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 .

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

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

4. 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 .

6. 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".

9. 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 .

12. 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.

Unit Four

F.cosystems: What They Are

 

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.

V. VALUES DISCUSSION

Answer the following questions, then discuss your answers with your classmates.

1. How do you define the biotic structure?

a. It is soil quality and climate.

b. It is the way the categories of organisms fit together,
с It is the environment.

d. other

2. What are the major abiotic factors?

a. Rainfall, temperature and light.

b. Species and organisms of a given region.
с Water, wind, chemical nutrients.

d. other

3. What is the key observation in any study of the abiotic side of ecology?

a. Plants may be grown in a series of chambers.

b. Plants grow increasingly well until they reach some maximum-

c. Different species thrive under different conditions.

d. other

4. What is called the range of tolerance?

a. Maximum growth.

b. A range of several degrees.

с The entire span that allows any growth at all. d. other

5. What is a fundamental biological principle?

a. The plants experience increasing stress until they cannot survive.

b. Every species (both plant and animal) has an optimal range
and zones of stress.

с Every species (both plant and animal) has limits of tolerance

with respect to every abiotic factor, d. other

6. What cannot some plants tolerate?

a. Intense freezing.

b. Several weeks of freezing temperatures,
с Any freezing temperatures.

d. other

7. What is called the limiting factor?

a. Any one factor being outside its optimal range.

b. The factor that is limiting the growth,
с Any factor that affects the organism,
d. other

8. What is known as the Law of Limiting Factors?

a. Many plants may grow under the same conditions.

b. Any factor affects the organism.

с Any one factor being outside its optimal range at any given time

will cause stress and limit the growth of an organism, d. other

9. Who and when first presented the Law of Limiting Factors?

a. JimBourgin 1840.

b. Nebel Wright in 1850.

с Justus von Liebig in 1840. d- other °- What do observations since Liebig's time show? ^a- His law has much broader application.

Unit Four

Ecosystems: What They Are

 

b. It may be applied to biotic factors as well, с His law may be applied to all abiotic factors, d. other

11. What does the biosphere consist of?

a. Plants, animals, and microbial species.

b. All abiotic factors.

с A great variety of environments, both aquatic and terrestrial, d. other

12. What is the spread of each species at some point limited by?

a. It's not being able to restrain its own spread and influence.

b. It's not being able to tolerate particular conditions,
с It's not being able to compete with other species,
d. other

13. What idea do many environmentalists promote?

a. Nothing can be changed without affecting everything else to a
greater or lesser degree.

b. Most if not all life may perish.

с We may be on the verge of a sudden and catastrophic "collapse

of the biosphere", d. other

14. What do cornucopians argue?

a. Humans have already caused the extinction of thousands of
species.

b. All our experience to date should lead to the quite opposite con­
clusion.

с Humans have already made manifold changes over most of the

earth, d. other

VI. ROLE-PLAY

Choose one of the following situations to act out.

1. A lecturer is explaining to a group of students the interplay of many physical and chemical, or abiotic factors. The audience (which can be the whole class) will ask questions after a short (5 minutes) talk.

2. An audience (which can be the whole class) is asking the lecturer questions about the abiotic side of ecology.

3 Xwo young researchers are discussing the results of their experi­ments on testing zones of stress for different plants.

4. You are taking your examination in environmental science and answering questions about the Law of Limiting Factors.

5. A group of students is asking the teacher about Justus von Liebig and his observations regarding the effects of chemical nutrients on plant growth.

6. You are one of the environmentalists and are talking about a major concern of many environmentalists with your friend.

7. You are a cornucopian and are arguing that all our experience to date does not pose an environmental threat.