Transcript Modern Amphibians
Modern Amphibians
• Part two
Modern Amphibians: Order Caudata • Includes salamanders (may also be called newts).
• Members may be fully aquatic, fully terrestrial, or amphibious.
• Many reproduce in water. Some reproduce on land, with no swimming larval stage.
Modern Amphibians: Order Caudata • Larvae and adults are carnivorous.
• Some have no lungs, and respire through their skin only.
Modern Amphibians: Order Gymnophiona • Includes caecilians (legless amphibians that resemble small snakes).
• Most are burrowing. They have small eyes beneath skin or bone, and are often blind.
Modern Amphibians: Order Gymnophiona • All are carnivorous.
• All are thought to have internal fertilization.
• Some lay eggs which the female guards, others develop inside the female.
Phylogenetic Diagram of Amphibians
Characteristics of Amphibians: Skin Amphibian skin serves two important functions: • Respiration - The skin is permeable to gases and water. Mucous glands secrete a lubricant that keeps the skin moist in air.
• Protection - The skin protects amphibians from infection and secretes a foul-tasting or poisonous mucus that protects amphibians from predators.
Characteristics of Amphibians: Skeleton A strong skeleton supports the body of amphibians against the force of gravity.
• Vertebrae interlock to form a strong, rigid structure.
• Strong limbs assist with standing and walking.
• Pectoral and pelvic girdles transfer weight to the limbs.
• Skeletons of frogs are specialized for jumping and landing.
Characteristics of Amphibians: Skeleton • Fused bones add strength to the forelimbs and hind limbs.
• Thick arm bones and pectoral girdle absorb shock of landing.
• Long hind legs allow frogs to jump farther.
• Lengthened pelvic girdle and fused vertebrae add support.
Characteristics of Amphibians: Circulatory System
The circulatory system is divided into two loops.
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Pulmonary circulation - carries deoxygenated blood from the heart to the lungs and back to the heart.
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Systemic circulation - carries oxygenated blood from the heart to the body and back to the heart.
Amphibian Heart Structure
Amphibians use positive pressure breathing
Amphibian Lung Structure
Characteristics of Amphibians: Digestive System • Includes the pharynx, esophagus, stomach, liver, gallbladder, small intestine, large intestine, and cloaca.
• The upper part of the small intestine is called the duodenum.
• The coiled middle portion of the small intestine is the ileum.
Characteristics of Amphibians: Digestive System • A membrane that holds the small intestine in place is called the mesentery.
• Waste materials are stored in the cloaca and exit the body through the vent.
Characteristics of Amphibians: Digestive System Accessory Glands • The liver produces bile, which is stored in the gallbladder and helps break down fat.
• The pancreas secretes enzymes that help break down food into particles that can be absorbed by the blood.
Internal Structure of a Frog
Characteristics of Amphibians: Excretory System • The kidneys are the primary excretory organ, and filter nitrogenous wastes from the blood.
• Wastes combined with water are known as urine.
• Urine flows from the kidneys to the cloaca and then to the urinary bladder, which branches off the cloaca.
Characteristics of Amphibians: Excretory System • Nitrogenous wastes are converted from ammonia to urea, which is highly concentrated and helps conserve water.
Characteristics of Amphibians: Nervous System • The olfactory lobes are larger in amphibians than in fish.
• The cerebrum is responsible for behavior and learning.
• The optic lobes process information from the eyes.
• The cerebellum is responsible for muscular coordination.
• The medulla oblongata controls heart rate and respiration rate.
Characteristics of Amphibians: Nervous System
Sense Organs
• Larvae have a lateral line, most adults do not.
• The eyes are covered by a nictitating membrane, a transparent moveable membrane that protects the eye.
Characteristics of Amphibians: Nervous System
Sense Organs
• Sound is detected by the inner ear. • Sounds are transmitted to the inner ear by the tympanic membrane, or eardrum, and the columella, a small bone that extends between the tympanic membrane and the inner ear.
Reproduction in Amphibians: Courtship and Fertilization • Males attract females with a mating call.
• Females only respond to males of the same species.
Reproduction in Amphibians: Courtship and Fertilization • The male clings to the female in an embrace called amplexus.
• Eggs and sperm are released into the water.
• Fertilization is external.
Reproduction in Amphibians: Courtship and Fertilization • Male - includes two bean-shaped testes located near the kidneys that produce sperm during the breeding season.
Reproduction in Amphibians: Courtship and Fertilization • Female - includes a pair of large ovaries containing thousands of tiny immature eggs. During the breeding season the eggs mature.
Reproduction in Amphibians: Life Cycle • When the eggs hatch, a tadpole is released.
• The tadpole grows and slowly changes from an aquatic larva into an adult in a process called metamorphosis.
• Metamorphosis is controlled by a hormone called thyroxine.
Reproduction in Amphibians: Life Cycle • Some amphibians do not produce thyroxine and remain in the larval stage their entire life.
• Some amphibians do not have a larval stage and hatch from the egg as small versions of the adult.
Life Cycle of Frog
Reproduction in Amphibians: Parental Care
Parental care increases the likelihood that the offspring will survive.
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Some species guard their eggs until they hatch.
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Some species sit on their eggs to prevent them from drying out.
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The male Darwin’s frog carries the eggs in his vocal sacs until the larvae finish metamorphosis.
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Female gastric brooding frogs swallow their eggs and the larvae mature in the stomach.