Which biome covers 75% of the Earth's surface and is organized by the depth of water?

The marine biome is the correct answer because it encompasses the vast oceans and seas that cover approximately 75% of the Earth's surface. This biome is characterized by its organization based on various factors, including the depth of water, which creates distinct habitats such as the intertidal zone, the pelagic zone, the benthic zone, and more. Each of these zones has unique environmental conditions and life forms adapted to them, influencing biodiversity and ecosystems within the marine biome. This classification highlights the significance of water depth in determining the types of organisms that can thrive in different regions of the ocean, making the marine biome a complex and vital aspect of Earth's ecology. Other biomes, such as tundra, desert, and forest, cover much less of the Earth's surface and do not primarily use water depth as a defining characteristic.