Phylum Chordata General Characteristics A. Have a notochord. What does this form? B. Have dorsal hollow nerve tube. What does this form? C. Have pharyngeal gill slits. What happens to these? D. Have tails at one point in their development. Embryonic Comparison II. Classification A. Subphylum Cephalochordata 1. Lancelets II. Classification B. Subphylum Urochordata 1. Sea Squirts (Tunicates) II. Classification C. Subphylum Hemichordata 1. Acorn Worms II.Classification D. Subphylum Vertebrata 1. Characteristics: a) Have a backbone (spinal column) b) Have endoskeleton made of calcium & phosphate. 2. Two major groups of vertebrates: ectotherms and endotherms. IV. Ectothermic (Cold-blooded) Classes A. Class Agnatha (Jawless fish) 1.Skeleton made of cartilage. 2.No scales with tubular body. 3.Lack paired appendages. e.g. lampreys and hagfish B. Class Chondrichthyes 1. Skeleton made of cartilage, e.g. Rays, Skates and Sharks 2. Lack gill covers (opercula) and swim bladders. 3. Have placoid scales C. Class Osteichthyes 1. Skeleton is made of bone e.g. trout, bass, salmon, sole etc. 2. Gills with opercula for protection and to move water over gills. 3. Have cycloid scales. 4. Most common fish class. D. Class Amphibia (means “dual life”) 1. Smooth skin and lack claws; e.g. frogs, toad, newts and salamanders. 2. Evolved from fleshy-lobed fish (Coelocanth) E. Class Reptilia E. 1. Dry (water proof), scaly skin with claws. F. 2. Evolved from amphibians G. 3. Snakes, lizards, turtles, crocodiles and alligators QuickTim e™ and a Sorenson Video 3 decompres sor are needed to s ee this picture. V. Problems with transition to land A. Drying out. B. Too heavy. Why? C. Extreme temperature changes. D. Respiration - why don’t gills work on land? E. Reproduction How to get egg & sperm together? How do chordates prevent their eggs from drying out? VI. Adaptations to land A. Waterproof skin coverings; scales, feathers and fur. B. Appendages move more ventral as opposed to lateral placement. C. Lungs replaced gills D. Amniotic eggs with internal fertilization. -Evolved first in reptiles D. Amniote Egg ** Water Tight but permeable to oxygen. 1. Chorion - used for respiration 2. Allantois - stores liquid wastes 3. Amnion - filled with fluid for a cushion 4. Yolk Sac - stores food (yolk) 5. Embryo 5 3 2 1 4 VII. Endothermic (homeothermic) Classes A. What is the advantage of being homeothermic? 1. Can live in cold environments or cold nights. B. What is the source of heat? 1. Muscles contraction C. Which body systems must adapt to be endothermic? A. Digestive system Why? a) Respiratory system Why? b) Circulatory system Why? c) Integumentary Why? D. Class Aves 1. Body covered with feathers 2. Have wings and beaks with no teeth. 3. Have hollow bones 4. All birds are oviparous. 5. Evolved from reptiles-Archaeopteryx E. Class Mammalia A. Body covered with hair B. Nurse young with mammary glands C. Warm blooded D. Give birth to live young E. Evolved from reptiles. VIII. Movement A. Fish 1. Fins used to stabilize and move fish through water 2. Fish are streamlined to move easily through the water. 3. Swim bladders filled with oil or gas to help fish float in the water. Movement (con’t) B. Amphibians, reptiles and mammals 1. Most use four muscular limbs, to hop, walk and run on land. a) Limbs gradually moved from the side to under an animal. 2. Snakes and legless lizards use large scales called scutes on ventral surface. VIII. Movement (con’t) C. Birds 1. Wings and feathers 2. What was the original function of feathers? Down Contour Quill Movement (con’t) C. Birds 3. Adaptations for flight a) Forearms modified into wings with feathers. b) Hollow bones with modified skeleton for muscle attachment and flight movement. c) Air sacs throughout make them less dense and ready supply of oxygen. d) Excretory wastes are crystalized combined with digestive waste. Why? IX. Feeding A. Most have teeth and were the first animals to have a hinged jaw (except jawless fish). B. Types of food depend on the species: herbivores, carnivores, omnivores, parasites, and scavengers. Hinged Jaw Evolution X. Protection A. Flight, schooling, camouflage, poison, spines, teeth, etc. B. Scales C. Feathers, fur and fat help insulate. XI. Digestion A. Highly specialized system with associated organs like the liver, pancreas, and gallbladder. XII. Circulation A. Closed circulatory system with different hearts. 1. Fish have a 2-chambered heart. 2. Amphibians most reptiles have a 3- chambered heart. 3. Birds and mammals have a four chambered heart. 4. What is the problem with a three chambered heart? Circulation 1. Birds & mammals have a 4-chambered heart. XIV. Respiration A. Fish use gills. B. Reptiles, birds and mammals use lungs. Respiration C. Amphibians use small lungs, but mostly through their skin. QuickTim e™ and a Sorenson Video decompres s or are needed to s ee this picture. XV. Excretion A. All use kidneys 1. Consisting of millions of nephrons. 2. We will study the structure and function of a kidney when we study the human body.. B. Problems with water balance: 1. Marine fish have salt-removing structures in gills that actively transport salt out of them. 2. Marine birds and reptiles secrete excess salt through specialized glands. 3. Fresh water animals are more waterproof and more active kidneys. Overall Excretory System XVI. Nervous A. All have complex systems. B. Cerebral cortex increases from fish to mammals. 1. This area is associated with higher functioning, so what does the above statement mean? Brain evolution Nervous QuickTim e™ and a Sorenson Video decompres s or are needed to s ee this picture. XVII. Reproduction A. Some are oviparous 1. Lay eggs which hatch and develop outside of mother’s body B. Some are ovoviviparous 1. Eggs hatch inside mother and give birth to live young, but no nourishment provided by mother. C. Some are viviparous 1. Bear live young, which are nourished by mother.