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
29
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
The word sole in the passage is closest in meaning to
选项
A、major
B、steady
C、only
D、ideal
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/LxfO777K
0
托福(TOEFL)
相关试题推荐
ChooseTWOletters,A-E.WhatTWOthingsdoesHowardsayaboutlibraryprovision?AStaffareparticularlyhelpfultoundergrad
Completethesentencesbelow.WriteNOMORETHANTWOWORDSforeachanswer.Theaboriginalstonecarvingsareinthe______
Completetheformbelow.WriteNOMORETHANTHREEWORDSAND/ORANUMBERforeachanswer.CUSTOMER’SINFORMATIONDETAILSName:【L
Choosethecorrectletter,A,BorC.Informationonthetestisfrom
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.CLIMATEANDARCHITECTURECasesandexamplesarefrom
Choosethecorrectletter,A,BorC.WhatdoesJimthinkaboutthedifferenceamongspeciesinnaturalandartificiallight?
Scientistshavediscoveredthatforthelast160,000years,atleast,there hasbeenaconsistentrelationshipbetween
NormanRockwellwasameticulousartist(who)paintingsportrayedfamilyincidentsandwell-defined(characters)withawealtho
A、Theyhaveonlyrecentlybeendiscovered.B、Theywerepaintedbythecolonistswhoknewher.C、Mostofthemportrayherasach
A、RecentlydiscoveredmanuscriptsB、SimilaritiesamongreligionsC、MethodsofanalyzingancientmanuscriptsD、Howancientmanusc
随机试题
某企业2005年流动资产平均余额为2000万元,流动资产周转次数为12次。若企业2005年销售利润为3300万元,则2005年销售利润率为()
Mostparents,Isuppose,havehadtheexperienceofreadingabedtimestorytotheirchildren.Andtheymusthave【C1】______howd
甲向乙借款500万元,丙提供了保证担保,丁提供了抵押担保。请根据民法原理、《合同法》《担保法》回答下列问题:设甲、乙均为生产性企业,甲到期无力还款,丙应否承担保证责任?为什么?
下列哪些行为不构成包庇罪?
某工程招标文件中,混凝土估计工程量为10000m3,合同中规定混凝土单价为400元/m3,若实际完成工程量与估计工程量的变动大于10%时,则进行调价,调价系数为0.9,竣工时实际完成混凝土工程量为15000m3,则混凝土工程款为()。
某国有企业的下列行为中正确的是()。
目前各家银行规定,只有()的存单才可用于在本行作质押贷款。
下列选项中,表述正确的包括()。
兴致:意兴阑珊
唐朝有关强奸罪的内容规定在《唐律疏议》的()中。
最新回复
(
0
)