Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Phylum Chordata 1. Chordates possess 4 characters at least once during their life time (in embryo or larva or adult): a) Notochord – an elastic chord, is replaced by vertebrae in most chordates called Vertebrates b) Dorsal and hollow nerve tube – develops into brain and spinal cord in vertebrates c) Pharyngeal Gill Clefts or pouches – are slit like openings in sides of pharynx and help in respiration in lower chordates. d) Post-anal Tail – is present in all chordates. Urochordate – Sea Squirt Cephalochordate – Amphioxus Vertebrates –fishmammal Notochord and nerve tube in tail of larva. Uro = tail Notochord extends into anterior end. Cephalo = head Notochord of embryo or larva replaced by vertebrae Body covered by test with spicules. No head or eyes. Fish like body has no head. Distinct head, eyes, fins or limbs Fixed to sea rocks Burrowed or free swimming Free swimming Filter feeder Filter feeder Mostly Predators or herbivores 2. Vertebrates have jawless fishes Cyclostomes or Agnatha and Gnathostomates the vertebrates with jaws in mouth. 3. Agnatha – Cyclostomes are jawless fishes only having unpaired fins. The circular mouth act as a sucker a rasping tongue helps in feeding. Lamprey is an ectoparasite of sharks. Hag fish is slimy and usually enters dead or dying animals and feeds on the soft viscera. Cyclostomes lack jaws and paired fins/limbs of other vertebrates. 4. Gnathostomates include fishes – animals with paired fins and Tetrapods – animals with 2 pairs of limbs. Fishes live in water, respire with gills, skin covered with scales, have 2 chambered heart both paired and unpaired fins. Fishes have 2 main classes Cartilaginous fishes and Bony fishes. Fish Class Chondrichthyes=cartilaginous fishes Osteichthyes = bony fishes Position of mouth Ventral, below the snout terminal Pharyngeal gill-slits Exposed and easily seen Covered by gill cover Scales Indistinct, small Distinct, large Tail fin Lobes asymmetrical Lobes symmetrical or unlobed Swim bladder – to regulate buoyancy absent Present in many fishes, helps to gain or lose depth in water For example Sharks and rays Salmon, Tuna, and gold fish 5. Amphibians (amphi = both, bios = living, can breathe in air as well as water) are naked vertebrates lacking scales/feathers / hair. They use skin as respiratory organ and developed lungs. Amphibians moved freely on land but have to return to water to release eggs. Fertilization is external and eggs hatch to form larva. The larva is the 1st feeding stage and is fish like having gills. It undergoes metamorphosis to become adult amphibian. Frog Egg tadpole larva Frog. For example Frogs, Toads, Salamanders, and mud puppies. Class Fishes Amphibians Reptiles Aves = birds Mammals Skin cover scales absent scales feathers hair heart 2 chambered 3 chambered 3 chambers 4 chambered 4 chambered Respiration by gills Skin, lungs lungs lungs lungs 2 pairs of fins legs legs legs legs Teeth used for Holding food holding holding Absent replaced by bill or beak Chewing food ears absent Ear drum at skin level Ear drum in Ear canal Ear drum in Ear canal Pinna outside ear canal Eggs Need water Need water Laid on land Laid on land Give birth 6. Reptiles developed the amniotic egg and became 1st true land vertebrates. Amnion is a fluid filled sac and protects embryo from desiccation (drying up) on land. This eliminated the need of external water, like amphibians, for fertilization. They have scales on skin to prevent water loss, and also have claws on digits and a 3-chambered heart. Eggs with lot of yolk and hatch into adults. No larval stage present. Reptiles include turtles, lizards, snakes, alligators and crocodiles. Dinosaurs, the most famous extinct animals, belonged to reptiles. Birds evolved as a direct line from dinosaurs. 7. Birds are endotherms and maintain high body temperature and can live in extreme cold climates like Antarctica. The bones are very light but strong. Body has feathers and wings. Feet are covered with scales to indicate close relationship to reptiles. Birds also lay amniotic eggs with large yolk and no larva needed. Due to marked parental care for the eggs and hatchlings most birds lay only 2-3 eggs. The evolution of beak or bill helped them to specialize for different kinds of food. Sternum developed a high flat vertical bone, keel, to accommodate bulky flight muscles. Lungs are supported by air sacs to get oxygen even during expiration (breathing out). Due to brilliance of colors Huxley called them ‘Glorified Reptiles’. 8. Mammals – body covered by hair, mammary glands to feed milk, specialized teeth (incisiors for cutting; canines for tearing; premolars and molars for chewing), ear canal covered with Pinna = auricle, and 7 vertebrae in neck. 9. Mammals include egg laying mammals, marsupials and placental mammals. 10. Monotremes = the egg laying (Oviparous) mammal – live only in Australia, lay eggs and feed hatchlings with milk. Duck bill platypus and spiny ant eater are only 2 examples. They are the connecting link between early reptiles and mammals. 11. Marsupials live only in Australian and South American regions. They give birth Viviparous) to premature babies and many carry them in an abdominal pouch = marsupium. Mammary glands are present in the pouch. Well known examples are Kangaroo, Koala and Opossum. 12. Placental Mammals – are most successful and most evolved animals including humans. Give birth (viviparous) to mature babies. Endotherms – maintain body temperature. Most live on land. Aquatic mammals include Whales, dolphins, seals etc and flying mammals are bats. In viviparous animals developing embryo draws nutrition and oxygen from mother’s blood and pass out wastes to it. Bear is omnivore but lion, tiger, wolf, cat and dog are carnivore mammals. Cattle, deer, zebra , and giraffe are grazing animals. Monkeys, apes and humans are primate mammals.