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Vertebrates Vertebrate Survey Anatomy and Physiology of Vertebrates Vertebrate Evolution Phylum Chordata is the group of animals with a notochord – a flexible, supporting structure along the back Contains the invertebrate chordates, and Subphylum Vertebrata, which have evolved vertebral columns Serves as site for muscle attachment, protects nerve cord Trends in Vertebrate Evolution Development of true bony jaws Development of paired pectoral and pelvic limb girdles Development of bones Most vertebrates have two sets of appendages (arms and legs), a closed circulatory system with a ventral heart, and either gills or lungs for breathing Class Agnatha Jawless fish Ex. Lampreys and hagfishes Only living vertebrates without jaws Parasites – survive by attaching themselves to other fish or aquatic animals, feeding on their blood and body fluids Scavengers – eat decaying carcasses Class Chondrichthyes Cartilaginous fish Ex. Sharks, skates, rays Skeletons made of cartilage Some are fearsome predators, other eat small fish, mollusks, or plankton Class Osteichthyes Bony fish Contain half of all vertebrate species, all aquatic habitats Ray-finned fish – sub-class containing almost all fish species – well-developed bone systems, specialized jaws with teeth Lobe-finned fish – sub-class with lungs and gills, relatives of amphibians Class Amphibia (amphibians) Lay eggs in water and spend part of their life cycle there (gills) As adults, live on land and breathe through lungs Most have moist skin, as part of their respiration occurs through skin Class Amphibia Examples include: Newts and salamanders (lay eggs in water, hatch into young that resemble adults – larvae have gills that disappear and are replaced by lungs as they grow) Frogs and toads (eggs hatch in water as tadpoles, which look completely different from adults) Class Reptilia (reptiles) Fully terrestrial Reproduce by internal fertilization – egg/sperm fuse within body of the female Produce leathery eggs to prevent water loss Dry scaly skin to retain moisture Developed lungs Class Reptilia Order Chelonia – turtles and tortoises, protective shell of bony plates (long fossil record) Order Crocodilia – crocodiles, alligators, caimans (long fossil record) Order Squamata – lizards and snakes, most abundant group Class Aves (Birds) Only vertebrates with feathers Used for flight and conservation of body heat Lay eggs Class Mammalia (mammals) Named for presence of mammary glands, enable females to nourish young with milk Have hair to retain body heat Class Mammalia Three groups: Monotremes – egg-laying mammals like duckbilled platypus – have body hair/fur, lay leathery eggs Marsupials – live young born very early in their development and continue to develop within marsupium – kangaroos, koalas, opossums Placental mammals – largest group, names for placenta (organ that connects mother with developing embryo, allows for nutrient, gas, and waste exchange) Support and Movement All have an endoskeleton surrounded by muscles and skin Vertebral column (backbone) is the main part of the skeleton Adapting to life on land led to changes in limb positions Amphibians had limbs that are horizontal while reptile limbs are vertical to support increased body mass Feeding and Digestion All food sources presented problems as vertebrates evolved Meat is easy to digest, but must first be caught then cut up for swallowing Plant matter is easy to find, but must be pulverized and shredded before swallowing, and cellulose is hard to digest Feeding and Digestion Adaptations are present in teeth Meat requires teeth that hold, shred Plants require teeth that grind/pulverize Feeding and Digestion Adaptations seen in digestive tracts Meat digests easily, so carnivores have short digestive tracts that secrete enzymes to break down proteins Plants need to be broken down slowly, so herbivores spend more time chewing/rechewing, and long digestive tracts full on bacteria help digest cellulose Respiration (gas exchange) Method/system depends on environment Fish rely on gills for respiration Amphibians have gills as tadpoles and poorly developed lungs as adults No muscles to inflate/deflate lungs Rely on diffusion through thin, moist skin Respiration (gas exchange) Reptiles are fully adapted to life on land and have more developed lungs that are divided into chambers to increase surface area Reptiles also have muscles to inflate/deflate lungs Respiration (gas exchange) Mammals require higher rate of gas exchange because of higher metabolic rate Most developed lungs Bronchi (air tubes) enter lungs then branch to create more surface area, ending in alveoli Respiration (gas exchange) Alveoli are bubblelike structures surrounded in capillaries Efficient at gas exchange, but inefficient because air must move in and out through the same passageway Respiration (gas exchange) Birds have highest requirements for lung efficiency because they fly Have branched bronchi and alveoli like mammals, but also have air sacs within some bones Air is pumped in one direction Internal Transport Closed circulatory systems Two types: single-loop and double loop Internal Transport Single-loop circulatory systems are found in fish – blood is pumped from the heart to the gills where respiration takes place, then flows from the gills to the rest of the body, returning to the heart Heart has two chambers – one atrium (receives) and one ventricle (pumps) Internal Transport Vertebrates with lungs have a doubleloop circulatory system First loop carries blood between the heart and lungs (pulmonary) Second loop carries blood between the heart and the rest of the body (systemic) Internal Transport Amphibians and reptiles have a threechambered heart – two atria and one ventricle Birds and mammals have a fourchambered heart – two atria and two ventricles Temperature Control Vertebrates need to control their body temperature because chemical reactions operate differently at various temperatures Need a way to heat the body, conserve that heat, and eliminate excess heat Temperature Control Fish, amphibians, and reptiles are ectothermic because they rely on interactions with their environment to control body temperature Lay in sun to warm themselves, stay in shade or burrow to cool down Temperature Control Mammals and birds are endothermic because they generate heat in body tissues through chemical reactions in the body Also have layers of fat and fur/feathers to conserve heat Shivering generates more heat, panting or sweating dissipates heat Excretion Elimination of nitrogen-containing wastes linked to maintaining water balance Aquatic vertebrates get rid of ammonia by diffusion (fish through gills, amphibians through skin) They also have the beginnings of a kidney (primitive, gets more complex) Excretion Mammalian kidney most complex Use the conversion to urea and uric acid and concentration to conserve water Urea eliminated in urine, uric acid in solid waste Response All vertebrates are cephalized Bundle of nerves and neural connections in head called the brain, and the long, thick collection of nerves running down the back is the spinal cord Spinal cord protected by vertebral column Response Pairs of nerves run out between individual vertebrae to connect muscles, organs, and sensory receptors around the body More complex behavior means more complex brain All vertebrates have a cerebrum (thinking) and cerebellum (balance, coordination, movement) Reproduction All vertebrates reproduce sexually Fish and amphibians have external fertilization Female lays thousands of eggs in water, male deposits sperm Young develop and hatch in water Reproduction Reptiles, birds, and mammals have internal fertilization (inside female) Fewer eggs are produced Developing embryo is nourished inside the egg by a yolk (food) and wrapped in membranes (called the amniotic egg) Membranes bathe embryo in liquid and receive and store wastes Reproduction Amniotic egg also has a shell for protection and allows for gas exchange Important step in evolution – no water necessary Reproduction How eggs are handled is different amongst vertebrates Oviparous animals lay their eggs, and the embryo completes its development and hatches outside of the female’s body Reproduction Ovoviviparous animals keep their eggs inside the body until the embryo fully develops and hatches Viviparous animals have eggs with very little yolk (if at all) because the female nourishes the embryo internally for a long period of time, and the young are born alive (do not hatch)