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
54
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.
The age of the female and the quality of the habitat are two major factors affecting a female koala’s reproduction.
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/n0A7777K
0
大学英语四级
相关试题推荐
Ifthereisanysinglefactorthatmakesforsuccessinliving,itistheabilitytoprofitbydefeat.EverysuccessIknowhas
A、AforeigntouristandhisScottishguide.B、AnAmericanbusinessmanandaScottishstudent.C、AnAmericanengineerandaScott
AlbertEinsteinBornin1879,inUlm,Germany,EinsteinwastwoyearsoldwhenhisparentsmovedtoMunich.Therehisfather
AccordingtoRandomHouse,thedigitalaudio-booksHarryPottercanbepurchasedthroughApple’sTunesstoreand____________.(从
Ofalltheareasoflearningthemostimportantisthedevelopmentofattitudes.Emotionalreactionsaswellaslogicalthought
TherailroadsplayedakeyroleinthesettlementoftheWest.Theyprovidedrelativelyeasyaccesstotheregionforthefirst
A、Amajorsearchengine.B、Amarketingsalescompany.C、Amoneyfundinginstitution.D、Awebsiteowner.A由短文开头第二句aprogramcalle
Theoceans,whichcovernearlythree-quartersofEarth’ssurface,remainlargelyunexploredbecauseoftheirvastnessandinacce
NorthPoleExplorationsIfSantaClansreallydoesresideattheNorthPole,hemustlivealonelylife.TheNorthPoleisn’
Charleswasamanofsettledhabitsand______routine.
随机试题
政治文化的外部表现是()。
MX公司的物流管理MX公司是一家大型建筑装饰工程公司,在行业内具有很高的品牌知名度。由于进入该行业门槛较低,竞争对手无数。行业经过数年洗牌,先后经历了广告战、品牌战、价格战、服务战,逐步形成了数强争霸、多足鼎立的格局。MX集团公司总部设在
()是一种身份(地位或职务等)。
中国革命统一战线中的两个联盟及其关系。
《中国共产党章程》明确规定:“党的思想路线是一切从实际出发,理论联系实际,实事求是,在实践中检验真理和发展真理,”把“实事求是”作为党的思想路线的实质和核心的原因在于()
A.三带喙库蚊B.中华按蚊C.格氏血历螨D.微小按蚊E.白纹伊蚊我国乙脑的主要传播媒介是
关于起重与吊装安全管理规定,说法正确的是()。
在许多大城市中,无家可归者和失业者流落街头似已_______,没几个驾驶者会停下来给予施舍或提供援助,一般都会_______。毫无疑问,大多数人都听过这样的告诫:一味地给这些人钱,只会养成他们懒惰、依赖的生活方式。填入画横线部分最恰当的一项是:
Bythe1820’sintheUnitedStates,whensteamboatswerecommononwesternwaters,theseboatsweremostlypoweredbyenginesbu
•Lookatthenotesbelow.•Someinformationismissing.•YouwillhearAlanFrench,theManagingDirectorofA2ZRacing,talking
最新回复
(
0
)