(完整版)环境科学交叉关系学科——5、6章重点句、词汇

第五章环境和生物间的相互作用Interactions: Environments and Organisms The science of ecology is the study of the ways organisms interact with each other, and with their nonliving surroundings.Ecology deals with the ways in which or ganisms are adapted to their surroundings,how they make use of these surroundings, and how an area is altered by the presence and activities of organisms.All organisms are dependent on other organisms in some way.Everything that affects an organism during its lifetime is collectively known as its environment.Abiotic factors can be organized into several broad categories: energy, nonliving matter, and processes that involve the interactions of nonliving matter and energy.All organisms require a source of energy to maintain themselves. The ultimate source of energy for almost all organisms is the sun.All forms of life require atoms of elements such as carbon, nitrogen, and phosphorus, and molecules such as water to construct and maintain themselves. Organisms constantly obtain these materials from their environment. The atoms become part of an organism's body structure for a short time period, and eventually all of them are returned to the environment through respiration, excretion, or death and decay.The structure and location of the space organisms inhabit is also an important abiotic aspect of their environment.Important ecological processes involve interactions of matter and energy.The climate (average weather patterns over a number of years) of an area involves energy in the form of solar radiation interacting with the matter that makes up the Earth.The biotic factors of an organism's environment include all forms of life with which it interacts.Although organisms interact with their surroundings in many ways, certain factors may be critical to a particular species' success. A shortage or absence of this factor restricts the success of the species; thus, it is known as a limiting factor.The limiting factor for many species of fishes is the amount of dissolved oxygen in the water.The environment influences the organism, and organisms affect the environment.The habitat of an organism is the space that the organism inhabits, the place where it lives (its address).The niche of an organism is the functional role it has in its surroundings(its profession).Genes are distinct pieces of DNA that determine the characteristics an individual displays.A population is considered to be all the organisms of the same kind found within a specific geographic region.A species is a population of all the organtisms potentially capable of reproducingnaturally among themselves and having offspring that also reproduce.The process that leads to this close fit between the characteristics organisms display and the demands of their environment is known as natural selection.natural selection is the mechanism that causes evolution to occur.When we look at the effects of natural selection over time, we can see considerable change in the characteristics of a species and kinds of species present. Some changes take thousands or millions of years to occur. Others, such as resistance to pesticides, can occur in a few years.Scientists have continuously shown that this theory of natural selection can explain the development of most aspects of the structure, function, and behavior of organisms. It is the central idea that helps explain how species adapt to their surroundings. When we discuss environmental problems, it is helpful to understand that species change and that as the environment is changed, either naturally or by human action, some species will adapt to the new conditions while others will not.The environment in which organisms exist does not remain constant over long time periods. Those species that lack the genetic resources to cope with a changing environment go extinct. Extinction is the loss of an entire species and is a common feature of the evolution of organisms.Natural selection is constantly at work shaping organisms to fit a changing environment.It is clear that humans have had a significant impact on the extinction of many kinds of species.Wherever humans have modified the environment for their purposes (farming, forestry, cities, hunting, and introducing exotic organisms), species are typically displaced from the area.If large areas are modified, entire species may be displaced. Ultimately, humans are also subject to evolution and the possibility of extinction as well.Coevolution is the concept that two or more species of organisms can reciprocally influence the evolutionary direction of the other. In other words, organisms affect the evolution of other organisms.Since all organisms are influenced by other organisms, this is a common pattern.Ecologists look at organisms and how they interact with their surroundings.One common kind of interaction called predation occurs when one organism, known as a predator, kills and eats another, known as the prey.A second type of interaction between species is competition, in which two organisms strive to obtain the same limited resource.Symbiosis is a close, long-lasting, physical relationship between two different species. There are three different categories of symbiotic relationships: parasitism, commensalism, and mutualism.If we examine our activities, we can see that we have complicated interactions with other organisms.Predator----Humans throughout the world use animals as food.Herbivore----Humans rely on many kinds of plants as their primary source of food.Scavenger----Scavenging involves finding and consuming animals that are already dead.Commensalism-----Humans find themselves on both sides of commensal relationships.Parasitism----Although humans do not live in or on other living things, we do engage in relationships that are parasitic in nature.Mutualism----Humans have many mutualistic relationships with plants and animals.Competition----Humans are in competition with all other organisms on Earth. As we convert land and aquatic resources to our uses, we deprive other organisms of what they need to survive.A community is an assemblage of all the interacting populations of different species of organisms in an area.An ecosystem is a defined space in which interactions take place between a community, with all its complex interrelationships, and the physical environment.While it is easy to see that the physical environment places limitations on the kinds of organisms that can live in an area, it is also important to recognize that organisms impact their physical surroundings.Every system has parts that are related to one another in specific ways.Producers are organisms that are able to use sources of energy to make complex, organic molecules from the simple inorganic substances in their environment.Primary consumers, also known as herbivores, are animals that eat producers (plants or phytoplankton) as a source of food.Secondary consumers or carnivores are animals that eat other animals.Decomposers are organisms that use nonliving organic matter as a source of energy and raw materials to build their bodies.Whenever an organism sheds a part of itself, excretes waste products, or dies, it provides a source of food for decomposers.Since decomposers carry on respiration, they are extremely important in recycling matter by converting organic matter to inorganic material.Many small animals, fungi, and bacteria fill this niche.A keystone species is one that has a critical role to play in the maintenance of specific ecosystems.Some species have pivotal roles, and their elimination or severe reduction can significantly alter ecosystems.The energy stored in the molecules of producers is transferred to other organisms when the producers are eaten.Each step in the flow of energy through an ecosystem is known as a trophic level. Producers (plants, algae, phytoplankton) constitute the first trophic level, and herbivores constitute the second trophic level. Carnivores that eat herbivores are the thir,trophic level, and carnivores that eat other ". carnivores are the fourth trophic level.As energy flows through an ecosystem, it passes through several levels known as trophic levels. Each trophic level contains a certain amount of energy. Each time energy flows to another trophic level, approximately 90 percent of the useful energy islost, usually as heat to the surroundings. Therefore, in most ecosystems, higher trophic levels contain less energy and fewer organisms.The passage of energy from one trophic level to the next as a result of one organism consuming another is known as a food chain.When several food chains overlap and intersect, they make up a food web.All matter is made up of atoms. These atoms are cycled between the living and nonliving portions of an ecosystem. The activities involved in the cycling of atoms include biological, geological, and chemical processes. Therefore, these nutrient cycles are often called biogeochemical cycles.All living things are composed of organic molecules that contain atoms of the element carbon. The carbon cycle includes the processes and pathways involved in capturing inorganic carbon-containing molecules, converting them into organic molecules that are used by organisms, and the ultimate release of inorganic carbon molecules back to the abiotic environment.Fossil fuels (coal, oil, and natural gas) are part of the carbon cycle as well.At one time, these materials were organic molecules in the bodies of living organisms.The organisms were buried and the organic compounds in their bodies were modified by geologic forces. Thus, the carbon atoms present in fossil fuels were removed temporarily from the active,short-term carbon cycle. When we burn fossil fuels, the carbon reenters the active carbon cycle. Another very important nutrient cycle, the nitrogen cycle,involves the cycling of nitrogen atoms between the abiotic and biotic components and among the organisms in an ecosystem.Because atmospheric nitrogen is not usable by plants, nitrogen-containing compounds are often in short supply and the availability of nitrogen is often a factor that limits the growth of plants. The primary way in which plants obtain nitrogen compounds they can use is with the help of bacteria that live in the soil. Bacteria, called nitrogen-fixing bacteria, are able to convert the nitrogen gas (N2) that enters the soil into ammonia that plants can use.Bacteria and other types of decay organisms are involved in the nitrogen cycle also. Dead organisms and their waste products contain molecules, such as proteins, urea, and uric acid, that contain nitrogen. Decomposers break down these nitrogen-containing organic molecules, releasing ammonia, which can be used directly by many kinds of plants. Still other kinds of soil bacteria called nitrifying bacteria are able to convert ammonia to nitrite, which can be converted to nitrate. Plants can use nitrate as a source of nitrogen for synthesis of nitrogen-containing organic molecules.Finally, bacteria known as denitrifying bacteria are, under conditions where oxygen is absent, able to convert nitrite to nitrogen gas (N2), which is ultimately released into the atmosphere. These nitrogen atoms can reenter the cycle with the aid of nitrogen-fixing bacteria.The phosphorus cycle differs from the carbon and nitrogen cycles in one important respect. Phosphorus is not present in the atmosphere as a gas. The ultimate source of phosphorus atoms is rock. In nature, new phosphorus compoundsare released by the erosion of rock and become dissolved in water. Plants use the dissolved phosphorus compounds to construct the molecules they need. Animals obtain the phosphorus they need when they consume plants or other animals. When an organism dies or excretes waste products, decomposer organisms recycle the phosphorus compounds back into the soil.Phosphorus compounds that are dissolved in water are ultimately precipitated as deposits. Geologic processes elevate these deposits and expose them to erosion, thus making these deposits available to organisms.Two activities have caused significant changes in the carbon cycle: burning fossil fuels and converting forests to agricultural land.One consequence of these actions is that the amount of carbon dioxide in the atmosphere has been increasing steadily since humans began to use fossil fuels extensively. It has become clear that increasing carbon dioxide is causing changes in the climate of the world, and many nations are seeking to reduce energy use and prevent deforestation.The burning of fossil fuels has also altered the nitrogen cycle.When fossil fuels are burned, the oxygen and nitrogen in the air are heated to high temperatures and a variety of nitrogen-containing compounds are produced.If too much nitrogen or phosphorus is applied as fertilizer or if they are applied at the wrong time, much of this fertilizer is carried into aquatic ecosystems.The presence of large amounts of these nutrients in either freshwater or saltwater results in increased rates of growth of bacteria, algae,and aquatic plnts. Increases in the number of these organisms can have many different effects. Many algae are toxic, and when their numbers increase significantly,fish are killed and incidents of human poisoning occur. An increase in the number of plants and algae in aquatic ecosystems also can lead to low oxygen concentrations in the water. When these organisms die, decomposers use oxygen from the water as they break down the dead organic matter. This lowers the oxygen concentrations and many organisms die.Everything that affects an organism during its lifetime is collectively known as its environment. The environment of an organism can be divided into biotic (living) and abiotic (non-living) components.The space an organism occupies is known as its habitat, and the role it plays in its environment is known as its niche.I The niche of a species is the result of natural selection directing the adaptation of the species to a specific set of environmental conditions.Organisms interact with one another in a variety of ways.A community is the biotic portion of an ecosystem that is a set of interacting populations of organisms. Those organisms and their abiotic environment constitute an ecosystem.About 90 percent of the energy is lost as it passes from one trophic level to the next. This means that the amount of biomass at higher trophic levels is usually much less than that at lower trophic levels.The flow of atoms through an ecosystem involves all the organisms in thecommunity. The carbon, nitrogen, and phosphorus cycles are examples of how these materials are cycled in ecosystems.Key Terms :abiotic factors非生物因子biogeochemical cycles 生物地球化学循环biomass 生物量biotic factors 生物因子carbon cycle 碳循环community 群落competition 竞争consumer 消费者decomposer 分解者ecology 生态学ecosystem 生态系统environment 环境evolution 进化extinction 灭绝food chain 食物链food web 食物网genes 基因habitat 生境limiting factor 限制性因素natural selection 自然选择niche 小生境nitrogen cycle 氮循环population 种群primary consumer 初级消费者range of tolerance 耐受范围secondary consumer 次级消费者species物种trophic level 营养级Review Questions:1. Define environment.3. How is natural selection related to the concept of niche?5. How is an ecosystem different from a community?8. What are some different trophic levels in an ecosystem?9. Describe the carbon cycle, the nitrogen cycle, and the phosphorus cycle.第六章生态系统及群落的种类Kinds of Ecosystems and Communities Ecosystems are dynamic, changing units.The concept that communities proceed through a series of recognizable, predictable changes in structure over time is called succession. The relatively stable, long-lasting community that is the result of succession is called a climax community.Primary succession is a successional progression that begins with a total lack of organisms and bare mineral surfaces or water.Secondary succession is much more commonly observed and generally proceeds more rapidly, because it begins with the destruction or disturbance of an existing ecosystem. Fire, flood, windstorm, or human activity can destroy or disturb a community of organisms.The general trend in succession is toward increasing complexity and more efficient use of matter and energy compared to the successional communities that preceded them.The principal concepts of land succession can be applied to aquatic ecosystems. Except for the oceans, most aquatic ecosystems are considered temporary. Certainly, some are going to be around for thousands of years, but eventually they will disappear and be replaced by terrestrial ecosystems as a result of normal successional processes. All aquatic ecosystems receive a continuous input of soil particles and organic matter from surrounding land, which results in the gradual filling in of shallow bodies of water such as ponds and lakes.The same processes and activities drive both primary and secondary succession. The major difference is that secondary succession occurs when an existing community is destroyed but much of the soil and some of the organisms remain. A forest fire, a flood, or the conversion of a natural ecosystem to agriculture may be the cause.As settlers removed the original forests or grasslands and converted the land to farming, the original "climax" community was destroyed. Eventually, as poor farming practices destroyed the soil, many farms were abandoned and the land was allowed to return to its "original" condition.Biomes are terrestrial climax communities with wide geographic distribution.The distribution of terrestrial ecosystems is primarily related to precipitation and temperature.A lack of water is the primary factor that determines that an area will be a desert. Deserts are areas that generally average less than 25 centimeters(10 inches) of precipitation per year.Since the rate of evaporation is high, plant growth and flowering usually coincide with the periods when moisture is available. Deserts are also likely to be windy. We often think of deserts as hot, dry wastelands devoid of life. However, many deserts are quite cool during a major part of the year.Another misconception about deserts is that few species of organisms live in the desert. There are many species, but they typically have low numbers of individuals.The desert has many kinds of animals. However, they are often overlooked because their populations are low, numerous species are of small size, and many are inactive during the hot part of the day. They also aren't seen in large, conspicuous groups.Grasslands, also known as prairies or steppes, are widely distributed over temperate parts of the world. As with deserts, the major factor that contributes to the establishment of a grassland is the amount of available moisture. Grasslands generally receive between 25 and 75 centimeters (10 to 30 inches) of precipitation per year.Most of the moist grasslands of the world have been converted to agriculture , since the rich, deep soil that developed as a result of the activities of centuries of soil building is useful for growing cultivated grasses such as corn (maize) and wheat. The drier grasslands have been converted to the raising of domesticated grazers such as cattle, sheep, and goats. Therefore, little undisturbed grassland is left, and those fragments that remain need to be preserved as refuges for the grassland species that once occupied huge portions of the globe.Tropical parts of Africa, South America, and Australia have extensive grasslands spotted with occasional trees or patches of trees. This kind of a biome is often called a savanna. Although savannas receive 50 to 150 centimeters (20 to 60 inches) of rain per year, the rain is not distributed evenly throughout the year. Typically, a period of heavy rainfall is followed by a prolonged drought. This results in a very seasonally structured ecosystem. The plants and animals time to their reproductive activities to coincide with the rainy period, when limiting factors are least confining. The predominant plants are grasses, but many drought-resistant, flat-topped, thorny trees are common.The Mediterranean shrublands are located near an ocean and have wet, cool winters and hot, dry summers. Rainfall is 40 to 100 centimeters (15 to 40 inches) per year. As the name implies, this biome is typical of the Mediterranean coast and isalso found in coastal southern California, the southern tip of Africa, a portion of the west coast of Chile, and southern Australia. The vegetation is dominated by woody shrubs that are adapted to withstand the ot, dry summer.Another biome that is heavily influenced by seasonal rainfall is known as the tropical dry forest.Tropical rainforests are located near the equator in Central and South America, Africa, Southeast Asia, and some islands in the Caribbean Sea and Pacific Ocean. The temperature is normally warm and relatively constant. There is no frost, and it rains nearly every day. Most areas receive in excess of 200 centimeters (80 inches) of rain per year. Some receive 500 cennmeters (200 inches) or more. Because of the warm temperatures and abundant rainfall, most plants grow very rapidly; however, soils are usually poor in nutrients because water tends to carry away any nutrients not immediately taken up by plants.Tropical rainforests are under intense pressure from logging and agriculture.Many of the countries where tropical rainforests are present are poor and seek to obtain jobs and money by exploiting this resource.Forests in temperate areas of the world that have a winter-summer change of seasons typically have trees that lose their leaves during the winter and replace them the following spring. This kind of forest is called a temperate deciduous forest and is typical of the eastern half of the United States, parts of south central and south- eastern Canada, southern Africa, and many areas of Europe and Asia. These areas generally receive 75 to 100 centimeters (30 to 60 inches) of relatively evenly distributed precipitation per year.In contrast to tropical rainforests, where individuals of a tree species are scattered throughout the forest, temperate deciduous forests generally have many fewer species, and many forests may consist of two or three dominant tree species.These forests are home to a great variety of insects, many of which use the leaves and wood of trees as food.Throughout the southern half of Canada, parts of northern Europe, and much of Russia, there is an evergreen coniferous forest known as the taiga, northern coniferous forest, or boreal forest. The climate is one of short, cool summers and long winters with abundant snowfall. The winters are extremely harsh and can last as long as six months. Typically, the soil freezes during the winter. Precipitation ranges between 25 and 100 centimeters (10 to 40 inches) per year. However, the climate is typically humid because there is a great deal of snowmelt in the spring and generally low temperatures reduce evaporation. The landscape is typically dotted with lakes, ponds, and bogs.North of the taiga is the tundra, a biome that lacks trees and has a permanently frozen subsurface soil. This frozen soil layer is known as permafrost. Because of the permanently frozen soil and extremely cold, windy climate (up to 10 months of winter), no trees can live in the area.Because of the very short growing season, damage to this kind of ecosystem is slow to heal, so the land must be handled with great care.Terrestrial biomes are determined by the amount and kind of precipitation and by temperatures. Other factors, such as soil type and wind, also play a part. Aquatic ecosystems also are shaped by key environmental factors. Several important factors are the ability of the sun's rays to penetrate the water, the depth ofthe water, the nature of the bottom substrate, the water temperature, and the amount of dissolved salts.An important determiner of the nature of aquatic ecosystems is the amount of salt dissolved in the water.Those that have little dissolved salt are called freshwater ecosystems, and those that have a high salt content are called marine ecosystems.Coral reef ecosystems are produced by coral animals that build up-shaped external skeletons around themselves.Because they require warm water, coral ecosystems are found only near the equator Coral ecosystems also require shallow, clear water since the algae must have ample sunlight to carry on photosynthesis.Coral reefs are considered one of the most productive ecosystems on Earth.Mangrove swamp ecosystems occupy a region near the shore. The dominant organisms are special kinds of trees that are able to tolerate the high salt content of the ocean.The trapping of sediment and the continual extension of mangroves into shallow areas result in the development of a terrestrial ecosystem in what was once shallow ocean.An estuary is a special category of aquatic ecosystem that consists of shallow, partially enclosed areas where freshwater enters the ocean.Estuaries are particularly productive ecosystems because of the large amounts of nutrients introduced into the basin from the rivers that run into them. This is further enhanced by the fact that the shallow water allows light to penetrate to most of the water in the basin.Estuaries are especially important as nursery sites for fish and crustaceans such as flounder and shrimp.Freshwater ecosystems differ from marine ecosystems in several ways. The amount of salt present is much less, the temperature of the water can change greatly, the water is in the process of moving to the ocean, oxygen can often be in short supply, and the organisms that inhabit freshwater systems are different.Freshwater ecosystems can be divided into two categories: those in which the water is relatively stationary, such as lakes, ponds, and reservoirs, and those in which the water is running downhill, such as streams and rivers.Large lakes have many of the same characteristics as the ocean.Farming and construction expose soil and release nutrients, as do other human activities such as depositing sewage into streams and lakes. Deep, clear, cold, nutrient-poor lakes are low in productivity and are called oligotrophic lakes. Shallow, murky, warm, nutrient-rich lakes are called eutrophic lakes.The dissolved oxygen content of the water is important since the quantity of oxygen determines the kinds of organisms that can inhabit the lake.When organic molecules enter water, they are broken down by bacteria andfungi. These decomposer organisms use oxygen from the water as they perform respiration. The amount of oxygen used by decomposers to break down a specific amount of organic matter is called the biochemical oxygen demand (BOD).Just as estuaries are a bridge between freshwater and marine ecosystems, swamps and marshes are a transition between aquatic and terrestrial ecosystems.Many swamps and marshes are successional states that eventually become totally terrestrial communities.summary:Ecosystems change as one kind of organism replaces another in a process called succession.Ultimately, a relatively stable stage is reached, called the climax community.Major regional terrestrial climax communities are called biomes.The primary determiners of the kinds of biomes that develop are the amount and yearly distribution of rainfall and the yearly temperature cycle.Aquatic ecosystems can be divided into marine (saltwater) and freshwater ecosystems.Coral reefs are tropical marine ecosystems dominated by coral animals. Mangrove swamps are tropical marine shoreline ecosystems dominated by trees. Estuaries occur where freshwater streams and rivers enter the ocean. They are usually shallow, very productive areas. Many marine organisms use estuaries for reproduction.KeyTerms:biochemical oxygen demand (BOD) 生化需氧量biome 生物群系climax community 顶级群落coral reef ecosystem 珊瑚礁生态系统desert 沙漠estuary 河口eutrophic lake 富营养湖freshwater ecosystem 淡水生态系统grassland 草地mangrove swamp ecosystem 红树林沼泽生态系统marine ecosystem 海洋生态系统marsh 草本沼泽plankton 浮游生物phytoplankton 浮游植物zooplankton 浮游动物primary succession 原生演替secondary succession 次生演替swamp 木本沼泽tropical rainforest 热带雨林Review Questions:1.Describe the process of succession. How does primary succession differ from secondary succession?4. What two primary factors determine the kind of terrestrial biome that will develop in an area?6. What areas of the ocean are the most productive?9. List three differences between freshwater and marine ecosystems.10. What is an estuary?Why are estuaries important?。