PTE考生目前最大的问题之一就是练习题缺乏。除了有限的基本官方书（PLUS，Testbuilder, OG）之外，就没有题了。很多英语基础不是很扎实的同学很难找到练习材料。墨尔本文波雅思PTE培训学校专门为墨尔本，悉尼PTE考生准备了适合PTE听力阅读练习的科学60秒。各位PTE同学可以练习PTE听力中的summarise spoken text和PTE口语中的retell lecture，练习记笔记技巧和复述。废话少说，下面开始：
60秒科学：Birds Roost on New Evolutionary Tree
听力内容：
60秒科学节目（SSS）是科学美国人网站的一套广播栏目，英文名称：Scientific American – 60 Second Science,节目内容以科学报道为主，节目仅一分钟的时间，主要对当今的科学技术新发展作以简明、通俗的介绍，对于科学的发展如何影响人们的生活环境、健康状况及科学技术，提供了大量简明易懂的阐释。
In a massive data crunching analysis, researchers have created a new evolutionary tree for birds. The effort required enormous computing power and new algorithms because it involved the whole genomes, rather than just a few genes, of 48 species of birds to establish their relatedness. The study is the first of its kind for vertebrates.
“It contradicts morphology-based trees. It contradicts mitochondrial trees. It supports more trees based upon nuclear genes, although those trees weren’t highly resolved and this one is.”
Erich Jarvis of the Howard Hughes Medical Institute and Duke University Medical Center, one of the leaders of the whole genome sequence analysis effort. Multiple papers related to this work are in the December 12th special issue of the journal Science. [Guojie Zhang, Erich D. Jarvis and M. Thomas P. Gilbert, A flock of genomes]
Jarvis previewed the studies in a talk he gave October 19th at the ScienceWriters2014 meeting in Columbus, Ohio:
“We decided we wanted to make a big effort to focus on birds, because each of us had some aspects that we liked about bird biology. But something was practical about that as well. Bird genomes, in terms of genome size, compared to other vertebrate groups like reptiles, amphibians, mammals, they’re on average smaller than other vertebrates. And this allows one to sequence their genomes easier, and also assemble them easier. The reason why: it’s thought that they have less repetitive genome in their genome, but yet a similar complement of genes encoding for proteins…so you can learn a lot about vertebrate biology more easily studying birds than you can in other groups where there’s a lot of this repetitive so-called junk DNA. “
Some of the major findings of the new bird tree:
“We can infer at least two independent gains of vocal learning…we’re also supporting two independent gains of water adaptions…and two independent origins of the predatory trait, suggesting that amongst this higher land-bird group that includes songbirds, parrots, hawks, eagles, falcons and so on, a top apex predator was the common ancestor of the higher land birds that most of you know about, including vocal learners.
“What’s also different compared to a number of trees that have been dated with fossils, with the whole genome scale dating we are arguing that avian diversity of 95 percent of the species did not occur 80 to 100 million years ago in the Cretaceous Period, but occurred right around the time of the extinction of the dinosaurs [what we call the meteor impact in the Yucatan peninsula], which was an alternative theory…right after that extinction event, we get all orders of birds diverge within 50 million years. And then from there on everybody else speciates.”
—Steve Mirsky
