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
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.
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. █
Paragraph 6: 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?
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.
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Opportunists
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Competitors
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●
●
●
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●
●
●
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Answer Choices
○Vary frequently the amount of energy they spend in body maintenance
○ Have mechanisms for protecting themselves from predation
○Succeed in locations where other organisms have been removed
○Have relatively short life spans
○Invest energy in the growth of large, strong structures
○Have populations that are unstable in response to climate conditions
○Can rarely find suitable soil for reproduction
○Produce individuals that can withstand changes in the environmental conditions
○Reproduce in large numbers
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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
机会主义者和竞争者
所有生物体都需要通过消耗能量来实现生长、繁殖和每日的新陈代谢。能量的消耗从根本上来说，是一个主体进行能量预算的过程，如同财政预算。如果一个人所有的钱都用来买衣服，可能就没钱购买食物或者看电影了。同样，动植物不能将所有的能量都浪费在生长巨大的躯体上，如果它们没有多余的能量用于繁殖，那么必将走向灭绝。
因此，所有生物体都会将自己的能量进行分配用以生长、繁殖、维系生命和进行储备。它们没有选择，这种分配方式是来自上一代遗传基因的一部分。维系生命对于一个特定生物的身体设计是相对恒定的。储备很重要，但储备的能量最终都将被用于维系生命、繁殖或者生长。因此，能量分配上的主要不同就在于生长和繁殖之间。
一个生物体所有的能量几乎都可以转用于繁殖，基本没有多少能量被分配用于生长。处于这个极端的生物体被称作“机会主义者”。处于另一个极端的是“竞争者”，“竞争者”几乎将其所有的能量都用于生长一个庞大的身躯，而仅用最低限度的能量进行繁殖。
蒲公英是“机会主义者”典型例子。蒲公英的种子的头部刚好生长到高出地面接触到风的高度，它们的体型也刚好是它们需要的最低尺寸，茎部是中空的，他们通过体内水分来维持自身的硬度。蒲公英对身体最低限度能量的分配，使得他们成为一个散布种子的平台。这些寿命短暂的植物大量繁殖；这就是说，他们在母体的周围下一场种子雨。一旦种子落在了适合生长的土壤表面，新的生命体便会会迅速生长，但是，因为他们长成的躯体并不大，因此无法与其他植物竞争空间、水或阳光。这些植物被称为机会主义者，因为他们依靠其种子落入那些竞争者们已经被大自然淘汰了的地方生长而成活，如被侵蚀了的河岸、山崩之处或在由于树木倒下而在森林冠层中形成的孔隙处等。
机会主义者必须不断侵入新的领域，以抵消更具竞争力的物种对他们的挤兑。人工草坪、田地或花圃提供的光秃秃的土地，以及没有竞争者的环境是“机会主义者”完美的栖息地。因此，人们田地和花园中常见的杂草多是擅长生长繁殖的机会主义植物。
因为每个个体的寿命短暂，机会主义植物的数量很可能受到干旱、恶劣的冬天天气或者洪水等不利因素的影响。跟踪它们一段时间，就会发现它们的数量特别不稳定，在不规则周期内飙升和暴跌。
与机会主义者相对应的是竞争者。这些生物体往往有拥有庞大的身躯、寿命较长并且每年用在繁殖上面的能量相对较少。橡树是典型的“竞争者”，一颗巨大的橡树占据它的领地长达200年甚至更久，通过制造浓密的树荫和吸收土壤中任何多余水分驱逐所有可能的冠层树木。橡树的树叶很难闻，其中富含丹宁酸，它会让很多生物体感到不适或无法消化的化学物质。丹宁酸是橡树长寿的防卫机制的一部分。虽然橡树可以产生数以千计的橡子，但是，它们对大量的橡子投入的能量，和用于树叶、树干和根部生长的能量相比，简直是微乎其微。一旦橡树长成，在短周期的干旱甚至火灾中它都能够轻易存活。橡树的数量在一段时期内似乎是相对稳定的，它的存活可能更多地取决于它善于面对竞争或掠食的压力，并非依赖于利用偶然事件。然而，值得关注的是，单纯机会主义者或竞争者在自然界中是很少见的，大多数的物种都属于这两个极端组成的区域中，显现出兼有二者的一些特征。
