Biology

5. an organism causing disease to its host
6. an infectious agent that can only replicate within a host organism
7. microscopic organisms
8. close ecological relationship between the individuals of two different species
12. organism that breaks down dead organic material
14. a substance that causes your immune system to fight against it
17. a classification system
18. most widely used method of generating phylogenetic trees
19. having a high degree of resistance to an illness or disease
20. chemical substance produced by a living organism,
21. origin of the chroloplast and mitochondria

1. proteins produced by the body's immune system
2. asexual reproduction by a separation of the body into two new bodies
3. part of the body's immune system
4. any member of a group of diverse eukaryotic any cell or organism that possesses a clearly defined nucleus
9. small single-celled organisms.
10. the science of naming, describing and classifying organisms
11. any organism that lacks a distinct nucleus and other organelles due to the absence of internal membranes
13. containing multiple cells
15. medicine that trains the body's immune system so that it can fight a disease it has not come into contact with before.
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