Sunlight. Based on the sunlight you receive you have three zones.
1. Sunlight zone- There is enough sunlight here and photosynthesis can happen. More than 90% of marine animals live in this zone.
2. Twilight zone- A small amount of light is here and no plants grow here. The fish who live here are the ones who have adapted to the little light. Lantern fish is an example.
3. Midnight Zone- 90% of the ocean is in this group. It is entirely dark and the temperature is freezing.
Hard, dense bone tissue that is beneath the outer membrane of bone <span />
One of the main functions of villi is to absorb nutrients.
