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
The Koala’s Life Cycle The breeding season for koalas runs roughly from September to March. This is a time of increased acti
The Koala’s Life Cycle The breeding season for koalas runs roughly from September to March. This is a time of increased acti
admin
2010-08-04
57
问题
The Koala’s Life Cycle
The breeding season for koalas runs roughly from September to March. This is a time of increased activity, and sound levels increase as males bellow more frequently. This is also when the young from the previous year are dispersing from their mothers. Where koalas live near suburban settlements and major roads, this period heralds the busiest time for koala carets, as koalas on the move cross paths with cars and dogs, and accompanying stress levels mean a higher incidence of sickness.
Females generally start breeding at about three or four years of age and usually produce only one offspring each year. However, not all females in a wild population will breed each year. Some produce offspring only every two or three years, depending on factors such as the age of the female and the quality of the habitat. In the average female’s life span of about twelve years, this means that one female may produce only 5 or 6 offspring over her lifetime.
Once a female has conceived it is a short 35 days before the birth of the new baby, called a "joey". The tiny baby which is roughly 2 centimetres long and weighs less than 1 gram, looks rather like a pink jellybean ms it is totally hairless, blind and has no ears.
The joey makes its way from the birth canal to the pouch completely unaided, relying on its already well-developed senses of smell and touch, strong forelimbs and claws and an innate sense of direction. Once inside the safety of the pouch, it attaches itself to one of the two teats, which swells to fill its mouth. This prevents the joey from being dislodged from its source of food The mother contracts her strong sphincter muscle at the pouch opening to prevent the baby from tailing out.
The young koala drinks only mother’s milk for the first six to seven months and remains in the pouch for that time, slowly growing and developing eyes, ears, fur etc. At about 22 weeks, its eyes open and it begins to peep out of the pouch. From about 22 to 30 weeks, it begins to feed upon a substance called "pap" which the mother produces in addition to milk. Pap is a specialised form of faeces, or droppings, which forms an important part of the young koala’s diet, ’allowing it to make the transition from milk to eucalyptus leaves, rather like a human baby is fed "mushy" food when it starts to eat solids. Pap is .soft and runny and thought to come from the eaecum. It allows the mother to pass on micro-organisms present in her own digestive system which are essential to the digestion of eucalyptus leaves, and is a rich source of protein.
The joey Leans out of the pouch opening on the centre of the mother’s abdomen to feed on the pap, stretching it open towards the source of the pap, and therefore "downwards" or "backwards". This is why koalas are sometimes said to have a "backward-opening" pouch, although this is not strictly true.
The baby feeds regularly on the pap and as it grows it emerges totally from the pouch and lies on its mother’s belly to feed. Eventually it begins to feed upon fresh leaves as it rides on its mother’s back. The young koala continues to take milk from its mother until it is about a year old, but as it can no longer fit in the pouch, the mother’s teat elongates to protrude from the pouch opening. Young koalas remain with their mothers until the appearance outside the pouch of the next season’s joey. Then it is time for the previous year’s joey to disperse and find its own home range. If a female does not reproduce each year, the joey stays with her longer and has a greater chance of survival when it does leave its mother.
Females generally live longer than males as the males are more often injured during fights, they tend to travel longer distances with the resulting increase in risks such as cars and dogs, and they more often occupy poorer habitats. Putting a life span on the average koala can be misleading because some survive only for a period of weeks or months, while others survive to old age. Koalas living in an undisturbed habitat would have a greater life expectancy than those living in suburbia. Some estimates for the average life-span of a wild adult male koala are ten years, but the average survival rate for a dispersing sub-adult hale living near a highway or a housing estate is closer to two or three years.
Well-developed senses of vision and direction and strong forelimbs enable the joey to make its way from the birth canal to the pouch completely unaided.
选项
A、Y
B、N
C、NG
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/B0A7777K
0
大学英语四级
相关试题推荐
Fewyoungpeopleknow______(二十世纪三十年代的北京是什么样子).
AuniversityStudentinNairobi,Kenya,wasstoppedforatrafficviolationtheotherday.Thepolicemantookouthisticketbo
AlbertEinsteinBornin1879,inUlm,Germany,EinsteinwastwoyearsoldwhenhisparentsmovedtoMunich.Therehisfather
Dalianurgentlyneedstoestablisha【B1】______oftalentedpeopletomeetthechallengesintheworldmarket.Ataconference
A、Governmentofficersarehardtoplease.B、Thelearnerhastogothroughseveraltoughtests.C、Thelearnerusuallyfailssever
Byall【B1】______,thetimeisrightforhousestobecome"【B2】______"Duringthelastdecade,【B3】______havereadilyacceptedsuch
A、Healthfood.B、Fastfood.C、Traditionalfood.D、Internationalfood.D
FlorenceStephenis77andlivesinDeganwy,NorthWales.Sheisreadingforartsdegree."I’mmoreofacreaturetopolishmym
ThefightagainstAIDSgotsomemorehelpearlierthismonth.TheSwissdrugmanufacturerRocheandtheClintonFoundationannou
A、Beforedinner.B、Duringdinner.C、Rightafterdinner.D、Thenextday.A语义推断题。男士表示他也不愿意在吃饭的时候讨论这件事。由此可见,男士同意在饭前讨论日程安排。选项A正确。
随机试题
下列哪项是急性肾功能衰竭的主要病机
(2008)一幅值为U0的无限长直角行波沿波阻抗为Z的输电线路传播至开路的末端时,末端节点上电压值是()。
根据《企业破产法》的规定,破产申请应以书面的形式提出。破产申请书应当载明的事项有()。
在财务报表审计中,注册会计师通常可能不向被审计单位的()进行函证。
在其他情况不变的情况下,仅考察经济生活在一定时间的某个变数对有关经济变量的影响的分析方法,称为()。
要实现人与自然的和谐发展,下列措施最合理的是()。
幸福小区一日召开业主大会,就筹集和使用建筑物及其附属设施的维修资金的事项进行讨论表决。根据相关法律的规定,下列说法正确的是()。
根据下列资料,回答问题。2013年上半年中,乐透数字型福利彩票销售额与即开型福利彩票销售额之比小T7的月份有()个。
被《中国科学技术史》作者、英国科学家李约瑟赞誉为“中国科技史上最卓越的人物”的沈括,创作了:
TheGuardianviewonclimateanxiety:weliveinfrighteningtimes[A]Butit’simportanttorememberthattherearereasons
最新回复
(
0
)