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1.
朱（huan,亦读“xuan”）是世界上最稀少的鸟,因其珍贵而有“东方宝石”的美誉。这一物种曾广泛分布于东亚地区,如俄罗斯、朝鲜、日本、和中国。自本世纪30年代以来,人类的某些经济活动改变了朱栖息地的生态环境,使朱难以适应此种变迁,导致种群数量和分布范围剧减。70年代末,相继在俄罗斯和朝鲜灭绝,日本至今仅剩一只。中国自1981年在陕西省洋县重新发现了世界上唯一幸存的7只野生朱以来做了大量的保护工作,先后成立了陕西朱保护观察站及陕西朱救护饲养中心。通过不懈的努力,目前朱的总数已增加到120多只,其中野生种群近60只,并… 相似文献
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1981年重新发现朱鹮后,至2000年的20年中,朱鹮的繁殖状况有了明显改善.朱鹮营巢地由1981年的两处,增加到36处,36处营巢地分属秦岭南坡中山区、秦岭南坡丘陵低山区、汉中盆地区和巴山低山丘陵区四种生态环境.20年中,朱鹮共计繁殖121窝,产卵364枚,窝卵数平均为3.06枚,孵化率75.54%,繁殖成功率85.95%,生产力1.8.死亡雏鸟60只,造成死亡的主要原因有疾病、天敌危害、人为因素和不良气候条件.1981年只发现两对亲鸟繁殖,出飞幼鸟3只,至2000年已有19个繁殖对,累计出飞幼鸟216只,种群数量增加了30.9倍,其自然增长率γ=0.9119/(只·a),周限增长率λ=1.220/a. 相似文献
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《生物学教学》2006,31(3):75-76
据2005年8月26日〈新民晚报》消息，1986年，39头世界珍稀动物糜鹿重返故乡，在江苏大丰安家，经过保护区专家和工作人员的辛勤培育，目前保护区糜鹿种群数量已达819头，繁殖速度和种群数量均居世界首位。而最令人们兴奋和骄傲的是保护区实现了糜鹿的野生放养，在历史上糜鹿的最后栖息地——江苏大丰沿海滩涂，已经拥有52头野生麇鹿。保护区副主任丁玉华说，2003年3月一头完全在野外出生、发育和成熟的麇鹿，在野外产下了它自己的仔鹿。它的诞生，结束了全世界300多年来没有野生麇鹿的历史，引起了动物学界的轰动。而仅在2005年1—8月间，保护区内的野生麇鹿就又产下了7头幼鹿。这意味中国麋鹿种群从真正意义上获得了“香火传承”。 相似文献
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调查得知集安市境内鱼类有56种.从分类上看这些鱼类隶属于6目13科45属.其中鲤形目最多,其次是鲑形目.从分布来看鸭绿江水系的鱼类种类最多有52种;其次是浑江水系有24种;再次是岭南水系有21种;而岭北水系只有15种.广泛分布于鸭绿江、浑江、岭南及岭北各水系的鱼类有9种;有24种鱼类只分布于鸭绿江水系.从种群数量来看,种群数量较多的有15种;种群数量较少的有22种,种群数量极少的有9种,处于濒危或濒临灭绝的种类有11种.调查中发现,集安市境内野生鱼类资源日趋减少. 相似文献
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济源太行山零星分布着野生牡丹种群，该区野生牡丹呈群集分布，具有生长空间隐蔽、现存数量少、观赏价值高的特点。从植株形态特征上分析，济源太行山区野生牡丹为矮牡丹。 相似文献
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种群增长率与种群增长速率虽一字之差,但内涵完全不同。增长率是指：单位数量的个体在单位时间内新增加的个体数,其计算公式为：（这一次总数-上一次总数）,上一次总数＊100％=增长率。如某种群现有数量为a,一年后,该种群数为b,那么该种群在当年的增长率为（b-a）／a。增长速率是指单位时间内增长的数量。其计算公式为：（这一次总数-上一次总数）／时间=增长速率。同样某种群现有数量为a,一年后,该种群数为b,其种群增长速率为：（b—a）／1年。即增长率=出生率一死亡率。故增长率不能等同于增长速率。 相似文献
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麝是亚洲古老而珍贵的野生经济动物,我国是亚洲麝的主产区,建国时,种群数量以百万计之.然而,人类社会经济的发展导致的资源过度开发和环境污染等,使麝资源逐步趋于枯竭.据此,国务院于2002年10月24日批准,将麝类所有种,由国家二级野生保护动物调整为一级野生保护动物.自1988年12月10日国务院批准《国家重点保护野生动物名录》后,麝是第一批由国家二级保护野生动物调整为国家一级保护野生动物的重点保护物种.这一重大举措,为保护麝类资源提供了强有力的法律保证和法律武器. 相似文献
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说起中国的大象,不得不提一个响当当的名字:野象谷.此地因野象众多而得名,传说有两三百头.人们想亲眼目睹野生的亚洲象,几乎必去野象谷.科研工作者初步估计,西双版纳勐养保护区的亚洲象种群数量在80～150头之间,连续几年出现在野象谷地区的亚洲象共有46头. 相似文献
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张丽娟 《呼伦贝尔学院学报》2015,(3)
在标准Penna模型的基础上,引入了参数疾病的影响程度α,和参数阈值Tnow,通过设定疾病的影响程度、域值(与年龄,疾病的影响程度有关)来控制种群的演化。在参数α取不同值时,给出了种群数量的演变、年龄结构及坏基因比例图,并分析了结果。疾病的影响程度对种群规模稳定所用时间长短、稳定后种群规模的大小、种群的年龄结构及存活下来的个体坏基因的分布有一定的影响作用。 相似文献
10.
福寿螺又称瓶螺、苹果螺、龙凤螺。原产南美洲亚马逊河流域（见本刊1986年第3期37页）。我国1984年引进,初期意在供人食用,但喜食者很少,加上福寿螺食性杂．对环境适应性强,生殖力又高,因而至今野生福寿螺已广布于长江南北,种群密度十分巨大。随处可见的福寿螺为我们提供了可利用的丰富资源,同时它常常危害刚插下的秧苗．成为农业一害。本文就野生福寿螺数量剧增的原因、福寿螺利用。控制策略等谈些浅见。1福寿螺野生数量剧增的原因福寿螺自1984年引进后．至今已遍布大江南北,池塘、湖泊、泽地、稻田随处可见,有益又有害。福寿螺数… 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
16.
Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
17.
Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
18.
Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
19.
Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献