What is a common mistake when writing a topic sentence?

Including too many ideas at once

Making it relevant to the paragraph

What role does a topic sentence play in connecting ideas within a paragraph?

It links all the supporting details to the main idea

It provides a summary of the entire essay

It serves as a conclusion for the paragraph

It introduces new topics unrelated to the main idea

Which of the following best illustrates an effective topic sentence?

Many animals have unique adaptations that help them survive.

There are many types of animals in the world.

Animals are cool and interesting.

Survival is important for all living things.

How can you improve a weak topic sentence?

Make it more specific and focused

Make it much longer without adding meaning

Write it as a question instead of a statement

Use complex words that are hard to understand

What effect does a good topic sentence have on a reader?

It helps them understand what to expect in the paragraph

It confuses them about the main idea

It offers too many details at once

It makes them want to stop reading

Which of the following options best describes a topic sentence?

It summarizes the main point of the paragraph

Where is the topic sentence usually located in a paragraph?

At the beginning of the paragraph

Scattered throughout the paragraph

Which of the following is a good characteristic of a strong topic sentence?

It expresses a clear and specific idea

It contains many unrelated details

It is the longest sentence in the paragraph

What is the main purpose of a topic sentence in a paragraph?

To introduce the main idea of the paragraph

To list all the important facts

To provide a concluding statement

How to write a topic sentence

SPANISH STUDENTS 10/22/25 In the sentence 'The author chose to juxtapose the wealthy neighborhood with the impoverished area to highlight social inequality,' what does 'juxtapose' most likely mean based on context clues? * 1 point to separate completely to describe in detail to criticize harshly to place side by side for comparison When reading 'This paradox confused everyone: the more he tried to save time, the less time he seemed to have,' what can you infer about a paradox? * 1 point a mathematical equation a simple solution a type of poem a contradictory statement that reveals truth The passage states: 'The author's use of symbolism was evident when the broken mirror represented the character's shattered dreams.' Based on this context, symbolism involves: * 1 point using objects to represent deeper meanings creating rhyming patterns writing in chronological order using literal descriptions only In the text 'Please elaborate on your answer by providing specific examples and detailed explanations,' the word 'elaborate' suggests the need to: * 1 point use simpler words change the topic add more detail make it shorter The critic wrote: 'The actor's performance captured every nuance of emotion, from subtle sadness to barely contained rage.' What does 'nuance' refer to in this context? * 1 point subtle variations in meaning simple emotions loud expressions obvious differences When the text says 'The implication of her silence was clear to everyone in the room, though she never spoke a word,' what does 'implication' mean? * 1 point a command given a direct statement a question asked a conclusion drawn indirectly The scientist stated: 'Based on our limited observations, our hypothesis suggests that plants grow faster with classical music.' What is a hypothesis? * 1 point a type of experiment a proven fact a final conclusion a possible explanation needing more evidence In 'Three witnesses were able to corroborate the defendant's alibi, strengthening his case significantly,' the word 'corroborate' most likely means: * 1 point to question or doubt to confirm or support to change the story to ignore completely The passage reads: 'The student needed to justify her controversial thesis with solid evidence and logical reasoning.' What does 'justify' mean here? * 1 point to make it longer to make excuses for to avoid explaining to prove something is reasonable When the text states 'The researcher was able to synthesize information from five different studies to create a comprehensive theory,' what does 'synthesize' involve? * 1 point copying one source exactly combining multiple sources to create something new rejecting all previous research focusing on only one idea When a reader encounters 'The symbolism in the novel was complex, with the recurring image of doors representing new opportunities throughout the story,' they should: * 1 point memorize all symbols skip symbolic passages look for deeper representational meanings focus only on the literal meaning If a teacher says 'Your essay needs more elaboration - expand on your main points with examples and analysis,' what critical thinking skill is being requested? * 1 point developing ideas with supporting details summarizing briefly using fewer examples changing the topic entirely In the passage 'The dark clouds gathering on the horizon seemed to foreshadow the troubles that would soon befall the village,' what literary technique is being demonstrated? * 1 point The author is using environmental details to hint at future plot developments The author is focusing on realistic weather descriptions The author is using weather to predict actual meteorological events The author is describing a coincidental weather pattern When analyzing 'Sarah knew the antagonist in her favorite novel wasn't just evil—he represented the fear of change that many people experience,' what deeper understanding about antagonists is revealed? * 1 point Antagonists are always completely evil characters Antagonists can represent abstract concepts or human struggles Antagonists must be human characters Antagonists only exist to create action scenes In the sentence 'The protagonist's journey wasn't just about reaching the destination—it was about discovering who she truly was,' what does this suggest about effective protagonists? * 1 point Protagonists must always succeed in their missions Protagonists should remain unchanged throughout the story Protagonists undergo both external and internal development Protagonists should focus only on external goals When the text states 'The word 'home' carried different connotations for each character—warmth and safety for some, confinement and obligation for others,' what critical reading skill is being highlighted? * 1 point Memorizing dictionary definitions Understanding that words have only one correct meaning Identifying grammatical structures Recognizing that word meanings can vary based on personal experience In 'While the denotation of 'snake' is simply a reptile, the author's use of it to describe the character suggests something far more sinister,' what analytical skill is required? * 1 point Understanding reptile biology Memorizing animal classifications Distinguishing between literal and figurative meanings Identifying sentence structure When examining 'The author's tone shifted from hopeful in the opening chapters to increasingly cynical as the story progressed,' what does this reveal about sophisticated writing? * 1 point Tone is unimportant in storytelling Tone changes reflect the author's developing attitude toward the subject Only the ending tone matters Authors should maintain the same tone throughout In analyzing 'The theme of the novel wasn't stated directly but emerged through the characters' repeated struggles with moral choices,' what does this demonstrate about themes? * 1 point Themes develop through patterns in the narrative Themes are only found in the conclusion Themes should always be explicitly stated Themes must be simple moral lessons When the passage reads 'From the character's nervous glances and hesitant speech, readers can infer that she's hiding something important,' what critical thinking process is being described? * 1 point Following explicit plot statements Memorizing character descriptions Making random guesses about character motivations Using textual evidence to draw logical conclusions In 'The ending was deliberately ambiguous, allowing readers to decide whether the character's actions were heroic or selfish,' what does this suggest about sophisticated literature? * 1 point Good stories always have clear, definitive endings Unclear endings indicate poor writing Ambiguity can enhance reader engagement and interpretation Authors should avoid confusing readers When analyzing 'The controversial decision to ban the book sparked debates about censorship versus protecting young readers,' what critical thinking skill is most important? * 1 point Choosing one side immediately Examining multiple perspectives before forming an opinion Avoiding difficult topics entirely Following popular opinion In 'Each character's perspective on the same event revealed how personal experiences shape our understanding of truth,' what deeper concept is being explored? * 1 point All perspectives are equally valid Perspective is unimportant in understanding events There is only one correct way to view any situation Personal background influences how we interpret events When the text states 'The community proved resilient, rebuilding not just their homes but their hope after the disaster,' what does this reveal about the concept of resilience? * 1 point Resilience encompasses both practical and emotional recovery Resilience is an innate trait that cannot be developed Resilience means avoiding all difficulties Resilience only involves physical recovery In analyzing 'The author's portrayal of the character's empathy—her ability to understand her enemy's pain even while fighting him—added complexity to the conflict,' what does this suggest about empathy? * 1 point Empathy means agreeing with everyone Empathy makes people weak in conflicts Empathy should be avoided in difficult situations Empathy can coexist with opposition and create moral complexity When examining 'The character's integrity was tested when telling the truth would hurt people she loved,' what does this reveal about integrity? * 1 point Integrity means always following rules regardless of consequences Integrity means never causing any harm to others Integrity is only important in public situations Integrity involves making difficult moral choices even when costly In 'The student learned to advocate for her ideas by presenting evidence rather than just stating opinions,' what critical skill is being developed? * 1 point Supporting positions with logical reasoning and evidence Avoiding controversial topics entirely Learning to argue loudly and persistently Always agreeing with authority figures If you rewrote a scene from 'The Birchbark House' from Omakayas's grandmother's first-person perspective instead of Omakayas's, how would this most likely change the reader's understanding? * 1 point Nothing would change since they're both female characters The language would become more formal and difficult The story would become less interesting because adults are boring Readers would gain wisdom from experience but lose the innocence of childhood discovery In a plot diagram, the rising action serves which critical purpose beyond simply building toward the climax? * 1 point To provide background information about the setting To confuse readers so the ending is surprising To develop character relationships and establish stakes that make the climax meaningful To make the story longer and more detailed When analyzing the falling action in 'The Birchbark House,' which element would be most important to consider when writing an alternate version? * 1 point Whether the consequences of the climax align with the new direction you want the story to take Making sure it's shorter than the rising action Including a moral lesson for readers How quickly the conflicts get resolved In the exposition of a story, conflict serves which essential function that many readers don't realize? * 1 point To immediately grab attention with action scenes To provide comic relief before serious events To show off the author's writing skills To establish what the characters characterization/personality, which determines what they' must learn to overcome as they face more problems

8/26/24 RTI & FIRE Lesson 8 RI.5.8 Explain how an author uses reasons and evidence to support particular points in a text, identifying which reasons and evidence support which point(s). RI.5.9 Integrate information from several texts on the same topic in order to write or speak about the subject knowledgeably.

To the Lakota, and other indigenous people on North America's Great Plains, the bison was an essential part of their culture ( expressed in the quote on the previous page). The bison provided meat for nutrition, a hide for clothing and shelter, bones for tools, and fat for soap. The bison was also central to their religious beliefs. So, when European settlers hunted the bison nearly to extinction, Lakota culture suffered. Culture is central to a society and the identity of its people, as well as its continued existence. Therefore, geographers study culture as a way to understand similarities and differences among societies across the world, and in some cases, to help preserve these societies. Analyzing Culture All of a group's learned behaviors, actions, beliefs, and objects are a part of culture. It is a visible force seen in a group's actions, possessions, and influence on the landscape. For example, in a large city you can see people working in offices, factories, and stores, and living in high-rise apartments or suburban homes. You might observe them attending movies, concerts, or sporting events. Culture is also an invisible force guiding people through shared belief systems, customs, and traditions. Culture is learned, in that it develops through experiences, and not merely transmitted through genetics. For example, many people in the United States have developed a strong sense of competitiveness in school and business, and believe that hard work is a key to success. These types of elements, visible and invisible, are cultural traits. A series of interrelated traits make up a cultural complex, such as the process of steps and acceptable behaviors related to greeting a person in different cultures. A single cultural artifact, such as an automobile, may represent many different values, beliefs, behaviors and traditions and be representative of a cultural complex. Since culture is learned there are many ways that one generation passes its culture to the next. Children and adults learn traits three ways: • imitation, as when learning a language by repeating sounds or behaviors from a person or television • informal instruction, as when a parent reminds a child to say "please" • formal instruction, as when students learn history in school 132 HUMAN GEOGRAPHY: AP" EDITION CULTURAL COMPLEX OF THE AUTOMOBILE The automobile provides much more than just transportation, as it reflects many values that are central to American culture. Origins of Culture The area in which a unique culture or a specific trait develops is a culture hearth. Classical Greece was a culture hearth for democracy more than 2,000 years ago. New York City was a culture hearth for rap music in the 1970s. Geographers study how cultures develop in hearths and diffuse-or spread-to other places. Geographers also study taboos, behaviors heavily discouraged by a culture. For example, many cultures have taboos against eating certain foods, such as pork or insects. What is considered taboo changes over time. In the United States, marriages between Protestants and Catholics were once taboo, but they are not widely opposed now. Traditional, Folk, and Indigenous Cultures With the beginning of the Industrial Revolution in the late 18th century, modern transportation and communication connected people as never before and led to extensive cultural mixing, especially as cities have grown. The world prior to this time was very different; however, remnants of the past are still evident in our modern cultures. Traditional, folk, and indigenous cultures share some important characteristics and are often grouped together, but they do have some subtle differences. Traditional Culture Recently, the meanings of traditional, folk, and indigenous culture have begun to merge, causing geographers to debate when each should be used. Increasingly, the term traditional culture is used to encompass all three cultural designations. All three types share the function of passing down long-held beliefs, values, and practices and are generally resistant to rapid changes in their culture. Folk Culture The beliefs and practices of small, homogenous groups of people, often living in rural areas that are relatively isolated and slow to change, are known as folk cultures. Like all cultures, they demonstrate the diverse ways that people have adapted to a physical environment. For example, people around the world learned to make shelters out of available resources, whether 3.1: INTRODUCTION TO CULTURE 133 it was snow or mud bricks or wood. However, people used similar resources such as wood differently. In Scandinavia, people used trees to build cabins. In the American Midwest, people processed trees into boards, built a frame, and attached the boards to it. Many traits of folk culture continue today. Corn was first grown in Mexico around 10,000 years ago, and it is still grown there today. While many elements of folk culture exist side by side with modern culture, there are people whose societies have changed little, if at all, from long ago. These people practice traditional cultures, those which have not been affected by modern technology or influences. They often live in remote regions, such as some small tribes in the Amazon rainforest, and have scant knowledge of the outside world. As the lines continue blurring between cultural designations, the Amish of Pennsylvania are often referenced as both folk and traditional culture. Indigenous Culture When members of an ethnic group reside in their ancestral lands, and typically possess unique cultural traits, such as speaking their own exclusive language, they are considered an indigenous culture. Some indigenous peoples have been displaced from their native lands, but still practice their indigenous culture. Native Americans in the United States, such as the Navajo, have kept indigenous cultural practices. First Nations of Canada, such as the Inuit, have also retained their indigenous culture. Globalization and Popular Culture As a result of the Industrial Revolution, improvements in transportation and communication have shortened the time required for movement, trade, or other forms of interaction between two places. This development, known as space-time compression (see Topics 1.4 and 3.6), has accelerated culture change around the world. In 1817, a freight shipment from Cincinnati needed 52 days to reach New York City. By 1850, because of canals and railroads, it took half that long. And by 1852, it took only 7 days. Today, an airplane flight takes only a few hours, and digital information takes seconds or less. Similar change has occurred on the global scale. People travel freely across the world in a matter of hours, and communication has advanced to a point where people share information instantaneously across the globe. The increased global interaction has had a profound impact on cultures, from spreading English across the world to instant sharing of news, events and music. Globalization specifically refers to the increased integration of the world economy since the 1970s. The process of intensified interaction among peoples, governments, and companies of different countries around the globe has had profound impacts on culture. The culture of the United States is intertwined with globalization. Through the influence of its corporations, Hollywood movies, and government, the United States exerts widespread influence in other countries. But other countries also shape American culture. For example, in 2019, the National Basketball Association included players from 38 countries or territories. When cultural traits- such as clothing, music, movies, and types of 134 HUMAN GEOGRAPHY: AP. EDITION businesses-spread quickly over a large area and are adopted by various groups, they become part of popular culture. Elements of popular culture often begin in urban areas and diffuse quickly through globalization processes such as the media and Internet. These elements can quickly be adopted worldwide, making them part of global culture. People around the world follow European soccer, Indian Bollywood movies, and Japanese animation known as anime. With people in many nations wearing similar clothes, listening to similar music, and eating similar food, popular cultural traits often promote uniformity in beliefs, values, and the cultural landscape across many places The cultural landscape, also known as the built environment (see Topic 3.2), is the modification of the environment by a group and is a visible reflection of that group's cultural beliefs and values. Traditional Culture to Popular Culture Popular culture emphasizes trying what is new rather than preserving what is traditional. Many people, especially older generations or those who follow a folk culture, openly resist the adoption of popular cultural traits. They do this by preserving traditional languages, religions, values, and foods. While older generations often resist the adoption of popular culture, they seldom are successful in keeping their traditional cultures from changing, especially among the young people of their society. One clash between popular and traditional culture is occurring in Brazil. As the population expands to the interior of the rain forest, many indigenous cultures, like the Yanamamo tribe, have more contact with outside groups. Remaining isolated by the forest is becoming increasingly difficult as many young people from the indigenous cultures become exposed to popular culture and begin to integrate into the larger Brazilian society. As the young people leave their communities, they are more likely to accept popular culture at the expense of their indigenous cultural heritage, which threatens the very existence of their folk culture. Traditional culture typically exhibits horizontal diversity, meaning each traditional culture has its own customs and language that makes it distinct from other culture groups. Yet, people people within each group are usually homogeneous, or very similar to each other. By contrast, popular culture typically exhibits vertical diversity, meaning that modern urban societies are usually heterogeneous, or exhibiting differences, within the society and usually contain numerous multiethnic neighborhoods. However, on a global scale popular cultures are relatively similar with the same type of malls, shops, fast food, and clothing. Urban global culture centers are not identical, yet, global cities often do not have as much horizontal diversity across space as folk cultures. 3.1: INTRODUCTION TO CULTURE 135 COMPARING TRADITIONAL AND POPULAR CULTURE Trait Traditional Culture Popular or Global Culture Society • Rural and isolated location • Urban and connected location • Homogeneous and • Diverse and multiethnic indigenous population population • Most people speak an • Many people speak a global indigenous or ethnic local language such as English or language Arabic • Horizontal diversity • Vertical diversity Social • Emphasis on community and • Emphasis on individualism and Structure conformity making choices • Families live close to each • Dispersed families other • Weakly defined gender roles • Well-defined gender roles Diffusion • Relatively slow and limited • Relatively rapid and extensive • Primarily through relocation • Often hierarchical • Oral traditions and stories • Social media and mass media Buildings and • Materials produced locally, • Materials produced in distant Housing such as stone or grass factories, such as steel or glass • Built by community or owner • Built by a business • Similar style for community • Variety of architectural styles • Different between cultures • Similar between cities • Traditional architecture • Postmodern / contemporary architecture Food • Locally produced • Often imported • Choices limited by tradition • Wide range of choice • Prepared by the family or • Purchased in restaurants community Spatial Focus • Local and regional • National and global Artifacts, Mentifacts, and Sociofacts Whether a cultural attribute is considered traditional, folk, indigenous, or popular in nature, it is valuable to differentiate between elements of culture that can be seen and those that can not. There are artifacts that comprise the material culture, which consists of tangible things, or those that can be experienced by the senses. Art, clothing, food, music, sports, and housing types are all tangible elements of culture. Another element of the study of artifacts is understanding the techniques to use or build a specific artifact. Artifacts can be unique to a particular culture, or can be shared. For example, people of all cultures need to communicate through language, yet there are many groups that possess languages unique to their culture. The ability to read, write and understand the English language is an artifact of importance for much of popular global culture. 136 HUMAN GEOGRAPHY: AP" EDITION Mentifacts comprise a group's nonmaterial culture and consist ofintangible concepts, or those not having a physical presence. Beliefs, values, practices, and aesthetics (pleasing in appearance) determine what a cultural group views as acceptable and desirable. Mentifacts can also be unique or shared. People of many cultures possess an belief in one or many deities, and often the deities are unique to that culture. The belief in a god is a mentifact-the religious building or symbols are artifacts. Cultural groups also possess sociofacts, which are the ways people organize their society and relate to one another. Taken altogether, people tend to see the whole of their culture as greater than the sum of its individual parts. Sociofacts are embodied through families, governments, sports teams, religious organizations, education systems, and other social constructs. As with artifacts and mentifacts, sociofacts may also be unique or similar to other societies. Families are the foundations of most societies, yet what constitutes the structure of a family may vary widely between cultural groups. For example, Western cultures tend to view the nuclear family, consisting of the parents and their children as the basic family unit. By contrast, in many Western African cultures the norm is the extended family, consisting of several generations and other family members such as cousins living under one roof.

SPANISH STUDENTS 10/20/25 STANDARDS LC.RL.5.2c Determine the theme of a story, drama, or poem including how characters in a story or drama respond to challenges or how the speaker in a poem reflects upon a topic LC.RL.5.3a Compare characters, settings, events within a story; provide or identify specific details in the text to support the comparison. LC.RL.5.3b Compare and contrast two or more characters, settings, or events in a story or drama, drawing on specific details in the text (e.g., how characters interact). LC.RL.5.4 Determine the meaning of words and phrases as they are used in a text including figurative language such as metaphors and similes. LC.RL.5.5a Use signal words (e.g., meanwhile, unlike, next) to identify common types of text structure (e.g., sequence, compare/contrast, cause/effect, description) within a text. LC.W.5.1a Produce an opinion piece which has an introduction that states an opinion and has an organizational structure in which ideas are logically grouped to support the writer's opinion

Make HOTS-SOLO based questions using why, how, which, in what, on topics - Appraise the unity of plot, setting and characterization in a material viewed to achieve the writer’s purpose Observe the language of research, campaigns, and advocacies

News Opinion Sport Culture Lifestyle Show more Books Music TV & radio Art & design Film Games Classical Stage ‘Hollywood doesn’t do very much of that business, they have the nice sign, and everything’s good, but they don’t do very much,’ said Trump. View image in fullscreen ‘Hollywood doesn’t do very much of that business, they have the nice sign, and everything’s good, but they don’t do very much,’ said Trump. Photograph: Lucy Nicholson/Reuters Film ‘I’m not trying to hurt the industry’: Trump softens tone on movie tariffs California governor Gavin Newsom announces a $7.5bn tax incentive scheme as Trump’s announcement of 100% tariffs on films ‘produced in foreign lands’ is mocked by Jimmy Kimmel and Fallon Andrew Pulver Tue 6 May 2025 11.24 BST Share Donald Trump appears to be softening his tone after widespread dismay in Hollywood and further afield at his bombshell announcement of 100% tariffs on films “produced in foreign lands”, saying he was “not looking to hurt the industry”. In remarks reported by CNBC, Trump said he was planning to discuss the plan with film industry leaders. “I’m not looking to hurt the industry, I want to help the industry.” He added: “So we’re going to meet with the industry. I want to make sure they’re happy with it because we’re all about jobs.” Trump also took aim again at California state governor Gavin Newsom, saying the film industry “has been decimated by other countries taking them out, and also by incompetence, like in Los Angeles, the governor [Gavin Newsom] is a grossly incompetent man, he’s just allowed it to be taken away from”. Trump added: “Hollywood doesn’t do very much of that business, they have the nice sign, and everything’s good, but they don’t do very much.” Trump’s talk of film tariffs makes no sense, but it’s already doing damage – to Hollywood Peter Bradshaw Peter Bradshaw Read more Newsom responded with a statement saying: “Governor Newsom continues to champion California’s iconic film and television industry – recognising it as a cornerstone of the state’s economy, one that sustains hundreds of thousands of good-paying jobs across every sector around the state.” “His plan to more than double the state’s film and television tax credit reflects a commitment to keeping production here at home, supporting workers and maintaining California’s global leadership in entertainment. If the President announces a proposal with more details, we will review it.” Newsom had earlier responded to Trump’s announcement by proposing a $7.5bn federal tax incentive scheme, saying in a statement to Variety: “Building on our successful state program, we’re eager to partner with the Trump administration to further strengthen domestic production.” Tax incentive schemes in the US currently operate on a state-by-state basis, and Newsom had announced a plan in April to boost California’s to $750m. California senator Adam Schiff also condemned Trump’s tariff proposal while backing calls for a federal tax credit scheme, saying in a statement: “Blanket tariffs on all films would have unintended and potentially damaging impacts, [but] we have an opportunity to work together to pass a major federal film tax credit to re-shore American jobs in the industry.” Late night TV hosts Jimmy Kimmel and Jimmy Fallon also joined the chorus of dismay and bafflement at Trump’s plan. Commenting that Trump was “now aiming his wrecking ball at Hollywood”, Kimmel questioned whether foreign-made movies were a “national security threat” as Trump claimed. “I don’t care where they’re made. I really don’t. I guess it’s what the late, great Hannibal Lecter would’ve wanted. Sonic, the illegal immigrant hedgehog, is a national security threat and he must be stopped!” Kimmel also mocked actor Jon Voight’s role in Trump’s thinking, saying: “This is where he reportedly got the tariff movies idea – from Angelina Jolie’s 86-year-old father she won’t talk to. What a great idea. Next year, The White Lotus is gonna be set at a Hampton Inn.” Fallon also took aim at Trump’s implication that foreign locations were somehow taboo, saying: “Gonna be fun seeing the next Lord of the Rings filmed in Bayonne, New Jersey,” adding: “If you don’t like that, you can also watch Emily in Des Moines [instead of Emily in Paris]. It’s just as charming.” Explore more on these topics Film Film industry Donald Trump Trump tariffs Gavin Newsom Jimmy Kimmel Jimmy Fallon news Share Reuse this content Most viewed Live German parliament votes again on Merz’s bid to be chancellor after humiliating first round – Europe live Trump and Carney to meet at White House in closely watched encounter Mushroom lunch’s sole surviving guest details deadly meal and its aftermath as trial of Erin Patterson continues ‘It’s the misogyny slop ecosystem!’ How Candace Owens and the American right declared war on Blake Lively Wisconsin woman missing for more than 60 years found ‘alive and well’

Plant cells have three kinds of structures that are not found in animal cells and that are extremely important to plant survival: plastids, central vacuoles, and cell walls. PLANT CELLS Most of the organelles and other parts of the cell just described are common to all eukaryotic cells. However, plant cells have three additional kinds of structures that are extremely important to plant function: cell walls, large central vacuoles, and plastids. To understand why plant cells have structures not found in ani- mal cells, consider how a plant’s lifestyle differs from an animal’s. Plants make their own carbon-containing molecules directly from carbon taken in from the environment. Plant cells take carbon diox- ide gas from the air, and in a process called photosynthesis, they convert carbon dioxide and water into sugars. The organelles and structures in plant cells are shown in Figure 4-21. SECTION 4 OBJECTIVES ● List three structures that are present in plant cells but not in animal cells. ● Compare the plasma membrane, the primary cell wall, and the secondary cell wall. ● Explain the role of the central vacuole. ● Describe the roles of plastids in the life of a plant. ● Identify features that distinguish prokaryotes, eukaryotes, plant cells, and animal cells. VOCABULARY cell wall central vacuole plastid chloroplast thylakoid chlorophyll Chloroplast Golgi apparatus Mitochondrion Cell membrane Nucleolus Nucleus Cytoskeleton Rough endoplasmic reticulum Pore Smooth endoplasmic reticulum Central vacuole Ribosome Cell wall In addition to containing almost all of the types of organelles that animal cells contain, plant cells contain three unique features. Those features are the cell wall, the central vacuole, and plastids, such as chloroplasts. FIGURE 4-21 Copyright © by Holt, Rinehart and Winston. All rights reserved. 88 CHAPTER 4 CELL WALL The cell wall is a rigid layer that lies outside the cell’s plasma membrane. Plant cell walls contain a carbohydrate called cellulose. Cellulose is embedded in a matrix of proteins and other carbohy- drates that form a stiff box around each cell. Pores in the cell wall allow water, ions, and some molecules to enter and exit the cell. Primary and Secondary Cell Walls The main component of the cell wall, cellulose, is made directly on the surface of the plasma membrane by enzymes that travel along the membrane. These enzymes are guided by microtubules inside the plasma membrane. Growth of the primary cell wall occurs in one direction, based on the orientation of the microtubules. Other components of the cell wall are made in the ER. These materials move in vesicles to the Golgi and then to the cell surface. Some plants also produce a secondary cell wall. When the cell stops growing, it secretes the secondary cell wall between the plasma membrane and the primary cell wall. The secondary cell wall is very strong but can no longer expand. The wood in desks and tabletops is made of billions of secondary cell walls. The cells inside the walls have died and disintegrated. CENTRAL VACUOLE Plant cells may contain a reservoir that stores large amounts of water. The central vacuole is a large, fluid-filled organelle that stores not only water but also enzymes, metabolic wastes, and other materials. The central vacuole, shown in Figure 4-22, forms as other smaller vacuoles fuse together. Central vacuoles can make up 90 percent of the plant cell’s volume and can push all of the other organelles into a thin layer against the plasma membrane. When water is plentiful, it fills a plant’s vacuoles. The cells expand and the plant stands upright. In a dry period, the vacuoles lose water, the cells shrink, and the plant wilts. Other Vacuoles Some vacuoles store toxic materials. The vacuoles of acacia trees, for example, store poisons that provide a defense against plant-eating ani- mals. Tobacco plant cells store the toxin nicotine in a storage vacuole. Other vacuoles store plant pigments, such as the colorful pigments found in rose petals. The central vacuole occupies up to 90 percent of the volume of some plant cells. The central vacuole stores water and helps keep plant tissue firm. FIGURE 4-22 Central vacuole Nucleus Chloroplast Copyright © by Holt, Rinehart and Winston. All rights reserved. CELL STRUCTURE AND FUNCTION 89 PLASTIDS Plastids are another unique feature of plant cells. Plastids are organelles that, like mitochondria, are surrounded by a double mem- brane and contain their own DNA. There are several types of plastids, including chloroplasts, chromoplasts, and leucoplasts. Chloroplasts Chloroplasts use light energy to make carbohydrates from carbon dioxide and water. As Figure 4-23 shows, each chloroplast contains a system of flattened, membranous sacs called thylakoids. Thylakoids contain the green pigment chlorophyll, the main mole- cule that absorbs light and captures light energy for the cell. Chloroplasts can be found not only in plant cells but also in a wide variety of eukaryotic algae, such as seaweed. Chloroplast DNA is very similar to the DNA of certain photosyn- thetic bacteria. Plant cell chloroplasts can arise only by the divi- sion of preexisting chloroplasts. These facts may suggest that chloroplasts are descendants of ancient prokaryotic cells. Like mitochondria, chloroplasts are also thought to be the descendants of ancient prokaryotic cells that were incorporated into plant cells through a process called endosymbiosis. Chromoplasts Chromoplasts are plastids that contain colorful pigments and that may or may not take part in photosynthesis. Carrot root cells, for example, contain chromoplasts filled with the orange pigment carotene. Chromoplasts in flower petal cells contain red, purple, yellow, or white pigments. Other Plastids Several other types of plastids share the general features of chloro- plasts but differ in content. For example, amyloplasts store starch. Chloroplasts, chromoplasts, and amyloplasts arise from a common precursor, called a proplastid. Thylakoid Inner membrane Outer membrane chloroplast from the Greek chloros, meaning “pale green,” and plastos, meaning “formed” Word Roots and Origins A chloroplast captures energy from sunlight and uses that energy to convert carbon dioxide and water into sugar and other carbohydrates. FIGURE 4-23 Copyright © by Holt, Rinehart and Winston. All rights reserved. 90 CHAPTER 4 COMPARING CELLS All cells share common features, such as a cell membrane, cyto- plasm, ribosomes, and genetic material. But there is a high level of diversity among cells, as shown in Figure 4-24. There are signifi- cant differences between prokaryotes and eukaryotes. In addition, plant cells have features that are not found in animal cells. Prokaryotes Versus Eukaryotes Prokaryotes differ from eukaryotes in that prokaryotes lack a nucleus and membrane-bound organelles. Prokaryotes have a region, called a nucleoid, in which their genetic material is concen- trated. However, prokaryotes lack an internal membrane system. Plant Cells Versus Animal Cells Three unique features distinguish plant cells from animal cells. One is the production of a cell wall by plant cells. Plant cells contain a large central vacuole. Third, plant cells contain a variety of plastids, which are not found in animal cells. Cell walls, central vacuoles, and plastids are unique features that are important to plant function. 1. Identify three unique features of plant cells. 2. List the differences between the plasma mem- brane, the primary cell wall, and the secondary cell wall. 3. Identify three functions of plastids. 4. Name three things that may be stored in vacuoles. 5. Describe the features that distinguish prokary- otes from eukaryotes and plant cells from animal cells. CRITICAL THINKING

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