galapagos giant tortoise

galápagos giant tortoise largest tortoises massive dome-shaped shell slow movements 900 pounds 400 4-5 feet 2-1 meters dark brown grayish-black protection predators thick legs sturdy heavy bodies long necks cacti grass leaves herbivorous diet small head eyes soulful beak-like mouth slow-moving mph longevity 100 years 150 charles darwin theory evolution archipelago variations islands populations herbivore vegetation reptile land endemic species ecuador conservation national parks endangered habitat metabolism biodiversity ecosystem unique adaptations environmental impact