II. Vocabulary

From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once.

spread	interplay	overfertilizing	biotic structure
influence	as a result	certain bounds	range of tolerance
volition	low point	optimal range	in response to
aquatic	life cycles	freezing temperatures	limits of tolerance
weeds	terrestrial	agricultural crops	maximum growth
pests	stressed	constant struggle
growth	overwatering	Law of Limiting Factors

1. The way the categories of organisms fit together is referred to as the .

1. The environment involves the of many physical and chem­ical, or abiotic factors, the major ones being rainfall and light.

1. We shall find that this difference environmental factors de­termines which species may or may not occupy a given region.

1. Experiments show that, as temperature is raised from a that

fails to support , plants grow increasingly well until they reach

some maximum.

5. Actually, since usually occurs over a range of several de­grees, we speak of an .

5. The points at the high and low ends of the are called the

7. Some plants actually require several weeks of in order to

complete their .

8. The includes the problem of "too much" as well as the prob­lem of "too little".

8. For example, plants may be or killed by or as

well as by underwatering and underfertilizing.

10. This is certainly the case with our , where it is a to

keep them from being limited or even eliminated by and

11. In summary, the biosphere consists of a great variety of environ­ments, both and .

11. At the same time, each species and, , each ecosystem, is kept

within by limiting factors. _;

13. Significantly, nowhere in nature do we find a species restraining its _oWn and in and of its own .

III. PREPOSITIONS Fill in the correct preposition for each blank space.

1.

2. 3. 4. 5. 6. 7.

There are two "sides" every ecosystem, the organisms

one hand and the environmental factors the other.

The way the categories

organisms fit together is referred

as the biotic structure.

each

However, different species may be affected differently

factor.

any study the abiotic side ecology, the key ob

different conditions.

chambers which

the range

all abiotic factors are controlled.

The points the high and low ends

tolerance are called the limits

servation is that different species thrive Plants may be grown a series

tolerance.

Every species has an optimum range, zones

its

stress, and lim-

tolerance

respect

every abiotic factor.

8. This line

experimentation also demonstrates that different

species differ markedly respect the values

which the optimum and limits tolerance occur.

9.

10. 11. 12. 13.

14.

For instance, what may be an optimal amount water

one species may stress a second and result the death

third.

Thus many plants may grow the same conditions, although

these conditions may not be optimal all the plants.

The factor that is limiting may change one time an­ other.

He observed that restricting any one the many different nu-

^tnents any given time had the same effect: it limited growth.

This is certainly the case our agricultural crops, it is

being limited or even elim-

^a constant struggle to keep them

^inated weeds and "pests".

the same time, each species and, a result, each eco­ system, is kept certain bound limiting factors.

46

Unit Four

F.cosystems: What They Are

47

15. The spread each species is some point limited

its not being able to tolerate particular conditions, compete

other species, or cross some physical barrier.

IV. DEFINITE/INDEFINITE ARTICLES

Use a/an or the where needed. If no article is needed, write an .Yin the blank space.

point that supports maximum growth is called

optimum. Actually, since maximum growth usually occurs over

range of several degrees, we speak of optimal range.

entire span that allows any growth at all is called range

of tolerance. points at high and low ends

of range of tolerance are called limits of

tolerance. Between optimal range and high or

low limit of tolerance, there are zones of stress.

That is, as temperature is raised or lowered from opti­ mal range, plants experience increasing stress, at either limit of

tolerance, they cannot survive. Similar experiments have been

run to test other factors, and results invariably follow

same general pattern.