时间:2019-01-22 作者:英语课 分类:自然百科2009年


英语课

 Hi, it’s Kasey-Dee Gardner, in this weekend Why Tell Me Why will answer an interesting viewer question. The viewer wants to know why certain species die after they reproduce. So, we're here to find out the answer.


 
Urn 1, so there are a bunch of species, both plant and animal that once have babies they just die. Is that correct?
 
Yes, that’s true. The viewer that asked the question asked about salmon 2 in particular. There are also plant species in particular annual plants(一年生植物), there are some a lot of annual plants that grow and reproduce in one summer and then die. There is actually a plant called “the century plant(龙舌兰)”, it’s called “the century plant” because it can live up to a hundred years without reproducing. And then reproduce one big event one time and then die.
 
Insects do it too, right?
 
Yes, yes, there is, there is a lot of organisms that do it. Things that have really high rates of predation or death due to environmental factors are competition. Those are the organisms that reproduce once and just die.
 
And what they are trying to do is maximize how many offspring they have at one point in order to ensure that at least one survives. Now in order to reproduce, an organism has to put resources into it. Resources can either go to current reproduction or it can store them up for future reproduction, or it can just put them toward maintenance of, urn, current survival basically.
 
And so, in order to produce as many offspring as possible, organisms put fewer resources towards survival and toward maintenance than they put into offspring. So they put all their resources in the offspring and basically at the end of that reproductive event they don’t have any energy left to survive, they put every effort possibly they can into producing just one more offspring. Because the probability of any one offspring surviving iss very very low.
 
And what’s really important in evolution of species is how many offspring you produce, but not just how many you produce but how many of those make it to reproduce some cells because that’s what keeps a species going.
 
It seems that it wouldn’t make sense to put all of your eggs in one basket. Why would you have all of them at once?
 
But actually, mathematically, it turns out if you can produce just one more, if an organism can produce one more offspring in one year than another organism will produce in multiple years. That, that’s actually beneficial to the organism because then, its offspring will reproduce the next year and have an equal number of offspring.
 

n.(有座脚的)瓮;坟墓;骨灰瓮
  • The urn was unearthed entire.这只瓮出土完整无缺。
  • She put the big hot coffee urn on the table and plugged it in.她将大咖啡壶放在桌子上,接上电源。
n.鲑,大马哈鱼,橙红色的
  • We saw a salmon jumping in the waterfall there.我们看见一条大马哈鱼在那边瀑布中跳跃。
  • Do you have any fresh salmon in at the moment?现在有新鲜大马哈鱼卖吗?
学英语单词
-faced
5-hydroxindoleacetic acid (5-hiaa)
abate a cause of action
absorption dynamometers
Actisan-5L
Adam's Bridge, Adams Bridge
Agamemnon
aluminium conductor steel rein- forced
Arenshausen
at the best
athyrium tozanense
atrophoderma vermiculata
bacciformis
bamian
bang-zone
bertall
bloomsdale
board the gravy train
bonding temperature
boron and water makeup system
cardo
centrale foramina
chittimwoods
citrous fruit
coacervation process
computer-aided design and drafting (cadd)
confidential adviser-advisee relations
Corydalis pseudorupestris
demergers
differential with side ring and radial cam plate
diks-diks
document of luggage transportation
Doshākh, Kuh-e
drivelers
empfindsamer Stil
european silver firs
ex-l
farouche
form pollen tubes
get sth. out of one's head
Gurjākhāni
hargis
Hermippe
horribilities
Hubble law
in-core instrumentation assembly
inductor dynamic loudspeaker
interrupt freeze mode
kelm
knotted chest with jaundice
learning-growth
lempel-ziv
lock state
lyg
Lythraceae
malagasy republics
margelov
Massay formula
Meesea
myeloarchitectures
non-locking shift character
nonconfessions
nonnegativity
numbersome
orbital septum
original accumulation
parkerization
pericardial disease
pseudoperichaeta roseanella
pulvis effervescens compositus
quasi cleavage fracture
quasi-real-time
radial servo
rajid
rapidly progressing glomerulonephritis
reluctates
roof and ground plummet
rural tourism
sagittal suture
senior analyst
sennit
septa intermusculare posterius
short-circuit line
sinistral transcurrent
slow cooking process
spoofing attack
stationary bar screen
steam lift
steel beaker
stiffened skin
sulfonio
Taiwan Relation Act
task schedule
toe slab
trolley lander
ultrasonic communication
unfoldedness
ungrabbable
Wabenzi
weatherpersons
zinjanthropera