This week in Marine Biology class we got a packet about marine reptiles, birds, and mammals. Vertebrates have invaded land 350 million years ago. Land vertebrates descended from bony fishes. The land vertebrates had to live on land meaning they had to breath air, and they evolved from fishes who had lungs for breathing. Reptiles today have evolved from now-extinct amphibians. There are 7,000 living species of reptiles, including lizards, snakes, turtles, and crocodiles. Their dry skin is covered with scales to prevent water loss. Most reptiles are ectothermic, commonly called "cold-blooded." Reptiles first appeared more than 300 million years ago, and several species have adapted to the sea. Birds have advantages over reptiles such as the ability of flight. Birds are endothermic, which is referred to as "warm-blooded." This allows them to live in a wide variety of environments. They have waterproof feathers that conserve body heat, and their flight is made easier by their light, hollow bones. Marine mammals evolved about 200 million years ago. They evolved from now-extinct reptiles, and they are air-breathing and warm-blooded. Their skin has hair instead of feathers to retain body heat. They are viviparous meaning the embryo receives nutrients and oxygen through the placenta. a new-born is fed by milk secreted by the mother's mammary glands. Their young are well-cared for. All these 3 types of animals have adapted and evolved from extinct animal groups millions and millions of years ago.
