Biology

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Across
  1. 5. an organism causing disease to its host
  2. 6. an infectious agent that can only replicate within a host organism
  3. 7. microscopic organisms
  4. 8. close ecological relationship between the individuals of two different species
  5. 12. organism that breaks down dead organic material
  6. 14. a substance that causes your immune system to fight against it
  7. 17. a classification system
  8. 18. most widely used method of generating phylogenetic trees
  9. 19. having a high degree of resistance to an illness or disease
  10. 20. chemical substance produced by a living organism,
  11. 21. origin of the chroloplast and mitochondria
Down
  1. 1. proteins produced by the body's immune system
  2. 2. asexual reproduction by a separation of the body into two new bodies
  3. 3. part of the body's immune system
  4. 4. any member of a group of diverse eukaryotic any cell or organism that possesses a clearly defined nucleus
  5. 9. small single-celled organisms.
  6. 10. the science of naming, describing and classifying organisms
  7. 11. any organism that lacks a distinct nucleus and other organelles due to the absence of internal membranes
  8. 13. containing multiple cells
  9. 15. medicine that trains the body's immune system so that it can fight a disease it has not come into contact with before.
  10. 16. occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely