Ch. 40 - AmphibiansAmphibians are thought to have evolved from fish. Why?–Fins into legs, gills into lungs, scales into skin,

stronger bonesEvidence shows to amphibians developed from a lobe-finned fish (crossopterygians)Amphibian is Greek for “double life”VideoThe term for land & water is quaiterrestrialVideo

Amphibian Characteristics1. Ectothermic – cold-blooded2. Moist skin with no scales3. Metamorphosis from an aquatic larva stage to an adult form.4. Respiration by gills, lungs, &/or skin5. Eggs fertilized externally6. Webbed feet (most)7. 2-chambered heart (larva), 3-chambered heart (adult)

Ectothermic

States of Dormancy called TorporWhy would they undergo torpor?How can they avoid torpor?2 types of torpor1. Hibernation – torpor during the winter.2. Estivation – torpor during the summer.

ClassificationPhylum: Chordata–Subphylum: Vertebrata

•Class: Amphibia–Order: Anura “without tails” –Order: Urodela “visible tails” –Order: Apoda “without legs”–Order: Trachystoma aquatic amphibians

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Apoda

Usually blind, slender-bodies, and limblessBurrowing, worm-like amphibiansSeldom seen by humansCaeciliansVideo

Urodela

Elongated bodies, long tails, moist skinLive in water or moist placesWhat is Kansas’ state amphibian–Tiger SalamanderVideo

AnuraWhat is the main difference between frogs & toads?How does a toad defend itself?–Granular glands, inflate their body, bury

themselvesWhat do toads & frogs feed on?–Insect Gardner’s best friendVideo

External Anatomy of a FrogNictitating membrane – transparent covering over the eye (3rd eyelid).–Allow them to see under water

Tympanic membrane – eardrum for mating seasonEustachian tube – connects the middle ear to the mouth cavity.Mucus glands – keep the skin moist for respiration.Granular glands – secretes toxins

Scientific Name Rans pipensWhy do frogs have such large eyes?–This is why they blink when they eatDo 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 ribsIt’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 jawPath 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 portionMesentery 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 adultWhy would a frog need a 3-chambered heart?(e.c.)–On land3 chambers are: 2 atria & 1 ventricle DrawThe ventricle receives oxygenated & deoxygenated blood, which mixed a little.

Respiratory System

What does a tadpole use?–GillsWhat does a frog use?–Lungs & skinPulmonary respiration is through the lungsCutaneous respiration is through the skinAir passes from the throat to the lungs through the glottis.

Nervous System

Same as the fish; only more developedOlfactory 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?–KidneysThey filter out nitrogenous wastes or urineThe 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 kidneysThe 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. 831Eggs 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

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