Arrange the jumbled words to form a correct sentence.

The moment, I, saw Elena, I realized, something, was wrong.

Mike, didn't see, the step;, he tripped, on it, and fell.

UNITS 1-8/vocabulary (1)/C

Figure 18-11 represents the amount of energy stored as organic material in each trophic level in an ecosystem. The pyramid shape of the diagram indicates the low percentage of energy transfer from one level to the next. On average, 10 percent of the total energy consumed in one trophic level is incor- porated into the organisms in the next. Why is the percentage of energy transfer so low? One reason is that some of the organisms in a trophic level escape being eaten. They eventually die and become food for decomposers, but the energy contained in their bodies does not pass to a higher trophic level. Even when an organism is eaten, some of the molecules in its body will be in a form that the consumer cannot break down and use. For example, a cougar cannot extract energy from the antlers, hooves, and hair of a deer. Also, the energy used by prey for cellu- lar respiration cannot be used by predators to synthesize new bio- mass. Finally, no transformation or transfer of energy is 100 percent efficient. Every time energy is transformed, such as during the reactions of metabolism, some energy is lost as heat. Limitations of Trophic Levels The low rate of energy transfer between trophic levels explains why ecosystems rarely contain more than a few trophic levels. Because only about 10 percent of the energy available at one trophic level is transferred to the next trophic level, there is not enough energy in the top trophic level to support more levels. Organisms at the lowest trophic level are usually much more abundant than organisms at the highest level. In Africa, for exam- ple, you will see about 1,000 zebras, gazelles, and other herbivores for every lion or leopard you see, and there are far more grasses and shrubs than there are herbivores. Higher trophic levels con- tain less energy, so, they can support fewer individuals.A population is a group of organisms that belong to the same species and live in a particular place at the same time. All of the bass living in a pond during a certain period of time make up a pop- ulation because they are isolated in the pond and do not interact with bass living in other ponds. The boundaries of a population may be imposed by a feature of the environment, such as a lake shore, or they can be arbitrarily chosen to simplify a study of the population. The humans shown in Figure 19-1 are part of the pop- ulation of a city. The properties of populations differ from those of individuals. An individual may be born, it may reproduce, or it may die. A population study focuses on a population as a whole—how many individuals are born, how many die, and so on. Population Size A population’s size is the number of individuals that the population contains. Size is a fundamental and important population property but can be difficult to measure directly. If a population is small and composed of immobile organisms, such as plants, its size can be determined simply by counting individuals. Often, though, individ- uals are too abundant, too widespread, or too mobile to be counted easily, and scientists must estimate the number of individuals in the population. Suppose that a scientist wants to know how many oak trees live in a 10 km2 patch of forest. Instead of searching the entire patch of forest and counting all the oak trees, the scientist could count the trees in a smaller section of the forest, such as a 1 km2 area. The scientist could then use this value to estimate the population of the larger area. SECTION 1 OBJECTIVES ● Describe the main properties that scientists measure when they study populations. ● Compare the three general patterns of population dispersion. ● Identify the measurements used to describe changing populations. ● Compare the three general types of survivorship curves. VOCABULARY population population density dispersion birth rate death rate life expectancy age structure survivorship curve FIGURE 19-1 A population can be widely distributed, as Earth’s human population is, or confined to a small area, as species of fish in a lake are. Copyright © by Holt, Rinehart and Winston. All rights reserved. 382 CHAPTER 19 If the small patch contains 25 oaks, an area 10 times larger would likely contain 10 times as many oak trees. A similar kind of sampling technique might be used to estimate the size of the pop- ulation shown in Figure 19-2. To use this kind of estimate, the sci- entist must assume that the distribution of individuals in the entire population is the same as that in the sampled group. Estimates of population size are based on many such assumptions, so all esti- mates have the potential for error. Population Density Population density measures how crowded a population is. This measurement is always expressed as the number of individuals per unit of area or volume. For example, the population density of humans in the United States is about 30 people per square kilome- ter. Table 19-1 shows the population sizes and densities of humans in several countries in 2003. These estimates are calculated for the total land area. Some areas of a country may be sparsely popu- lated, while other areas are very densely populated. Dispersion A third population property is dispersion (di-SPUHR-zhuhn). Dispersion is the spatial distribution of individuals within the popu- lation. In a clumped distribution, individuals are clustered together. In a uniform distribution, individuals are separated by a fairly con- sistent distance. In a random distribution, each individual’s location is independent of the locations of other individuals in the popula- tion. Figure 19-3 illustrates the three possible patterns of dispersion. Clumped distributions often occur when resources such as food or living space are clumped. Clumped distributions may also occur because of a species’ social behavior, such as when animals gather into herds or flocks. Uniform distributions may result from social behavior in which individuals within the same habitat stay as far away from each other as possible. For example, a bird may locate its nest so as to maximize the distance from the nests of other birds. These migrating wildebeests in East Africa are too numerous and mobile to be counted. Scientists must use sampling methods at several locations to monitor changes in the population size of the animals. FIGURE 19-2 TABLE 19-1 Population Size and Density of Some Countries Population size Population density Country (in millions) (in individuals/km2) China 1,289 135 India 1,069 325 United States 292 30 Russia 146 8 Japan 128 337 Mexico 105 54 Kenya 32 54 Australia 20 3 dispersion from the Latin dis-, meaning “out,” and spargere, meaning “to scatter” Word Roots and Origins Copyright © by Holt, Rinehart and Winston. All rights reserved. POPULATIONS 383 The social interactions of birds called gannets, which are shown in Figure 19-3b, result in a uniform distribution. Each gannet chooses a small nesting area on the coast and defends it from other gannets. In this way, each gannet tries to maximize its distance from all of its neighbors, which causes a uniform distribution of individuals. Few populations are truly randomly dispersed. Rather, they show degrees of clumping or uniformity. The dispersion pattern of a population sometimes depends on the scale at which the popu- lation is observed. The gannets shown in Figure 19-3b are uni- formly distributed on a scale of a few meters. However, if the entire island on which the gannets live is observed, the distribution appears clumped because the birds live only near the shore. POPULATION DYNAMICS All populations are dynamic—they change in size and composition over time. To understand these changes, scientists must know more than the population’s size, density, and dispersion. One important measure is the birth rate, the number of births occur- ring in a period of time. In the United States, for example, there are about 4 million births per year. A second important measure is the death rate, or mortality rate, which is the number of deaths in a

All living things are made up of one or more cells. A cell is the smallest unit that can carry on all of the processes of life. Beginning in the 17th century, curious naturalists were able to use microscopes to study objects too small to be seen with the unaided eye. Their studies led them to propose the cellular basis of life. Hooke In 1665, English scientist Robert Hooke studied nature by using an early light microscope, such as the one in Figure 4-1a. A light micro- scope is an instrument that uses optical lenses to magnify objects by bending light rays. Hooke looked at a thin slice of cork from the bark of a cork oak tree. “I could exceedingly plainly perceive it to be all perforated and porous,” Hooke wrote. He described “a great many little boxes” that reminded him of the cubicles or “cells” where monks live. When Hooke focused his microscope on the cells of tree stems, roots, and ferns, he found that each had similar little boxes. The drawings that Hooke made of the cells he saw are shown in Figure 4-1b. The “little boxes” that Hooke observed were the remains of dead plant cells, such as the cork cells shown in Figure 4-1c. SECTION 1 OBJECTIVES ● Name the scientists who first observed living and nonliving cells. ● Summarize the research that led to the development of the cell theory. ● State the three principles of the cell theory. ● Explain why the cell is considered to be the basic unit of life. VOCABULARY cell cell theory Robert Hooke used an early microscope (a) to see cells in thin slices of cork. His drawings of what he saw (b) indicate that he had clearly observed the remains of cork cells (300) (c). FIGURE 4-1 (a) (b) (c) Copyright © by Holt, Rinehart and Winston. All rights reserved. 70 CHAPTER 4 Leeuwenhoek The first person to observe living cells was a Dutch trader named Anton van Leeuwenhoek. Leeuwenhoek made microscopes that were simple and tiny, but he ground lenses so precisely that the magnification was 10 times that of Hooke’s instruments. In 1673, Leeuwenhoek, shown in Figure 4-2a, was able to observe a previ- ously unseen world of microorganisms. He observed cells with green stripes from an alga of the genus Spirogyra, as shown in Figure 4-2b, and bell-shaped cells on stalks of a protist of the genus Vorticella, as shown in Figure 4-2c. Leeuwenhoek called these organisms animalcules. We now call them protists. THE CELL THEORY Although Hooke and Leeuwenhoek were the first to report observ- ing cells, the importance of this observation was not realized until about 150 years later. At this time, biologists began to organize information about cells into a unified understanding. In 1838, the German botanist Matthias Schleiden concluded that all plants were composed of cells. The next year, the German zoologist Theodor Schwann concluded the same thing for animals. And finally, in his study of human diseases, the German physician Rudolf Virchow (1821–1902) noted that all cells come from other cells. These three observations were combined to form a basic theory about the cel- lular nature of life. The cell theory has three essential parts, which are summarized in Table 4-1. Anton van Leeuwenhoek (1632–1723) is shown here with one of his hand-held lenses (a). Leeuwenhoek observed an alga of the genus Spirogyra (b) and a protist of the genus Vorticella (c). FIGURE 4-2 TABLE 4-1 The Cell Theory All living organisms are composed of one or more cells. Cells are the basic units of structure and function in an organism. Cells come only from the reproduction of existing cells. (a) (b) (c) www.scilinks.org Topic: Cell Theory Keyword: HM60241 mb06se_csfs01.qxd 5/18/07 10:54 AM Page 70

Insider B2: Unit 2 (thematic vocabulary: 1-18)

Caractéristiques générales de la synthèse de documents La synthèse est un exercice assez simple, car très technique. Pour réussir, il faut néanmoins faire preuve de rigueur car elle est très codifiée. Les pièges de la synthèse La plupart des étudiants ignorent la technique de synthèse telle qu’elle est attendue en BTS. Aussi plusieurs pièges sont à éviter. La synthèse n’est pas une dissertation personnelle Premier écueil : si l’on se souvint de la consigne vue plus avant, le travail demandé doit être objectif. Aucun point de vue personnel ou même appréciation subjectif sur les documents ne doit apparaître dans la rédaction. On recommande d’ailleurs aux étudiants de ne pas utiliser le pronom « je » dans leur travail de façon à éviter tout malentendu. Le candidat doit donc rapporter les idées des auteurs de façon neutre, sans jugement de valeur. La synthèse n’est pas un résumé des documents La plus grande erreur commise en première année de BTS consiste à résumer les documents, les uns après les autres. Un petit détour par l’étymologie nous permettra de mieux comprendre le travail attendu. Le terme « synthèse » vient du grec sunthesis qui signifie « mise en commun ». Il s’agit donc de rassembler les informations collectées dans les différents documents en un ensemble organisé, donc cohérent. Les idées doivent être confrontées en établissant des liens entre les documents. La synthèse n’est pas un montage de citations Le Bac de français est derrière vous. Oubliez (en partie) cette épreuve. Ici, pas de citations, de numéros de lignes pour appuyer votre rédaction. Votre travail consiste à reformuler de façon synthétique le contenu et les enjeux des documents. La nature du travail demandé Une consigne codifiée pour rédiger votre synthèse Trois adjectifs dans cette consigne. Tout d’abord, la synthèse doit être concise, c’est-à-dire courte et dense. Quatre pages maximum sont généralement attendues à l’épreuve. Nous l’avons déjà évoqué plus haut, la synthèse est un exercice absolument objectif. Aucune idée extérieure aux documents ni commentaire personnel ne doivent figurer dans la rédaction. Enfin, la synthèse est un travail ordonné. Un plan soutient donc la rédaction, on attend ainsi : • une introduction; • un développement; • une conclusion. La démarche à adopter pour votre synthèse La préparation de la synthèse se décompose en deux temps : • Un premier temps consacré à la lecture active de chaque document. Les idées importantes sont relevées, les arguments sont listés, le raisonnement de l’auteur est analysé. • Un second temps consacré à la mise en relation des différents documents de façon à établir des liens entre eux : il s’agit en fait de recomposer un débat entre les auteurs. Sont-ils d’accord ? S’opposent-ils ? Si oui sur quels point ? … La synthèse : un acte de communication On veut donc vérifier que vous savez « lire » : c’est-à-dire que vous êtes capable de comprendre ce qui est écrit dans les documents et de reformuler selon des contraintes de longueur de texte. L’étymologie du verbe « lire » nous le confirme : legere, en latin, signifique « choisir » La méthodologie de synthèse en 10 points Voici un récapitulatif des 10 maladresses principales à éviter et des 10 règles à adopter Les interdits de la synthèse 1. Faire des citations des auteurs des documents pour soutenir les idées avancées. 2. Donner son avis, émettre des remarques subjectives : ex : l’auteur oublie malheureusement que… 3. Faire des références à des documents hors corpus, faire allusion à une autre œuvre de l’auteur. 4. Rédiger un « catalogue » des idées sans lien logique entre elles. Rédiger au fil de son inspiration. 5. Rédiger une synthèse longue et détaillée. 6. Laisser de côté un document, parce que l’on ne l’a pas compris ou qu’il nous semble inintéressant… 7. Utiliser le pronom « je ». 8. Faire un plan apparent (A, B…) avec des titres. 9. Juxtaposer des résumés des documents. 10. Faire référence aux documents par le numéro attribué dans le dossier. Ce qu’il faut faire 1. Reformuler les idées. 2. Rester neutre, objectif. 3. Ne traiter que les documents proposés. 4. Traiter les idées selon un plan précis. 5. Quatre pages maximum 6. Traiter tous les documents, même de façon inégale, certains documents sont plus « riches » en idées que d’autres. 7. Préférer le « on » ou le « nous ». 8. Rédiger sans titres avec des phrases de transition. 9. Confronter les idées communes aux documents. 10. Faire référence aux documents par le nom de l’auteur et l’initiale du prénom. Si ces 10 règles sont respectées, une importante partie de la méthode est acquise ! L'évaluation du travail de synthèse On se rappelle que cette épreuve est notée sur 40 points. En règle générale, les correcteurs adoptent le barème suivant qui vise à valider 4 grandes compétences, chacune notée sur 40 points. Comprendre les documents Ces 10 premiers points valident vos compétences de lecture : Les idées essentielles ont-elles été bien relevées ? Tous les documents ont-ils été bien compris ? L’unité thématique des documents doit apparaître ans le traitement des informations collectées. Confronter Le correcteur vérifiera notamment que tous les documents ont bien été exploités, qu’aucune « impasse » n’a été faite. Il sanctionnera, le cas échéant, l’ajout d’idées extérieures. Certains étudiants pensent que l’introduction d’idées extérieures vient enrichir leur travail et montre leur connaissance du sujet. Il faudra attendre l’épreuve d’écriture personnelle pour le faire. Ici, rappelons-le, seuls les documents proposés à l’étude figurent dans la synthèse. La confrontation des idées sera également évaluée : Le candidat a-t-il établi des liens entre les idées des auteurs ? Chaque partie de la rédaction repose-t-elle sur plusieurs documents ? Structurer Quelle que soit la logique suivie, la synthèse suit un plan. Introduction et conclusion doivent apparaître clairement. La rédaction suit une ligne directrice et un parcours. Les documents sont référencés, l’ensemble est organisé. Utilisez des connecteurs logiques pour lier les parties entre elles. Ils faciliteront grandement la lecture et la progression de vos idées sera plus claire. Rédiger & reformuler Une expression écrire claire est attendue. Elle respecte les normes et usages de la langue écrite courante. La richesse du vocabulaire sera valorisée. Le tout est rédigé : pas de tirets, de titres ou de tissage de citations. Les propos des auteurs sont reformulés, on sanctionnera ici toute formulation d’appréciations personnelles.

UNITS 1-8/vocabulary (1)/B

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