Transcript document
Ch. 40 - Amphibians Amphibians are thought to have evolved from fish. Why? – Fins into legs, gills into lungs, scales into skin, stronger bones Evidence shows to amphibians developed from a lobe-finned fish (crossopterygians) Amphibian is Greek for “double life” The term for land & water is quaiterrestrial Amphibian Characteristics 1. Ectothermic – cold-blooded 2. Moist skin with no scales 3. Metamorphosis from an aquatic larva stage to an adult form. 4. Respiration by gills, lungs, &/or skin 5. Eggs fertilized externally 6. Webbed feet (most) 7. 2-chambered heart (larva), 3-chambered heart (adult) Ectothermic States of Dormancy called Torpor Why would they undergo torpor? How can they avoid torpor? 2 types of torpor 1. Hibernation – torpor during the winter. 2. Estivation – torpor during the summer. Classification Phylum: Chordata –Subphylum: Vertebrata • Class: Amphibia –Order: Anura “without tails” –Order: Caudata “visible tails” –Order: Gymnophiona “without legs” Gymnophiona Usually blind, slender-bodies, and limbless Burrowing, worm-like amphibians Seldom seen by humans Caecilians Caudata Elongated bodies, long tails, moist skin Live in water or moist places What is Kansas’ state amphibian –Tiger Salamander Anura What is the main difference between frogs & toads? How does a toad defend itself? –Granular glands, inflate their body, bury themselves What do toads & frogs feed on? –Insect Gardner’s best friend External Anatomy of a Frog Nictitating membrane – transparent covering over the eye (3rd eyelid). – Allow them to see under water Tympanic membrane – eardrum for mating season Eustachian tube – connects the middle ear to the mouth cavity. Mucus glands – keep the skin moist for respiration. Granular glands – secretes toxins Scientific Name Rans pipens Why do frogs have such large eyes? – This is why they blink when they eat Do frogs swim as well as a fish? Why are a frogs legs folded under them? Why are frogs easily mutated? Frog’s Internal Anatomy Have no ribs It’s tongue is attached to the front of it’s mouth. 2 vomerine teeth on the roof of their mouth for holding food. Maxillary teeth along their upper jaw Path of Digestion: esophagus, stomach, small intestine, large intestine, cloaca (the whole system is called the alimentary canal) A frog’s esophagus & stomach expand to allow them to swallow insects. The food moves from the stomach to the S.I. By passing through the pyloric sphincter. Parts of the S.I. – 1. Duodenum –upper portion – 2. Ileum- lower portion Mesentery is a membrane that holds the S.I. In place. The liver produces bile to break down wastes & fats; its stored in the gall bladder. The pancreas is next to the stomach. It enters the S.I. To break down food & sugars. Circulatory System 2–chamber as a tadpole, 3-chamber as an adult Why would a frog need a 3-chambered heart?(e.c.) – On land 3 chambers are: 2 atria & 1 ventricle Draw The ventricle receives oxygenated & deoxygenated blood, which mixed a little. Respiratory System What does a tadpole use? – Gills What does a frog use? – Lungs & skin Pulmonary respiration is through the lungs Cutaneous respiration is through the skin Air passes from the throat to the lungs through the glottis. Nervous System Same as the fish; only more developed Olfactory lobe – which does what? Cerebrum – which does what? Cerebellum – which does what? Optic lobe – which does what? Medulla oblongata – which does what? Excretory System What are the primary excretory organs of a frog? –Kidneys They filter out nitrogenous wastes or urine The urine travels through the urinary ducts to the urinary bladder, which empties out into the cloaca, then out through the anus. Reproduction The male has yellowish white testis that lie in front of the kidneys The female have a pair of large lobed ovaries. The eggs migrate into the oviducts where a jellylike substance is secreted to protect them. The eggs are then stored in ovisacs until they leave the body out the cloacal opening. External fertilization occurs once a year in most frogs. A frog’s croak is produced by air moving back & forth across the vocal cords. The male stays attached to the female’s back during mating this is called amplexus. Metamorphosis Pg. 811 Eggs develop into tadpoles (gills, 2-chambered heart) adult (lungs, 3-chambered heart) As the tadpole develops into an adult hind legs appear, front legs start to form, & then finally the tail is reabsorbed into the body. What is the study of amphibians & reptiles? (e.c.) – Herpetology