Amphibians are a group of vertebrates which evolved from lobe-finned fishes. Most amphibians spend at least part of their life-cycles in watery environments.
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Birds are warm-blooded vertebrates distinguished by bodies and wings covered in feathers. Most birds are able to fly and all reproduce by laying eggs.
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Fish are aquatic vertebrates with bodies covered with scales, two sets of paired fins and gills. Fish are generally classified as “bony” and “cartilaginous."
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Invertebrates make up 97% of all animals on Earth. Invertebrates lack backbones and therefore the category includes all animals that are not vertebrates.
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