The Evolution of Amphibians

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

The Evolution of Amphibians — page 9 — EVOLUTION How did an animal like Ichthyostega become a modern amphibian The answer lies in evolution Evolution is the scientific theory that all life on Earth changes over time All life on Earth evolved from microorganisms that lived billions of years ago Across countless generations and hundreds of millions of years these life forms evolved into the species we see today Throughout Earth's history these changes have taken place across countless generations and hundreds of millions of years All modern plants animals insects and other organisms evolved from common ancestors that lived billions of years ago EVOLUTION OF DIGITS Approximately 340 MYA tetrapods started walking rather than swimming Walking required feet that could balance and push off varying surfaces Ankles and wrists needed to move in new ways as well As these joints changed so did the number of digits on hands and feet Today most animals have just five digits though some have fewer Why five Scientists aren't sure but they do know that species tend to lose digits over time and almost never gain new ones Charles Darwin was an influential scientist in studying evolution From 1831 to 1836 he sailed around the world on the HMS Beagle As a naturalist he became fascinated with fossil bones in Argentina and animals he observed on the Galapagos Islands in Ecuador He took more than 1,700 pages of notes and kept a 770 page diary 5 When he came home to the United Kingdom he studied his notes and performed

The Evolution of Amphibians — page 10 — People around the world are familiar with Charles Darwin's research on evolution

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