1. Yes.
2. Energy in an ecosystem flows unidirectionally from producers to different consumers through different tropic level. The constant supply of matter (nutrients like C, N„, P, Ca, etc.) are never lost from the ecosystem. Their constant supply is maintained by nutrient cycling.
3. The mass of living material in a tropic level at a particular time is a standing crop. The amount of nutrients present in a soil at a given time is called standing state.