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Across 1. the exchange of matter through the biosphere 5. a method of gathering information in an orderly way 8. units that are divisions with the powers of ten 9. a body of knowledge based on the study of the natural world 10. soil bacteria convert fixed nitrogen compounds back into nitrogen gas 13. information gained from observations 14. each step in the food chain 18. anything that has mass and takes up space 20. the process of natural changes that take place during the life of an organisam 24. the close relationship that exists when two or more species live together 25. a set of moral principles or values 26. an explanation of a natural phenomenon supported by observations and experiments 27. made of one or more cells, displays organization, grows and develops,reproduces, responds to stimuli, requires energy, maintains homeostasis, and adaptions evolve overtime 28. the role or position that an organism has in its enviorment

Down 1. a group of interacting poputations that occupy teh same geographical area 2. a nonliving condition or thing, like a climate or habitat, that influences or affects an ecosystem and the organisms in it 3. group exposed to the factor being tested 4. a group of organisms that can breed with one another and produce fertile offspring 6. regions of the surface of the earth that are occupied by organisms 7. the relationship in which one organism benefits and the other organism is neither helped nor harmed 11. the production of offspring 12. any inherited characteristic that results from changes to a species over time 15. a model representing the many interconnected food chains and pathways in which energy flows 16. an organism that collects energy from sunlight or inorganic substances to produce food 17. investigating a phenomenon in a controlled setting to test a hypothesis 19. a heterotroph that only eats plants 21. organisms that eat both plants and animals 22. a factor that remains fixed during an experiment 23. a large group of ecosystems thsat share the same climate