首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
"Producers, Consumers, and Decomposers" P1 Organisms that are capable of using carbon dioxide as their sole source of carbon
"Producers, Consumers, and Decomposers" P1 Organisms that are capable of using carbon dioxide as their sole source of carbon
admin
2018-06-21
52
问题
"Producers, Consumers, and Decomposers"
P1 Organisms that are capable of using carbon dioxide as their sole source of carbon are called autotrophs (self-feeders), or producers. These are the plants. They chemically fix carbon through photosynthesis. Organisms that depend on producers as their carbon source are called heterotrophs (feed on others), or consumers. Generally, these are animals. From the producers, which manufacture their own food, energy flows through the system along a circuit called the food chain, reaching consumers and eventually detritivores. Organisms that share the same basic foods are said to be at the same trophic level. Ecosystems generally are structured in a food web, a complex network of interconnected food chains. In a food web, consumers participate in several different food chains, comprising both strong interactions and weak interactions between species in the food web.
P2 Primary consumers feed on producers. A Because producers are always plants, the primary consumer is called an herbivore, or plant eater. A carnivore is a secondary consumer and primarily eats meat. B A consumer that feeds on both producers (plants) and consumers (meat) is called an omnivore. C
P3 Detritivores (detritus feeders and decomposers) are the final link in the endless chain. D Detritivores renew the entire system by releasing simple inorganic compounds and nutrients with the breaking down of organic materials. Detritus refers to all the dead organic debris—remains, fallen leaves, and wastes—that living processes leave. Detritus feeders—worms, mites, termites, centipedes, snails, crabs, and even vultures, among others—work like an army to consume detritus and excrete nutrients that fuel an ecosystem. Decomposers are primarily bacteria and fungi that digest organic debris outside their bodies and absorb and release nutrients in the process. This metabolic work of microbial decomposers produces the rotting that breaks down detritus. Detritus feeders and decomposers, although different in operation, have a similar function in an ecosystem.
P4 An example of a complex community is the oceanic food web that includes krill, a primary consumer. Krill is a shrimplike crustacean that is a major food for an interrelated group of organisms, including whales, fish, seabirds, seals, and squid in the Antarctic region. All of these organisms participate in numerous other food chains as well, some consuming and some being consumed.
Phytoplankton
begin this chain by harvesting solar energy in photosynthesis. Herbivorous zoo-plankton such as krill and other organisms eat Phytoplankton. Consumers eat krill at the next
trophic level
. Because krill are a protein-rich, plentiful food, increasingly factory ships, such as those from Japan and Russia, seek them out. The annual krill harvest currently surpasses a million tons, principally as feed for chickens and livestock and as protein for human consumption.
Efficiency in a Food Web
P5 Any assessment of world food resources depends on the level of consumer being targeted. Let us use humans as an example. Many people can be fed if wheat is eaten directly. However, if the grain is first fed to cattle (herbivores) and then we eat the beef, the yield of available food energy is cut by 90% (810 kg of grain is reduced to 82 kg of meat); far fewer people can be fed from the same land area.
P6 In terms of energy, only about 10% of the kilocalories (food calories, not heat calories) in plant matter survive from the primary to the secondary trophic level. When humans consume meat instead of grain, there is a further loss of biomass and added inefficiency. More energy is lost to the environment at each progressive step in the food chain. You can see that an omnivorous diet such as that of an average North American and European is quite expensive in terms of biomass and energy.
P7 Food web concepts are becoming politicized as world food issues grow more critical. Today, approximately half of the cultivated acreage in the United States and Canada is planted for animal consumption—beef and dairy cattle, hogs, chickens, and turkeys. Livestock feed includes approximately 80% of the annual corn and nonexported soybean harvest. In addition, some lands cleared of rain forest in Central and South America were converted to pasture to produce beef for export to restaurants, stores, and fast-food outlets in developed countries. Thus, lifestyle decisions and dietary patterns in North America and Europe are perpetuating inefficient food webs, not to mention the destruction of valuable resources, both here and overseas.
Glossary
phytoplankton: a plant that lives in the sea and produces its own energy source
trophic level: category measured in steps away from the energy input in an ecosystem
According to paragraph 7, food webs are inefficient because
选项
A、consumers in developed nations prefer animal protein
B、politicians are not paying attention to the issues
C、there are not enough acres to grow crops efficiently
D、too much of the corn and soybean harvests are exported
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/nxfO777K
0
托福(TOEFL)
相关试题推荐
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.Researchingtheoriginofmedievalmanus
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.Researchingtheoriginofmedievalmanus
Completethenotesbelow.WriteONEWORDONLYforeachanswer.TheTawnyOwlMost【L31】______owlspeciesinUKStronglynocturna
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.HowtoChooseFlooringMaterialsSourceUseamathemati
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.HowtoChooseFlooringMaterialsSourceBeforeusing,m
Writethecorrectletter,A-F,nexttoquestions21-26.AVideoResourceCentreBReadingRoomCFoodServiceCentreDPeriodic
Completetheformbelow.WriteONEWORDONLYforeachanswer.HOUSESERVICEINFORMATIONExampleAnswerNameBarbaraHill
CompletethenotesbelowWriteONEWORDONLYforeachanswer.TheGherkinBuildingCommissionedby:【L31】______firmcalledFoste
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.CLIMATEANDARCHITECTURECasesandexamplesarefrom
Completethenotesbelow.WriteONEWORDforeachanswer.PotterynotesEarthenwareadvantages:-po
随机试题
在计算机中表示一个圆时,用圆心和半径来表示,这种表示方法称为______。
在Oyz正交坐标系中,设图形对y、z的惯性矩分别为Iy和Iz,则图形对坐标原点的极惯性矩为()。
在()方式下可看到Word文档中绘制的图形。
课外辅导是适应学生个别差异、因材施教的重要途径和措施。()
求幂级数的和函数.
在考生文件夹下的“samp1.acedb”数据库文件中已建立了表对象“tEmployee”。请按以下操作要求,完成表的设计。(1)判断并设置“tEmployee”表的主键。(2)设置“性别”字段的默认值为“男”。(3)删除表中
下面是一个栈类的模板,其中push函数将元素i压入栈顶,pop函数弹出栈顶元素。栈初始为空,top值为0,栈顶元素在stack[top-1)中,在下面横线处填上适当语句,完成栈类模板的定义。template<classT>classTs
下列关于模板形参的叙述中,错误的是
AndrenaGravidaisthenameofawildbeedecliningintheUnitedKingdomandtheNetherlands.A(31)ofmonthsagotherecentd
A=ColtB=LancerC=GrandisD=OutlanderWhichcar(s)….isforthosewhowantbothlooksandperformance?
最新回复
(
0
)