It is the trigeminal. check my spelling though.
Answer:
13000 would be avalable because 10% is taken every time it is eaten so 65,000 with 10% taken out twice (20% of 65,000) is only 13,000 kcal available to the secondary consumers.
Answer:
It affects populations, It occurs when there is genetic variation, It selects organisms with certain traits to survive. I'm not 100% sure this is completely correct, but I just studied this in school and this sounds right. :)