1. What are called the "building blocks of life"? A. amino acids B. cells C. producers D. tissues 2. Which trophic level has the most energy available? A. producer B. tertiary consumer C. primary consumer D. secondary consumer 3. What is the term for the specific environment of the ecosystem in which organisms live? A. species B. habitat C. niche D. biotic factor 4. In how many directions does energy flow in an ecosystem? A1 B. 2 C. 4 D. many ​