Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Introduction to Chordates
Document related concepts
Transcript
Chordates What is a Chordate? Chordates are animals that are characterized by a notochord, a dorsal hollow nerve chord, and pharyngeal slits at some stage of their development. Characteristics Notochord: Dorsal Nerve Chord: Flexible rod of specialized cells along its dorsal side Becomes the vertebral column (in vertebrates) Hollow tube just above the notochord Eventually becomes the brain and spinal cord Pharyngeal Slits: Eventually becomes gills in aquatic organisms Becomes throat and ear structures in terrestrial organisms Contains 3 subphlya: Urochordates (inverts) Cephalochordates (inverts) Vertebrates (verts) Invertebrate Chordates: Urochordates 2,000 species Have gill slits as larvae and adults Have notochord and dorsal nerve cord as larvae Metamorphosis results in loss of notochord and tail, and the nerve chord shortens Examples: tunicates (sea squirts) Invertebrate Chordates: Cephalochordates 28 species Small fishlike creatures Have notochord, dorsal nerve cord, and gill slits as adults Lancelet is the closest living relative to early animals Vertebrate Chordates: Vertebrates 41,ooo species – 95% of chordates Bones or cartilage surround the dorsal nerve cord Contain skull and endoskeleton Have organs organized into systems How Vertebrates Regulate Body Temperature Endothermic – warm-blooded An animal that generates its own body heat Examples – birds and mammals Ectothermic – cold-blooded Body temperature is determined by the environment Examples – reptiles, fish, and amphibians Vertebrate Reproductive Development: How long the eggs remain within the female Oviparous – “egg birth” Ovoviviparous – “egg-live birth” Lay eggs and eggs hatch outside mother’s body Examples – Most fish, most reptiles, all birds, and 3 species of mammals Fertilized eggs remain inside of mother Nourished by egg yolk – not the mom May lay the eggs and then hatch shortly thereafter OR eggs hatch inside of mother and young are born live Examples – Some fish, some reptiles Viviparous – “live birth” Young develop within the uterus Nourished by placenta Example – Placental mammals (humans) Taxonomy of Vertebrates Class Major Characteristics Examples Agnatha Jawless fish Chondrichthyes Cartilaginous fish Lamprey, hagfish Sharks, stingrays Osteichthyes Amphibians Flounder, trout, etc. Frogs, toads, salamanders Turtles, alligators, snakes Birds Reptiles Aves Mammals Bony fish Part life in water, part life on land Amniote egg and scales Feathers, hollow bones Warm blooded, hair, produce milk Humans, primates, dogs, etc. Agnatha – Jawless Fish AKA cyclostomes (round mouth) Most primitive living vertebrates Ostracoderms (extinct); lamprey (extant) Lack paired appendages cartilaginous skeleton rasping mouth to suck blood Chondrichthyes – Cartilaginous Fish Sharks, skates, rays Well developed jaws and paired fins; continual water flow over gills (gas exchange); lateral line system (detects water pressure changes) Sexual reproduction with internal fertilization Osteichthyes – Bony Fish Ossified (bony) endoskeleton; scales; operculum (gill covering); swim bladder (buoyancy); 2 chambered heart with a single circulatory circuit through body Most numerous vertebrate Sexual Reproduction, most with external fertilization Amphibians – “Double Life” 1st tetrapods on land Frogs, toads, salamanders 3 chambered heart with a double circulatory circuit (travels twice through body for complete trip) Double life & metamorphosisaquatic (larva) & terrestrial (adult) Must have moist skin for gas exchange Must use WATER for reproduction Reptiles Lizards, snakes, turtles, crocs and gators Amniote (shelled) egg with extraembryonic membranes (gas exchange, waste storage, nutrient transfer) Waterproof scales of the protein keratin Well-developed lungs for gas exchange Most have 3 1/2 chambered heart; crocodilians have 4 No WATER needed for reproduction- first to truly adapt to life on land Aves – Birds (Flighted Reptiles) Flight adaptations: wings (honeycombed bone) and feathers (keratin) Toothless Airfoil wing Evolved from reptiles (amniote egg and leg scales) 4-chambered heart – double circuit Internal fertilization Archaeopteryx (evolutionary link between reptiles & birds) Mammals Mammary glands that produce milk hair (keratin) 4-chambered heart large brain teeth differentiation Monotremes (egg-laying): duck-billed platypus and echidnas (spiny anteater), Marsupials (pouch): opossums, kangaroos, koalas Eutherian (placenta):all other mammals Vertebrate Chordates Endo/Ectotherm Circulation (# of chambers) Respiration Fertilization (where sperm unites w/egg) Fish Ectotherms Single loop (2) Gills Internal or external Amphibians Ectotherm Double loop (3) Larvae-gills Adult- lungs & skin External Reptiles Ectotherm Double loop (most 3 1/2 Crocodilians-4) Lungs Internal (some external) Birds Endotherm Double loop (4) Lungs (more complex) Internal Mammals Endotherm Double loop (4) Lungs (most complex) Internal
