Complete the crossword, then click on "Check" to check your answer.

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 Check 

Across: 3. When certain individuals are better suited to their environment, they survive and breed. 6. The remains of dead plants and animals, found in rocks and used as evidence in the theory of evolution 7. Energy that is manufactured by using an energy resource such as coal or wind 8. A clinical trial where neither doctor nor patient know if the drug is actually being used 9. White blood cells that remain after and infection and 'remember' the shape of antibody to make 10. Trials where the drug is tested on humans to find out if it is safe or not 12. THe principle of taking steps to reduce the risks where nobody knows just how serious it could be 13. When your body has had an infection before and can stop it from being infected again quickly 14. The most penetrating form of radioactive radiation 16. The correct term for natural radiation all around you 20. The theory of how different species came to be 21. The chemical in chromosomes that controls how an organism develops 23. A group of organisms that can breed together and produce fertile young 25. The special shapes on the outside of a cell that antibodies stick onto. 26. An energy resource that can be used to generate electricity without being used up itself. 28. When there is evidence that one thing leads to another and the linking science is understood 29. A change in the DNA of an organism 31. Radiation that can cause damage to living cells

Down: 1. A section of DNA 2. Your stomach produces this and it kills bacteria 4. Fatty deposits that build up in ateries and lead to hardening of the arteries 5. A 'dummy drug' given in clinical trials 11. An injection given to people to help their bodies develop antibodies for particular diseases 15. The least penetrating and most harmful radioactive radiation 17. The viruses in a vaccination are often this! 18. Microbes that are not killed by antibiotics 19. A type of micro-organism that is killed by antibiotics but not by antibodies 22. A type of micro-organism that is killed by antibiotics, and also by your white blood cells 24. The name of the injection given for 11 down 27. Your white blood cells produce these in response to infection by viruses 30. Micro-organisms thta can only reproduce inside other living cells