美国科学60秒 SSS 2013-06-06
时间：2019-01-20 作者：英语课 分类：Scientific American(六)月
Most birds don't have penises. Good, I have your attention. Of course, female birds don't have penises. But, neither do most males. Now researchers have unravel 1 the genetics behind the dispearance of this anatomical apparatus 3. Their penetrating 4 insights are in the journal Current Biology. Only 3% of avian species have males with obvious organs of intromission. Ducks and other water fowl 5 are fairly well endowed. But most birds have just rudimentary gear, if anything at all. To get rid of this penile puzzle, researchers compared the embryos 6 of chickens and ducks. Both types of birds start to develop a member. But in chickens, the so-called 'genital tubercle' shrinks before the little guys hatch. It's because of a gene 2 called Bmp4. Bmp4 basically tell cells to comitte suicide. This form of cell death keeps birds from sprouting 7 teeth, and in developing male chickens, it causes the phallus to regress. Why this happens is still a mystery. It may allow females birds to be more selective about their mates. Because males with external equipement tend to impose it where they will. Whereas those without have to let the ladies roll the roost.
- He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧，其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线，他都能解开。
- This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。
- A single gene may have many effects.单一基因可能具有很多种效应。
- The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。
- The school's audio apparatus includes films and records.学校的视听设备包括放映机和录音机。
- They had a very refined apparatus.他们有一套非常精良的设备。
- He had an extraordinarily penetrating gaze. 他的目光有股异乎寻常的洞察力。
- He examined the man with a penetrating gaze. 他以锐利的目光仔细观察了那个人。
- Fowl is not part of a traditional brunch.禽肉不是传统的早午餐的一部分。
- Since my heart attack,I've eaten more fish and fowl and less red meat.自从我患了心脏病后，我就多吃鱼肉和禽肉，少吃红色肉类。
- Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段，而且其行为象胚。 来自辞典例句
- Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句