Answer:
1. consumer (think "consume")
2. community (organism -> population -> community -> ecosystem)
3. abiotic factor (abiotic, as in not living)
4. decomposer (think "de"compose: they take things and break them down; as opposed to scavengers, these are small, like fungi or bacteria)
5. food chain
6. biosphere (think of the Earth: it's a sphere)
7. ecology (studies always end with -ology)
8. producer (think "produce")
9. biotic factor (biotic, as in biology, as in life)
10. ecosystem (organism -> population -> community -> ecosystem)
11. scavenger (as opposed to decomposers, these are normal animals, like vultures or bears)
12. population (organism -> population -> community -> ecosystem)