Evolution of rotifers in saline and subsaline lakes-- A molecular phylogenetic approach

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适应现象例子

适应现象例子【篇一：适应现象例子】感觉适应“入芝兰之室，久而不觉其香；入鲍鱼之肆，久而不闻其臭。

”刚走进花园，你会闻到一股花香味，但过了几分钟，就闻不到了。

这种现象就是感觉适应。

由于刺激对感受器的持续作用从而使感受性发生变化的现象，叫感觉适应（sensory adaptation）。

这是在同一感受器中，由于长时间的刺激作用，导致感受性发生变化的现象。

感觉适应既可引起感受性的提高，也可引起感受性的降低。

所有感觉都存在适应现象，但适应的表现方式和速度不尽相同。

视觉的适应可分为暗适应和明适应。

在夜晚由明亮的室内走到室外时，开始时我们的眼前一片漆黑，什么也看不清楚，一段时间后，眼睛就能分辨出黑暗中物体的轮廓了。

这种现象叫暗适应（dark adaptation）。

相反，由漆黑的室外走进明亮的室内时，开初感到耀眼炫目，什么都看不清楚，只要稍过几秒钟，就能清楚地看到室内物体了。

这种现象叫明适应（light daptation）。

视觉适应是环境刺激由强（或弱）向弱（或强）过渡时，由于一系列相同的弱（或强）光刺激的持续作用，导致对后续的弱（或强）光刺激感受性的不断提高（降低）。

现代神经生理学的研究表明，暗适应产生的原因是由于视网膜的视杆细胞的视紫红质被分解，突然进入暗处时尚未恢复，所以不能立即看清物体。

进入暗处后需要等待一段时间来恢复，即视紫红质的合成增多，含量逐渐增加，对弱光刺激的感受性逐渐提高，这样就能逐渐看清物体了。

反之，明适应是由于感光物质被大量分解，对强光刺激的感受性很高。

此时神经细胞受到过强的刺激，因而只感到眼前一片光亮，甚至引起疼痛，睁不开眼，同样看不清物体。

几秒钟后，感光物质被分解掉一部分后，对强光的感受性就迅速降低，从而能看清物体。

在视觉适应过程中，除视网膜的感光细胞发生变化外，还有中枢机制参与。

与视觉适应相比，听觉适应就不那么明显。

在听觉适应问题上一般存在两种观点。

一种观点认为，一般的声音作用之后，听觉感受性有短暂的降低，并认为听觉适应具有选择性，即在一定频率的声音的持续作用下，只降低对该频率声音（包括邻近频率的声音）的感受性，而不降低对其他频率声音的感受性。

英文外刊，抗击疟疾的科学家们，陷入了生物伦理学的争论

英文外刊，抗击疟疾的科学家们，陷入了生物伦理学的争论Scientists at this lab in Burkina Faso have deployed gene warfare against the parasite carrying mosquitoes that spread malaria.布基纳法索一个实验室的科学家已经对传播疟疾同时携带寄生虫的蚊子进行了基因改造。

The conventional tools at our disposal today have reached a ceiling and can't become more efficient than they are right now.我们现在使用的传统工具已经达到了极限，不能比现在的效率更高。

We have no choice but to look at complementary methods.我们别无选择，只能寻找辅助性疗法。

That is why we're using genetically modified mosquitoes.这就是我们对蚊子进行转基因的原因。

Professor Diabate runs the experiment for target malaria, a research consortium backed by the Bill and Melinda Gates Foundation.迪亚巴特教授为目标疟疾组织(比尔和梅琳达.盖茨基金会支持的研究联盟)开展了这项实验。

The group developed an enzyme that sterilizes male mosquitoes.研究小组研发出一种可以使雄蚊绝育的酶，可以使雄蚊绝育。

The action of the enzyme continues after fertilization which means if the male copulates with a female, the embryo is dead and the female can no longer have offspring.这种酶在雌蚊子受精后继续发挥作用，这意味着如果雄蚊子与雌蚊子交配，胚胎就会死亡，雌蚊子就不能再生育后代。

新进化论英语

新进化论英语Evolutionary TheoryThe concept of evolution has captivated the scientific community and the general public for centuries. From the groundbreaking work of Charles Darwin to the modern advancements in genetic research, the theory of evolution has undergone a remarkable transformation, shedding light on the intricate processes that govern the natural world. This paper delves into the foundations of evolutionary theory, its key principles, and the evidence that supports its validity, ultimately highlighting its significance in our understanding of the world around us.At the core of evolutionary theory lies the principle of natural selection proposed by Charles Darwin. This mechanism suggests that individuals within a species possess variations in their traits, and those with the most advantageous characteristics are more likely to survive and reproduce, passing on their advantageous traits to their offspring. Over successive generations, this process leads to the gradual adaptation and transformation of species, enabling them to better suit their respective environments.One of the primary lines of evidence supporting the theory of evolution is the fossil record. The discovery of a vast array of fossilized remains, ranging from simple single-celled organisms to complex multicellular life forms, has provided a tangible timeline of the Earth's biological history. The systematic arrangement of these fossils, with the oldest and most primitive forms at the bottom and the more advanced species towards the top, corroborates the notion of gradual change over time. Furthermore, the presence of transitional fossils, such as the famous Tiktaalik, a fish-like creature with limb-like appendages, demonstrates the gradual evolution of organisms and the interconnectedness of various species.Another compelling evidence for evolutionary theory comes from the field of comparative anatomy. Researchers have observed striking similarities in the anatomical structures of diverse organisms, ranging from the pentadactyl (five-fingered) limb structure shared by mammals, birds, and reptiles to the vestigial structures, such as the remnants of pelvic bones in whales, which point to their ancestral land-dwelling origins. These shared characteristics, often referred to as homologous structures, provide strong evidence for the common evolutionary origin of these species.The advent of modern molecular biology has further bolstered the theory of evolution. The discovery of DNA and the understanding of genetic inheritance have shed light on the mechanisms ofevolutionary change at the most fundamental level. Comparative analysis of the genetic sequences of different species has revealed striking similarities, indicating their shared evolutionary lineage. Moreover, the phenomenon of genetic mutations, which can introduce beneficial or deleterious changes, has been observed to drive the process of natural selection and adaptation.In addition to the fossil record, comparative anatomy, and molecular biology, the theory of evolution is supported by numerous other lines of evidence, including biogeography, developmental biology, and the observed instances of evolution in action, such as the development of antibiotic resistance in bacteria.Despite the overwhelming scientific consensus on the validity of evolutionary theory, it has not been without its critics. Some individuals, motivated by religious or ideological beliefs, have challenged the theory, proposing alternative explanations for the origin and diversity of life. However, the scientific community has consistently reaffirmed the robustness of evolutionary theory, and the vast majority of the evidence continues to support its fundamental principles.In conclusion, the theory of evolution has emerged as one of the most comprehensive and well-supported scientific theories in the modern era. From the groundbreaking work of Charles Darwin to thelatest advancements in molecular biology, the evidence for evolution has continued to accumulate, providing a deep understanding of the mechanisms that govern the natural world. As our scientific knowledge continues to expand, the theory of evolution remains a crucial framework for understanding the origins, adaptations, and diversification of life on Earth.。

Inhibition of Phytophthora vignae and Stem and Root Rot of Cowpea by Soil Bacteria

ABSTRACT
Bacteria isolated from Sri Lankan cowpea fields significantly reduced in vitro mycelial growth and sporangia! production of Phytophthora vignae by producing agar-diffusable and volatile inhibitors. Bacterial volatile inhibitors were evolved when the bacteria were grown on tryptic soy agar, nutrient agar, or King's B medium, although relatively less on the latter two media. The pH of agar exposed to the volatiles rapidly increased, suggesting that ammonia was involved in the inhibition. Volatile inhibitors were produced by the bacteria in soil amended with tryptic soy broth or cowpea seed extract, but not in unamended soil. Oosporeinduced disease by P. vignae was inhibited by Brevibacterium strain DF-3101 in soil. Soil or seed treatment with three Sri Lankan bacteria, Brevibacterium linens (DF-3101); Bacillus thuringiensis (DF-7107), and Bacillus pumilus (DF-1481) in greenhouse studies suppressed the disease on cowpea caused by P. vignae. None of the bacteria tested functioned as plant growth-promoting rhizobacteria (PGPR) on cowpea. Colonization of roots by strain DF3101-R, a rifampicin-resistant mutant of Brevibacterium linens DF-3101 was initially lower on resistant 'Mississippi Purple' (6 log cfu/g root) than on susceptible 'California Blackeye' (8 log cfu/g root) but, after two weeks, the population level on both varieties was equal at 6 log cfu!g root.

tpo35三篇阅读原文译文题目答案译文背景知识

tpo35三篇阅读原文译文题目答案译文背景知识阅读-1 (1)原文 (2)译文 (5)题目 (8)答案 (17)背景知识 (18)阅读-2 (21)原文 (21)译文 (24)题目 (27)答案 (36)背景知识 (36)阅读-3 (39)原文 (39)译文 (43)题目 (46)答案 (54)背景知识 (55)阅读-1原文Earth’ s Age①One of the first recorded observers to surmise a long age for Earth was the Greek historian Herodotus, who lived from approximately 480 B.C. to 425 B.C. He observed that the Nile River Delta was in fact a series of sediment deposits built up in successive floods. By noting that individual floods deposit only thin layers of sediment, he was able to conclude that the Nile Delta had taken many thousands of years to build up. More important than the amount of time Herodotus computed, which turns out to be trivial compared with the age of Earth, was the notion that one could estimate ages of geologic features by determining rates of the processes responsible for such features, and then assuming the rates to be roughly constant over time. Similar applications of this concept were to be used again and again in later centuries to estimate the ages of rock formations and, in particular, of layers of sediment that had compacted and cemented to form sedimentary rocks.②It was not until the seventeenth century that attempts were madeagain to understand clues to Earth's history through the rock record. Nicolaus Steno (1638-1686) was the first to work out principles of the progressive depositing of sediment in Tuscany. However, James Hutton (1726-1797), known as the founder of modern geology, was the first to have the important insight that geologic processes are cyclic in nature. Forces associated with subterranean heat cause land to be uplifted into plateaus and mountain ranges. The effects of wind and water then break down the masses of uplifted rock, producing sediment that is transported by water downward to ultimately form layers in lakes, seashores, or even oceans. Over time, the layers become sedimentary rock. These rocks are then uplifted sometime in the future to form new mountain ranges, which exhibit the sedimentary layers (and the remains of life within those layers) of the earlier episodes of erosion and deposition.③Hutton's concept represented a remarkable insight because it unified many individual phenomena and observations into a conceptual picture of Earth’s history. With the further assumption that these geologic processes were generally no more or less vigorous than they are today, Hutton's examination of sedimentary layers led him to realize that Earth's history must be enormous, that geologic time is anabyss and human history a speck by comparison.④After Hutton, geologists tried to determine rates of sedimentation so as to estimate the age of Earth from the total length of the sedimentary or stratigraphic record. Typical numbers produced at the turn of the twentieth century were 100 million to 400 million years. These underestimated the actual age by factors of 10 to 50 because much of the sedimentary record is missing in various locations and because there is a long rock sequence that is older than half a billion years that is far less well defined in terms of fossils and less well preserved.⑤Various other techniques to estimate Earth's age fell short, and particularly noteworthy in this regard were flawed determinations of the Sun's age. It had been recognized by the German philosopher Immanuel Kant (1724-1804) that chemical reactions could not supply the tremendous amount of energy flowing from the Sun for more than about a millennium. Two physicists during the nineteenth century both came up with ages for the Sun based on the Sun's energy coming from gravitational contraction. Under the force of gravity, the compressionresulting from a collapse of the object must release energy. Ages for Earth were derived that were in the tens of millions of years, much less than the geologic estimates of the lime.⑥It was the discovery of radioactivity at the end of the nineteenth century that opened the door to determining both the Sun’s energy source and the age of Earth. From the initial work came a suite of discoveries leading to radio isotopic dating, which quickly led to the realization that Earth must be billions of years old, and to the discovery of nuclear fusion as an energy source capable of sustaining the Sun's luminosity for that amount of time. By the 1960s, both analysis of meteorites and refinements of solar evolution models converged on an age for the solar system, and hence for Earth, of 4.5 billion years.译文地球的年龄①希腊历史学家希罗多德是最早有记录的推测地球年龄的观察家之一，他生活在大约公元前480年到公元前425年。

物种进化的英文作文

物种进化的英文作文英文：Evolution is the process of change in all forms of life over generations. It is driven by natural selection, which is the process by which organisms with advantageous traits survive and reproduce more successfully than those without these traits. Over time, advantageous traits become more common in a population, while disadvantageous traits become less common or disappear altogether.One example of evolution is the development ofantibiotic resistance in bacteria. When antibiotics are used to treat bacterial infections, some bacteria may survive due to a mutation that makes them resistant to the antibiotic. These resistant bacteria can then reproduce and pass on their resistant traits to their offspring, leading to a population of bacteria that is resistant to the antibiotic.Another example is the evolution of the giraffe's long neck. It is believed that giraffes with longer necks were able to reach higher branches and leaves to feed on, giving them an advantage over giraffes with shorter necks. Over time, the giraffes with longer necks survived and reproduced more successfully, passing on their longer neck traits to their offspring and leading to the evolution of the giraffe's long neck.中文：进化是指所有生命形式在多代之间发生变化的过程。

【精品】生物专业英语翻译+蒋悟生+第3版

生物专业英语翻译+蒋悟生+第3版------------------------------------------作者------------------------------------------日期Lesson One（4学时）Inside the Living Cell: Structure andFunction of Internal Cell Parts1.Cytoplasm: The Dynamic, Mobile Factory细胞质：动力工厂Most of the properties we associate with life are properties of the cytoplasm. Much of the mass of a cell consists of this semifluid substance, which is bounded on the outside by the plasma membrane. Organelles are suspended within it, supported by the filamentous network of the cytoskeleton. Dissolved in the cytoplasmic fluid are nutrients, ions, soluble proteins, and other materials needed for cell functioning.生命的大部分特征表现在细胞质的特征上。

细胞质大部分由半流体物质组成，并由细胞膜（原生质膜）包被。

细胞器悬浮在其中，并由丝状的细胞骨架支撑。

细胞质中溶解了大量的营养物质，离子，可溶蛋白以及维持细胞生理需求的其它物质。

2．The Nucleus: Information Central（细胞核：信息中心）The eukaryotic cell nucleus is the largest organelle and houses the genetic material (DNA) on chromosomes. (In prokaryotes the hereditary material is found in the nucleoid.) The nucleus also contains one or two organelles-the nucleoli-that play a role in cell division. A pore-perforated sac called the nuclear envelope separates the nucleus and its contents from the cytoplasm. Small molecules can pass through the nuclear envelope, but larger molecules such as mRNA and ribosomes must enter and exit via the pores.真核细胞的细胞核是最大的细胞器，细胞核对染色体组有保护作用（原核细胞的遗传物质存在于拟核中）。

1982年诺贝尔生理学医学奖

1982年诺贝尔生理学医学奖
—关于前列腺素和有关活性物质的发现
The Nobel Prize in Physiology or Medicine 1982
"for their discoveries concerning prostaglandins and related biologically active substances"
Sune K. Bergström – Autobiography
I was born January 10th, 1916 in Stockholm, Sweden. 1944 1946 - 47 1947 - 58 1958 - 80 1963 - 66 D. Med. Sci., Biochemistry, Karolinska Institutet, Stockholm Research Fellowship, Basel University, Basel Professor of Physiological Chemistry, The University of Lund, Lund Professor of Chemistry, Karolinska Institutet, Stockholm Dean of the Medical Faculty, Karolinska Institutet, Stockholm Rector of Karolinska Institutet, Stockholm Chairman of the Board of Directors, The Nobel Foundation, Stockholm Nobel Laureate in Physiology or Medicine,Stockholm President of the Royal Swedish Academy of Sciences

2022届上海市实验学校高三上学期10月摸底考试英语试题(解析版)

C.The woman hadn't expected the maintenance service to take so long.
D.The woman was satisfied with the improvement in the garage's service
9.A.The man didn't intend to make the woman unhappy.
C.Ask the woman which floor she's going to. D.Stay in the same lift to go down to his floor.7.
7.A.The size of the electric vehicle market.
B.A new trend in the car making industry.
10.A.The man may need to re-evaluate her priorities.
B.The man should deal with the urgent matters first.
C.The man has failed to take care of the urgent matters.
B.The man thought the woman was being unreasonable.
C.The man believed the woman had misunderstood him.
D.The man wanted to say something upsetting to the woman.
Questions 11through 13are based on the following passage.

多细胞生物演化英语

多细胞生物演化英语The Evolution of Multicellular OrganismsMulticellular organisms have long been a subject of fascination and study for scientists and researchers. The transition from single-celled to multicellular life forms is considered one of the most significant evolutionary events in the history of life on Earth. This remarkable transformation has led to the emergence of a vast array of complex and diverse organisms, each with their own unique adaptations and capabilities.The evolution of multicellular organisms can be traced back to the early stages of life on our planet. The first known multicellular organisms emerged during the Precambrian era, approximately 2.5 billion years ago. These early life forms were relatively simple, consisting of colonies of similar cells that worked together to perform basic functions such as nutrient acquisition and waste disposal.Over time, these primitive multicellular organisms underwent a series of evolutionary changes and adaptations, leading to the development of more complex and specialized cell types. Thisprocess, known as cellular differentiation, allowed for the emergence of specialized tissues and organs, each with their own unique functions. As these organisms continued to evolve, they became increasingly complex, with the development of complex nervous systems, circulatory systems, and other advanced features.One of the key driving forces behind the evolution of multicellular organisms was the need for more efficient resource utilization and protection from environmental stresses. Single-celled organisms, while highly adaptable, often faced challenges in obtaining and distributing resources, as well as in defending against predators and other environmental threats. By forming multicellular colonies, these organisms were able to divide labor, with different cells specializing in different tasks, such as nutrient acquisition, defense, and reproduction.Another important factor in the evolution of multicellular organisms was the development of cell-to-cell communication. As these organisms became more complex, the need for effective communication between cells became increasingly important. This led to the evolution of specialized signaling pathways and mechanisms, allowing cells to coordinate their activities and respond to changes in their environment.The evolution of multicellular organisms has also been shaped by theinterplay between cooperation and competition. While the formation of multicellular colonies provided significant advantages in terms of resource utilization and protection, it also introduced new challenges in terms of maintaining cohesion and coordinating the activities of individual cells. Over time, various mechanisms, such as programmed cell death and the development of complex regulatory systems, have emerged to help maintain the integrity and function of multicellular organisms.The diversity of multicellular organisms we see today is a testament to the remarkable adaptability and resilience of these life forms. From the simple colonial organisms of the Precambrian era to the highly complex and specialized organisms of the modern era, the evolution of multicellular life has been a continuous and dynamic process, driven by a complex interplay of environmental, genetic, and developmental factors.As our understanding of the evolution of multicellular organisms continues to deepen, we are gaining valuable insights into the fundamental mechanisms that underlie the emergence and diversification of life on our planet. These insights have important implications for a wide range of fields, from evolutionary biology and ecology to medicine and biotechnology.In conclusion, the evolution of multicellular organisms is afascinating and complex topic that has captured the attention of scientists and researchers for centuries. By studying the historical development and ongoing adaptations of these life forms, we can gain a deeper understanding of the fundamental principles that govern the evolution of life on Earth, and potentially unlock new avenues for scientific discovery and technological innovation.。

复杂进化关系类群英文

复杂进化关系类群英文The Intricate Evolutionary Relationships of Complex TaxaThe study of evolutionary relationships among organisms has long been a subject of fascination for scientists and naturalists alike. One particularly intriguing aspect of this field is the examination of complex taxa, which often exhibit intricate and multifaceted evolutionary histories. These taxa, characterized by their diverse morphological features, ecological adaptations, and genetic compositions, present a unique challenge in unraveling the intricate web of their evolutionary connections.At the heart of this endeavor lies the concept of phylogenetics, the study of the evolutionary relationships among organisms based on their shared characteristics. Phylogenetic analyses, employing a variety of techniques such as morphological comparisons, molecular sequencing, and computational algorithms, have been instrumental in shedding light on the complex evolutionary histories of many taxa. By carefully examining the similarities and differences between organisms, scientists can construct hypothetical evolutionary trees, or phylogenies, that illustrate the branching patterns and divergence points that have shaped the diversity of life on our planet.One such example of a complex taxon is the order Carnivora, which includes a diverse array of mammals such as cats, dogs, bears, and seals. These animals exhibit a wide range of morphological and behavioral adaptations, reflecting their varied ecological niches and evolutionary trajectories. Phylogenetic studies of the Carnivora have revealed intricate relationships, with some species sharing more recent common ancestors than others, and the emergence of distinct clades or lineages that have diversified over time.Another compelling example can be found in the class Reptilia, which encompasses a broad range of organisms, from the iconic dinosaurs to the modern-day crocodiles, snakes, and lizards. The evolutionary history of reptiles has been a subject of intense scrutiny, with ongoing debates and revisions to their phylogenetic relationships. The emergence of new fossil evidence and the application of advanced molecular techniques have helped to refine our understanding of the complex evolutionary connections within this diverse group of animals.The study of complex taxa is not limited to the animal kingdom; the plant world also presents numerous examples of intricately related organisms. The angiosperm, or flowering plant, clade is a prime illustration, with its vast diversity of species exhibiting a wide range of morphological, ecological, and genetic characteristics. Unravelingthe evolutionary relationships among angiosperms has been a major focus of botanical research, with phylogenetic analyses providing insights into the origins and diversification of this dominant group of land plants.One of the key challenges in studying the evolutionary relationships of complex taxa lies in the inherent complexity of their histories. Many organisms have undergone multiple episodes of speciation, extinction, and adaptation, resulting in a tangled web of evolutionary connections that can be difficult to disentangle. Additionally, the acquisition of new traits, the loss of ancestral features, and the phenomenon of convergent evolution can further complicate the interpretation of phylogenetic data.To address these challenges, scientists have developed increasingly sophisticated tools and techniques for phylogenetic analysis. Advances in DNA sequencing, computational algorithms, and statistical modeling have allowed researchers to delve deeper into the genetic underpinnings of evolutionary relationships, providing a more robust and nuanced understanding of the complex taxa under study.Furthermore, the integration of multiple lines of evidence, such as morphological, ecological, and developmental data, has become crucial in constructing comprehensive and reliable phylogenetichypotheses. By considering a diverse array of characteristics, scientists can better account for the multifaceted nature of evolutionary processes and arrive at more accurate representations of the intricate connections within complex taxa.The study of complex taxa and their evolutionary relationships holds immense value for our understanding of the natural world. It not only sheds light on the historical patterns and mechanisms that have shaped the diversity of life but also has practical applications in fields such as conservation biology, disease ecology, and biotechnology. By unraveling the complex evolutionary histories of organisms, we can gain insights into their adaptations, vulnerabilities, and potential for future diversification, ultimately informing our efforts to protect and manage the natural world.In conclusion, the study of complex taxa and their evolutionary relationships is a fascinating and multifaceted field of inquiry. Through the application of advanced phylogenetic techniques and the integration of diverse lines of evidence, scientists are continuously expanding our understanding of the intricate web of life on our planet. As we delve deeper into the complexities of evolutionary histories, we unlock new insights that have the potential to transform our perspectives and guide our stewardship of the natural world.。

风景园林专业英语试题

1 Why Pagodas Don't Fall DownIn a land swept by typhoons and shaken by earthquakes, how have Japan's tallest and seemingly flimsiest old buildings - 500 or so wooden pagodas - remained standing for centuries? Records show that only two have collapsed during the past 1400 years. Those that have disappeared were destroyed by fire as a result of lightning or civil war. The disastrous Hanshin earthquake in 1995 killed 6,400 people, toppled elevated highways, flattened office blocks and devastated the port area of Kobe. Yet it left the magnificent five-storey pagoda at the Toji temple in nearby Kyoto unscathed, though it levelled a number of buildings in the neighbourhood.Japanese scholars have been mystified for ages about why these tall, slender buildings are so stable. It was only thirty years ago that the building industry felt confident enough to erect office blocks of steel and reinforced concrete that had more than a dozen floors. With its special shock absorbers to dampen the effect of sudden sideways movements from an earthquake, the thirty-six-storey Kasumigaseki building in central Tokyo - Japan's first skyscraper - was considered a masterpiece of modern engineering when it was built in 1968.Yet in 826, with only pegs and wedges to keep his wooden structure upright, the master builder Kobodaishi had no hesitation in sending his majestic Toji pagoda soaring fifty-five metres into the sky - nearly half as high as the Kasumigaseki skyscraper built some eleven centuries later. Clearly, Japanese carpenters of the day knew a few tricks about allowing a building to sway and settle itself rather than fight nature's forces. But what sort of tricks?The multi-storey pagoda came to Japan from China in the sixth century. As in China, they were first introduced with Buddhism and were attached to important temples. The Chinese built their pagodas in brick or stone, with inner staircases, and used them in later centuries mainly as watchtowers. When the pagoda reached Japan, however, its architecture was freely adapted to local conditions - they were built less high, typically five rather than nine storeys, made mainly of wood and the staircase was dispensed with because the Japanese pagoda did not have any practical use but became more of an art object. Because of the typhoons that batter Japan in the summer, Japanese builders learned to extend the eaves of buildings further beyond the walls. This prevents rainwater gushing down the walls. Pagodas in China and Korea have nothing like the overhang that is found on pagodas in Japan.为什么宝塔不会倒塌在这片被台风席卷、地震撼动的土地上，日本最高、看起来最脆弱的老建筑——500多座木制宝塔——是如何屹立了几个世纪的?记录显示，在过去的1400年里，只有两处坍塌。

生物化学的发现英文

生物化学的发现英文In the realm of biochemistry, the discovery of DNA's double helix structure stands as a monumental breakthrough.It revolutionized our understanding of genetic informationand paved the way for modern molecular biology.The intricate dance of enzymes and substrates, orchestrating the metabolic pathways within cells, is amarvel of nature's design. Each enzyme, with its unique shape, ensures the specificity and efficiency of biochemical reactions.Another significant revelation in biochemistry is therole of amino acids in protein synthesis. The sequence ofthese building blocks determines the structure and functionof proteins, which are the workhorses of the biological world.The exploration of lipid bilayers and their role in cell membranes has deepened our comprehension of how cellsmaintain their integrity and selectively interact with their environment.The study of biochemistry also unveils the mysteries of cellular energy production. The citric acid cycle andoxidative phosphorylation are processes that convertnutrients into the energy currency of the cell, ATP.Understanding the molecular mechanisms of disease hasbeen greatly advanced by biochemistry. For instance, the identification of the molecular basis of cystic fibrosis has led to more targeted and effective therapies.The emerging field of epigenetics, where biochemistry intersects with genetics, has shed light on how environmental factors can influence gene expression without altering the DNA sequence itself.Finally, the ongoing quest to decode the human proteomeis a testament to the vastness of biochemical knowledge. Each protein's unique function contributes to the symphony of life, and understanding them is key to unlocking the mysteries of health and disease.。

形态学变化英文

形态学变化英文Morphological TransformationThe study of morphological transformation is a fascinating field that delves into the intricate changes that occur in the form and structure of organisms over time. This process, driven by various evolutionary forces, can lead to the emergence of new species, the adaptation of existing ones, and the extinction of others. Understanding the mechanisms behind these transformations is crucial for biologists, as it sheds light on the complex interplay between an organism's genetic makeup, its environment, and the selective pressures that shape its development.At the heart of morphological transformation lies the concept of adaptation. As organisms face changing environmental conditions, they must adapt to ensure their survival and reproduction. This adaptation can manifest in various ways, such as the development of new physical features, the modification of existing ones, or the complete restructuring of an organism's form. The process of natural selection, where individuals with advantageous traits are more likely to survive and reproduce, plays a pivotal role in driving these transformations.One of the most well-known examples of morphological transformation is the evolution of the whale. Millions of years ago, whales were land-dwelling mammals that resembled small, four-legged creatures. Over time, as they adapted to an aquatic lifestyle, their bodies underwent remarkable changes. Their limbs transformed into flippers, their tails became flukes for propulsion, and their nostrils migrated to the top of their heads, allowing them to breathe while submerged. These adaptations, driven by the need to thrive in the marine environment, have resulted in the diverse array of whale species we observe today.Another intriguing example of morphological transformation is the metamorphosis of insects, such as butterflies and dragonflies. During their life cycle, these creatures undergo a remarkable transformation, transitioning from a larval stage (e.g., caterpillar or nymph) to a completely different adult form. This process involves the reorganization of the organism's body structure, the development of new organs and appendages, and the shedding of the larval exoskeleton. The transformation is orchestrated by complex hormonal signals and genetic pathways, allowing the insect to adapt to its changing environmental demands and reproductive needs.Morphological transformation is not limited to the animal kingdom; it is also observed in plants. For instance, the development of flowersfrom simple leaf-like structures is a remarkable example of morphological transformation. The petals, sepals, stamens, and carpels that make up a flower are all modified leaves, each serving a specific function in the plant's reproductive cycle. This transformation is driven by the expression of specific genes that regulate the development and patterning of these floral structures.Furthermore, the study of morphological transformation has important implications for understanding the evolution of species. By analyzing the fossil record and comparing the physical characteristics of related organisms, scientists can reconstruct the ancestral forms and trace the evolutionary pathways that have led to the diversity of life we observe today. This knowledge not only enhances our understanding of the past but also provides valuable insights into the future adaptations and transformations that may occur in response to environmental changes.In conclusion, the study of morphological transformation is a fundamental aspect of biology, offering a window into the dynamic and ever-changing nature of life on our planet. From the evolution of whales to the metamorphosis of insects and the development of flowers, these remarkable transformations illustrate the incredible adaptability and resilience of living organisms. As we continue to explore and unravel the mysteries of morphological transformation,we gain a deeper appreciation for the intricate processes that have shaped the diversity of life on Earth.。

唾液酸化修饰的英语

唾液酸化修饰的英语英文回答：Saliva is a complex fluid that plays a crucial role in maintaining oral health. It contains a variety of proteins, enzymes, and other molecules that help to protect the teeth and gums from damage. One of the most important functions of saliva is to neutralize acids that are produced by bacteria in the mouth. This helps to prevent tooth decay and other oral health problems.In addition to its buffering capacity, saliva also contains a number of antimicrobial substances that help to kill bacteria. These substances include lysozyme, lactoferrin, and immunoglobulins. Lysozyme is an enzymethat breaks down the cell walls of bacteria, while lactoferrin is a protein that binds to iron, which is essential for bacterial growth. Immunoglobulins are antibodies that recognize and bind to specific bacteria, helping to neutralize them.Saliva also plays a role in taste perception. The proteins in saliva bind to taste molecules and carry them to the taste buds on the tongue. This allows us to perceive the different tastes of food and drink.The composition of saliva can vary depending on a number of factors, including age, diet, and health status. For example, the saliva of young children contains more antimicrobial substances than the saliva of adults. This is because young children are more susceptible to oral infections. The saliva of people who eat a healthy diet is also more likely to contain antimicrobial substances than the saliva of people who eat a diet high in sugar and processed foods.Saliva is an essential fluid for oral health. It helps to protect the teeth and gums from damage, kill bacteria, and perceive taste. The composition of saliva can vary depending on a number of factors, but it is always an important part of a healthy mouth.中文回答：唾液是维持口腔健康的重要液体。

乙醛脱氢酶突变的进化意义

乙醛脱氢酶突变的进化意义英文回答：The evolutionary significance of aldehyde dehydrogenase mutations is a complex and multifaceted topic that has been the subject of extensive research. Aldehyde dehydrogenase (ALDH) is a key enzyme in the metabolism of alcohol, and mutations in the ALDH gene can have significant effects on an individual's ability to process alcohol. These mutations can lead to a variety of health conditions, includingalcohol intolerance, liver damage, and an increased risk of certain types of cancer.One of the most well-studied ALDH mutations is the East Asian variant, which is common in people of East Asian descent. This mutation results in a decreased activity of ALDH, which leads to a build-up of acetaldehyde in the body. Acetaldehyde is a toxic compound that can cause a varietyof harmful effects, including DNA damage and inflammation.The East Asian ALDH variant is thought to have evolved as a result of selective pressure from alcohol consumption. In East Asia, rice cultivation has been a major part of the diet for centuries, and rice contains significant amounts of alcohol. It is hypothesized that individuals with the ALDH mutation were able to better tolerate the effects of alcohol, and thus had a selective advantage in this environment.Another ALDH mutation that has been studied extensively is the African-American variant. This mutation is common in people of African descent, and it also results in a decreased activity of ALDH. However, the African-American ALDH variant is thought to have evolved as a result of selective pressure from malaria. Malaria is a mosquito-borne disease that is common in Africa, and it is thought that individuals with the ALDH mutation were better able to survive malaria infections.The evolutionary significance of ALDH mutations isstill being debated, but it is clear that these mutations have had a major impact on human populations. ALDHmutations can have significant effects on health, and they may have also played a role in the evolution of human behavior.中文回答：乙醛脱氢酶突变的进化意义是一个复杂且多方面的课题，已经成为广泛研究的主题。

巨噬细胞分化英语

巨噬细胞分化英语Diving into the fascinating world of macrophage differentiation, we uncover a complex and intricate process that plays a pivotal role in the immune system. Macrophages, the versatile sentinels of our body, are derived from the monocyte lineage and are crucial in both innate and adaptive immunity. The journey of a macrophage begins in the bone marrow, where hematopoietic stem cells give rise to monocytes, which then circulate in the bloodstream. Upon sensing tissue-specific signals, these monocytes migrate into various tissues, where they differentiate into resident macrophages.The differentiation process is regulated by a myriad of factors, including cytokines, growth factors, and the extracellular matrix. These signals orchestrate thematuration of macrophages into their functional forms, equipped with the ability to phagocytose pathogens, present antigens, and produce inflammatory mediators. The versatility of macrophages is further highlighted by their ability to adopt different activation states, such as the classically activated M1 phenotype, which is pro-inflammatory and microbicidal, and the alternatively activated M2 phenotype, which is anti-inflammatory and involved in tissue repair and immune regulation.Moreover, the differentiation of macrophages is not aone-size-fits-all scenario; it is highly context-dependent, with the local environment dictating the specific functionsthese cells will perform. For instance, in the context of a wound, macrophages differentiate into a phenotype that promotes healing and tissue regeneration, while in the presence of cancer, they may adopt a phenotype that either supports or inhibits tumor growth.Recent advancements in our understanding of macrophage differentiation have opened up new avenues for therapeutic intervention. By modulating the differentiation process, researchers aim to enhance the immune response against infections or to dampen inflammation in chronic diseases. The quest to harness the power of macrophages is ongoing, with each discovery bringing us closer to unlocking their full potential in the realm of immunology and medicine.。

古生物学家的英语

古生物学家的英语Delve into the fascinating world of paleontology, where the whispers of the past echo through the ages, and every fossil tells a story. Paleontologists, the modern-day detectives of the ancient world, wield the power of science to piece together the puzzle of life's history on Earth. With a trowel in one hand and a brush in the other, they uncover the remnants of creatures that once roamed, swam, or flew in a time before human memory. Their work is a delicate dance between patience and passion, as they sift through layers of sediment to reveal the secrets of our planet's prehistoric inhabitants. From the colossal dinosaurs that once dominated the land to the tiny trilobites that left their mark in the sea, paleontologists bring the extinct to life, one fossil at a time. Their discoveries not only expand our understanding of the natural world but also offer a glimpse into the evolutionary processes that have shaped life as we know it today. As they continue their quest for knowledge, these dedicated scientists are the keepers of the ancient, ensuring that the voices of the past are heard loud and clear in the present.。

蝶变英语作文

蝶变英语作文Title: Metamorphosis。

Metamorphosis is a natural phenomenon that occurs throughout the biological world, from the humblecaterpillar transforming into a majestic butterfly to the development of tadpoles into frogs. However, beyond the realm of biology, metamorphosis also holds significant symbolism in the human experience. It represents a profound change or transformation, often from one state to another, and is a theme that resonates deeply within literature, art, and personal narratives.One of the most iconic representations of metamorphosis in literature is Franz Kafka's novella, "The Metamorphosis." In this surreal tale, the protagonist, Gregor Samsa, wakes up one morning to find himself transformed into a giant insect. Through this bizarre transformation, Kafka explores themes of alienation, existentialism, and the absurdity of human existence.Gregor's physical transformation mirrors his inner turmoil and serves as a metaphor for the dehumanizing effects of modern society.Beyond literature, the concept of metamorphosis pervades various cultural and religious traditions. InGreek mythology, the story of Narcissus, who transformsinto a flower after falling in love with his own reflection, symbolizes the dangers of vanity and self-absorption. Similarly, the Hindu concept of reincarnation suggests a continuous cycle of death and rebirth, with each life representing a new stage of transformation and spiritual evolution.In art, metamorphosis is often depicted as a process of growth and renewal. The paintings of Salvador Dali often feature surreal landscapes populated by bizarre, hybrid creatures, reflecting his fascination with the subconscious mind and the transformative power of the imagination. Likewise, the work of Renaissance artists such as Michelangelo and Leonardo da Vinci often depicted scenes of metamorphosis, such as the transformation of humans intomythical beings or the evolution of life forms from simpleto complex.On a personal level, metamorphosis can represent a journey of self-discovery and personal growth. Just as caterpillars undergo a radical transformation to become butterflies, individuals may undergo significant changes in their lives that propel them towards a new sense ofidentity or purpose. These transformations can be spurredby major life events such as marriage, parenthood, career changes, or spiritual awakenings. Through these experiences, individuals shed old habits, beliefs, and relationships,and emerge with a renewed sense of self and direction.In conclusion, metamorphosis is a multifaceted concept that transcends the boundaries of biology to encompass themes of change, transformation, and renewal in literature, art, religion, and personal experience. Whether depicted in the pages of a novel, the strokes of a painting, or the chapters of one's life, metamorphosis serves as a powerful reminder of the constant flux and evolution of the human condition. As we navigate the complexities of existence,may we embrace the opportunities for growth and renewal that metamorphosis affords us, and emerge from each transformation stronger, wiser, and more fully alive.。

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675676Derry etal.Fig.1.Locations of lakes in Wood Buffalo National Park and near Fort McMurray,Alberta,Canada from which rotifers were collected.Brachionus plicatilis (BP)COI haploptypes clustered according to the lakes from which they were collected and are indicated on the map (BP1–3ϭHC Lake;BP4–14ϭGrosbeak Lake/Salt Pan Lake;BP15–16ϭFP Lake).Brachionus plicatilis has shown that it is a complex of at least three sibling species (Ciros-Pe ´rez et al.2001;Go ´mez et al.2002b ),with varying salinity,thermal,and seasonal preferences (Ciros-Pe ´rez et al.2001).It is probable that there are additional sibling species in this complex (Ortells et al.2000;Go ´mez et al.2002b ).A mitochondrial DNA (mtDNA)study of these organisms showed considerable genetic di-vergence (2.8%uncorrected COI nucleotide sequence diver-gence)between B.plicatilis populations from Spanish salt lakes,which was thought to reﬂect their origin from different glacial refugia (Go ´mez et al.2000).The objectives of this study were to address whether phe-notypic plasticity has concealed reproductively isolated spe-cies of rotifers and to determine whether rotifers inhabiting saline environments show greater population divergence than freshwater species.This study employed DNA sequenc-es to evaluate the extent of population divergence in four of the most common rotifers from inland waters.Speciﬁcally,this investigation examines the role of genetic factors in ex-plaining variance in spine development among members of the genus Keratella (K.cochlearis,K.hiemalis,and K.quad-rata ).The second genus selected for analysis,Brachionus,has been the target of prior molecular studies.The present analysis sought to ascertain the extent of genetic divergence among populations of B.plicatilis from saline lakes in one region of North America.We hypothesized that greater in-traspeciﬁc genetic diversity would be detected in this species because of the prior evidence for accelerated rates of mo-lecular evolution in halophilic taxa.Materials and methodsSample collection —Rotifers were collected using 64-␮m Nitex tow net at the point of maximum lake depth in nine lakes that spanned a salinity gradient (556to 26,318mg L Ϫ1total dissolved solids (TDS),summer means;Derry et al.in press).These lakes were located within an 85-km radius in Wood Buffalo National Park,Alberta,Canada (59Њ30ЈN,111Њ80ЈW)(Fig.1).In addition,Brachionus urceolaris,Ker-atella cochlearis robusta,and one Keratella quadrata pop-ulation were obtained from three mine-tailing ponds 330km south of these lakes,near Fort McMurray,Alberta (56Њ55ЈN,111Њ29ЈW)(Fig.1).Individuals of B.calyciﬂorus from Gainesville,Florida (29ЊN,82ЊW)(Snell et al.1991)were used as an outgroup for other Brachionus species.Members of the genus Asplanchna sp.were collected from southern Ontario (44ЊN,80ЊW)and served as an outgroup in other phylogenetic analyses.Vertical net hauls were performed in lakes that were sufﬁciently deep (2to 10m)for vertical migration of zooplankton,while horizontal tows were con-ducted in shallow (0.3to 0.5m)lakes.Rotifers were iden-677Molecular phylogenetics of rotifersTable1.GenBank accession numbers for16S DNA sequencesisolated from rotifers.Species Haplotype Accession numberAsplanchna sp.1AF499036Brachionus calyciﬂorus Brachionus plicatilis12511AF499037AF499040AF499039AF499038Brachionus urceolaris1AF499041Keratella cochlearis var.faluta Keratella cochlearis var.robusta Keratella cochlearis var.tecta Keratella hiemalisKeratella quadrata 111211AF499042AF499043AF499044AF499047AF499045AF499046Synchaeta sp. Synchaeta c.f.pectinata 2312AF499050AF499049AF499048AF499051Table2.GenBank accession numbers for COI DNA sequencesisolated from rotifers.Species Haplotype Accession numberAsplanchna sp.1AF499052Brachionus calyciﬂorusBrachionus plicatilis112345678910111213141516AF499053AF499054AF499065AF499064AF499057AF499063AF499061AF499058AF499060AF499059AF499062AF499068AF499069AF499066AF499067AF499055AF499056Brachionus urceolaris123AF499070AF499072AF499071Keratella cochlearis var.falutaKeratella cochlearis var.robustaKeratella cochlearis var.tectaKeratella hiemalisKeratella quadrata112121231234567AF499073AF499074AF499075AF499076AF499087AF499077AF499085AF499086AF499078AF499081AF499080AF499084AF499079AF499083AF499082Synchaeta sp.Synchaeta c.f.pectinata123123AF499090AF499092AF499091AF499088AF499093AF499089tiﬁed to genus for Synchaeta and to species for other taxa using the keys in Stemberger(1979).Molecular techniques—Total DNA was extracted from single rotifers using proteinase K methods(Schwenk1996), and15-␮l extracts were stored frozen atϪ20ЊC.Two mi-tochondrial(mt)genes with different rates of molecular evo-lution were employed to examine levels of genetic variability within and between selected rotifer families.Cytochrome ox-idase subunit I(COI)was used to investigate variation among conspeciﬁc populations,while16S rDNA(16S)was used to examine deeper phylogenetic relationships(Palumbi 1996).The polymerase chain reaction(PCR)was used to amplify a447base pair(bp)fragment of the16S gene with the primer pair16S-AR and16S-BR(Palumbi1996).Each 50-␮l PCR reaction contained7␮l of DNA template,4.5␮lof10ϫPCR buffer(Roche),2.2␮l of50␮mol LϪ1MgCl2,0.25␮l of each10␮mol LϪ1dNTP(C,G,A,T),1␮l of each10␮mol LϪ1primer,0.4␮l of1:10Taq DNA poly-merase(Qiagen),and32.9␮l of sterile,double-distilled wa-ter.PCR was also employed to amplify a633bp fragment of cytochrome c oxidase subunit I with the LCOI490andHCO2918primers(Folmer et al.1994).Each50-␮l PCR reaction used to amplify the COI fragment consisted of the same ingredients as16S,with the exception of3␮l of DNA template and36.9␮l of water.Procedures for PCR ampli-ﬁcation involved one cycle of1min at94ЊC;40cycles of 1min at94ЊC,1.5min at45ЊC,and1.5min at72ЊC;fol-lowed by one cycle of5min at72ЊC in an MJ Research PCR machine(PTC-100).PCR products were gel puriﬁed (1.6%agarose)using the Qiaex II kit(Qiagen).DNA frag-ments were sequenced with an ABI Prism377automated sequencer(Applied Biosystems),with primers16S-AR and LCO1490respectively,and the Taq FS dye rhodamine se-quencing kit(Perkin-Elmer).All sequences were checked for accidental ampliﬁcation of contamination DNA by searching the Genbank/EMBL database(Altschul et al.1997).Phylogenetic analyses—16S sequences were aligned with Sequence Navigator(ABI Prism,Applied Biosystems,Per-kin Elmer)using the clustal alignment default parameters. Segments of the16S gene were omitted where alignments were ambiguous as a result of gap hypervariability.As a result,387bp were used in the phylogenetic analyses of the 16S sequence data with gaps treated as missing data because of the difﬁculty of modeling insertions and deletions (GenBank accession numbers AF499036to AF499051;Ta-ble1).The COI sequences were aligned with Seqapp1.9a sequence editor(ftp:///molbio/seqapp/) using default parameters,and an unambiguous alignment was produced because of the absence of gaps(GenBank ac-cession numbers AF499052to AF499093;Table2).COI se-quences were obtained from GenBank database for Bra-678Derry et al.chionus plicatilis from Spain(accession numbers AF266853to AF266950;Go´mez et al.2000)and Australia(AF387279to AF387280),as well as for B.ibericus(AF387270toAF387280)and B.rotundiformis(AF387287to AF387293)(Go´mez et al.2002b).These sequences were used to providea more comprehensive understanding of geographic diver-gence within the B.plicatilis species complex.Phylogenetictrees were generally rooted with an outgroup taxon(Asplan-chna sp.)of a species belonging to the same order,but adifferent family than the family under study.For compari-sons of intraspeciﬁc divergence within the B.plicatilis spe-cies complex,phylogenetic trees were rooted with the fresh-water species,B.calyciﬂorus.All characters were treated asunordered and equally weighted because neither transitionsnor transversions appeared to be saturated for16S or COI.Analyses were conducted with PAUP4.02b(Swofford1998)except where otherwise noted.A chi-square goodness-of-ﬁt test was performed on the sequence data for each generegion to determine whether shifts in nucleotide compositionoccurred among taxa.Whereas base frequencies were ho-mogeneous among16S sequences(homogeneity,␹2ϭ15.2, dfϭ45,pϾ0.99),nucleotide composition was variable forCOI(homogeneity,␹2ϭ397.3,dfϭ129,pϽ0.01)when all taxa were included.COI base composition was also het-erogeneous for comparisons within the B.plicatilis speciescomplex when data from GenBank were included(homo-geneity,␹2ϭ232.2,dfϭ171,pϽ0.01).The Kimura two-parameter distance model(Kimura1980)was employed tocorrect for the possibility of multiple superposed substitutionevents in the16S sequences because the assumption of ho-mogeneous base composition was met and there was no ev-idence of transitional saturation(Kumar et al.1993).Thissimple measure was chosen because more complex distancemodels yielded similar topologies for phylogenetic trees,andvariances are lower when fewer parameters are estimated.The Log Det distance transformation(Lake1994)was em-ployed to correct pairwise differences between COI sequenc-es involving all of the taxa from this study and for compar-isons within the B.plicatilis species complex because thismeasure compensates for base heterogeneity.Matrices ofdistance measures with standard errors were determined withMEGA1.02(Kumar et al.1993)for the Kimura two-param-eter model and with PAUP4.02b for Log Det calculations.Mean nucleotide diversity(␲),the average proportion of pairwise nucleotide base differences at a particular sequence position,was calculated for selected interspeciﬁc compari-sons(Hartl2000).Both phenetic(neighbor joining)and cladistic(maximumparsimony)analyses were employed in the phylogeneticstudies.Whereas phenetic techniques are based on pairwisedistances among taxa,cladistic methods infer common an-cestry and operate on phylogenetically informative sites.Aphylogenetically informative site is a character that is bothdifferent from the outgroup(variable)and shared within thetaxonomic group in question at a particular position withina set of aligned sequences.Matrices of distance measureswere used to estimate neighbor-joining(NJ)phenogramswith conﬁdence limits determined with1,000bootstrappseudoreplicates for16S rDNA and COI nucleotide sequenc-es.Maximum parsimony(MP)analyses of phylogenetically informative sites employed heuristic searches with a starting tree obtained by1,000replicates of random stepwise se-quence addition.Optimal trees were found with the tree bi-section–reconnection(TBR)branch swapping algorithm and the MulTrees and steepest descent options invoked in PAUP 4.02b.Groups appearing inՆ70%of the bootstrap replicates were considered well supported(Hillis and Bull1993).Con-ﬁdence was assessed in the cladistic analyses both a priori, by estimation of the g1skewness statistic from100,000ran-dom tree length distributions,and a posteriori,by bootstrap analysis with1,000pseudoreplicates.A monophyletic clade is a taxonomic set of common descendents(e.g.,species) that cluster on a common branch of a phylogenetic tree.Results16S Comparisons among rotifer taxa—Sequence vari-ability:The sequence alignment was387base pairs(bp),of which150bp were variable and113bp were phylogeneti-cally informative using cladistic criteria.Mean base fre-quencies were0.32(A),0.14(C),0.18(G),and0.36(T), and there was no evidence of heterogeneity in nucleotide composition among taxa(homogeneity␹2ϭ15.22,dfϭ45, pϾ0.99).Table3shows the number of16S haplotypes per species and the number of individuals detected with each haplotype.Phylogenetic analyses:NJ analysis indicated that members of the families Brachionidae and Synchaetidae showed an average of23.0%sequence divergence at16S,while mem-bers of the two brachionid genera,Brachionus sp.and Ker-atella sp.,showed a mean divergence of22.1%(Table4). The two freshwater species(B.calyciﬂorus and B.urceolar-is)and the single saltwater species(B.plicatilis)showed 8.0%divergence,while the two freshwater species were 4.1%divergent.Keratella cochlearis showed17.3%se-quence divergence from K.hiemalis and K.quadrata,while K.hiemalis was10.7%divergent from K.quadrata. Maximum parsimony heuristic searches yielded two equally parsimonious trees of length297(consistency index [CI]ϭ0.72,homoplasy index[HI]ϭ0.28,retention index [RI]ϭ0.83).These trees were equivalent with respect to the position of clades,differing only in the branch arrange-ment for haplotypes2and5of B.plicatilis,and this varia-tion was collapsed in the70%majority rule tree(Fig.2). The g1skewness statistic was highly signiﬁcant(g1ϭϪ0.80,g1critϭϪ0.20,pϭ0.01),which indicates strong phyloge-netic signal in the16S data set.Both phenetic and cladistic analyses of the16S sequence data were congruent with re-spect to branch arrangement,and the bootstrap support for these nodes was strong(Ͼ70%).Resolution of the two fam-ilies and three genera were in agreement with prior morpho-logical assignments,and all three genera were monophyletic (Fig.2).COI comparisons among rotifer taxa—Sequence vari-ability:Sequence alignments and amino acid translations were unambiguous,since there were no gaps or nonsense codons among the84COI sequences(Table5).The aligned sequences corresponded to nucleotide position1543to2173679Molecular phylogenetics of rotifersTable 3.Species,number of individuals sequenced,number of haplotypes,locations of sample collection,and number of different lakes from which samples were collected at each location for 16S rotifer sequences.SpeciesNumber of 16S haplo-typesNumber of individuals sequencedLocations(number of different lakes)Brachionus calyciﬂorus Brachionus plicatilis Brachionus urceolaris 131451Gainesville,FloridaWood Buffalo National Park (3)Fort McMurray,Alberta (1)Keratella cochlearis 45Wood Buffalo National Park (2),Fort McMurray,Alberta (1)Keratella hiemalis Keratella quadrata 1113Wood Buffalo National Park (1)Wood Buffalo National Park (1),Fort McMurray,Alberta (1)Synchaeta sp.Synchaeta c.f.pectinata2225Wood Buffalo National Park (1)Wood Buffalo National Park (3)Table 4.Mean 16S divergence ϮSE between phylogenetic clusters of rotifers identiﬁed by NJ.*Clade B.calyciﬂorus B.plicatilis B.urceolaris K.cochlearisK.hiemalisK.quadrataSynchaeta sp.S.c.f.pectinataB.calyciﬂorus ———————B.plicatilis 0.0861Ϯ9.8ϫ10Ϫ40.0053؎1.5؋10Ϫ3—————B.urceolaris 0.04060.0739Ϯ9.7ϫ10Ϫ4—————K.cochlearis 0.2154Ϯ3.0ϫ10Ϫ30.2085Ϯ1.3ϫ10Ϫ40.2082Ϯ1.8ϫ10Ϫ30.0120؎1.5؋10Ϫ3———K.hiemalis 0.21860.2279Ϯ1.2ϫ10Ϫ30.22570.1.624Ϯ1.7ϫ10Ϫ3———K.quadrata 0.21910.2406Ϯ2.1ϫ10Ϫ30.22960.1842Ϯ8.1ϫ10Ϫ40.01067——Synchaeta sp.0.1641Ϯ3.5ϫ10Ϫ30.1673Ϯ2.0ϫ10Ϫ30.1661Ϯ8.4ϫ10Ϫ30.2906Ϯ3.9ϫ10Ϫ30.2975Ϯ2.3ϫ10Ϫ20.3105Ϯ1.6ϫ10Ϫ20.0803S.c.f.pectinata0.16380.1675Ϯ2.0ϫ10Ϫ30.16100.2823Ϯ1.8ϫ10Ϫ30.29740.2928Ϯ2.0ϫ10Ϫ30.0688Ϯ4.0ϫ10Ϫ30.0026*The mean nucleotide sequence divergence within clusters is shown on the diagonal (bold).The mean nucleotide divergence between clusters is shown below the diagonal.The distance estimates were corrected with Kimura’s (1980)two-parameter model.of Drosophila yakuba (Folmer et al.1994).The length of the nucleotide sequence alignment was 630bp,of which 294bp were variable for distance-based analysis and 284were phylogenetically informative using cladistic criteria.Base frequencies among rotifer species were heterogeneous and averaged at 0.21(A),0.20(C),0.18(G),and 0.41(T)(ho-mogeneity,␹2ϭ397.32,df ϭ129,p Ͻ0.001).When trans-lated to amino acids using the Drosophila mtDNA code,54of 210positions were variable and 51were phylogenetically informative according to MP .Phylogenetic analyses:The average nucleotide sequence divergence between members of the families Brachionidae (A,B)and Synchaetidae (C)was 29.9%(Fig.3),while the two brachionid genera differed by 29.1%(Table 6).Fresh-water and saltwater Brachionus species showed a sequence divergence of 24.6%.Pairwise nucleotide sequence diver-gence between selected species of Brachionus ranged from 20to 25%,those of Keratella from 23to 27%,while Syn-chaeta isolates ranged from 1to 20%.The various isolates of Keratella cochlearis clustered ac-cording to the presence (K.cochlearis var.faluta [f-1]and K.cochlearis var.robusta [r-1and r-2])or absence (K.coch-learis var.tecta [t-1and t-2])of posterior spines (Fig.3),with 4.4%mean COI nucleotide sequence divergence (Table 6).The divergence of spined and unspined K.cochlearis types was also apparent at the amino acid level,as the two groups showed 0.9%divergence (Table 6).By comparison,different morphs of K.hiemalis (one-and two-spined)showed only 0.21%sequence divergence and no amino acid divergence.K.quadrata showed low intraspeciﬁc nucleotide divergence,ranging from 0.1to 0.7%,and little amino acid divergence (0to 0.5%).K.quadrata 7was from the most geographically distant location (330km away)but showed only slightly greater mean nucleotide sequence divergence from the other haplotypes (0.5%,Fig.3).The average nu-cleotide diversity (␲)of seven haplotypes identiﬁed among 27K.quadrata sequences was 0.09,and the mean number of nonsynonymous changes between these haplotypes was just 0.3.680Derry etal.Fig.2.Seventy percent majority rule consensus of two equallyparsimonious trees for1516S rotifer sequences rooted with As-planchna sp.Bootstrap support(1,000pseudoreplicates)for majorclades is indicated above the nodes.Numbers at the terminalbranches give the haplotype and correspond with the numberingassigned to equivalent COI taxa.Numbers in brackets after the ter-minal branches indicate the number of sequences obtained for eachhaplotype.Capitalized letter clades indicate monophyletic clustersrepresenting different genera:AϭBrachionus sp.,BϭKeratellasp.,and CϭSynchaeta sp.Table5.Species,number of individuals sequenced,number of haplotypes,locations of samplecollection,and number of different lakes from which samples were collected at each location forCOI rotifer sequences.Species Number ofCOI haplo-typesNumber ofindividualssequencedLocations(number of different lakes)Brachionus calyciﬂorus Brachionus plicatilis Brachionus urceolaris11642227Gainesville,FloridaWood Buffalo National Park(4)Fort McMurray,Alberta(1)Keratella cochlearis59Wood Buffalo National Park(3),Fort McMurray,Alberta(1)Keratella hiemalis Keratella quadrata 37726Wood Buffalo National Park(2)Wood Buffalo National Park(4),Fort McMurray,Alberta(1)Synchaeta sp. Synchaeta c.f.pectinata 3357Wood Buffalo National Park(1)Wood Buffalo National Park(3)Sequence divergence at COI between haplotypes of Bra-chionus plicatilis ranged from0.1to1.4%,with haplotypes15and16demonstrating the greatest mean divergence(0.9%)from the other isolates(Table6).The average nucle-otide diversity(␲)of the16haplotypes of B.plicatilis fromWood Buffalo National Park,Canada,was0.74,and themean number of amino acid substitutions between haplo-types was0.8.Four amino acid variants of B.plicatilis weredetected(Fig.3:clades a,b,and c),showing0.5to0.9%amino acid sequence divergence(Table6).These variantsclustered according to the lakes from which they were col-lected.Clade a was obtained from saline Hay Camp lake(Fig.1),while clade c was collected from a subsaline lake(Forgotten Pass),which was only10km away(Fig.1).Clade b was collected from two interconnected saline lakes(Grosbeak and Salt Pan)that were45km away from theother two lakes(Fig.1).Haplotypes15and16(clade c)showed a mean nucleotide sequence divergence of0.5%from clade a and0.9%from clade b.COI amino acid NJ and MP trees were congruent with16S and COI nucleotide trees for recent evolutionary events(genus and species)but did not resolve some of the deepertaxonomic relationships.One thousand random additionsearch replicates yielded a single COI amino acid MP treeof length92(CIϭ0.77,HIϭ0.23,RIϭ0.96).K.hiemaliswas more closely allied with K.quadrata(2.3%)than withK.cochlearis(6.5%)according to the amino acid sequencedata(Table4),a result congruent with the16S MP tree.However,the COI amino acid phenetic and cladistic analysesfailed to resolve the families Brachionidae and Synchaetidae.Phenetic and cladistic COI amino acid analyses were con-gruent with16S data for all other deep internal nodes,andbootstrap values were high for recent evolutionary events.COI comparisons within Brachionus plicatilis—Sequencevariability:Brachionus plicatilis COI haplotypes detected inthis study(Table5)were aligned with B.plicatilis haplo-types from Spain(Go´mez et al.2000)and Australia,as wellas with B.ibericus and B.rotundiformis(Go´mez et al.2002b).The length of the sequence alignment(nucleotideposition1543to2141in Drosophila yakuba)was603bp,of which227bp were variable and206bp were phyloge-681Molecular phylogenetics ofrotifers Fig.3.Neighbor-joining phenogram of 42COI rotifer nucleotide sequences based on Log Det distances (Lake 1994)and rooting with Asplanchna sp.Bootstrap support (1,000pseudoreplicates)for major clades is indicated above the nodes.Numbers at the terminal branches give the nucleotide haplotype and correspond with the numbering assigned to equivalent 16S taxa.Numbers in brackets after the terminal branches indicate the number of sequences obtained for each haplotype.Capitalized letter clades indicate clusters representing different genera:A ϭBrachionus,B ϭKeratella,and C ϭSynchaeta.Lowercase letter clades indicate Brachionus plicatilis haplotypes that clustered according to lakes from which the animals were collected:clade a ϭHay Camp Lake,clade b ϭGrosbeak/Salt Pan lakes,and clade c ϭForgotten Pass Lake.Spined (S)and unspined (NS)subspecies of Keratella cochlearis as well as one-(1S)and two-(2S)spined morphs of K.hiemalis are indicated.netically informative using cladistic criteria.The base com-position of these sequences was heterogeneous (␹2ϭ232.2,df ϭ171,p Ͻ0.01)with 0.20(A),0.21(C),0.20(G),and 0.39(T).Nucleotide sequences translated to 201amino acids according to Drosophila mtDNA code,of which 17amino acid positions were variable,and only seven characters were phylogenetically informative for cladistic analysis.Phylogenetic analyses:The NJ and MP phylogenetic trees for the COI nucleotide sequence data revealed that haplo-types collected from Canadian salt lakes clustered with B.plicatilis sequences from Spain and Australia rather than with B.ibericus or B.rotundiformis within the B.plicatilis species complex (Fig.4).While Canadian and Spanish pop-ulations of B.plicatilis had an average nucleotide sequence divergence of 4.1%,Canadian and Australian varieties were divergent by 5.7%.Average nucleotide sequence divergence between the two major Spanish lineages was 2.6%,which represents divergence among two different glacial refugia (Go ´mez et al.2000).Nucleotide sequence divergences with-682Derry et al.Table 6.Mean COI divergence Ϯstandard errors among rotifer species identiﬁed by NJ.*Clade B.calyciﬂorus B.plicatilisB.urceolaris K.cochlearis K.hiemalis K.quadrata Synchaeta sp.S.c.f.pectinata B.calyciﬂorus —0.0379Ϯ4.7ϫ10Ϫ40.05090.11110.11110.0979Ϯ6.7ϫ10Ϫ40.1358Ϯ3.1ϫ10Ϫ30.1173Ϯ4.1ϫ10Ϫ3P.plicatilis 0.2339Ϯ4.4ϫ10Ϫ40.0060؎2.2؋10Ϫ40.0550Ϯ2.3ϫ10Ϫ40.1198Ϯ1.8ϫ10Ϫ40.1213Ϯ2.6ϫ10Ϫ40.1067Ϯ2.3ϫ10Ϫ40.1409Ϯ6.3ϫ10Ϫ40.1315Ϯ3.6ϫ10Ϫ4B.urceolaris 0.2017Ϯ1.0ϫ10Ϫ30.2511Ϯ3.3ϫ10Ϫ4—0.10650.11570.0965Ϯ3.6ϫ10Ϫ40.1450Ϯ1.3ϫ10Ϫ30.1296Ϯ2.0ϫ10Ϫ3K.cochlearis 0.2710Ϯ5.3ϫ10Ϫ30.3146Ϯ7.5ϫ10Ϫ40.2921Ϯ6.8ϫ10Ϫ40.0277؎6.8؋10Ϫ30.08330.0654Ϯ2.8ϫ10Ϫ40.1250Ϯ1.8ϫ10Ϫ30.1173Ϯ1.6ϫ10Ϫ3K.hiemalis 0.2582Ϯ1.5ϫ10Ϫ30.3059Ϯ4.9ϫ10Ϫ40.2785Ϯ7.3ϫ10Ϫ40.2610Ϯ8.4ϫ10Ϫ40.0021؎5.1؋10Ϫ40.0227Ϯ3.7ϫ10Ϫ40.1482Ϯ2.3ϫ10Ϫ30.1358Ϯ2.8ϫ10Ϫ3K.quadrata 0.2724Ϯ1.1ϫ10Ϫ30.2738Ϯ2.9ϫ10Ϫ40.2893Ϯ6.7ϫ10Ϫ40.2676Ϯ5.3ϫ10Ϫ40.2315Ϯ6.1ϫ10Ϫ40.0039؎4.3؋10Ϫ40.1303Ϯ1.5ϫ10Ϫ30.1180Ϯ1.8ϫ10Ϫ3Synchaeta sp.0.2710Ϯ1.6ϫ10Ϫ20.3208Ϯ8.6ϫ10Ϫ40.2633Ϯ1.0ϫ10Ϫ20.3071Ϯ5.5ϫ10Ϫ30.2984Ϯ4.6ϫ10Ϫ30.3197Ϯ6.4ϫ10Ϫ30.1409؎1.7؋10Ϫ20.0463Ϯ2.9ϫ10Ϫ3S.c.f.pectinata0.2269Ϯ2.8ϫ10Ϫ30.3272Ϯ8.5ϫ10Ϫ70.2440Ϯ1.2ϫ10Ϫ30.2648Ϯ2.3ϫ10Ϫ20.2836Ϯ2.7ϫ10Ϫ30.3063Ϯ2.0ϫ10Ϫ30.1705Ϯ5.5ϫ10Ϫ30.0343؎2.0؋10Ϫ2*The mean uncorrected (p distance)amino acid sequence divergence between clusters is shown above the diagonal.The mean nucleotide sequence divergence within clusters is shown on the diagonal (bold),while the mean nucleotide sequence divergence between clusters is shown below the diagonal.The nucleotide distance estimates were corrected with the Log-Det transformation (Lake 1994).in these two Spanish lineages,however,were similar to that observed among B.plicatilis haplotypes (0.1to 1.4%)from Canada.Canadian B.plicatilis haplotypes had average nu-cleotide divergences of 25.6%and 22.8%,respectively,from B.ibericus and B.rotundiformis.The phylogenetic signal was strong for the nucleotide data (g 1ϭϪ0.56,g 1crit ϽϪ0.12,p ϭ0.01).Maximum parsimony heuristic searches yielded 75parsimonious trees of length 387(CI ϭ0.74,HI ϭ0.26,RI ϭ0.77).These MP trees varied in haplotype branch arrangement within Spanish and Canadian clades of B.plicatilis,but all trees resolved these two groups of pop-ulations.Additionally,resolution among B.plicatilis,B.ib-ericus,and B.rotundiformis was conserved among MP trees.DiscussionBetween-gene comparisons —Past morphological studies have placed the genera Keratella and Brachionus in the fam-ily Brachionidae,while Synchaeta sp.are in the family Syn-chaetidae (Pennak 1989).The tree topologies derived through NJ and MP analyses of 16S and COI sequence data were largely congruent with these conclusions.However,COI nucleotide data varied from 16S in the placement of Keratella hiemalis and in the positioning of freshwater Bra-chionus taxa in the NJ tree.As expected,the COI amino acid trees resolved these uncertain branch positions accord-ing to 16S,but were poor at resolving deep evolutionary relationships (e.g.,families).The similarity in levels of nucleotide sequence divergence between the Brachionidae and Synchaetidae (Tables 4and 6)likely reﬂects homoplasy (Page and Holmes 1998).This was particularly likely for COI,which evolves much faster than 16S (1.4to 2.3%versus 0.4to 0.9%per million years)(e.g.,Knowlton and Weight 1998;Schubart et al.1998).COI bootstrap values could not be resolved for deep nodes be-tween families and genera (Fig.3).It is likely that 18SrRNA,a more slowly evolving nuclear gene (0.1%per mil-lion years)(Spears et al.1992),would provide better reso-lution of familial boundaries than 16S rRNA.The rapidly evolving COI gene was,however,very appropriate for res-olution of recent evolutionary relationships at the population level.Phenotypic plasticity among keratella species —Because environmental and genetic factors cause morphological var-iability in rotifers,the delineation of species boundaries is often difﬁcult (Pennak 1989).Keratella cochlearis has long been recognized as a complex of morphs that vary in their degree of posterior spine development (Dumont 1983).Long-spined individuals dominate oligotrophic and cold habitats,while morphs with shorter or no spines are abun-dant in eutrophic,warm environments (e.g.,Hillbricht-Il-kowska 1983).Although spine development in K.cochlearis is induced by predators (Stemberger and Gilbert 1984;Con-de-Porcuna et al.1993),the biometric analysis of Hofmann (1983)did not detect any transitional forms between spined and unspined morphs,which suggests genetic divergence rather than phenotypic plasticity.Our COI sequence data support this conclusion,indicating that the K.cochlearis complex is comprised of two clades:a spined clade con-sisting of two ‘‘subspecies’’(K.cochlearis var.robusta and K.cochlearis var.faluta )and an unspined clade comprised of K.cochlearis var.tecta.The marked genetic divergence (4.4%nucleotide sequence divergence)between the spined and unspined morphs suggests that K.cochlearis is,in fact,a species complex.The taxonomy of K.hiemalis has been much debated be-cause some European populations have low morphological variability (Ruttner-Kolisko 1993),while the taxon shows much phenotypic variation in North America (Stemberger in the addendum for Ruttner-Kolisko 1993).Our results suggest that this variation reﬂects phenotypic plasticity,since we did。