I think it's 420,000 kcal, because 10% of energy is lost as you move up each trophic level. To find what you started with you would multiply by 10 instead of dividing by 10. You have to multiply by 10 twice, because of the primary consumers and producers.
I would go with c because its tells you right in there that the ecosystem help who lives around that area.
The answer is A it takes a million of years to form
A cell wall shapes and protects the plant cell at the same time.
<span>This statement is true. Aquaculture involves the farming of different sea organisms that can provide food for humans and other water-dwelling species. It also is used to increase sustainability of resources by creating renewable energy and taking the strain off existing aquatic systems.</span>