The Evolution of Amphibians

The Evolution of Amphibians — page 5 — There are more than 7,900 species of amphibians in the world and they can be broken up into three main groups Frogs comprise the largest group and they are of the order Anura They have short bodies with no tails and their hind legs are strong longer than their front legs and ideal for leaping Salamanders make up the second largest group and they are of the order Caudata They have tails and their front and back limbs are about the same size Finally the smallest group of amphibians is called the caecilians of the order Gymnophiona Caecilians resemble large earthworms and have no limbs Their bodies are ideal for burrowing GOLDEN POISON FROG Many frogs produce a poison in glands of their skin to keep predators at bay But the golden poison frog of Colombia produces one of the deadliest ones Named for its often yellow color it can also be orange or pale green Measuring approximately one to two inches 2.5-5 cm in length it can produce enough poison to kill ten adult humans

The Evolution of Amphibians — page 6 — CLASSIFICATION Golden Poison Frog Phyllobates terribilis DOMAIN Eukaryota This domain includes plants animals and fungi These organisms are grouped together because their cells each have a nucleus a cell structure that contains the DNA KINGDOM Animalia All animals including mammals and amphibians are in this group PHYLUM Chordata Organisms in this phylum have a nerve cord down their backs supported by a rod of cartilage at some point in life All animals with spines including mammals and fish are in this group CLASS Amphibia This class contains caecillans frogs and salamanders ORDER Anura This order contains frogs and toads FAMILY Dendrobatidae Frogs in this family are typically small poisonous and have colorful skin GENUS Phyllobates These small poisonous frogs are active during the day and live in Central and South America SPECIES terribilis Golden poison frogs are often yellow and live in the Amazon rain forest Taxonomic classification is the science of identifying living things grouping them together and naming them When this is done each organism is assigned a place in eight different categories ranging from domain the most general category to species the most specific category When the scientific name of an animal is given it includes the genus which is capitalized and the species which is not Golden poison frogs are Phyllobates terribilis Scientific names are often abbreviated after first use P. terribilis

The Evolution of Amphibians — page 7 — Tadpoles are the Larvae of frogs Like birds and mammals amphibians are vertebrates They have a spinal column and a brain that is part of their nervous system Amphibians have moist skin and can breathe through the surface of their skin They also have glands on their skin that produce proteins These proteins

The Evolution of Amphibians — page 8 — fight bacteria move water into and out of their bodies and help defend against predators This defense can take the form of poison The dart frog for instance produces a chemical called curare on its skin which causes paralysis Most amphibians breed by laying eggs in fresh water though some lay eggs on leaves in damp soil in tree holes or in a foamy nest made from mucus The larvae immature versions of the adult animal grow inside the eggs Once the larvae hatch they grow and develop in the water away from the adults of their species They must find their own food and evade predators on their own Larvae mainly eat plants and the adults eat other animals As the larvae mature they go through a metamorphosis or change from aquatic animals to terrestrial or land based animals Most grow limbs and develop lungs Once this is complete most amphibians leave the water to live on the land Amphibians cannot regulate their own body temperature internally so this means they are always the same temperature as their environment If the environment is cold they are cold If it's hot they're hot In addition too much sun can damage their cells and too much wind can dehydrate them For this reason amphibians are more sensitive to changes in the environment than many other animals

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