Complete the crossword, then click on "Check" to check your answer. If you are stuck, you can click on "Hint" to get a free letter. Click on a number in the grid to see the clue or clues for that number.

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 Check 

Across: 3. External surroundings of an organism. (11) 6. Trap designed to catch tiny soil organisms by making them move away from heat and light. (7,6) 7. Instrument which measures light intensity. (5,5) 10. A group of organisms of the one species. (10) 12. Any living thing. (8) 13. Small part of a much larger whole. (6) 15. Measure of the extent to which an organism occurs in an ecosystem. (9) 16. Means of identifying organisms. (3) 17. Sampling technique used to catch aquatic organisms. (7) 18. A factor that relates to a living feature of an ecosystem. (6)

Down: 1. Arrangement of living organisms within an ecosystem. (12) 2. Used to catch small invertebrates on the soil surface. (7,4) 4. A square-shaped sampling unit of a known area. (7) 5. Instrument used to measure the moisture content of the soil. (8,5) 8. Natural biological unit made up of living and non-living parts. (9) 9. All the organisms that live together in an ecosystem. (9) 11. A measure of the moisture in the air. (8) 14. The place where an organism lives. (7) 15. A factor that relates to a non-living feature of an ecosystem. (7)