What is the layer of the atmosphere closest to the Earth called?

What are the by-products of fertiliser industries? How do they affect the environment?

What is transferred through a food chain in an ecosystem?

$15 \%$ can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.

Which trophic level is occupied by primary carnivores in a food chain?

Suggest suitable mechanism$(s)$ for waste management in fertiliser industries.