Consider the following statements and choose the correct answer:
1. The carbon, nitrogen and various cycles in nature operate to conserve the limited amount of usable matter on the earth
2. The flow of energy is both cyclic and one-way
3. The transfer of energy through a biological community begins when the energy of sunlight is fixed in a green plant by photosynthesis
4. It is estimated that only 8 percent of the energy of the sun reaching the planet strikes green plants and that only 2 percent of this is utilized in photosynthesis