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
专升本
Tundra ecosystems are treeless regions found in the Arctic and on the tops of mountains, where the climate is cold and windy and
Tundra ecosystems are treeless regions found in the Arctic and on the tops of mountains, where the climate is cold and windy and
admin
2022-06-23
80
问题
Tundra ecosystems are treeless regions found in the Arctic and on the tops of mountains, where the climate is cold and windy and rainfall is low. Tundra lands are snow-covered for most of the year, until summer brings a burst of wild flowers.
The Arctic tundra, where the average temperature is rather low, supports a variety of animal species, including Arctic foxes, polar bears, Arctic wolves, caribou, snow geese and musk oxen. The summer growing season is just 50 to 60 days, when the sun shines 24 hours a day.
The few plants and animals that live in the harsh conditions of the tundra are essentially clinging to life. They are highly vulnerable to environmental stresses like reduced snow cover and warmer temperatures brought on by global warming.
The Arctic tundra is changing dramatically due to global warming. Already, more southern animals like the red fox have moved onto the tundra. The red fox is now competing with the Arctic fox for food and territory.
Another major concern is that the melting of the permafrost (永冻土层) is contributing to global warming. Estimates suggest that about 14 percent of the Earth’s carbon is tied up in the permafrost. Until recently, the tundra acted as a carbon sink and captured huge amounts of carbon dioxide from the atmosphere as part of photosynthesis(光合作用). This process helped keep the amount of this greenhouse gas from accumulating in the atmosphere. Today, however, as the permafrost melts and dead plant material rots(腐烂) and releases CO
2
, the tundra has changed from a carbon sink to a carbon contributor.
The tundra used to be a carbon sink because ________.
选项
A、it supported a variety of animal species
B、it captured huge amounts of carbon dioxide from the atmosphere
C、the temperature was extremely low there
D、the tundra ecosystems were treeless regions
答案
B
解析
根据最后一段第三句“…the tundra acted as a carbon sink and captured huge amounts of carbon dioxide from the atmosphere…”可知,苔原在过去充当着碳汇的作用,从大气中捕获大量的二氧化碳。故选B。
转载请注明原文地址:https://kaotiyun.com/show/TtQD777K
本试题收录于:
英语题库普高专升本分类
0
英语
普高专升本
相关试题推荐
Manyayoungpersontellsmehewantstobeawriter,Ialwaysencouragesuchpeople,butIalsoexplainthatthere’sabigdiff
A.Heisseniortoeveryoneelseinthecompany.B.Thatman’stemperisnotsobadasyouhavedescribed.C.Suchpeopleaswis
Majorcompaniesarealreadyinpursuitofcommercialapplicationsofthenewbiology.Theydreamofplacingenzymesinthea
Majorcompaniesarealreadyinpursuitofcommercialapplicationsofthenewbiology.Theydreamofplacingenzymesinthea
Ididn’tknowanythingaboutanyofthebookssomychoicewasquite________.
ThefirstEnglishwindowwasjustaslitinthewall.Itwascutlong,sothatitwouldletinasmuchlightaspossible,andna
Communityservicecan________anythingfromgardeningtohelpinginoldpeople’shomes.
Collegeisaplacetoexploremanypossibilities:youreallycan’Idothemall—unlessyoumanageyourtimewisely.Herearesom
Whatisyourfavoritecolor?Doyoulikeyellow,orange,orred?Ifyoudo,youmustbeanoptimist(乐观主义者),aleader,anactive
Afterdinnerthenewministermadeashort________totheemployeespresent.
随机试题
20世纪初期,下列公司成为世界旅行社行业排名前三位的有()。
Ifhehadnotbeenhurt______much,he’dneverresignfromoffice.
男性,46岁,间断上腹痛3年,加重2个月,胃镜检查发现胃角切迹溃疡,幽门螺杆菌阳性。其治疗方案首选
申请个人经营贷款的经营实体一般不包括()。
长江公司属于核电站发电企业,2010年1月1日正式建造完成并交付使用一座核电站核设施,全部成本为200000万元,预计使用寿命为60年。根据国家法律和行政法规、国际公约等规定,企业应承担环境保护和生态恢复等义务。该核电站核设施60年后弃置时,将发生弃置费用
股东在决定公司利润分配政策时,通常考虑的主要因素有()。
主张“教育目的要根据社会需要来决定,个人只是教育加工培养的对象,教育的目标在于把受教育者培养成符合社会准则文化教育的公民”观点的是()。
“不经历风雨,怎能见彩虹”。一个人担当大任之前,如孟子在《生于忧患,死于安乐》中所说:“必先苦其心志,_________,_________,空乏其身。”目的是让其经受磨炼,增长才干。
()对于血液循环相当于引擎对于()
1Thefieldofeconomicsstudiesthebasicproblemsthateveryeconomymustface:whatgoodswillbeproducedandforwhomthey
最新回复
(
0
)