Why are trophic levels important?

If there is no producers (such as a plant), you cannot sea any primary consumers there. That is why trophic levels are important. They show availability of food/energy in a defined ecosystem, complexity of "who eats what", dependency of any one to others, etc.

Explanation:

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.