Amphibians Evolution It is believed that amphibians evolved form lobe-finned fishes called Crossopterygians. They had short, limblike fins, no gills, internal nostrils and a primitive lung. All have a bony skeleton. They probably evolved due to environmental pressures such as: 1. Competition for food among fish in the water 2. Periodic droughts of bodies of water Possible food supply on land They would have to adapt to the harsh environment of the land to survive. These problems include: drying of gills, gravity pulling on a weak skeletal system, lack of limbs, and greater temperature changes than in water.
Vocab Amphibians Vomerine teeth atrium cerebellum viviparous ventricle Amplexus ovoviviparous notochord vertebra cloaca Oviparous Pharyngeal pouch nictitating membrane cerebrum hibernation Ectotherm estivation torpor chordate metamorphosis keratin tetrapod Chromatophores tympanic membrane internal nares cutaneous respiration countershading
Amphibians Amphibians Evolution of Amphibians
Adaptations of amphibians to life on land: Legs in place of fins stronger bones and muscles to adjust to gravity lungs instead of gills skin that would cover and protect from some water loss (keratin- a protein) necks that could see and feed more easily oral glands to moisten dry food of plants and insects Facts about amphibians:They are coldblooded. This means they go into a stage of dormancy or torpor when temperature conditions are unfavorable. Hibernation- winter torpor and Estivation - summer torpor. Land animals are exposed to 20% more oxygen than animals which live in water.
Amphibians Amphibian Diversity http://www.nicerweb.com/sketches/video/BBC-LifeOnEarth/2.6_InvasionOfTheLand/ image library • Scientists classify modern amphibians into three orders. 1. Order Anura includes frogs and toads (5283 species) The largest is the Conraua from West Africa at 7 ½ pounds. 2. Order Caudata includes salamanders, axolotl, mudpuppy and newts. Some give birth to live young. (553 species) 3. Order Gymnophiona includes caecilians (3 species)
Bull frog African giant frog
Amphibians Characteristics of Amphibians • Most amphibians begin life as aquatic organisms. Tadpole • After metamorphosis, they are equipped to live life on land. Frog
Amphibians Feeding and Digestion • Most frog larvae are herbivores, whereas salamander larvae are carnivores. Frogs swallow prey whole. • As adults, their diets are similar as both groups become predators. • The digestive system of an amphibian is very similar to that of a fish. (esophagous, stomach, intestine)
Amphibians Excretion • Amphibians filter wastes from the blood through their kidneys, and excrete either ammonia or urea as the waste product. • Ammonia is excreted by amphibians that live in the water. • Urea is stored in the urinary bladder until it is eliminated from the body through the cloaca. • Frogs that live in the water must get rid of extra water taken in form osmosis by secreting dilute urine.
Amphibians Circulation • Amphibians have a double-loop circulatory system. • Adult amphibians have three-chambered hearts. (larvae -2) • Land dwelling animals expend more energy than those that live in the water. Gravity pulls more on those out of the water. The three- chambered heart of adult frogs partially separates oxygenated and deoxygenated blood and allows more oxygen-rich blood to circulate.
Amphibians Respirationbreathe Oxygen • As larvae, most amphibians exchange gases through their skin and gills. • As adults, most breathe through lungs, their thin, moist skin, and cavities in the mouth. • They must do this because the lungs are very small and they can get oxygen when dormant in mud.
Amphibians The Brain and Senses • Amphibians use sight to locate and capture prey that fly (insects) at high speeds and to escape predators. Have color vision. • Frogs have nictitating membranes that protect their eyes. • Frogs use their tympanic membrane to hear high-pitched sounds and to amplify sounds from the vocal cords.
Amphibians Reproduction and Development • In most amphibians, fertilization is external sexes separate. Some do have internal fertilization with live young born. • Shell-less eggs must be laid and fertilized in water. • Larvae hatch from the egg and undergo metamorphosis from a fishlike animal to an air-breathing one. Virtual Frog Dissection
The Life Cycle of a Frog Section 30-3 Adults are typically ready tobreed in about one to two years. Adult Frog Frog eggs are laid in water and undergo external fertilization. The eggs hatch into tadpoles a few days to several weeks later. Young Frog Fertilized Eggs Tadpoles Tadpoles gradually grow limbs, lose their tails and gills, and become meat-eaters as they develop into terrestrial adults.
Crazy Frog reproduction Surinam Toad (female) Darwin’s Frog (male) Froglet emerges from vocal pouch South American pygmy marsupial frog (female) Poison Arrow Frog (male)
Frog Reproduction (Order Anura) Males are recognized by their heavier muscles and larger first fingers, used to hold the females. Sperm develop in the testes of males. Immature eggs are found in the ovaries of females. External fertilization in water. Many eggs must be laid due to high predation. Metamorphosis - tadpoles hatch out of eggs and live off of the yolk for awhile as they grow three pairs of gills. They have a 2-chambered heart. They can regenerate body parts in this stage. A saclike bladder in the throat turns into two lungs. The heart develops a third chamber.
Males are territorial and have vocal sacs to make their calls louder than female calls to attract a mate. Tree frog with vocal sac
Frogs and Toads (O. Anura) “without tail” Live in any habitat from polar to subartic regions. Frogs- near water, smooth moist skin and long hind legs Eggs are in clumps. Toads – bumpy, dry skin and short legs; can tolerate dry conditions, but need water for reproduction (eggs tadpole adult) Eggs are in strings. Toads and frogs can have poison glands and antimicrobial chemicals on their skin. Chromatophores- pigment cells in the skin of amphibians.
O. Urodela – Salamanders, newts, axolotl, mud puppy. The name means “visible tail”. Long tails and legs; live in moist places. Terrestrial species skip the larvae stage Reproduction is external in most. Eggs are laid in water (oviparous) which hatch into tadpoles. Some lay eggs that hatch into small adults and others give birth to live young –viviparous (internal fertilization.) Axolotls- can metamorphoses to a terrestrial form losing gills and breathing with lungs when a pond dries up. Some American newts have very complex development aquatic larvae terrestrial juveniles aquatic adults
axolotl leg lab- regeneration research
O. Gymnophiona (Caecilians) “naked snake” Found in tropical forests of S. America, Africa and Asia Have a long, slender body with small dermal scales in the skin, long ribs, no limbs Eyes are small and most blind as adults Eat worms and small insects Internal fertilization Oviparous and Viviparous (eat the wall of oviduct)
Amphibians are found in ponds, streams, wetlands of all types, under rotten logs, in leaf litter, in trees, underground, even in pools of rain water inside large leaves. The can not live in salt water. Wet tropics, amphibians active all year round Temperate zone become inactive in winter In the autumn, environmental cues direct amphibians to find moist, sheltered places like muddy pond bottoms or deep leaf litter to hibernate. Spadefoot toad- (really a frog)burrows under the sand in the desert and makes a cocoon. Habitat
Amphibian decline: silence of the frogs? In the late 1980s, amphibian researchers noticed that amphibian populations, especially frogs and toads, were declining in numbers, and in some cases, to the point of extinction around the world. These amphibian declines are a reflection of a serious ecological problem and that amphibians, like a canary in a coal mine, could be indicators to humans of environmental quality. Some declining populations include the following: The Mountain Yellow-legged Frog The Golden Toad The Stomach-brooding Frog The Northern Leopard Frog Amphibian issues
Water Land Bones Lungs Ribs Efficientmovement Breathingair Support andprotection Review Amphibians means “Double life” as larvæ they live in adults they live on and have special adaptations such as are that allow for that allow that provide are
Fishes and Amphibians Chapter Resource Menu Chapter Diagnostic Questions Formative Test Questions Chapter Assessment Questions Standardized Test Practice biologygmh.com Glencoe Biology Transparencies Image Bank Vocabulary Animation Click on a hyperlink to view the corresponding lesson.
Fishes and Amphibians Chapter Diagnostic Questions What body part developed in terrestrial vertebrates and functions like the lateral line system in fish? lungs ears limbs cloaca
Amphibians It increases the efficiency of the exoskeleton. 28.1 Formative Questions Why is a vertebral column an important adaptation in vertebrate animals? It enhances an animal’s movement. It decreases the need for muscles. It protects the ventral notochord.
Fishes and Amphibians Chapter 28 28.3 Formative Questions How is a frog able to survive the winter at the bottom of a frozen pond? It breathes through its skin. It develops gills for absorbing oxygen. Its circulatory system shuts down. Its lungs extract oxygen from the water.
Fishes and Amphibians Chapter 28 28.3 Formative Questions How many heart chambers does an amphibian have? one atrium and one ventricle two atria and one ventricle one atrium and two ventricles two atria and two ventricles
Fishes and Amphibians Chapter 28 28.3 Formative Questions What part of an amphibian’s body does the nictitating membrane cover? eardrums eyes skin lungs
Fishes and Amphibians Chapter 28 28.3 Formative Questions What does an amphibian sense with its tympanic membrane? light movement sound taste
Fishes and Amphibians Chapter 28 28.3 Formative Questions Which is a global factor that might be causing a decline in amphibian populations worldwide? decreasing temperature exotic competitors longer dry seasons habitat destruction
Fishes and Amphibians right atrium receives deoxygenated blood from the body Chapter 28 Chapter Assessment Questions Which is not a characteristic of the circulatory system of amphibians? two-chambered heart double loop system undivided ventricle
Fishes and Amphibians Chapter 28 Chapter Assessment Questions What structure is indicated? cerebellum medulla oblongata optic lobe olfactory bulb
Fishes and Amphibians Chapter 28 Standardized Test Practice What level of classification is Vertebrata? subkingdom phylum subphylum superclass
Fishes and Amphibians Chapter 28 Standardized Test Practice Which amphibian, when picked up by a dog, may cause the dog to get sick and vomit? frog newt toad salamander
Fishes and Amphibians Chapter 28 Glencoe Biology Transparencies
Fishes and Amphibians Chapter 28 Image Bank
Fishes and Amphibians Chapter 28 Vocabulary Section 1 cartilage neural crest fin scale operculum atrium ventricle nephron lateral line system spawning swim bladder
Fishes and Amphibians Chapter 28 Vocabulary Section 2 tetrapod
Fishes and Amphibians Chapter 28 Vocabulary Section 3 cloaca nictitating membrane tympanic membrane ectotherm