Predators are an essential factor in maintaining communities that are rich and diverse in species.
捕食者是维持群落物种丰富多样的一个重要因素。
They prevent fish migrations and change aquatic habitats essential for native species.
它们阻止了鱼类迁徙，并改变了对本地物种至关重要的水生栖息地。
Such assistance was essential in identifying potential dangers—poisonous species, unpredictable rivers, uncharted territories—which could mean the difference between life and death.
这种援助对于查明潜在危险——有毒物种、不可预测的河流、未知领域——至关重要，那些危险可能意味着生死之差。
The ability of a species to compete and adapt to a gradually changing environment is not the only ability that is essential for survival.
一个物种竞争和适应逐渐变化的环境的能力并不是生存所必需的唯一能力。
These birders participate in annual counts and report their findings to the appropriate organizations, and they also seek to promote conservation of bird species and their essential habitats.
这类鸟人会参加年度的计数工作，并将他们的结果报告给相关机构。他们也会努力倡导保护鸟种和它们必要的栖息地。
Because some species are protected and others are not, it is essential that wildlife crime investigators determined the exact species of their victims.
因为有些物种受保护有些不受，对野生动物罪案调查者来说确定受害者正确的物种是很关键的。
Listing species is the beginning of that essential process, "Attenborough said in a statement accompanying the report."
编制物种名录是保护物种这一重要进程的开始。
People often ask me, "Why should I care if a species goes extinct? It's not essential to my daily life, is it?"
人们总是问我：“我为什么要关注物种灭绝呢？它在我的日常生活中又无关紧要，不是吗？”
Coral reefs in tropical oceans are home to myriad species of fish, animal and plant life which are essential to reef productivity and the benefits they provide.
热带海洋的珊瑚礁是无数鱼类和动植物物种的栖息地，而这些物种对珊瑚礁的生产力及其所产生的效益所不可或缺的。
Wild animals are essential components of the delicate ecosystem, and the extinction of one species is likely to cause the disappearance of another.
野生动物是脆弱的生态系统中的一个重要组成部分，一种物种的灭绝会带来其它物种的相继灭绝。
It is essential that endangered species of animals be protected against being killed.
保护濒危的动物物种免遭残杀是必需的。
By showing algae's essential role in the evolution of photosynthesis, it also explores the innumerable species of plants which all have their origins in this one-celled life form.
从展示有关藻类生物的在光学作用进化过程中的必要角色，本纪录片同时显示所有庞大植物品种皆是源自这个单细胞形式生物。
But the essential reasons for making the species different are the genes on the chromosome and the other genes (ie. the hereditary background).
但是造成物种不同的根本原因是染色体上的有关基因及其以外的其他基因组成(即遗传背景)。
Although not depicted in a story, The Essential Guide to Alien Species reveals that when Chirpa died, his position fell to Kneesaa.
虽然没有在故事中体现，但《异族基本指南》透露，彻帕去世后，妮莎继位。
Therefore, a further study of the distributions and controlling of invasive species is very essential.
对入侵生物的分布和危害防治的深入研究是十分必要的。
Taurine is a conditionally essential amino acid that is found in the tissues of most animal species.
牛磺酸是一种条件性必需氨基酸，在大部分动物组织中都存在。
Tea contains 1.5-4% of the free amino acids, over 20 kinds of species, most essential amino acids.
茶叶中含有1.5 - 4%的游离氨基酸，种类达20多种，大多是人体必需的氨基酸。
The advance in the production of essential oil of 38aromatic plant species by tissue culture including cell suspension is reviewed.
综述了利用植物细胞与组织培养技术在38种香料植物中精油生物合成的研究进展。
The main chemical constituents from dipsacaceae species were triterpenoid saponins, iridoidal glycosides, flavonoids, essential oils, etc.
该科植物主要含三萜皂苷、环烯醚萜苷、黄酮、挥发油等类型的化合物。
Look at the reproductive system - reproduction is essential for survival of the species.
看看生殖系统，繁殖对物种的生存至关重要。
Look at the reproductive system - reproduction is essential for survival of the species.
看看生殖系统，繁殖对物种的生存至关重要。
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