Unit 2

2. — source of power for belt-driven machines as well as for pulling.
4. — machine that is used to cut and thresh seed crops such as grain.
5. — plow with a curved bottom that will turn prairie soils.
7. — machine that cuts grain.
8. — popular potato variety of the 1930s.
9. — plant or animal offspring from crossing two different species or varieties.
11. — organism that lives in or on other organisms with no benefit to the hosts.
13. — machine that milks cows and goats.
14. — process in which many countries became self-sufficient in food production.
17. one of a row of houses connected by common side walls.
20. apartment building or unit in which the apartments are individually owned.
21. — selecting the strongest plants of each generation to parent the next generation.
23. — food made by boiling and crushing soybeans and letting it coagulate into curds.
25. — plant in which certain nitrogen-fixing bacteria utilize nitrogen gas from the air and convert it to nitrates that the plant can use as food.
26. — machine that removes ears of corn from stalks.

1. — natural substances in blood that fight diseases and infections.
3. — physically putting certain genes into the cells of a plant or animal.
6. receives and treats human waste.
10. — superior baking potato bred to grow well in the Northeast.
12. — adding material that will change the purity or usefulness of a substance.
15. containing harmful chemicals or organisms.
16. — widespread starvation.
18. — potato grown in volcanic soils of Idaho and the Northwest; greater resistance to disease and insects results in greater yields.
19. — any edible material used for animal feed.
22. — machine that removes cotton seed from cotton fiber.
24. — devices used to determine wavelengths given off by plants.