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
122
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.
Female koalas generally have a longer life span than males as they arc less frequently involved in fights.
选项
A、Y
B、N
C、NG
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/o0A7777K
0
大学英语四级
相关试题推荐
A、Theuniversityisalsothetowncenter.B、OneofthecrossroadsiscalledCarfax.C、Theuniversityisontheedgeofthetown.
MakeaMummyTombIntroductionAncientEgyptiansbelievedinlifeafterdeath.WealthyEgyptiansmadecarefulpreparatio
Moststudentsthinkofthelibraryonly【C1】______aplacewherebooksarestored,butalibraryalso【C2】______manyvaluables
Theuseofchemicalsinalmostallareasoflifehasbecomeacommonplacephenomenon.Thereisgrowingevidence,however,thatc
A、Theymovesomepartoftheirbody.B、Theystopwhattheyaredoingandlistening.C、Theywanttodirecttheorchestraplaying
A、Theirsonwillbealittlebitaffected.B、Theirsonwillnottaketheexaminationowingtotheweather.C、Theweatherwillaf
GlobalWaterProblemTheUN’sWorldSummitonSustainableDevelopmenttobeheldinJohannesburgfromAugust26toSeptember
HOLLYWOOD,theworld’sfactoryforturningouthotmovies,hasdiscovereditsnextbigthing:familyfilms.Theindustrymad
MoreattentionwaspaidtothequalityofproductioninFranceatthetimeofReneCoty.CharlesDeschanelwasthenthefinancia
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
下列属于重组人促红素禁忌证的是
Educationisnotanend,butameanstoanend.Inotherwords,wedonoteducatechildrenonlyforthepurposeofeducatingthe
患者男性,52岁。糖尿病史5年,1周来低热37.8℃,伴咳嗽,痰中偶带血丝,胸片示在肺中多发片状结节状明影,ESR85mm/h,痰涂片抗酸染色(+)。该患者最可能的诊断是
牙周组织破坏程度与局部刺激物的量不成比例的是()
牙周袋底位于釉牙骨质根方,从袋底到釉牙骨质界的距离称为
高桩码头工程施工组织设计编制中,“技术经济条件”包括:预制构件加工、机械设备租赁、劳动力市场情况等建设项目地区的施工能力;钢材、木材、水泥、黄沙和石子等大宗建筑材料供应情况;交通条件和()。
下列货币政策操作中,能够引起货币供应量增加的是()。
甲公司专营A地至B地的旅客运输业务。2006年11月1日,由于正值客运淡季,甲公司将一使用空调车的班次取消,购买了该班次车票的旅客被合并至没有空调的普通客车中。该批旅客认为甲公司的做法不合理,要求退还部门票款,但甲公司以近期多雨雾、路不好走,两种票价金额相
我国民法规定,法人亭有以下哪些人格权()
MoreandmoreAmericansarereadingtheirowncreditreport.Creditreportsare【B1】______bylenderstodecidehowriskyitwoul
最新回复
(
0
)