Need more info make sure to add the pictures or at least explain it better
Complex organisms need cells that can perform many different functions. they need to be supported on a cellular level. Without specialized cells you they won't be able to perform different functions.
Organisms such as producers who make their own food.
How to remember: "auto" means they make it automatically by their own.
<span>The nutrient in question has an exhausted supply due to which cellular growth is limited. Usually nutrient limitation which limits productivity consist of such essential nutrients which are required by organisms in that environment to survive and grow.
Hope i helped.</span>
