Problem:

Question 1: Where (at what level) does nitrogen enter the food chain?

A) From the atmosphere when "fixed" by the photosynthetic machinery of plants.
B) Primarily through soil-dwelling bacteria that "fix" it by attaching it to other atoms .
C) When rocks dissolved by rainwater become soil and are utilized by plants as they grow.
D) Through soils erosion followed by runoff into streams and ponds.
E) Through photosynthesis by plants.

Question 2: Which of the following is an example of an abiotic factor?

A) Mean annual rainfall in an ecosystem.
B) Rate of predation on a prey population.
C) Average litter size.
D) The density of a population.
E) Average lifespan.

Give reasoning with your answer.