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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” • Video • The term for land & water is quaiterrestrial • Video
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: Urodela “visible tails” • Order: Apoda “without legs” • Order: Trachystoma aquatic amphibians • Video
Apoda • Usually blind, slender-bodies, and limbless • Burrowing, worm-like amphibians • Seldom seen by humans • Caecilians • Video
Urodela • Elongated bodies, long tails, moist skin • Live in water or moist places • What is Kansas’ state amphibian • Tiger Salamander • Video
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 • Video
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. 831 • 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 • Video