10 Percent Intervention Day

1.1945-1949: The immediate years after the Second World War ● At the end of 1945, Mao Zedong had come to see the USA as the greatest threat to his aspirations. a. He understood that East Asians were looking to the USA as the true liberator from Japanese imperialism. b. The USA’s support for the Kuomintang(KMT) and the restoration of U.S. authority in formerly Japanese Manchuria clashed with the CCP’s plans to use the region for its own needs in the impending civil war between the CCP and the GMD. ■ To compound matters, while the KMT was recognised internationally as the official government in China, Mao and the CCP saw the party as a puppet of U.S. imperialism. ● While Mao saw the USA as the greater threat to the CCP’s plans, Soviet actions also frustrated him. a. The USSR provided minimal and incoherent support for the Chinese Communists in Yan’an and Manchuria. b. Stalin also attempted to extract territorial and economic concessions from the Guomindang government in the Friendship and Alliance Treaty China signed in August 1945 under American and Soviet pressure in exchange for Soviet entry into the Second World War against Japan. ● The emerging superpower conflict over Europe and over American intervention in the impending civil war in China led to Mao’s ideological perception of the 8838/01 H1 History Paper 1 Theme II: The Cold War and East Asia (1945-1991) \ Page | 8 USA as an aggressive imperialist power that was hostile towards other countries, especially the USSR and China. ● In 1946, Mao promoted the theory of the intermediate zone, which envisioned a global united front against American imperialism. a. Mao saw the emerging superpower conflict as an American-Soviet contest for the intermediate zones, the capitalist, colonial and semi- colonial countries of West Europe, Africa, and Asia. b. Mao believed that the USSR was the defender of world peace. c. The intermediate zone, which included China, would not be part of the socialist camp. d. Despite the tremendous potential that U.S. aid held for China’s reconstruction, Mao’s ideological worldview and the impending civil war against the Guomindang prevented him from seeking normalised relations with the USA. In 1949, Mao decided to lean towards the side of the USSR despite two decades of unreliable support from them. e. Mao saw the anti-bourgeois campaigns in East Europe as evidence that China should isolate capitalist-bourgeois forces within it.2 f. Stalin had expelled Yugoslavia from the socialist camp as its leader, Tito was seen to have directly challenged Stalin’s authority. ■ Mao thus saw it as imperative to stress close unity to the USSR lest he was seen as a second Josip Broz Tito. At the same time, Mao sought a loose partnership with the USSR because Mao believed that China should preserve a high measure of self- reliance and zili gengsheng (自力更生) (regeneration through one’s own efforts). ● When the People’s Republic of China was formed on 1 October, 1949, relations between China’s and the USSR’s communists had improved substantially. a. However, the Chinese Communist Party (CCP) was also aware that the USSR never treated Chinese interests as a priority. What the CCP failed to fully understand was that Stalin ruled East Europe much like it was his empire and how this would have implications for China. b. In Mao’s first visit to the USSR in December 1949, Stalin was non- committal regarding the interests raised by the Chinese, and treated Mao as an underling as he feared that closer relations with the PRC would cause the USSR to lose privileges gained from the KMT. _________________________ 2 What Mao did not realise at that point was that the anti-bourgeois campaigns in East European countries were part of Stalin’s intentional design to consolidate the power of communists in them. 8838/01 H1 History Paper 1 Theme II: The Cold War and East Asia (1945-1991) \ Page | 9 A note on Sino-American relations 2. Early 1950: The USA’s hands-off policy towards Taiwan begins to change ● By early 1950, the Truman administration had written off Taiwan and believed it was only a matter of time before the island fell to the PLA. ● Two events in early 1950 changed the USA’s position on East Asia. ○ The formation of the USSR-PRC alliance in February 1950 ○ The North Korean invasion of South Korea in June 1950 3. 1950: The Sino-Soviet Friendship, Alliance and Mutual Assistance Treaty ● Signed on 14 February, 1950. 3.1Implications for Sino-Soviet relations ● Stalin saw it as a means to get concessions that he had failed to get from the Kuomintang (KMT) government in 1945. ● For Mao and the newly founded People’s Republic of China (PRC), the alliance would provide security against U.S. imperialism and allow the PRC to get economic aid for reconstruction from the USSR. ● The Chinese realised soon after the 1950 treaty had been signed that the Soviet Union was intent on exploiting the agreement in its own favour. 8838/01 H1 History Paper 1 Theme II: The Cold War and East Asia (1945-1991) \ Page | 10 ● The Sino-Soviet alliance was officially directed against Japanese militarism and its allies, especially the USA. ● The Sino-Soviet alliance comprised three elements: party, military and economic relations. ○ Party: The Chinese Communist Party (CCP) was included in the customs of communist party internationalism, such as regular exchange of party delegations to congresses of the fraternal parties in Stalin’s socialist camp. ■ This move was meant to bring the PRC’s ideological beliefs about communism into greater alignment with the USSR’s. ○ Military: The alliance was supposed to provide the newly formed and weak PRC with a strategic deterrent and military aid against the USA on three fronts: Guomindang-held Taiwan, divided Korea, and Vietnam where France attempted to reestablish its colonial control. ■ Convinced that the USA would aggressively seek ways to undermine the CCP-led PRC through Taiwan, Korea and Vietnam, Mao sought an active defence. ● While in Moscow, Mao unsuccessfully asked Stalin to provide military assistance for the liberation of Taiwan. ● At the beginning of 1950, the PRC delivered large-scale military aid to Hanoi. The PRC was the first country to grant the communist-led Democratic Republic of Vietnam diplomatic recognition on 18 January 1950; Mao persuaded Stalin to do so on 30 January 1950. ● The PRC committed itself to North Korea, where Mao saw the commitment to North Korea both as a defence against U.S. imperialism and as support for a fellow communist country. ○ Economic: During Mao’s first stay in Moscow, Stalin had personally promised the delivery of fifty projects for primary industrialisation. ■ The agreement also led to a series of supplementary ones, such as a US$ 300 million loan that the PRC would repay with a mixture of strategic materials, rubber, agricultural products, goods for daily use and hard currency. ■ Significantly, Stalin used Soviet military and economic aid to extract concessions similar to those he failed to get from the Guomindang government in 1945. ■ The USSR and PRC would disagree on the pace and extent of the PRC’s planned development. ● In the last five weeks of Stalin’s life in early 1953, he attempted to pressure the PRC to reduce the planned 8838/01 H1 History Paper 1 Theme II: The Cold War and East Asia (1945-1991) \ Page | 11 development speed to a mere annual growth of 13-14 percent, and to plan individual projects in detail beforehand. These moves would potentially result in the PRC’s economy growing at a slower rate than initially projected. ● However, after Stalin’s death on 5 March 1953, the PRC’s Zhou Enlai decided to use his visit of condolence to the USSR to press forward negotiations. ○ When talks resumed in 1 April 1953, Beijing pressed for 150 Soviet industrial projects, but Moscow reduced them to 91 on the basis of insufficient data provided by the Chinese. ■ The economic disarray after China’s civil war and the economic pressures that came with the Korean War influenced recovery and reconstruction in the early years of the PRC. ● Despite the PRC being unable to tap into Soviet economic assistance immediately, mutual trade between China and the USSR nevertheless increased 6.5 times from 1950 to 1956. ● Together with the 50 projects promised by Stalin in 1950, the final version of the First FYP for the PRC included 141 Soviet and 68 East European projects in a total of 649 planned. Three thousand Soviet advisers sent to China in subsequent years were directly linked to the First FYP. ● By 1955, over 60 percent of China’s goods exchange was with the USSR. ● Soviet economic assistance to China added up to the largest foreign development venture in the socialist camp ever. ○ The total number of planned projects amounted to between 300 and 360 projects. ○ However, the number of total finished projects ranged between 134 and 150. ● Transfers of knowledge and expertise were important to China’s economic development. ○ A study on Soviet experts counts 1,445 political advisers and 9,313 technical specialists sent to China until their sudden withdrawal in mid-1960. ■ For political reasons, the gradual withdrawal of advisers began after late 1956.

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

A solution is composed of a solute dissolved in a solvent. In the sugar water described in Figure 5-1, the solute was sugar and the solvent was water, and the solute molecules diffused through the solvent. It is also possible for solvent molecules to diffuse. In the case of cells, the solutes are organic and inorganic compounds, and the solvent is water. The process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration is called osmosis (ahs-MOH-sis). Because water is moving from a higher to lower concentration, osmosis does not require cells to expend energy. Therefore, osmosis is the passive transport of water. Direction of Osmosis The net direction of osmosis depends on the relative concentra- tion of solutes on the two sides of the membrane. Examine Table 5-1. When the concentration of solute molecules outside the cell is lower than the concentration in the cytosol, the solution outside is hypotonic to the cytosol. In this situation, water diffuses into the cell until equilibrium is established. When the concentration of solute molecules outside the cell is higher than the concentration in the cytosol, the solution outside is hypertonic to the cytosol. In this situation, water diffuses out of the cell until equilibrium is established. Observing Diffusion Materials 600 mL beaker, 25 cm dialysis tubing, funnel, 15 mL starch solution (10 percent), 20 drops Lugol’s solution, 300 mL water, 100 mL graduated cylinder, 20 cm piece of string (2) Procedure 1. Put on your disposable gloves, lab apron, and safety goggles. 2. Pour 300 mL of water in the 600 mL beaker. 3. Add 20 drops of Lugol’s solution to the water. CAUTION: Lugol’s solution is a poison and eye and skin irritant. 4. Open the dialysis tubing, and tie one end tightly with a piece of string. 5. Using the funnel, pour 15 mL of 10 percent starch solution into the dialysis tubing. 6. Tie the other end of the dialysis tubing tightly with the second piece of string, forming a sealed bag around the starch solution. 7. Place the bag into the solution in the beaker, and observe the setup for a color change. Analysis What happened to the color in the bag? What happened to the color of the water around the bag? Explain your observations. Quick Lab www.scilinks.org Topic: Osmosis Keyword: HM61090 mb06se_homs01.qxd 11/27/07 8:52 AM Page 98 HOMEOSTASIS AND CELL TRANSPORT 99 When the concentrations of solutes outside and inside the cell are equal, the outside solution is said to be isotonic to the cytosol. Under these conditions, water diffuses into and out of the cell at equal rates, so there is no net movement of water. Notice that the prefixes hypo-, hyper-, and iso- refer to the relative solute concentrations of two solutions. Thus, if the solution outside the cell is hypotonic to the cytosol, then the cytosol must be hyper- tonic to that solution. Conversely, if the solution outside is hypertonic to the cytosol, then the cytosol must be hypotonic to the solution. Water tends to diffuse from hypo- tonic solutions to hypertonic solutions. How Cells Deal with Osmosis Cells that are exposed to an isotonic external environment usually have no difficulty keeping the movement of water across the cell membrane in balance. This is the case with the cells of ver- tebrate animals on land and of most other organ- isms living in the sea. In contrast, many cells function in a hypotonic environment. Such is the case for unicellular freshwater organisms. Water constantly diffuses into these organisms. Because they require a relatively lower concentration of water in the cytosol to function normally, unicel- lular organisms must rid themselves of the excess water that enters by osmosis. Some of them, such as the paramecia shown in Figure 5-2, do this with contractile vacuoles (kon-TRAK-til VAK-y ̄ ̄o ̄ ̄o-OL), which are organelles that remove water. Contractile vacuoles collect the excess water and then contract, pumping the water out of the cell. Unlike diffusion and osmosis, this pumping action is not a form of passive trans- port because it requires the cell to expend energy. Copyright © by Holt, Rinehart and Winston. All rights reserved. (a) (b) Vacuole filling with water Vacuole contracting TABLE 5-1 Direction of Osmosis Condition External solution is hypotonic to cytosol External solution is hypertonic to cytosol External solution is isotonic to cytosol Net movement of water into the cell out of the cell none H2O H2O H2O H2O H2O H2O The paramecia shown below live in fresh water, which is hypotonic to their cytosol. (a) Contractile vacuoles collect excess water that moves by osmosis into the cytosol. (b) The vacuoles then contract, returning the water to the outside of the cell. (LM 315) FIGURE 5-2 100 CHAPTER 5 (a) HYPOTONIC Cell walls (b) HYPERTONIC (a) ISOTONIC (b) HYPOTONIC (c) HYPERTONIC Other cells, including many of those in multicellular organisms, respond to hypotonic environments by pumping solutes out of the cytosol. This lowers the solute concentration in the cytosol, bring- ing it closer to the solute concentration in the environment. As a result, water molecules are less likely to diffuse into the cell. Most plant cells, like animal cells, live in a hypotonic environ- ment. In fact, the cells that make up plant roots may be surrounded by water. This water moves into plant cells by osmosis. These cells swell as they fill with water until the cell membrane is pressed against the inside of the cell wall, as Figure 5-3a shows. The cell wall is strong enough to resist the pressure exerted by the water inside the expanding cell. The pressure that water molecules exert against the cell wall is called turgor pressure (TER-GOR PRESH-er). In a hypertonic environment, water leaves the cells through osmosis. As shown in Figure 5-3b, the cells shrink away from the cell walls, and turgor pressure is lost. This condition is called plasmolysis (plaz-MAHL-uh-sis), and is the reason that plants wilt if they don’t receive enough water. Some cells cannot compensate for changes in the solute con-

President Xi Jinping, who is also general secretary of the Communist Party of China Central Committee and chairman of the Central Military Commission, visits Luoyang Bearing Group Co on Monday afternoon during his inspection of Luoyang, Henan province. During the visit, Xi called for continuous efforts to make the manufacturing industry even stronger to advance Chinese modernization. YAN YAN/XINHUA President Xi Jinping has stressed the importance of keeping businesses, employment, the market and expectations stable in the face of a complex international environment, saying that China will respond to various uncertainties with the certainty of its high-quality development. Xi, who is also general secretary of the Communist Party of China Central Committee and chairman of the Central Military Commission, made the remarks on Tuesday as he wrapped up a two-day fact-finding trip to Central China's Henan province. Speaking to provincial Party and government officials at a work briefing on Tuesday in Zhengzhou, the provincial capital, Xi said that high-quality development is essential to Chinese modernization. Faced with the complex external environment, it is necessary to firm up confidence, unwaveringly manage China's own affairs well, and steadfastly expand high-level opening-up, he said. He also urged Henan, one of the country's economic powerhouses, to further consolidate the foundation of its real economy, and promote the development of new quality productive forces suited to local conditions and led by technological innovation, in order to enhance the capacity of its modern industrial system to support high-quality development. When visiting Luoyang Bearing Group Co in the city of Luoyang on Monday, Xi said: "China has always adhered to the path of developing the real economy. From the past reliance on imported matches, soap and iron, to now becoming the world's largest manufacturing country with the most complete industrial categories, we have taken the right path." As a traditional manufacturing enterprise specializing in bearings, Luoyang Bearing Group's products are widely used in fields such as aerospace, construction machinery, wind power generation, rail transit, port machinery and ships. After learning about the company's efforts to accelerate the development of advanced manufacturing, Xi said that China must continue to strengthen the manufacturing sector, adhere to the principles of building self-reliance and strength, and master core technologies in key fields. "The hope is placed on you," he told the on-site workers. He also called for efforts to strengthen collaboration between industries, universities and research institutes, and cultivate a large number of high-quality talent. Despite internal challenges and increasing external shocks, China's manufacturing industry has withstood pressure and maintained stable growth. In April, the manufacturing sector saw its value-added output climb 6.6 percent year-on-year, with that of equipment manufacturing and high-tech manufacturing up 9.8 percent and 10 percent, respectively, according to data released by the National Bureau of Statistics on Monday. Advanced manufacturing is the high ground in global industrial competition and the main battlefield for technological innovation. Xi has repeatedly emphasized the need to upgrade the country's modernized industrial system, supported by advanced manufacturing. In a resolution adopted at the third plenary session of the 20th CPC Central Committee in July last year, it was clearly stated that China will move faster to advance new industrialization, promote the growth and expansion of advanced manufacturing clusters, and make the manufacturing sector higher-end, smarter and more eco-friendly. On Monday, Xi also visited the White Horse Temple, the first Buddhist temple in China, and the Longmen Grottoes, a UNESCO World Heritage site. Contact the writers at mojingxi@chinadaily.com.cn

Cell Size Cells differ not only in their shape but also in their size. A few types of cells are large enough to be seen by the unaided human eye. For example, the nerve cells that extend from a giraffe’s spinal cord to its foot can be 2 m (about 6 1/2 ft) long. A human egg cell is about the size of the period at the end of this sentence. Most cells, how- ever, are only 10 to 50 μm in diameter, or about 1/500 the size of the period at the end of this sentence. The size of a cell is limited by the relationship of the cell’s outer surface area to its volume, or its surface area–to-volume ratio. As a cell grows, its volume increases much faster than its surface area does, as shown in Figure 4-5. This trend is important because the materials needed by a cell (such as nutrients and oxygen) and the wastes produced by a cell (such as carbon dioxide) must pass into and out of the cell through its surface. If a cell were to become very large, the volume would increase much more than the surface area. Therefore, the surface area would not allow materials to enter or leave the cell quickly enough to meet the cell’s needs. As a result, most cells are microscopic in size. Comparing Surface Cells Materials microscope, prepared slides of plant (dicot) stem and ani- mal (human) skin, pencil, paper Procedure Examine slides by using medium magnification (100). Observe and draw the sur- face cells of the plant stem and the animal skin. Analysis How do the surface cells of each organism differ from the cells beneath the surface cells? What is the function of the surface cells? Explain how surface cells are suited to their function based on their shape. Quick Lab Small cells can exchange substances more readily than large cells because small objects have a higher surface area–to-volume ratio. FIGURE 4-5 mb06se_csfs02.qxd 5/18/07 10:54 AM Page 73 74 CHAPTER 4 BASIC PARTS OF A CELL Despite the diversity among cells, three basic features are common to all cell types. All cells have an outer boundary, an interior sub- stance, and a control region. Plasma Membrane The cell’s outer boundary, called the plasma membrane (or the cell membrane), covers a cell’s surface and acts as a barrier between the inside and the outside of a cell. All materials enter or exit through the plasma membrane. The surface of a plasma mem- brane is shown in Figure 4-6a. Cytoplasm The region of the cell that is within the plasma membrane and that includes the fluid, the cytoskeleton, and all of the organelles except the nucleus is called the cytoplasm. The part of the cytoplasm that includes molecules and small particles, such as ribosomes, but not membrane-bound organelles is the cytosol. About 20 percent of the cytosol is made up of protein. Control Center Cells carry coded information in the form of DNA for regulating their functions and reproducing themselves. The DNA in some types of cells floats freely inside the cell. Other cells have a mem- brane-bound organelle that contains a cell’s DNA. This membrane- bound structure is called the nucleus. Most of the functions of a eukaryotic cell are controlled by the cell’s nucleus. The nucleus is often the most prominent structure within a eukaryotic cell. It maintains its shape with the help of a protein skeleton called the nuclear matrix. The nucleus of a typical animal cell is shown in Figure 4-6b. Most animal cells have a cell membrane, a nucleus, and a variety of other organelles embedded in a watery substance. The surface of the cell membrane can be seen in (a). The organelles inside the cell are labeled in the diagram (b). FIGURE 4-6 (a) (b) Mitochondrion Microfilaments Lysosome Golgi apparatus Smooth ER Ribosomes Cell membrane Microtubules Rough ER Nuclear pore Nuclear envelope Nucleolus Nucleus Copyright © by Holt, Rinehart and Winston. All rights reserved. Cell wall Ribosome Cell membrane Peptidoglycan Pili Flagellum DNA CELL STRUCTURE AND FUNCTION 75 A prokaryotic cell lacks a membrane- bound nucleus and membrane-bound organelles. Most prokaryotic cells are much smaller than eukaryotic cells are. FIGURE 4-7 A white blood cell (eukaryotic) changes shape as it attacks purple- stained bacterial cells that are much smaller (prokaryotic). FIGURE 4-8 TWO BASIC TYPES OF CELLS Fossil evidence suggests that the earliest cells on Earth were simple cells similar to some present-day bacteria. As cells evolved, they differentiated into two major types: prokaryotes and eukaryotes. Prokaryotes Prokaryotes (proh-KAR-ee-OHTS) are organisms that lack a membrane- bound nucleus and membrane-bound organelles. Although prokaryotic cells lack a nucleus, their genetic information—in the form of DNA—is often concentrated in a part of the cell called the nucleoid. Figure 4-7 shows a typical prokaryotic cell. Prokaryotes are divided into two domains: Bacteria and Archaea (ahr-KEE-uh). The domain Bacteria includes organisms that are similar to the first cellular life-forms. The domain Archaea includes organisms that are thought to be more closely related to eukaryotic cells found in all other kingdoms of life. Eukaryotes Organisms made up of one or more cells that have a nucleus and membrane-bound organelles are called eukaryotes (yoo-KAR-ee-OHTS). Eukaryotic cells also have a variety of subcellular structures called organelles, well-defined, intracellular bodies that perform specific functions for the cell. Many organelles are surrounded by a mem- brane. The organelles carry out cellular processes just as a person’s pancreas, heart, and other organs carry out a person’s life processes. Eukaryotic cells are generally much larger than prokary- otic cells, as seen in Figure 4-8, which shows a white blood cell (eukaryote) destroying tiny bacterial cells (prokaryotes).

Shopping 1. a shop assistant - продавець в магазині 2. a customer - покупець 3. a fitting room - примірочна 4. a receipt - чек 5. How can I help you?/May I help you? - Як я можу вам допомогти?/Чи можу я вам допомогти? 6. Excuse me, I am looking for ... - Вибачте, я шукаю … 7. How much is this? - Скільки це коштує? 8. I’ll take it. - Я візьму це. 9. Can I try it on? - Чи можу я це приміряти? 10. Have you got it in a different color/size? - Чи є у вас це в іншому кольорі/розмірі? 1. to go shopping - ходити по магазинах 2. to shop online - купувати онлайн 3. to pay - платити 4. to spend - витрачати 5. a price - ціна 6. a discount - знижка 7. a shopping list - список покупок 8. a shop window - вітрина магазину 9. These boots are 50 percent off. - На ці черевики знижка 50%. 10. expensive - дорогий 11. cheap - дешевий

Cells of different organisms and even cells within the same organism are very diverse in terms of shape, size, and internal organization. One theme that occurs again and again throughout biology is that form follows function. In other words, a cell’s function influences its physical features. Cell Shape The diversity in cell shapes reflects the different functions of cells. Compare the cell shapes shown in Figure 4-4. The long extensions that reach out in various directions from the nerve cell shown in Figure 4-4a allow the cell to send and receive nerve impulses. The flat, platelike shape of skin cells in Figure 4-4b suits their function of covering and protecting the surface of the body. As shown below, a cell’s shape can be simple or complex depending on the function of the cell. Each cell has a shape that has evolved to allow the cell to perform its function effectively. SECTION 2 OBJECTIVES ● Explain the relationship between cell shape and cell function. ● Identify the factor that limits cell size. ● Describe the three basic parts of a cell. ● Compare prokaryotic cells and eukaryotic cells. ● Analyze the relationship among cells, tissues, organs, organ systems, and organisms. VOCABULARY plasma membrane cytoplasm cytosol nucleus prokaryote eukaryote organelle tissue organ organ system Cells have various shapes. (a) Nerve cells have long extensions. (b) Skin cells are flat and platelike. (c) Egg cells are spherical. (d) Some bacteria are rod shaped. (e) Some plant cells are rectangular. FIGURE 4-4 (a) Nerve cell (b) Skin cells (c) Egg cell (d) Bacterial cells (e) Plant cells Copyright © by Holt, Rinehart and Winston. All rights reserved. 1. All cubes have volume and surface area. The total surface area is equal to the sum of the areas of each of the six sides (area = length X width). 2. If you split the first cube into eight smaller cubes, you get 48 sides. The volume remains constant, but the total surface area doubles. 3. If you split each of the eight cubes into eight smaller cubes, you have 64 cubes that together contain the same volume as the first cube. The total surface area, however, has doubled again. CELL STRUCTURE AND FUNCTION 73 Cell Size Cells differ not only in their shape but also in their size. A few types of cells are large enough to be seen by the unaided human eye. For example, the nerve cells that extend from a giraffe’s spinal cord to its foot can be 2 m (about 6 1/2 ft) long. A human egg cell is about the size of the period at the end of this sentence. Most cells, how- ever, are only 10 to 50 μm in diameter, or about 1/500 the size of the period at the end of this sentence. The size of a cell is limited by the relationship of the cell’s outer surface area to its volume, or its surface area–to-volume ratio. As a cell grows, its volume increases much faster than its surface area does, as shown in Figure 4-5. This trend is important because the materials needed by a cell (such as nutrients and oxygen) and the wastes produced by a cell (such as carbon dioxide) must pass into and out of the cell through its surface. If a cell were to become very large, the volume would increase much more than the surface area. Therefore, the surface area would not allow materials to enter or leave the cell quickly enough to meet the cell’s needs. As a result, most cells are microscopic in size. Comparing Surface Cells Materials microscope, prepared slides of plant (dicot) stem and ani- mal (human) skin, pencil, paper Procedure Examine slides by using medium magnification (100). Observe and draw the sur- face cells of the plant stem and the animal skin. Analysis How do the surface cells of each organism differ from the cells beneath the surface cells? What is the function of the surface cells? Explain how surface cells are suited to their function based on their shape. Quick Lab Small cells can exchange substances more readily than large cells because small objects have a higher surface area–to-volume ratio. FIGURE 4-5 mb06se_csfs02.qxd 5/18/07 10:54 AM Page 73 74 CHAPTER 4 BASIC PARTS OF A CELL Despite the diversity among cells, three basic features are common to all cell types. All cells have an outer boundary, an interior sub- stance, and a control region. Plasma Membrane The cell’s outer boundary, called the plasma membrane (or the cell membrane), covers a cell’s surface and acts as a barrier between the inside and the outside of a cell. All materials enter or exit through the plasma membrane. The surface of a plasma mem- brane is shown in Figure 4-6a. Cytoplasm The region of the cell that is within the plasma membrane and that includes the fluid, the cytoskeleton, and all of the organelles except the nucleus is called the cytoplasm. The part of the cytoplasm that includes molecules and small particles, such as ribosomes, but not membrane-bound organelles is the cytosol. About 20 percent of the cytosol is made up of protein. Control Center Cells carry coded information in the form of DNA for regulating their functions and reproducing themselves. The DNA in some types of cells floats freely inside the cell. Other cells have a mem- brane-bound organelle that contains a cell’s DNA. This membrane- bound structure is called the nucleus. Most of the functions of a eukaryotic cell are controlled by the cell’s nucleus. The nucleus is often the most prominent structure within a eukaryotic cell. It maintains its shape with the help of a protein skeleton called the nuclear matrix. The nucleus of a typical animal cell is shown in

A solution is a mixture in which one or more substances are uniformly distributed in another substance. Solutions can be mixtures of liquids, solids, or gases. For example, plasma, the liquid part of blood, is a very complex solution. It is composed of many types of ions and large molecules, as well as gases, that are dissolved in water. A solute (SAHL-YOOT) is a substance dissolved in the solvent. The particles that compose a solute may be ions, atoms, or molecules. The solvent is the substance in which the solute is dissolved. For example, when sugar, a solute, and water, a solvent, are mixed, a solution of sugar water results. Though the sugar dissolves in the water, neither the sugar molecules nor the water molecules are altered chemically. If the water is boiled away, the sugar molecules remain and are unchanged. Solutions can be composed of various proportions of a given solute in a given solvent. Thus, solutions can vary in concentra- tion. The concentration of a solution is the amount of solute dis- solved in a fixed amount of the solution. For example, a 2 percent saltwater solution contains 2 g of salt dissolved in enough water to make 100 mL of solution. The more solute dissolved, the greater is the concentration of the solution. A saturated solution is one in which no more solute can dissolve. Aqueous (AY-kwee-uhs) solutions—solutions in which water is the solvent—are universally important to living things. Marine microorganisms spend their lives immersed in the sea, an aqueous solution. Most nutrients that plants need are in aqueous solutions in moist soil. Body cells exist in an aqueous solution of intercellu- lar fluid and are themselves filled with fluid; in fact, most chemical reactions that occur in the body occur in aqueous solutions. Copyright © by Holt, Rinehart and Winston. All rights reserved. Liquid water Solid water Ice (solid water) is less dense than liquid water because of the structure of ice crystals. The water molecules in ice are bonded to each other in a way that creates large amounts of open space between the molecules, relative to liquid water. FIGURE 2-12 solvent from the Latin solvere, meaning “to loosen” Word Roots and Origins CHEMISTRY OF LIFE 43 ACIDS AND BASES One of the most important aspects of a living system is the degree of its acidity or alkalinity. What do we mean when we use the terms acid and base? Ionization of Water As water molecules move about, they bump into one another. Some of these collisions are strong enough to result in a chemical change: one water molecule loses a proton (a hydrogen nucleus), and the other gains this proton. This reaction really occurs in two steps. First, one molecule of water pulls apart another water molecule, or dissociates, into two ions of opposite charge: H2O ∏ H OH The OH ion is known as the hydroxide ion. The free H ion can react with another water molecule, as shown in the equation below. H H2O ∏ H3O The H3O ion is known as the hydronium ion. Acidity or alkalin- ity is a measure of the relative amounts of hydronium ions and hydroxide ions dissolved in a solution. If the number of hydronium ions in a solution equals the number of hydroxide ions, the solution is said to be neutral. Pure water contains equal numbers of hydro- nium ions and hydroxide ions and is therefore a neutral solution. Acids If the number of hydronium ions in a solution is greater than the number of hydroxide ions, the solution is an acid. For example, when hydrogen chloride gas, HCl, is dissolved in water, its mol- ecules dissociate to form hydrogen ions, H, and chloride ions, Cl, as is shown in the equation below. HCl ∏ H Cl These free hydrogen ions combine with water molecules to form hydronium ions, H3O. This aqueous solution contains many more hydronium ions than it does hydroxide ions, making it an acidic solution. Acids tend to have a sour taste; how- ever, never taste a substance to test it for acidity. In concentrated forms, they are highly corrosive to some materials, as you can see in Figure 2-13. Bases If sodium hydroxide, NaOH, a solid, is dissolved in water, it dissociates to form sodium ions, Na, and hydroxide ions, OH, as shown in the equation below. NaOH ∏ Na OH Copyright © by Holt, Rinehart and Winston. All rights reserved. Eco Connection onnection Acid Precipitation Acid precipitation, more commonly called acid rain, describes rain, snow, sleet, or fog that contains high levels of sulfuric and nitric acids. These acids form when sulfur dioxide gas, SO2, and nitrogen oxide gas, NO, react with water in the atmosphere to produce sulfuric acid, H2SO4, and nitric acid, HNO3. Acid precipitation makes soil and bodies of water, such as lakes, more acidic than normal. These high acid levels can harm plant and animal life directly. A high level of acid in a lake may kill mollusks, fish, and amphibians. Even in a lake that does not have a very elevated level of acid, acid precipitation may leach aluminum and magnesium from soils, poisoning water- dwelling species. Reducing fossil-fuel consump- tion, such as occurs in gasoline engines and coal-burning power plants, should reduce high acid levels in precipitation. Sulfur dioxide, SO2, which is produced when fossil fuels are burned, reacts with water in the atmosphere to produce acid precipitation. Acid precipitation, or acid rain, can make lakes and rivers too acidic to support life and can even corrode stone, such as the face of this statue. FIGURE 2-13 44 CHAPTER 2 This solution then contains more hydroxide ions than hydronium ions and is therefore defined as a base. The adjective alkaline refers to bases. Bases have a bitter taste; however, never taste a substance to test for alkalinity. They tend to feel slippery because the OH ions react with the oil on our skin to form a soap. In fact, commercial soap is the product of a reaction between a base and a fat. pH Scientists have developed a scale for comparing the relative con- centrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14, as shown in Figure 2-14. A solution with a pH of 0 is very acidic, a solution with a pH of 7 is neutral, and a solution with a pH of 14 is very basic. A solution’s pH is measured on a logarithmic scale. That is, the change of one pH unit reflects a 10-fold change in the acidity or alkalinity. For example, urine has 10 times the H3O ions at a pH of 6 than water does at a pH of 7. Vinegar, has 1,000 times more H3O ions at a pH of 3 than urine at a pH of 6, and 10,000 times more H3O ions than water at a pH of 7. The pH of a solution can be measured with litmus paper or with some other chemical indicator that changes color at various pH levels. Buffers The control of pH is important for living systems. Enzymes can function only within a very narrow pH range. The control of pH in organisms is often accomplished with buffers. Buffers are chemi- cal substances that neutralize small amounts of either an acid or a base added to a solution. As Figure 2-14 shows, the composition of your internal environment—in terms of acidity and alkalinity— varies greatly. Some of your body fluids, such as stomach acid and urine, are acidic. Others, such as intestinal fluid and blood, are

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