Amphibians and Reptiles

Amphibians and Reptiles Ron Chakrabarty Mark Juhn Daniel Montgomery Andrew Tung

Amphibians Family Amphibia

Amphibians – General/Unique Characteristics • Moist, glandular skin with no scales • Feet lack claws and are often webbed • Possession of gills at some point in its life • Lack of amnion in the egg • Embryonic membrane and surrounds and protects the embryo

Amphibians - Evolution • First vertebrates to begin exploring terrestrial land • Earliest fossil found about 400 million years • Most likely evolved from fish • Air bladder mutated/adapted to lungs • Fins evolved into limbs? • To give stronger support

Amphibians – Classification into Orders • There are three different orders for an amphibian • Anura – 4200 species of frogs and toads • Urodela – 430 species of newts and salamanders • Gymniophiona – 165 known species of caecilians

Amphibians - Anura • Consists of frogs and toads • Have tails as tadpoles, but lack tails as adults • Long hind legs for jumping and swimming • Live mostly in freshwater, but some live in drier habitats • Common Anurans – bullfrog, spring peeper, American toad, spade-foot toad • The difference between a frog and a toad is that toads have shorter legs, drier skin, and more warts than frogs. • Length – 1 to 12 inches • Eat mainly insects and small invertebrates

Amphibians – Urodeles – also called Caudata • Consist of newts and salamanders • Have long tails and small, underdeveloped feet. • Includes the largest amphibian in the world – the Giant Salamander lives in Japan and can be up to 5 feet long. • Live near water or in moist soil • Eat insects and some smaller invertebrates • Includes one genus that is shaped like an eel – no legs or pelvis and has gills and lungs

Amphibians - Gymniophiona • Consists of caecilians • Small, worm-shaped amphibians • Blind • Legless • Only 165 species known because some are so small • Largest caecilian is 4.5 feet long

Amphibians - Symmetry • Amphibians have bilateral symmetry • They can be divided into identical halves across exactly one plane • Cephalized • Concentration of brain cells near the anterior end of the amphibian

Amphibians – Body cavity • All amphibians are coelomates • All have a true coelom • A coelom is a hollow, fluid-filled body cavity that is lined both internally and externally by mesoderm. • Provides support for the chest

Amphibians – Structural Support • Skeleton - General • Vertebrae – form a backbone • Limbs – support while walking or standing • Pectoral girdle – shoulder and supporting bones from front limbs • Pelvic girdle – “hips” from back limbs • Cervical vertebra – neck movement

Amphibians – Skeleton • Frogs – specialized bones in skeleton, different from other amphibians • Radio-ulna – “forearm” • Tibiofibula – “calf” • Phalanges – fingers adapted for jumping – on all four limbs • Bones are generally thicker (for impact when landing)

Amphibians – Skin • Serves as method of respiration and as a method of protection • Makes them more affected by pollution – chemicals can diffuse into the body • Health of amphibians in one habitat represents the condition of their environment

Amphibians - Respiration • Larvae have gills • Allow oxygen into the organism when it is underwater • Larvae undergoes metamorphosis • Gills disappear and lungs are made

Amphibians - Respiration • Adult amphibians can breathe through their skin and lungs. • Pulmonary respiration (breathing through lungs) – takes in air through nostrils and mouth • Adult frogs have to voluntarily force air down their throats (buccal pumping) because they lack a diaphragm, and this is why they mainly use cutaneous respiration.

Amphibians - Respiration • Cutaneous respiration (breathing through skin) – many amphibians use this type of respiration as their main type of breathing and use their lungs as backup • Skin is moist and permeable • Allows diffusion of oxygen, water, and carbon dioxide • However, this makes amphibians vulnerable to dehydration

Amphibians – Transportation and Circulation • Amphibians have a three-chambered heart • Circulatory system has two loops • Pulmonary circulation • Carries deoxygenated blood to lungs from heart • Moves through contraction of atrium • Systemic circulation • Oxygenated blood from heart to rest of body

Amphibians – Transportation and Circulation • Blood in heart • Deoxygenated blood enters right atrium • Pulmonary veins carry oxygenated blood from lungs to left atrium • Oxygenated and deoxygenated blood mix in ventricle • Ventricle pumps blood to lungs • All known as the “double-loop” system

Amphibians – Digestive System • All adults are carnivorous • Many larva are herbivorous • Frogs • Other larva are carnivorous • Salamander

Amphibians - Digestive System • Pharynx – opens into the esophagus • Esophagus – elastic tube that brings food down from the pharynx to the stomach • Allows amphibian to swallow large amounts of food • Stomach – has tiny glands that secrete gastric juices • Digests/breaks down food • Small intestine – Digestion is completed • Duodenum – upper portion • Ileum – coiled middle portion of small intestine • Mesentery – holds small intestine in place • Large Intestine – Holds waste

Amphibians – Excretion • Small intestine empties into the large intestine • Indigestible waste is collected • Processed by kidneys • Pushed into cloaca • Waste from kidneys, urinary bladder, eggs and sperm pass through cloaca • Waste exits through vent

Amphibians – Water Balance • Amphibians skin is permeable • Water and nutrients can come in through the skin • However, this also makes it more vulnerable to dehydration because water can diffuse out of their skin in dry environments • Therefore, amphibians must live in wet environments • Many are active only at night when water loss is minimized

Amphibians – Water Balance • Urine • Flows from kidneys to cloaca through urinary ducts • Goes to urinary bladder • Water-storing organ • Amphibian larva excrete nitrogen compounds as ammonia • Very toxic, so must be excreted quickly or diluted with water • To conserve water, adults instead transform ammonia into urea • Less toxic • Excreted with less water although uses energy

Amphibians – Reproduction • Frogs come out of hibernation in the first days of spring • Migrate to ponds and streams, where males attract females by using vocal sacs • Females only respond to frogs of the same species • When females come, males climb onto their backs and “hug” them – called amplexus – until eggs are laid through the vent . • Into the water for most amphibians • When eggs are laid, males discharge sperm onto the eggs – direct external fertilization

Amphibians – Reproductive System • Males • Sperm cells develop in the testes • Goes to urinary tract during mating season • Female • Eggs develop in the ovaries • Eggs enlarge, mature, and move to the body cavity during breeding season • Leave female through oviducts and are coated with a protective slime

Amphibians - Development • Tadpoles hatch within a few days and develop gills • Eventually, a mouth opens • Goes through metamorphosis – Changes from an aquatic larva to an adult • Legs • Lungs • Teeth • Tail disappears • Metamorphosis happens because of thyroxine • Produced in thyroid, circulates through blood, stimulates metamorphosis

Amphibians – Development • Alternative reproductive patterns • Some amphibians lay eggs in a warmer environment • Under a rock, in a log, in a tree • Some frogs build a nest • Made out of mucus, whipped into a frothy material by kicking it rapidly • Some do not go through metamorphosis • Salamanders that remain in the larval stage for their whole life • No thyroxine produced • Some do not go through the larval stage • Hatch from eggs as small version of adult

Amphibians – Nervous System • Tympanic Membrane – eardrum • Columella – bone that transmits sounds from the eardrum to the inner ear • Olfactory Lobes – sense of smell • Optic Lobes - sight

Amphibians – Nervous System • Brain • Same size as fish • Cerebrum – responsible for learning • Cerebellum – muscle coordination • Nerves extend directly from brain to body, protected by spinal cord • Lateral line – detect vibrations in water • Lost during metamorphosis

Reptiles Family Reptilia

History • Evolved from amphibians • Oldest known reptiles date back to early carboniferous period (359- 299 m.y.a) • Small, four-legged • Ate insects • Lived in dry climates

Dinosaurs • Evolved from thecodonts. • Success • Legs placed under body • Adapted to dry climates • Mass extinction

Dinosaurs • Extinction • Asteroid Impact Hypothesis • Huge asteroid hit Yucatán Peninsula • Dust cloud • Supported by high amount of iridium in sediments • Multiple Impact Hypothesis • Bad environmental conditions • Many asteroid impacts

Reptiles – Structural Support/ Body Cavity/Symmetry • Symmetry- Bilateral • Body Cavity- Coloem • Structural Support- Endoskeleton • Have breast bone to guard lungs and heart

Reptiles - Respiration • Have large lungs for gas exchange • Lunges divided into chambers • Alveoli- small sacs that are created by the folding of the lungs. (more oxygen) • Snakes • Only right lung functions, as big as half the length of body • Left is nonfunctional or gone

Reptiles - Respiration • Lungs are filled by expanding rib cage • Ribs contract to normal and air is released from lungs • Similar to human respiration

Reptiles - Water Balance/Excretion • Respiratory and excretion systems help reptiles conserve water • All tissues for respiration are internal to keep moisture • Land reptiles give of nitrogenous waste in the form of uric acid • Reptiles lose little water in urine

Reptiles – Water Balance/Excretion • Respiratory and excretion systems help reptiles conserve water • All tissues for respiration are internal to keep moisture • Land reptiles give of nitrogenous waste in the form of uric acid • Reptiles lose little a water in urine

Reptiles - Classification • Classified into four orders • Chelonia – Turtles and tortoises • Crocodilia – Alligators and crocodiles • Squamata – Lizards and snakes • Rhynchocephalia - tuataras

Reptiles - Chelonia • 250 species of turtles and tortoises • Tortoise- Terrestrial • Turtle- Aquatic • Ancient chelonians- like modern turtles and tortoises • Turtle design • Body enveloped in a shell • Carapace- Dorsal of the shell • Plastrons- Underside of shell • Ribs attached to inner carapace • Pelvic and pectoral girdles- inside ribs • Sharp beak

Amphibians and Reptiles