河 北 科 技 大 学 教 案 用 纸
第 14 次课 2 学时
上次课复习：
Nuclear fission is the splitting of the nucleus of the atom.
The resulting energy can be used for a variety of purposes.
However, several accidents have raised questions about safety, for example:
1.Reactor safety
2.Exposure to radiation
3.Thermal pollution
4.Decommissioning costs
5.Radioactive waste disposal
本次课题（或教材章节题目）
： Ch 11 Biodiversity Issues
教学要求：了解生物多样性种类、丧失和灭绝的原因；熟悉生物多样性的价值；掌握生物多样性
面临的威胁
重
点：生物多样性所面临的各种威胁
难
点：生物多样性的各种价值
教学手段及教具：利用多媒体进行课堂讲授，图文并茂，增加认知的直观性；进行课堂讨论，
活跃课堂气氛。
讲授内容及时间分配：
Revision
11.1 Biodiversity Loss and Extinction
11.2 Describing Biodiversity
11.3 The Value of Biodiversity
11.4 Threats to Biodiversity
Summary
课后作业
参考资料
3min
15min
22min
22min
25min
3min
任选课后讨论题，完成 50-80 字英文短文。
《Environmental Science》 Andrew R.W.Jackson．世界图书出版社，2001．
《Environmental Science》 William P.Cunningham．McGraw-Hill，1997．
注：本页为每次课教案首页
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Ch 11 Biodiversity Issues (232-263)
There are mainly three parts in this chapter:
1. Causes of biodiversity loss and extinction
2. Describing biodiversity (categories, value and threats)
3. How to preserve biodivesity
This Chapter Objectives (pp232)
1/ Recognize that humans significantly modify natural ecosystems.
2/ State the major causes of biodiversity loss.
3/ Give examples of genetic diversity, species diversity, and ecosystem diversity.
4/ Describe the values of biodiversity.
5/ Appreciate the ways humans modify forests.
6/ Identify causes of desertification.
7/ Describe the role of endangered species legislation and the biodiversity treaty.
8/ Describe techniques that foster sustainable use of wildlife and fisheries resources.
11.1 Biodiversity Loss and Extinction (pp233)
Biodiversity is a broad term used to describe the diversity of genes, species, and ecosystems in a region.
Extinction is the death of a species, the elimination of all the individuals of a particular kind. Biodiversity is
lost when all the individuals of a particular kind die off – that is, when a species becomes extinct. Extinction
is a natural and common event in the long history of biological evolution. However, as we will see later in
this section, extinction – and the resulting loss of biodivesity – is also a major consequence of human
domination of the Earth.
●Over the past few hundred years, humans have increased the species extinction rate by as much as 1000
times above background rates typical over the planet’s history.
●Currently,the most rapid changes are taking place in developing countries.
 11.1.1 Causes of Extinction (pp233)
Complete extinction occurs when all the individuals of a species are eliminated. We commonly observe local
extinctions of populations.
Studies of modern local extinctions suggest that certain kinds of species are more likely than others to
become extinct.
Most Likely to Become Extinct:
Low population density
Found in small area
Specialized niche
Low reproductive rates
Least Likely to Become Extinct:
High population density
Found over large area
Generalized niche
High reproductive
 11.1.2 Extinction as a Result of Human Activity(pp234)
At one time, a human was just another consumer somewhere in the food chain. Humans fell prey to
predators and died as a result of disease and accident just like other animals .
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The simple tools they used would not allow major changes in their surroundings, so these people did not
have a long-term effect on their surroundings. They only minimally exploited mineral and energy resources.
As human populations grew , and as their tools and methods of using them became more advanced, the
impact that a single human could have on his or her surroundings increased tremendously .
The purposeful use of fire was one of the first event that marked the capability of humans to change
ecosystems .
The use of fire by humans can destroy climax communities and return them to earlier successional stages
more frequently than normal.
Today, with over 6 billion people on the Earth , nearly all of the Earth`s surface has been affected in some
way by human activity . One of the major impacts of human activity has been to reduce biodiversity.
 11.2 Describing Biodiversity (pp234)
Biodiversity is a broad term used to describe the diversity of genes, species, and ecosystems in a region.
Loss of biodiversity is recognized by many as a major consequence of human domination of the Earth.
 11.2.1 Genetic Diversity(pp234)(遗传多样性)
Genetic diversity is a term used to describe the number of different kinds of genes present in a population or
a species. Several things influence the genetic diversity of a population.
1. Mutations(突变) are changes in the genetic information of an organism. Mutations introduce new genetic
information into a population by modifying genes that are already present.
2. Migration of individuals of a species from one population to another is also an important way to alter the
genetic diversity of a population.
3. Sexual reproduction is another process that influences genetic diversity.
4. Population size is a very important factor related to genetic diversity. The smaller the population, the less
genetic diversity is can contain and the fewer the variations in the genes for specific characteristics. In
addition, random events often can significantly alter the genetic diversity in small populations, with rare
characteristics being lost from the population.
5. Selective breeding also can affect the genetic diversity of a species. Domesticated plants and animals
have been modified over many generations by our choosing certain desired characteristics. Undesirable
characteristics were eliminated, and desirableones selected for.
 11.2.2 Species Diversity(pp235)（物种多样性）
Species diversity is a measure of the number of different species present in an area. Some localities
naturally have high species diversity, while others have low species diversity.
Several things influence the species diversity of a particular location. Over the long term, the evolutionary
and geologic history of a region impacts its species diversity. In the shorter term, migration can introduce
new species to an area where they were not present previously.
The size of the area being considered also affects species diversity.
Human activities have a great effect on the species diversity of a region. They convert natural ecosystems to
human-managed agricultural, forest, aquaculture, and urban ecosystems.
 11.2.3 Ecosystem Diversity(pp236)（生态系统多样性）
Ecosystem diversity is a measure of the number of kinds of ecosystems present in an area. Many regions of
the world appear to be quite uniform in terms of the kinds of ecosystems present. For example, large parts of
central Austualia, North Africa, and southwestern United States and adjacent Mexico are deserts.Each of
these deserts is different and has specific organisms typical to the region. In many cases, natural events such
as hurricanes, fires, floods, or volcanic eruptions may have destroyed the original vegetation, resulting in
patches of early successional stages that contribute much to the diversity of organisms present.
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11.3 The Value of Biodiversity (pp236)（生物多样性的价值）
There are many different ways to assign value to biodiversity. Some involve understanding the ecological
roles played by organisms, others involve cold economic analysis, and still others stem from ethical
consideration.
 11.3.1 Biological and Ecosystem Services Values(pp236)(生物或生态系统的服务价值)
Our species is totally dependent on the diversity of organisms on Earth. As consumer organisms in the food
chain, we rely on the organic molecules produced by other organisms for food. For example, agriculture
makes use of many kinds of plants to provide us with food. If we cause the extinction of a potentially useful
organism, we have lost the opportunity to use it for our own ends. However, agriculture is more than just
growing plants. It involves understanding fungal and insect pests and the organisms that either spread or
inhibit the pests.
It is important to recognize that each organism is involved in a vast network of relationships with other
organisms. (take the sea otter 海獭 and prairie dog 草原犬 for example)
Other services:
1. The network of roots in forested areas and grasslands ties the soil together and protects watersheds.
2. Mangrove forests, marshes, and other wetlands protect shore lands from erosion.
3. Plants can remove carbon dioxide from the atmosphere though the process of photosynthesis.
4. Bacteria play a dominant role in the cycling of nitrogen in ecosystems.
5. Decomposer organisms recycle both natural and human-produced organic wastes.
All of these services can be converted into monetary terms, since it takes money to purify water, purchase
land, and buy and plant trees. (Table 12.3 presents approximate values for ecosystems services assigned by a
panel of experts including ecologists, geographers, and economists.)
 11.3.2 Direct Economic Values(pp240)
Firewood is one of the major sources of energy in much of the less developed word. Much of this is collected
by individuals and used by them for heating homes and cooking. Timber sources harvested to about ＄US
140 billion. Fisheries resources amounted to about ＄US 57 billion.
In many parts of the world, biological sources of food and energy never enter the formal economy of a
region and are difficult to assign specific monetary value to.
The potential value of biodiversity should be considered. Protecting biodiversity can be thought of as
protecting future economically important resources.
 11.3.3 Ethical Values(pp240)（道德价值）
A case can be made that all species have an intrinsic value and a fundamental right to exist without being
needlessly eliminated by the unthinking activity of the human species. This is an ethical position that is
unreleated to social or economic considerations.
As the shift from rural to urban continues, there is a continual erosion of the nature experiences that can
shape the values of people. These values are important in determining how society will approach threats to
biodiversity.
 11.4 Threats to Biodiversity (pp240)
Four major human activities threaten to reduce biodiversidy:
Habitat loss occurs when human activities result in the conversion of natural ecosystems to
human-dominated system. The resulting changes eliminate or reduce the numbers of species that were a part
of the original ecosystem.
Overexploitation occurs when humans harvest organisms faster than the organisms are able to
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reproduce, which has driven some organisms to extinction and threatens many others.
Introduction of exotic species can also have a significant effect on biodiversity. Often exotic species
compete with native species and drive them to extinction.
Another major threat to biodiversity is persecution of pest organisms. Many large carnivores were
hunted to extinction because of their threat to humans and their livestock.
 11.4.1 Habitat loss(pp240)
The World Conservation Union (IUCN) estimates that about 80 percent to 90 percent of threatened species
are under threat because of habitat loss or fragmentation.
Often the destruction of nttural habitats is not total but leaves patches of relatively unaltered habitat
interspersed with human-modified landscapes.
 11.4.1.1 Conversion to agriculture (pp241)
As the human population grows, it needs more space to grow food. The pressures to modify the environment
are greatest in areas that have high population density. About 40 percent of the world’s land surface has been
converted to cropland and permanent pasture (永久牧场).
 11.4.1.2. Forestry Practices (pp241)
The function of Forest: the economic worth of the standing timber; the importance of forests for wildlife
and watershed protection. And today there are many existing forests that are changed by human activities.
1. Economic and Energy Costs of Utilizing Forest Ecosystems
Economic costs: Purchase or leasing of land, paying for equipment and labor, and building roads for
transportation.
Energy costs: Costs in harvesting activities and transportation.
Major factor: The efficiency of the methods of harvest and transportation.
2. Environmental Costs of Utilizing Forest Ecosystems
It does not rely on monetary terms but relies on ethical or biological arguments.
We should balance the economic exploitation and maintaining some of the environmental value of the forest.
1) But more or less tree-harvesting destroys the natural forest which provides habitats for many species of
plants and animals. It will have a negative impact on endangered species.
2) Secondly it deteriorates climate, causes rapid runoff, flooding and decreases the recreational opportunities,
and even negatively affects species in other ecosystems.
3) Thirdly it disturbs the wildlife in the area. Roads for transportation are special problems. Properly
engineered roads and appropriate harvesting methods should be adopted.
4) Because wilderness and logging cannot coexist, it becomes necessary to designate specific forests as
wilderness or harvestable resources.
 11.4.1.3Environmental Implications of Various Harvesting Methods(pp242)
Clear cutting: All of the trees in a large area are removed.
It is very economical but it slows the reestablishment of forest and has significant effects on wildlife.
It is suited for the gentle slopes areas especially those forest with the border along the bank of the stream.
When it is used in the area where regrowth is slow, reforestation (a process of replanting trees) should be
adopted especially for conifer species.
Patchwork clear-cutting: Smaller areas are clear-cut among patches of untouched forest.
It is suited for those areas with steep slopes or where regrowth is slow.
Selective harvesting: Harvesting individual trees from the whole forest. It is relatively less efficient or
economical. It affects the unselected trees and roads for transportation are also destructive
 11.4.1.4 Special concerns About Tropical Deforestation(pp243) (对热带森林砍伐的特别关
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注)
Tropical forests have the greatest species diversity in terrestrial ecosystems.
The diverse mixture of tree species requires harvesting techniques different from those traditionally used in
northern temperate forests. Regeneration is difficult. Short-term production for economic values is adopted
and these forests in the world is decreasing.
Several concerns are raised by tropical deforestation.
First ,the deforestation of large tracts of tropical forest is significantly reducing the species diversity of the
world .
Second, because tropical forests very effectively trap rainfall and prevent rapid runoff and the large amount
of water transpired from the leaves of trees tends to increase the humidity of the air, the destruction of these
forests also can significantly alter climate, generally resulting in a hotter , more arid climate .
Finally, people have become concerned about preserving the potential of forests to trap carbon dioxide.
 11.4.1.5 Plantation Forestry (pp244)
Many forest products companies manage forest plantations in the same way farmers manage crops.
Biodiversity is low. Many are exotic species. Main method of harvesting is clear-cutting.
A single-species, even-aged forest is ideal for producing wood but does not support as wide a variety of
wildlife as does a mixed-age, mixed-species forest.
For the woodpecker example
 11.4.1.6 Rangeland and Grazing Practices(pp244)
Rangelands consist of the many arid and semiarid lands of the world that support grasses or a mixture of
grasses and drought-resistant shrubs.
They are usually used to raise the domesticated or semidomesticated animals. The animals are maintained on
permanent ranges or moved for grazing. They are usually not native to the region.
The economic and energy costs are small, and the main costs are the environmental costs.
The grazing of domesticated animals in rangelands has major impacts on biodiversity. Other plants and
animals that do no good to the grazing of the domesticated animals are eliminated.
Because rainfall is low and often unpredictable, it is important to adjust the number of livestock to meet the
capacity of the range.
In many parts of the world where human population pressures are great, overgrazing is a severe problem.
Overgrazing causes the desertification (the process of converting arid and semiarid land to desert because of
improper use by humans).
 11.4.1.7 Habitat Loss in Aquatic Ecosystems(pp245)
In marine ecosystems, the typical method used to harvest bottom-dwelling fish and shellfish(贝壳类动物)
involves the use of trawls(拖网) which are nets that are dragged along the bottom.
The nets capture various species, many of which are not commercially valuable.
The trawls disturb the seafloor and create conditions that make it more difficult for the fish populations to
recover.
Freshwater lakes, streams, and rivers are modified for navigation, irrigation, flood control, or power
production purposes, all of which may alter the natural ecosystem and change the numbers or kinds of
aquatic organisms present.
 11.4.1.8 Conversion to Urban and Industrial Uses(pp245)
Urban areas are the most heavily impacted by human activity. A large proportion of such areas are covered
with impermeable surfaces that prevert plant growth and divert rainfall to local streams and rivers.
Biodiversity is drastically reduced, and only the most adaptable organisms can survive in such settings.
Many industrial sites are associated with urban centers. Their impact is similar to that of an urban center. The
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land is altered in such a way that the natural ecosystems are destroyed.
 11.4.2 Overexploitation (pp246)
Overexploitation is a serious problem in several situations. According to the World Conservation Union,
overexploitation is responsible for over 30 percent of endangered species of animals and 8 percent of plants.
We use organisms for a variety of purpose in addition to food. Many plants and animals are used as
ornaments. Flowers are picked, animals skins are worn, and animal parts are used for their purported
aphrodisiac qualities. Because some people are willing to pay huge amounts of money for these products,
unscrupulous(肆无忌惮的) people are willing to break the law and poach(偷猎) these animals for the quick
profit they can realize.
 11.4.2.1 Overfishing of Marine Fisheries(pp246)
Environmental costs related to utilizing marine ecosystems fall into two broad categories: overfishing and
the damaging effect of harvesting practices.
Overfishing:
Two indications of overfishing: the amount of fish captured, the change in the kinds of fish being
caught.
The most productive areas of the ocean are those close to land. Because:
First, the water is relatively nutrient rich.
Second, the water is shallow and fishing for them is practical.
Many conflicts about the fishing limits rise up between countries.
Open-ocean species of fish are also subject to overexploitation such as Peruvian anchovy.
The damaging effect of harvesting practices:
One of the major problems associated with the management of marine fisheries resources is the
difficulty in achieving agreement on limits to the harvest.
Another environmental problem associated with these shallow-water, near-shore fisheries is the method
used to harvest the fish. For example the trawls-nets(拖网) used for bottom-dwelling fish. It damages the
bottom of the seafloor, and it alter the ecological nature of the seafloor.
 11.4.2.2 Aquaculture(pp247)（水产养殖）
Aquaculture is becoming increasingly important especially the salmon farming. The farming method of
producing fish still has its environmental effects which are similar to those of aquaculture in marine systems:
(1) Nutrient overloads: Raising fish in such concentrated settings results in increased nutrients in the
surrounding water from uneaten food and the wastes the fish release.
(2) Escape of exotic species: If the fish raised is exotic, it may have negative impact on native species.
(3) The conversion of land which should be protected to a new use.
Prospective: Regardless of environmental concerns, the productivity of freshwater aquaculture has the
potential to provide for the protein needs of a growing population, so it is likely to continue to increase at a
rapid rate.
 11.4.2.3 Unsustainable Harvast of Wildlife and Plants(pp248)
Wildlife may be harvested for a variety of reasons:
1. Primary among them is the need for food in much of the world. Meat from wild wild animals is often
referred to as bush meat.
2. Trade in bush meat and other animal products has become a major problem for several reasons: (1)
Hunting of wildlife is a part of all subsistence cultures, so it is considered a normal activity;(2) Poor people
can earn money; Many kinds of wildlife are highly prized for the home and restaurant trade; (3) Regulations
regarding the preservation of wildlife are pooly developed or widely ignored. (4)The roads associated with
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logging operations in tropical forests give access to a greater part of the forest; (5)Modern technology( guns
and artificial lights ) allows more efficient location and killing of animals.
3. Living animals be harvested for the pet and aquarium trade.
4. Parts of the animal may have paticular value. For example, parts of some animals are thought to have
paticular medicinal properties, and others are hunted because of their use in traditional cultural practices.
Ivory and animal skins are highly valued in many cultures as art objects or clothing.
 11.4.3 Introduction of Exotic Species(pp249)（外来物种的引入）
●Ecosystems
have been significantly influenced by people in virtually al parts of the world; some have even
called these “engineered ecologies.”
The introduction of exotic species occurs for a variety of reasons.
1. Some are purposeful: Most agriculturally important plants and animals are introductions. Others were
introduced because people had a fondness for a particular plant or animal. Many plants were introduced for
horticultural(园艺的)purposes.
2. Others are accidental and arrived as stowaways(偷渡者) on imported materials.
Threats to exotic species:
Native species are threatened because they are unable to successfully compete against invasive exotic
species; Introduction of diseases has also had considerable impact.
■For example ------The introduction of cats and foxes caused the extinction of many kinds of native mammals on the Australian
mainland.
Various kinds of insects and diseases have had effect on American forests.
■ For example ------Freshwater ecosystems also have been greatly affected by introductions (take Zebra mussels and Eurasian
milfoil for example)
The second alteration: The introduction of exotic fish species has greatly affected naturally occurring
freshwater ecosystems.
Great Lakes ------
 11.4.4 Control of Pest Organisms(pp250)
The systematic killing of certain organisms because they interfere with human activities also results in
reduced biodiversity.
At one time, it was thought that populations of game species could be increased substantially if predators
were controlled.
This theory of predator control to increase populations of game species has not proven to be valid in most
cases, for the predators do not normally take the prime animals anyway. 证明是无效的。For example, the
population of bald eagle is decreasing because of the killing to protect the salmon.
But, still some places in the world adopt this management and some specific laws are established to control
the using of this management.
This management is not considered to be most effective in most cases. One exception is the hunting and
trapping of wolves in Alaska and Canada. In most cases, humans have a greater impact through habitat
modification and hunting than do the natural predators. Control of hunting is a form of predator control.
The control of cowbird populations is helpful to the reproduction of endangered Kirtland’s warbler.
Many species benefit from the exclusion of competing species or human interference.
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