Which of the following is not included in a freshwater ecosystem?

What is meant by 'non-biodegradable' waste? Identify biodegradable waste from the following:
Empty packet of chips,empty plastic bottle of mineral water,empty paper box of sweets,empty tin of a cold drink.

What is the difference between the food habits of organisms belonging to the second and fourth trophic levels? Give one example of organisms belonging to each of these two trophic levels.

Suggest one word for each of the following statements/definitions:
$(a)$ The physical and biological world where we live in
$(b)$ Each level of food chain where transfer of energy takes place
$(c)$ The physical factors like temperature,rainfall,wind and soil of an ecosystem
$(d)$ Organisms which depend on the producers either directly or indirectly for food

What are the two main components of our environment?

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