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Read the statements then checklist (ѵ) the option that suit on you.

Statements Definitely Yes Maybe No No at all
The explanation is easy to
understand.

The task is easy to do.

I fully understand the material in

this chapter.

K. Formative Test

Cognitive Assessment

A. Read the questions and choose the best answer

The text is for number 1-5

Cultivation of a single crop on a given tract of land leads eventually to decreased yields. One
reason for this is that harmful bacterial phytopathogens, organisms parasitic on plant hosts, increase
in the soil surrounding plant roots. The problem can be cured by crop rotation, denying the
pathogens a suitable host for period of time. However, even if crops are not rotated, the severity of
diseases brought on by such phytopathogens often decreases after a number or years as the
microbial population of the soil changes and the soil becomes “suppressive” to those diseases. While
there may be many reasons for this phenomenon, it is clear that levels of certain bacteria, such as
Pseudomonas fl uorescens, a bacterium antagonistic to a number of harmful phytopathogens, are
greater in suppressive than in nonsuppressive soil. This suggests that the presence of such bacteria
suppresses phytopathogens. There is now considerable experimental support for this view. Wheat
yield increases of 27 percent have been obtained in fi eld trials by treatment of wheat seeds with fl
uorescent pseudomonads. Similar treatment of sugar beets, cotton, and potatoes has had similar
results.
These improvements in crop yields through the application of Pseudomonas fl uorescens
suggest that agriculture could benefi t from the use of bacteria genetically altered for specifi c
purposes. For example, a form of phytopathogen altered to remove its harmful properties could be
released into the environment in quantities favorable to its competing with and eventually excluding
the harmful normal strain. Some experiments suggest that deliberately releasing altered
nonpathogenic Pseudomonas syringae could crowd out the nonaltered variety that causes frost
damage. Opponents of such research have objected that the deliberate and large-scale release of
genetically altered bacteria might have deleterious results. Proponents, on the other hand, argue
that this particular strain is altered only by the removal of the gene responsible for the strain’s

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