Vertebrates: Part I Fishes, Reptiles, & Amphibians

Vertebrates Animals that have backbones are called vertebrates All vertebrates belong to the phylum Chordata –Animals in this phylum are called chordates Fish, amphibians, reptiles, birds, and mammals

Chordate Traits Presence of gill slits at some stage of development Have a flexible skeletal rod called a notochord –In vertebrates, the notochord is present only in the embryo stage It gets replaced by a backbone that surrounds and protects the spinal cord Endoskeleton

Vertebrate Evolution The first vertebrates appeared on the earth about 500 million years ago They were water-dwelling, fish-like animals Over time they evolved into many different kinds of fishes Gradually some fish developed adaptations that permitted them to move from the water onto the land

Section 30-1 Nonvertebrate chordates Fishes Amphibians Reptiles Birds Mammals Invertebrate ancestor

Fish Characteristics Live in freshwater or saltwater Ectotherms: animals with bodies that receive heat from the outside –Body temperature depends on the temperature of the environment –Often described as cold-blooded Gills for respiration Have streamlined bodies and use fins for locomotion Very good sense of smell Highly developed nervous systems Mostly external fertilization

Classes of Fishes Agnatha (Jawless Fish) –Lampreys Chondrichthyes (Cartilaginous Fish) –Sharks, rays Osteichthyes (Bony Fish) –Most common fish

Jawless Fish Lampreys and hagfish Do not have jaws Only vertebrate without a vertebral column as an adult Parasites and scavengers –Lampreys attach to a host, rip into their host’s flesh, then feed upon the blood and body fluids of the host

Cartilaginous Fish Cartilage is a firm yet flexible connective tissue that occurs at most joints of your skeleton and makes up the skeleton in cartilaginous fishes. Includes sharks, rays, and skates Unlike the jawless fish, cartilaginous fish have jaws that evolved from the first pair of skeletal rods that supported the gills of jawless fish

Cartilaginous Fish continued Most cartilaginous sharks are carnivores –Sharp senses and sharp teeth make them well adapted for life as predators Some of the largest sharks are filter feeders –Whale shark strains water to remove plankton More dense than ocean water so they must keep swimming to float above the sea floor –For some, swimming is also what makes a current of water pass over the gills so the fish can get oxygen

Bony Fishes Greatest number of fish species are bony fishes Have skeletons made of bone Have other adaptations that help them live in many kinds of water habitats –Buoyancy control –Scales –Gills and lungs

Buoyancy Control Have an organ called a swim bladder –Similar to a balloon –Helps them adjust their depth in the water by adding or subtracting air –Allows the fish to maintain a buoyancy Buoyancy is the force of fluid pushing an object up

Gills and Lungs Most bony fish depend only upon gills for their gas exchange –They do not rely on movement to get oxygen from the water –They can pump water through the mouth and into the gill chamber by a movement by the gill cover Some have both gills and lungs such as the African lungfish –Go to the surface to gulp air when they need more oxygen

Scales and Fins The outside of a bony fish is covered with a layer of smooth scales that overlap each other Scales are also covered with a thin layer of mucus These are adaptations that help the fish move through water with little resistance Bony fishes have paired and unpaired fins –The paired pectoral and pelvic fins are used to steer, brake, back up, and move up and down –The caudal fin propels the fish

Fish Structure

Homework due tomorrow List 3 characteristics of fish that make them adapted to life in water. Why does a cartilaginous fish have to swim constantly? What adaptations make it unnecessary for a bony fish to swim all the time? What is an ectotherm?

Reptile Characteristics Dry, waterproof body covering made of scales –Helps to conserve water while living on land –Prevents gas exchange through the skin Spongy lung with an increased internal surface area for gas exchange 3-chambered heart with a partial wall dividing the chambers to prevent mixing of stale and fresh blood Jacobson’s organ: sense organ on the roof of reptile’s mouth for smelling

Reptile Temperatures Ectotherms, but most can regulate their internal temperature well anyway Adaptations that reptiles have to keep their body temperatures about as warm as yours for much of the day –They bask in the sun when the air is too cool –Seek shade when it is too hot

Reptile Reproduction Reproduce entirely on land Eggs fertilized internally –Eggshell is tough and leathery that keeps the embryo from drying out –Special membranes transfer food from the egg yolk, remove wastes, and take in oxygen

Lizards and Snakes They may look different, but lizards and snakes are closely related Carnivores Snakes still have hipbones and remnants of hind legs even though they don’t have appendages Snakes have limited hearing and poor eyesight –Great sense of smell and taste –Use their tongues to find prey and gather information about the environment

Turtles and Tortoises All have shells –When in danger, they pull their heads, legs, and tails into their shells –Formed from bony plates connected to their ribs and vertebrae –Shell covered by a layer of tough material Makes the markings and color patterns on the shell

Turtles and Tortoises Turtles –Shells are flat and streamlined –Live in ponds, lakes, rivers, or the ocean Lay eggs on land Tortoises –Dome-shaped shells –Live on land

Alligators and Crocodiles Closest living relative to dinosaurs Have large, deep scales Unlike most reptiles, alligators and crocodiles care for their young –Females guard their eggs –Both males and females protect their babies

Alligators and Crocodiles Alligators –Broad head with a rounded snout –Live mostly in North America and Asia Crocodiles –Narrow head with a triangle shaped snout –Live in tropical areas of America, Africa, Asia, and Australia

Homework due TOMORROW Identify the characteristics of reptiles that make them suited to life on land. Explain the similarities and differences among the three groups of reptiles. The largest reptiles all live in areas where it is warm year-round. Based on what you know about reptiles, why is this so?

Amphibians The word amphibian means “double life” –Most spend part of their live in water and part on land Mud puppies spend their whole live in water Tree frogs live entirely on land Respiratory gases are exchanged through the skin as well as in their lungs They are ectotherms and are cool to the touch Require moist environment even though they can live on land

Amphibian Reproduction Must reproduce in water –Female lays eggs in a pond, swamp, or stream –Fertilized externally by the male –If water is scarce, some amphibians have adaptations to make up for it Desert toads produce a moist foam to lay their eggs in

Amphibian Metamorphosis Many amphibians go through a metamorphosis where they have a tadpole stage –In amphibian species where the adult remains a water-dweller, the changes from tadpole to adult are minor –Frogs and toads change completely as it becomes an adult

Frog Life Cycle

Groups of Amphibians Salamanders and newts –Amphibians with tails –Smooth, moist skin –Habitats Some live in relatively dry habitats Some in very moist Some even live in water their entire lives Frogs and toads –Amphibians without tails –Most frogs live their lives in and around water

Eat or Be Eaten Frogs and toads eat insects, worms, small crustaceans, and small mollusks –Eaten by herons, large fish, and snakes Most amphibians can defend themselves only by jumping or swimming away Toads have bumps on their bodies which secrete a bad tasting material so most animals leave toads alone

Dormant Amphibians In cold climates… –Frogs and salamanders burrow into the mud at the bottom of lakes or rivers that do not freeze completely –Toads and land salamanders burrow deep into the ground over the cold winter Body activities slow down tremendously –Heart barely beats –Blood barely flows –Lungs stop working entirely

Frogs Well developed hind legs for jumping and swimming – strong, powerful 5 toes with webbing for swimming Eyes bulging above head –Can pull against roof of mouth to help hold food in mouth –Can float just under the water with only their eyes showing Tympanic Membrane just behind their eyes – no external ears Mouth –Insect trap –Extends from ear to ear –Sticky tongue –No teeth on lower jaw –Vomerine teeth to hold prey

Problems with life on land Drying out Respiration Reproduction Movement Temperature Control

Homework due tomorrow Describe how amphibians hibernate. List 3 characteristics of amphibians. For each, explain whether it is an adaptation to land or to water. How is an adult frog like a tadpole? How is an adult frog different from a tadpole?

AMPHIBIANS means Breathes with reproduction Have tails No tails ______ toes _____ teeth to hold prey ________ bulge & can drop into mouth to hold prey Torpor Reproduce in ________ ____________ fertilization metamorphosis Sticky _________ attached to front of bottom jaw ___________& ___________ Secrete bad tasting mucus as defense Ectotherms

FISH Breathes with Most fish No vertebral column as an adult ____________ fertilization Whole skeleton made of cartilage No jaws Examples Skeletons made of _________ _______________ for depth control Pump water into gills with _____ ________ Paired and unpaired ______ Have to keep swimming For water to move over _______ for respiration Examples

REPTILES Closest relatives to dinosaurs Great sense of ______ & ______ ____________ on roof of mouth for smelling Water-dwellers Limited hearing & eyesight Unlike other reptiles, care for their _________ __________ & __________ Use ______ to gather information ___ chambered heart with division to prevent blood mixing Ectotherms _________ fertilization reproduction Reproduce on _________ Live on land ________-shaped shell Shells ________ & streamlined Shells formed by bony plates attached to _____ & _____ Tuck into ____ when in danger