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Across 1. in a biological community, the number and abundance of different species (2 Words) 5. technique of adding essential materials to a degraded ecosystem (2 Words) 7. occurs when the birthrate equals the death rate (3 Words) 11. movement of individuals into a population 12. nonnative species deliberately or accidentally introduced into a new habitat (2 Words) 17. habitat loss from separation of an ecosystem into small pieces of land (2 Words) 21. environmental factor, such as storms and extreme heat or cold, that affects populations regardless of their density (2 Words) 28. largest number of individuals in a species that an environment can support long-term (2 Words) 29. any material or organism in the biosphere, including water, soil, fuel, and plants and animals (2 Words) 30. a large-scale dying out of a large percentage of all living organisms in an area within a short time (2 Words) 31. the disappearance of a species when the last of its members dies

Down 2. environmental factor, such as predation, disease, and competition, that depends on the number of members in a population per unit area. (2 Words) 3. any natural resource available in limited amounts or replaced extremely slowly by natural processes (2 Words) 4. increasing concentration of toxic substances, such as DDT, in organisms as trophic levels increase in food chains or food webs (2 Words) 5. gradual process of a species becoming extinct (2 Words) 6. water pollution from nitrogen-rich and phosphorus-rich substances flowing into waterways, causing algal overgrowth 8. overuse of species with economic value-a factor in species extinction 9. technique using living organisms to detoxify a polluted area 10. number of organisms per unit of living area (2 Words) 13. variety of ecosystems in the biosphere (2 Words) 14. any resource replaced by natural processes more quickly than it is consumed (2 Words) 15. population change from high birth rates and death rates to low birth rates and death rates (2 Words) 16. how fast a specific population grows (3 Words) 18. number of different species living in a specific area 19. variety of inheritable characteristics or genes in an interbreeding population (2 Words) 20. found only in one specific geographic area 22. use of resources at a rate that they can be replaced or recycled (2 Words) 23. in any population, the number of individuals in their pre-reproductive, reproductive, and post-reproductive years (2 Words) 24. movement of individuals away from a population 25. any different environmental condition occurring along an ecosystem's boundaries (2 Words) 26. study of human populations based on size, density, movement, distribution, and birth and death rate 27. arrangement of a population in its environment