Survival of Plants and Animals in Dert Conditions
The harsh conditions in derts are intolerable for most plants and animals. Despite the conditions, however, many varieties of plants and animals have adapted to derts in a number of ways. Most plant tissues die if their water content falls too low: the nutrients that feed plants are transmitted by water; water is a raw material in the vital process of photosynthesis; and water regulates the temperature of a plant by its ability to absorb heat and becau water vapor lost to the atmosphere through the leaves helps to lower plant temperatures. Water controls the volume of plant matter produced. The distribution of plants within different areas of dert is also controlled by water. Some areas, becau of their soil texture, topographical position, or distance from rivers or groundwater, have virtually no water available to plants, whereas others do.
The nature of plant life in derts is also highly dependent on the fact that they have to adapt to the prevailing aridity. There are two general class of vegetation: long-lived perennials, which may be succulent (water-storing) and are often dwarfed and woody, and annuals or ephemerals, which have a short life cycle and may form a fairly den stand immediately after rain.
The ephemeral plants evade drought. Given a year of favorable precipitation, such plants will develop v
igorously and produce large numbers of flowers and fruit. This replenishes the ed content of the dert soil. The eds then lie dormant until the next wet year, when the dert blooms again.
The perennial vegetation adjusts to the aridity by means of various avoidance mechanisms. Most dert plants are probably best classified as xerophytes. They posss drought-resisting adaptations: loss of water through the leaves is reduced by means of den hairs covering waxy leaf surfaces, by the closure of pores during the hottest times to reduce water loss, and by the rolling up or shedding of leaves at the beginning of the dry ason. Some xerophytes, the succulents (including cacti), store water in their structures. Another way of countering drought is to have a limited amount of mass above ground and to have extensive root networks below ground. It is not unusual for the roots of some dert perennials to extend downward more than ten meters. Some plants are woody in type —an adaptation designed to prevent collap of the plant tissue when water stress produces wilting. Another class of dert plant is the phreatophyte. The have adapted to the environment by the development of long taproots that penetrate downward until they approach the assured water supply provided by groundwater. Among the plants are the date palm, tamarisk, and mesquite. They commonly grow near stream channels, springs, or on the margins of lakes.
Animals also have to adapt to dert conditions, and they may do it through two forms of behavioral
adaptation: they either escape or retreat. Escape involves such actions as aestivation, a condition of prolonged dormancy, or torpor, during which animals reduce their metabolic rate and body temperature during the hot ason or during very dry spells.
Seasonal migration is another form of escape, especially for large mammals or birds. The term retreat is applied to the short-term escape behavior of dert animals, and it usually assumes the pattern of a daily rhythm. Birds shelter in nests, rock overhangs, trees, and den shrubs to avoid the hottest hours of the day, while mammals like the kangaroo rat burrow underground.
Some animals have behavioral, physiological, and morphological (structural) adaptations that enable them to withstand extreme conditions. For example, the ostrich has plumage that is so constructed that the feathers are long but not too den. When conditions are hot, the ostrich erects them on its back, thus increasing the thickness of the barrier between solar radiation and the skin. The spar distribution of the feathers, however, also allows considerable lateral air movement over the skin surface, thereby permitting further heat loss by convection. Furthermore, the birds orient themlves carefully with regard to the Sun and gently flap their wings to increa convection cooling.
Paragraph 1: The harsh conditions in derts are intolerable for most plants and animals. Despite th
e conditions, however, many varieties of plants and animals have adapted to derts in a number of ways. Most plant tissues die if their water content falls too low: the nutrients that feed plants are transmitted by water; water is a raw material in the vital process of photosynthesis; and water regulates the temperature of a plant by its ability to absorb heat and becau water vapor lost to the atmosphere through the leaves helps to lower plant temperatures. Water controls the volume of plant matter produced. The distribution of plants within different areas of dert is also controlled by water. Some areas, becau of their soil texture, topographical position, or distance from rivers or groundwater, have virtually no water available to plants, whereas others do.
1: According to paragraph 1, water provides all of the following esntial functions for plants EXCEPT
○ improving plants’ ability to absorb sunlight
○ preventing plants from becoming overheated
○ transporting nutrients
○ rving as a raw material for photosynthesis
Paragraph 2: The nature of plant life in derts is also highly dependent on the fact that they have to adapt to the prevailing aridity. There are two general class of vegetation:
long-lived perennials, which may be succulent (water-storing) and are often dwarfed and woody, and annuals or ephemerals, which have a short life cycle and may form a fairly den stand immediately after rain.
热字
Paragraph 3: The ephemeral plants evade drought. Given a year of favorable precipitation, such plants will develop vigorously and produce large numbers of flowers and fruit. This replenishes the ed content of the dert soil. The eds then lie dormant until the next wet year, when the dert blooms again.
2: Paragraph 3 suggests that during a dry year ephemerals
○ produce even more eds than in a wet year
○ do not sprout from their eds
○ bloom much later than in a wet year
○ are more plentiful than perennials有缘相聚
3: How is paragraph 2 related to paragraph 3?
○Paragraph 2 provides a general description of dert plants, and paragraph 3 provides a scientific explanation for the obrvations.
○Paragraph 2 divides dert plants into two categories, and paragraph 3 provides further information about one of the categories.
麦秸画
○Paragraph 2 propos one way of dividing dert plants into categories, and paragraph 3 explains one problem with this method of classification.
○ Paragraph 2 discuss two categories of dert plants, and paragraph 3 introduces a third category of plants.补充协议模板
4: In saying that ephemerals will develop “vigorously" when there is favorable precipitation, the author means that their development will be
○ sudden
月圆圆○ early
参苓白术丸说明书○ gradual
○ strong and healthy
Paragraph 4: The perennial vegetation adjusts to the aridity by means of various avoidance mechanisms. Most dert plants are probably best classified as xerophytes. They posss drought-resisting adaptations: loss of water through the leaves is reduced by means of den hairs covering waxy leaf surfaces, by the closure of pores during the hottest times to reduce water loss, and by the rolling up or shedding of leaves at the beginning of the dry ason. Some xerophytes, the succulents (including cacti), store water in their structures. Another way of countering drought is to have a limited amount of mass above ground and to have extensive root networks below ground. It is not unusual for the roots of some dert perennials to extend downward more than ten meters. Some
plants are woody in type —an adaptation designed to prevent collap of the plant tissue when water stress produces wilting. Another class of dert plant is the phreatophyte. The have adapted to the environment by the development of long taproots that penetrate downward until they approach the assured water supply provided by groundwater. Among the plants are the date palm, tamarisk, and mesquite. They commonly grow near stream channels, springs, or on the margins of lakes.
5: The word “countering” in the passage is clost in meaning to
○ eliminating
○ making u of
○ acting against
○ experiencing
6: According to paragraph 4, some dert plants with root systems that are extraordinarily well developed have
小班语言游戏
○ relatively little growth aboveground
○ very leafy aboveground structures中国世界遗产名录
○ non woody plant tissue resistant to wilting
○ water stored within their roots
7: The word “assured” in the passage is clost in meaning to
○ pure
○ diminished
○ guaranteed
○ deep
8: What do “the date palm, tamarisk, and mesquite" have in common?
○ They are always found together.
○ They depend on surface water provided by streams, springs, and lakes.
○ They are phreatophytes.
○ Their roots are capable of breaking through hard soils
Paragraph 5: Animals also have to adapt to dert conditions, and they may do it through two forms of behavioral adaptation: they either escape or retreat. Escape involves such actions as aestivation, a condition of prolonged dormancy, or torpor, during which animals reduce their metabolic rate and b
ody temperature during the hot ason or during very dry spells.
9: Which of the ntences below best express the esntial information in the highlighted ntence in the passage? Incorrect choices change the meaning in important
ways or leave out esntial information.
○ One way animals escape is by entering a state of extended dormancy, known as aestivation, during the hottest and driest times of year.
○Animals can escape without using direct action, or aestivation, simply by reducing their metabolic rate and body temperature.
○The actions that an animal us to escape are known as aestivation, which sometimes involves a reduction in metabolic rate or body temperature.
○When the weather is especially hot and dry, an animal may suffer from a condition known as aestivation, at which point the animal needs to escape.
Paragraph 6:Seasonal migration is another form of escape, especially for large mammals or birds. T
he term retreat is applied to the short-term escape behavior of dert animals, and it usually assumes the pattern of a daily rhythm. Birds shelter in nests, rock overhangs, trees, and den shrubs to avoid the hottest hours of the day, while mammals like the kangaroo rat burrow underground.
10: It can be inferred from paragraph 6 that all of the places dert animals retreat to ○ provide shade from the sun
○ sometimes become crowded
○ are places where supplies of food are plentiful
○ leave the animals vulnerable to predators
Paragraph 7: Some animals have behavioral, physiological, and morphological (structural) adaptations that enable them to withstand extreme conditions. For example, the ostrich has plumage that is so constructed that the feathers are long but not too den. When conditions are hot, the ostrich erects them on its back, thus increasing the thickness of the barrier between solar radiation and the skin. The spar distribution of the feathers, however, also allows considerable lateral air mo
vement over the skin surface, thereby permitting further heat loss by convection. Furthermore, the birds orient themlves carefully with regard to the Sun and gently flap their wings to increa convection cooling.
11: According to paragraph 7, what special adaptation helps the ostrich cope with hot dert conditions?
○ Each of its feathers is very short and den.
○ Its wings produce only lateral air movement when flapping.
○ Its feathers are very thickly t on both its back and its wings.
○ It can make its feathers stand up on its back.
Paragraph 1: The harsh conditions in derts are intolerable for most plants and animals. Despite the conditions, however, many varieties of plants and animals have
