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Across 3. total mass level of living matter at each trophic level 6. group exposed to the factor being tested (2 Words) 9. an organism that gets its energy requirements by consuming other organisms 10. living factors in an organism's environment (2 Words) 13. information gathered from observations 14. anything that takes up space and has mass 15. uses units with divisions that are powers of ten (2 Words) 17. simple model that shows how energy flows through an ecosystem (2 Words) 18. a direct method of gathering information in an orderly way 24. symbiotic relationship where one organism benefits at the expense of another organism 26. biological community and all the abiotic factors that affect it 27. an explanation of a natural phenomenon that is supported 28. the addition of mass to an organism, or the formation of new cells 29. area where an organism lives 30. reaction to a stimulus

Down 1. regulation of an organism's internal conditions to maintain life 2. a factor that remains fixed during an experiment 3. the exchange of matter through the biosphere (2 Words) 4. some soil bacteria convert fixed nitrogen compounds back into nitrogen gas 5. an organism which eats fragments of dead matter in an ecosystem 7. a set of moral principles or values 8. living things arranged in an orderly way 11. relationship between two or more organisms that live closely and benefit from each other 12. heterotrophs that prey on other heterotrophs 16. a scientific _____ describes relationships under certain conditions in nature 19. investigating a phenomenon in a controlled setting to test a hypothesis 20. individual organisms of a single species that are in the same location and time 21. branch of biology that deals with how organisms react and their relationships 22. one organism pursuing and consuming another for food 23. the study of life 25. part of either environment and causes a reaction by the organism