在生态系统中，各种生物的和所占的总是维持在相对稳定的状态，这种现象就叫。-八年级生物

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• 某牧场为了防止鸟类捕食草籽，用细网将其罩住，结果草籽的产量大幅度减少，其原因可能是[]A．影响了鸟类帮助牧草传粉B．使牧草场不能很好地通风透光C．使昆虫大量繁殖，严重危害-八年级生物
• 人们应该注意保护农田蜘蛛，因为蜘蛛可以[]A．增加农田肥力B．给农作物传粉C．防治农业害虫D．吃掉农田中的杂草-八年级生物
• 环保学家和生物学家提倡保护要保护农田蜘蛛，因为农田蜘蛛可以[]A．吃掉农田中的害虫B．防治农田中的杂草C．给农作物传粉D．给农作物施肥-八年级生物
• 呼伦贝尔草原是我国最大的牧业基地，过去那里有许多狼，对牧业的发展构成严重的威胁，所以当地牧民曾组织过大规模的猎捕狼的活动。但随后兔以惊人的速度发展起来，兔与牛羊争-八年级生物
• Don’t blame yourself too much. Everyone has his ______ and weaknesses.A．powersB．strengthsC．forcesD．e
• 洞庭湖某棉产区，在较早些年由于瓢虫、草蛉、蚜寄蜂等棉蚜天敌的控制，使害虫棉蚜数量一直维持在较低水平，没有造成棉花减产，但是后来由于长期不合理使用有机杀虫剂，天敌被-八年级生物
• 捕杀森林中的全部肉食动物后，鹿、兔等植食动物的平均奔跑速度将会[]A．减小B．增大C．不变D．先减后增-八年级生物
• 下列关于动物在自然界中的作用说法错误的是[]A．有助维持生态平衡B．能释放氧气C．能帮助植物传粉和传播种子D．能促进生态系统的物质循环-八年级生物
• 下列关于动物在自然界中的作用叙述，不正确的是[]A．动物在生态平衡中起着重要作用B．动物能促进生态系统中的物质循环C．动物的数量越多，对植物的生长越有利D．动物能帮助植物传-八年级生物
• 下列动物中能帮助植物传粉的是[]A．蝗虫B．松鼠C．蜜蜂D．猫头鹰-八年级生物
• (2014·湖南师大附中一模)The first successful space walk in 2013 is an important historical________in Chinese
• If you are looking for a ______, you can make it when it is on sale.A．priceB．bargainC．costD．bill-高一
• The great _______ of my plan is that it’s so cheap compared to the others.A．powerB．strengthC．energyD
• 从20世纪40年代起，人们开始大量生产和使用六六六、DDT等剧毒杀虫剂以提高粮食产量，这些剧毒物质的确在短期内起到了杀虫的效果，粮食产量得到了空前的提高。然而，这些杀虫-八年级生物
• 在生态平衡的状态中，生物有生有死，有迁进也有迁出，每个物种的数量经常处在一个动态变化之中。[]-八年级生物
• 在食物链“草→鼠→鹰”中，若将鹰杀绝，那么鼠的数量变化会是[]A．B．C．D．-八年级生物
• The traditional approach __________ with complex problems is to break them down into smaller，more ea
• You are _________ to have such a good teacher.A．fortuneB．fortunateC．fortunatelyD．unfortunately-高一英语
• Don't leave matches or cigarettes on the table within the _____ of little children.A．handB．reac
• 下列属于生产者和消费者之间的关系的是[]A．青蛙捕昆虫B．猫头鹰捉田鼠C．蝗虫吃庄稼D．麻雀吃虫子-八年级生物
• 许多动物都成了人类的盘中餐，有的人吃腻了平时常吃的动物，又把目光瞄准了野生动物，认为野味更有营养，更好吃。一些饭店也迎合这些人的口味，推出了一些野味菜肴，不少野生-八年级生物
• Next week there will be a basketball match between the ________ and the ________of our school. A．wom
• The________of life is being________ what I am or what I have.A．pride；proudB．pride in；proud ofC．pride
• As a result of the destruction of the forest, a large ________ of animals ________ lost their living
• The poor man made a_____after doing business forthree years.A．treasureB．pleasureC．moneyD．fortune-高三英
• Working hard is not only a _____ of great success, but it is among the essential requirement.A．sign
• In the _____ of proof, who is the thief is still not announced.A．presence B．absence C．direction D．fa
• ______ came that he and his girlfriend had broken up just because he didn’t keep his ______ again.A
• The people from the south enjoy the________in the north during the winter because they have never se
• 我国河北省北部地区，在麦收时节，据统计，每公顷麦田约有750~1500只青蛙，一只青蛙一天可食20~200只害虫。因此，依靠这种天然的“除虫剂”，基本上可以控制害虫，保证小麦的收-八年级生物
• The short-answer test is a kind of____between the composition and selection types.A．mixtureB．collect
• 为了防止鸟吃草籽，有人把人工种草的实验区用网子罩起来。过一段时间发现，实验区里草的叶子几乎都被虫吃光了，而未加罩网的天然草场，草反而生长良好。造成这一后果的主要原-八年级生物
• As we all know，life is a long________full of happiness as well as hardships.A．journeyB．tripC．travelD
• There is a(n) ________ of peace and calm in the country, quite different from that of a big city.A．
• 家鼠是同学们熟悉的动物，下列对于家鼠的认识不正确的是[]A．家鼠在食物链或食物网中占据一环，过多过少对生态系统都会产生不良影响B．家鼠在帮助植物传播果实和种子方面有一定-八年级生物
• Bill was doing a lot of physical exercise to build up his_________.A．energyB．forceC．strengthD．power
• British students only have a language ____ for jobs in the USA and Australia.A．chanceB．abilityC．poss
• 在“玉米→蝗虫→蛇”食物链中，如果人们大量捕食蛇，其后果是：蝗虫________，玉米。-八年级生物
• When I was a little boy，I lived in a small fishing village.The visit to the village made me think of
• Some cyclists make the ______ that traffic laws do not ______ them. It is not true, _____.A．assumpti
• 在生态系统中，绝大部分动物属于[]A．生产者B．消费者C．分解者D．非生物的成分-八年级生物
• 草原上野兔的数量上升的主要原因可能是[]A．草太多B．兔的天敌减少C．兔的繁殖力强D．兔的天敌增多-八年级生物
• As we know, too much ________ to Xrays can cause skin burns, cancer or other damage to the body.A．c
• The manager of the company told us that very little ________ was made of the waste material in the p
• At the meeting they discussed three different __________ to the study of mathematics.A．approaches B．
• Many countries are increasing their use of natural gas, wind and other forms of ____.A．energyB．sourc
• The soldiers have to stand for hours without changing.A．positionB．situationC．locationD．condition-高一英
• I can't say which wine is better—it's a(n)________of personal taste. A．matterB．affairC．eve
• —Was the proposal passed at yesterday’s meeting?—Yes, but some members of the committee expressed __
• The CCTV show Chinese Characters Dictation Competition has taken the country by storm, which is par