatory system present
  • Examples: Nereis, Pheretima (Earthworm), Hirudinaria (Blood sucking leech)
• Phylum Arthropoda:

  • Largest phylum in Animalia, includes insects
  • Organ-system level of organisation
  • Bilateral symmetry, triploblastic, segmented, and coelomate animals
  • Body covered by chitinous exoskeleton
  • Body consists of head, thorax, and abdomen
  • Jointed appendages for locomotion
  • Respiratory organs include gills, book gills, book lungs, or tracheal system
  • Open circulatory system
  • Sensory organs like antennae, eyes, and statocysts present
  • Excretion through malpighian tubules
  • Mostly dioecious, fertilisation usually internal
• • Examples: Apis (Honey bee), Bombyx (Silkworm), Anopheles, Culex, Aedes (Mosquitoes)
• Phylum Mollusca:

  • Second largest animal phylum
  • Terrestrial or aquatic with organ-system level of organisation
  • Bilateral symmetry, triploblastic, and coelomate animals
  • Body covered by a calcareous shell
  • Body has head, muscular foot, and visceral hump
  • Mantle cavity with feather-like gills for respiration
  • Sensory tentacles in the anterior head region
  • Mouth contains radula for feeding
  • Usually dioecious and oviparous with indirect development
  • Examples: Pila (Apple snail), Pinctada (Pearl oyster), Octopus, Squid, Aplysia (Sea-hare)
• Phylum Echinodermata:

  • Endoskeleton of calcareous ossicles
  • Marine animals with organ-system level of organisation
  • Adult echinoderms are radially symmetrical
  • Triploblastic and coelomate animals
  • Water vascular system aids in locomotion, food capture, and respiration
  • Sexes are separate, reproduction is sexual
  • Examples: Asterias (Star fish), Echinus (Sea urchin), Cucumaria (Sea cucumber)
• Phylum Hemichordata:

  • Marine animals with organ-system level of organisation
  • Bilateral symmetry, triploblastic, and coelomate animals
  • Body composed of proboscis, collar, and trunk
  • Circulatory system is of open type
  • Respiration through gills
  • Sexes are separate, fertilisation is external
  • Examples: Balanoglossus, Saccoglossus
• Phylum Chordata:

  • Fundamentally characterised by the presence of a notochord, dorsal hollow nerve cord, and paired pharyngeal gill slits
  • Bilateral symmetry, triploblastic, coelomate with organ-system level of organisation
  • Possess a post-anal tail and a closed circulatory system
  • Divided into three subphyla: Urochordata, Cephalochordata, and Vertebrata
  • Examples: Branchiostoma (Amphioxus or Lancelet), Ascidia, Salpa, Doliolum
• Class Cyclostomata:

  • Ectoparasites on fishes
  • 6-15 pairs of gill slits for respiration
  • Sucking and circular mouth without jaws
  • Devoid of scales and paired fins
  • Examples: Petromyzon (Lamprey), Myxine (Hagfish)
• Class Chondrichthyes:

  • Marine animals with cartilaginous endoskeleton
  • Tough skin with minute placoid scales
  • Powerful jaws, predaceous
  • Lack air bladder, swim constantly to avoid sinking
  • Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark)
• Class Osteichthyes:

  • Marine and freshwater fishes with bony endoskeleton
  • Streamlined body with terminal mouth
  • Four pairs of gills covered by operculum
  • Air bladder for buoyancy
  • Examples: Exocoetus (Flying fish), Labeo (Rohu), Betta (Fighting fish)
• Class Amphibia:

  • Can live in aquatic and terrestrial habitats
  • Two pairs of limbs, body divisible into head and trunk
  • Moist skin
  • Examples: Frogs, Toads, Salamanders
• Amphibians:

  • Body is divisible into head and trunk
  • Tail may be present in some
  • Skin is moist without scales
  • Eyes have eyelids
  • Respiration is by gills, lungs, and through skin
  • Heart is three-chambered
  • Sexes are separate
  • Fertilisation is external
  • Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia)
• Reptiles:

  • Body is covered by dry and cornified skin, epidermal scales or scutes
  • Limbs, when present, are two pairs
  • Heart is usually three-chambered, but four-chambered in crocodiles
  • Reptiles are poikilotherms
  • Snakes and lizards shed their scales as skin cast
  • Sexes are separate
  • Fertilisation is internal
  • They are oviparous and development is direct
• • Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator), Hemidactylus (Wall lizard), Poisonous snakes - Naja (Cobra), Bangarus (Krait), Vipera (Viper)
• • They are oviparous and development is direct
  • Examples: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture)
• Birds (Aves):

  • Have feathers and most can fly except flightless birds
  • Possess beak
  • Forelimbs are modified into wings
  • Hind limbs generally have scales and are modified for walking, swimming, or clasping tree branches
  • Skin is dry without glands except the oil gland at the base of the tail
  • Endoskeleton is fully ossified (bony) and long bones are hollow with air cavities
  • Digestive tract has additional chambers, the crop and gizzard
  • Heart is completely four-chambered
  • They are warm-blooded (homoiothermous)
  • Respiration is by lungs
  • Sexes are separate
  • Fertilisation is internal
• Mammals (Mammalia):

  • Found in a variety of habitats
  • Presence of milk producing glands (mammary glands)
  • Two pairs of limbs adapted for various activities
  • Skin possesses hair
  • External ears or pinnae are present
  • Heart is four-chambered
  • They are homoiothermous
  • Respiration is by lungs
  • Sexes are separate
  • Fertilisation is internal
  • They are viviparous with few exceptions and development is direct
• • Examples: Ornithorhynchus (Platypus), Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion)