chapter 18.2: bacteria

Chapter 18.2: Bacteria

1. Prokaryotes are unicellular organisms that do not have a nucleus

or membrane-bound organelles.

2. They are classified into two kingdoms-- archaebacteria and

eubacteria.

3. There are three types of archaebacteria that live mainly in extreme habitats where there is usually no free oxygen available.

4. One type of archaebacterium lives in oxygen-free environments and

produce methane gas.

5. A second type lives only in water with high concentrations of salt.

6. The third type lives in the hot, acidic

water of sulfur

springs.

7. Eubacteria, the other kingdom of prokaryotes, include those prokaryotes

that live in places more hospitable than archaebacteria inhabit.

8. Some bacteria are parasites, obtaining their nutrients from living

organisms

9. Others are saprobes--organisms that feed on dead organisms or

organic wastes.

10. Some eubacteria live in places with sunlight because they need light to

make the organic molecules that are their food.

11. Some eubacteria break down and release the energy of inorganic

compounds containing sulfur and nitrogen in the process called

chemosynthesis.

12. A bacterium consists of a very small cell.

13. Prokaryotic cells have ribosomes, but they are smaller than those of

eukaryotes.

14. They also have genes that are located in a single circular

chromosome.

15. One structure that supports and protects a bacterium is the cell

wall.

16. Draw, color, and

label Figure

18.10 from the book.

17. In 1928, Sir Alexander Fleming

accidentally discovered

penicillin, the first

antibiotic--a substance that

destroys bacteria.

18. Biologists discovered that penicillin can interfere with the ability of some

bacteria to make cell walls.

19. The three most common shapes of bacteria are spheres called cocci;

rods called bacilli; and spirals called spirilli.

20. Bacterial cells often grow in characteristic patterns that provide

another way to categorize them.

21. Diplo- is a prefix that refers to a paired arrangement of cell growth.

22. The prefix staphlo- describes an arrangement of cells that resemble

grapes.

23. Strepto- is a prefix that refers to an arrangement of chains of cells.

24. Bacteria reproduce asexually by a process known as binary fission.

25. The resulting cells are genetically identical.

26. Some bacteria

have a form of sexual

reproduction called

conjugation.

27. During conjugation, one

bacterium transfers its

chromosome to another cell through a

bridgelike structure called a pilus that connects the two

cells.

28. Conjugation results in a bacterium with a new

genetic composition.

29. Many bacteria require oxygen for respiration. These bacteria are

called obligate aerobes.

30. There are other bacteria, called obligate anaerobes, that are killed

by oxygen.

31. Some bacteria, when faced with unfavorable environmental

conditions, produce endospores.

32. An endospore is a tiny structure that contains a

bacterium’s DNA, encased by a tough outer

covering that resists drying out,

temperature extremes, and

harsh chemicals.

33. When environmental conditions improve, the endospore

germinates, or produces a cell that begins to grow and reproduce.

34. Some bacteria

produce a powerful

and deadly poison, called a

toxin, as they grow.

35. Disease-causing bacteria are few compared with the number of

harmless and beneficial bacteria on Earth.

36. Several species of bacteria have enzymes that convert nitrogen gas into ammonia in a

process known as nitrogen fixation. Bacteria are the only organisms that can

perform these chemical changes.

37. Life could not exist if decomposing bacteria did not break down the organic materials in

dead organisms and wastes, returning nutrients to the environment.

38. Some foods that you eat would not exist without bacteria.

39. List three foods that are made using bacteria.

40. Bacteria also inhabit your intestines and produce vitamins

and enzymes that help digest food.

41. Some bacteria produce important antibiotics that destroy other types

of bacteria.

42. Bacteria cause diseases in plants and animals.

43. Bacterial diseases harm people in two ways. The growth of the bacteria can interfere with the

normal functioning of body tissue, or it can release a toxin that

directly attacks the host.

44. List three bacterial diseases.