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Opportunists and Competitors
Growth, reproduction, and daily metabolism all require an organism to expend energy. The expenditure of energy is essentially a process of budgeting, just as finances are budgeted. If all of one’s money is spent on clothes, there may be none left to buy food or go to the movies. Similarly, a plant or animal cannot squander all its energy on growing a big body if none would be left over for reproduction, for this is the surest way to extinction.
All organisms, therefore, allocate energy to growth, reproduction, maintenance, and storage. No choice is involved; this allocation comes as part of the genetic package from the parents. Maintenance for a given body design of an organism is relatively constant. Storage is important, but ultimately that energy will be used for maintenance, reproduction, or growth. Therefore the principal differences in energy allocation are likely to be between growth and reproduction.
Almost all of an organism’s energy can be diverted to reproduction, with very little allocated to building the body. Organisms at this extreme are “opportunists.” At the other extreme are “competitors,” almost all of whose resources are invested in building a huge body, with a bare minimum allocated to reproduction.
Dandelions are good examples of opportunists. Their seed heads raised just high enough above the ground to catch the wind, the plants are no bigger than they need be, their stems are hollow, and all the rigidity comes from their water content. Thus, a minimum investment has been made in the body that becomes a platform for seed dispersal. These very short-lived plants reproduce prolifically; that is to say they provide a constant rain of seed in the neighborhood of parent plants. A new plant will spring up wherever a seed falls on a suitable soil surface, but because they do not build big bodies, they cannot compete with other plants for space, water, or sunlight. These plants are termed opportunists because they rely on their seeds’ falling into settings where competing plants have been removed by natural processes, such as along an eroding riverbank, on landslips, or where a tree falls and creates a gap in the forest canopy.
Opportunists must constantly invade new areas to compensate for being displaced by more competitive species. Human landscapes of lawns, fields, or flowerbeds provide settings with bare soil and a lack of competitors that are perfect habitats for colonization by opportunists. Hence, many of the strongly opportunistic plants are the common weeds of fields and gardens.
Because each individual is short-lived, the population of an opportunist species is likely to be adversely affected by drought, bad winters, or floods. If their population is tracked through time, it will be seen to be particularly unstable—soaring and plummeting in irregular cycles.
The opposite of an opportunist is a competitor. These organisms tend to have big bodies, are long-lived, and spend relatively little effort each year on reproduction. An oak tree is a good example of a competitor. A massive oak claims its ground for 200 years or more, outcompeting all other would-be canopy trees by casting a dense shade and drawing up any free water in the soil. The leaves of an oak tree taste foul because they are rich in tannins, a chemical that renders them distasteful or indigestible to many organisms. The tannins are part of the defense mechanism that is essential to longevity. Although oaks produce thousands of acorns, the investment in a crop of acorns is small compared with the energy spent on building leaves, trunk, and roots. Once an oak tree becomes established, it is likely to survive minor cycles of drought and even fire. A population of oaks is likely to be relatively stable through time, and its survival is likely to depend more on its ability to withstand the pressures of competition or predation than on its ability to take advantage of chance events. It should be noted, however, that the pure opportunist or pure competitor is rare in nature, as most species fall between the extremes of a continuum, exhibiting a blend of some opportunistic and some competitive characteristics.
Paragraph 1: Growth, reproduction, and daily metabolism all require an organism to expend energy. The expenditure of energy is essentially a process of budgeting, just as finances are budgeted. If all of one’s money is spent on clothes, there may be none left to buy food or go to the movies. Similarly, a plant or animal cannot squander all its energy on growing a big body if none would be left over for reproduction, for this is the surest way to extinction.
1. The word squander in the passage is closest in meaning to
○ Extend
○Transform
○ Activate
○ Waste
2. The word none in the passage refers to
○ Food
○ Plant or animal
○ Energy
○ Big body
3. In paragraph 1, the author explains the concept of energy expenditure by
○ Identifying types of organisms that became extinct
○ Comparing the scientific concept to a familiar human experience
○ Arguing that most organisms conserve rather than expend energy
○ Describing the processes of growth, reproduction, and metabolism
Paragraph 3：Almost all of an organism’s energy can be diverted to reproduction, with very little allocated to building the body. Organisms at this extreme are “opportunists.” At the other extreme are “competitors,” almost all of whose resources are invested in building a huge body, with a bare minimum allocated to reproduction.
4. According to the passage, the classification of organisms as “opportunists” or “competitors” is determined by
○ How the genetic information of an organism is stored and maintained
○ The way in which the organism invests its energy resources
○ Whether the climate in which the organism lives is mild or extreme
○ The variety of natural resources the organism consumes in its environment
dispersal.
Paragraph 4：Dandelions are good examples of opportunists. Their seed heads raised just high enough above the ground to catch the wind, the plants are no bigger than they need be, their stems are hollow, and all the rigidity comes from their water content. Thus, a minimum investment has been made in the body that becomes a platform for seedThese very short-lived plants reproduce prolifically; that is to say they provide a constant rain of seed in the neighborhood of parent plants. A new plant will spring up wherever a seed falls on a suitable soil surface, but because they do not build big bodies, they cannot compete with other plants for space, water, or sunlight. These plants are termed opportunists because they rely on their seeds’
falling into settings where competing plants have been removed by natural processes, such as along an eroding
riverbank, on landslips, or where a tree falls and creates a gap in the forest canopy.
5. The word dispersal in the passage is closest in meaning to
○Development
○ Growth
○ Distribution
○ Protection
6. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
○Because their seeds grow in places where competing plants are no longer present, dandelions are classified as opportunists.
○Dandelions are called opportunists because they contribute to the natural processes of erosion and the creation of gaps in the forest canopy.
○The term opportunists apply to plants whose seeds fall in places where they can compete with the seeds of other plants.
○The term opportunists apply to plants whose falling seeds are removed by natural processes.
Paragraph 7：The opposite of an opportunist is a competitor. These organisms tend to have big bodies, are long-lived, and spend relatively little effort each year on reproduction. An oak tree is a good example of a competitor. A massive oak claims its ground for 200 years or more, outcompeting all other would-be canopy trees by casting a dense shade and drawing up any free water in the soil. The leaves of an oak tree taste foul because they are rich in tannins, a chemical that renders them distasteful or indigestible to many organisms. The tannins are part of the defense mechanism that is essential to longevity. Although oaks produce thousands of acorns, the investment in a crop of acorns is small compared with the energy spent on building leaves, trunk, and roots. Once an oak tree becomes established, it is likely to survive minor cycles of drought and even fire. A population of oaks is likely to be relatively stable through time, and its survival is likely to depend more on its ability to withstand the pressures of competition or predation than on its ability to take advantage of chance events. It should be noted, however, that the pure opportunist or pure competitor is rare in nature, as most species fall between the extremes of a continuum, exhibiting a blend of some opportunistic and some competitive characteristics.
7. The word massive in the passage is closest in meaning to
○ Huge
○ Ancient
○ Common
○ Successful
8. All of the following are mentioned in paragraph 7 as contributing to the longevity of an oak tree
EXCEPT
○ The capacity to create shade
○ Leaves containing tannin
○ The ability to withstand mild droughts and fire
○ The large number of acorns the tree produces
9. According to the passage, oak trees are considered competitors because
○ They grow in areas free of opportunists
○ They spend more energy on their leaves, trunks and roots than on their acorns
○ Their population tends to increase or decrease in irregular cycles
○ Unlike other organisms, they do not need much water or sunlight
10. In paragraph 7, the author suggests that most species of organisms
○ Are primarily opportunists
○ Are primarily competitors
○ Begin as opportunists and evolve into competitors
○ Have some characteristics of opportunists and some of competitors
Paragraph 5：Opportunists must constantly invade new areas to compensate for being displaced by more competitive species. Human landscapes of lawns, fields, or flowerbeds provide settings with bare soil and a lack of competitors that are perfect habitats for colonization by opportunists. █Hence, many of the strongly opportunistic plants are the common weeds of fields and gardens. █
Because each individual is short-lived, the population of an opportunist species is likely to be adversely affected by drought, bad winters, or floods. █If their population is tracked through time, it will be seen to be particularly unstable—soaring and plummeting in irregular cycles. █
11.Look at the four squares █ that indicate where the following sentence could be added to the passage.
Such episodic events will cause a population of dandelions, for example, to vary widely.
Where would the sentence best fit?
Click on a square [■] to add the sentence to the passage.
12.Directions: Complete the table by matching the phrases below
Directions: Select the appropriate phrases from the answer choices and match them to the type of organism to which they relate. TWO of the answer choices will NOT be used. This question is worth 4 points.
Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it. To review the passage, click on View Text.
Opportunists Competitors
Answer Choices
1.Vary frequently the amount of energy they spend in body maintenance
2.Have mechanisms for protecting themselves from predation
3.Succeed in locations where other organisms have been removed
4.Have relatively short life spans
5.Invest energy in the growth of large, strong structures
6.Have populations that are unstable in response to climate conditions
7.Can rarely find suitable soil for reproduction
8.Produce individuals that can withstand changes in the environmental conditions 9. Reproduce in large numbers
参考答案：
1.○4
2.○ 3
3.○ 2
4.○ 2
5.○3
6.○ 1
7.○1
8.○ 4
9.○2
10.○ 4
11.○ 3
12. ○ Opportunists：3 4 6 9 Competitors：2 5 8