Loading...

was-were basic Exercises
Quiz by Ismael Reynaga Chumacero
Customize this quiz to suit your class
Instantly translate to 100+ languages
Tag the questions with any skills you have. Your dashboard will track each student's mastery of each skill.
Give this quiz to my class
I __________ late for work on Monday.

We _________ at Kate's house yesterday.

I __________ late for work on Monday.

We _________ at Kate's house yesterday.

They ___________ in the bank at three o'clock.

Mark __________ 7 years old in 2010.

There ____________ a red book in his bag.

You __________ Brian's best friend at school.

There __________ five people in the room.

Last week, Mason and his friends ___________ in the playground.

The film ___________ awful.

The cats ___________ hungry.

Earlier in 2019 there was a lot of femicide uh girls being killed by their boyfriends because they did one or two things there are also cultures of if there is violence in terms of a marital relationship that that is fine if there's a marital rape that that is fine so you find such situations being normalized and it being also a taboo to speak about those issues the 2030 agenda for sustainable development is grounded in respect for human rights and the power of people to change the world every individual on the planet has the right to health and well-being in all aspects of their sexuality their body and their reproductive choices ensuring these rights is integral to addressing poverty education violence against women and gender equality sexual and reproductive health rights are agreed in international law they were fought for by courageous women's rights activists and advocates across a broad range of professional fields and frontline experiences by movements of all ages levels and backgrounds they are still being fought for while progress has been made globally many barriers remain especially for those most marginalized excluded or discriminated against human rights are central to delivering the 17 sustainable development goals in the sustainable development agenda indeed each sdg target is simultaneously a metric and a claim for human rights the interplay between these political commitments and human rights obligations is particularly important when it comes to achieving sexual and reproductive health rights for decades human rights-based tactics have been used to drive progress in this episode of right to a better world experts share challenges they have faced and tactics they have used to address them the challenges they describe occur in settings all around the world the strategies used are ones that they have found to be successful in their own settings viewers are encouraged to learn from these experiences and consider how tactics could be adapted to their own context when sexual and reproductive health begins with equality the discussions decisions programs and policies which follow can build towards a future where every individual is not only born free but lives free and equal in dignity and rights without violence or discrimination the time to take action is now violence against women is any act that results in or is likely to result in physical sexual or psychological harm or suffering to women this includes threats of such acts coercion or arbitrary deprivation of liberty in public or private life it happens everywhere in every country in the home in communities at work and at school crises including health and humanitarian crises frequently contribute to higher rates of violence against women violence against women is directed at women because of their status as women the consequences are dire jeopardizing women's health including sexual and reproductive health and mental health hampering their ability to participate fully in society causing tremendous physical and psychological suffering for both women and their children the majority of women survivors of violence do not disclose or seek any type of services efforts to address violence against women must recognize the many different contexts in which it occurs and the many different forms it can take the majority of violence against women is committed by an intimate partner her current or previous boyfriend or husband globally around 30 of women have experienced physical and or sexual violence by an intimate partner in their lifetime this increases the risk of acquiring an sti or in some regions hiv by 1.5 fold when a woman is experiencing violence especially from her partner she's really unable to keep safe from hiv men have power to decide how when and where sex should be done and the woman is at risk of being infected because she cannot say no schools are another setting where violence against girls can take place assault and harassment during their commute bullying sexual harassment and mental or physical abuse on school property are all challenges across various country contexts this has a direct impact on girls access to inclusive quality education a target of sdg4 and an indirect impact on many of their other human rights young girls are taking advantage of at a very young age and they do not understand the choices and the avenues whereby they can exercise their rights when it comes to sexual productive health and rights and so you find a lot of dropouts and a lot of girls also going through a lot of traumatic experiences that would be avoided if they had guidance promoting a safe and secure working environment for all is a cornerstone of sdg 8. this includes a workplace free from sexual harassment and violence but for many women especially women migrant workers and others in precarious employment this is far from reality so we went to naivasha which is a flower farm and we've met the informal workers the casual liberals working for the flower farms when for example the sexual violence cases are reported companies don't take them very seriously a wide range of tactics have been used to prevent and address violence against women and girls and to recognize it as a fundamental violation of human rights prevention of intimate partner violence is possible when interventions are informed by evidence of what works we started out by describing the problem we've now moved to research on what works what are the kinds of interventions that are successful both for preventing the problem from happening in the first place and also from interventions to respond the respect women framework on preventing violence against women developed by the who un women ohchr and other international agencies promotes seven strategies which focus on relationship skills strengthening empowerment of women services for health justice police and social sector poverty reduction environments made safer including schools workplaces and public spaces child and adolescence abuse prevented and transformation of gender attitudes beliefs and norms this action-oriented framework can enable policy makers and health implementers to design plan implement monitor and evaluate interventions and programs to prevent violence against women we have come a long way for sure we still have some ways to go and we need to do more to stop this violence from happening in the first place this involves addressing the social norms that still prevail in many settings that make this form of violence acceptable women are not exposed to gender-based violence by accident all because of an inbuilt vulnerability violence against women is rooted in discriminatory social norms and power dynamics dismantling these underlying causes of violence against women and girls is at the heart of achieving gender equality and empowering all women and girls as set out in the targets and indicators of sdg 5 ensuring healthy lives in sdg3 and reducing inequalities in sdg 10. women and men are valued differently society has heap privileges on the men while the women are looked at as subordinate power is not only the problem but also the solution to preventing violence against women we are making it personal everyone connects with power every day people living with power or grappling with power they find themselves within this whole conversation if you're working to create gnome change there has to be change at all levels strategies to raise awareness in communities about violence against women and girls are critical as there is still a lot of stigma and shame which inhibits many women and girls from talking about it intervention is like a big complicated word sometimes it's just about talking about dialogue i mean the fact that we went into schools and just began a conversation with parents um bringing them together in the school along with the school personnel and then having the conversation start from there and we also sort of train providers within schools to appropriately refer children to health facilities for care what we found was that this dialogue began to spark other conversations in the community and i guess they just felt that oh it's actually okay to talk about this openly rather than pretend that nothing is going on sassa is a community mobilization approach to prevent violence against women and hiv and aids it is activist led it's not workshop heavy based it comes away from the traditional programming of organizations going to do things themselves instead they support activists who do the activities with their friends and neighbors health systems play a critical role in responding to violence wherever it occurs supporting health workers to respond appropriately to violence as well as ensuring their work environment enables them to provide safe effective and quality survivor centred care are important strategies for better addressing violence against women and girls um we came to learn not to ask direct questions not to give our opinion or our judgment on them and let her speak and once with that flow starts once that connection is established that doctor-patient relationship emotionally is established she will actually tell you the whole history legal frameworks to promote enforce and monitor equality and non-discrimination on the basis of sex are an important sdg 5 indicator but putting laws in place does not automatically make them effective there are existing protections for women in the workplace or for individuals in the workplace in relation to harassment but we know from our call for evidence that they are not actually addressing the problem the recommendations that we developed included government implementing a mandatory duty for employers to take preventative steps to address harassment in the workplace so what we would like to see is government implement a much stronger legislative duty it has taken decades of struggle by the women's rights movement to persuade the international community to view violence against women as a human rights concern and a sustainable development priority not a private matter governments have obligations to respect protect and fulfill the right to a life free of violence and to provide for sanctions when they fail when seeking accountability the priority consideration must always be the safety and well-being of survivors respecting their wishes and autonomy and supporting them to make informed choices about the type of justice they want context is vitally important there are many strategies to hold perpetrators accountable including strategic litigation and public campaigns when the teachers impregnate the girls that means the system has failed and okay what they do is they blacklist the teachers and they are always removed from the payroll but we think that is not enough the case that was quite interesting is where one of the judges she did find a ruling against the teacher service commission the commission that is responsible for hiring teachers asking them that they must take responsibility and they were ordered to pay compensation to the girls who had gotten pregnant while in school the justice police issue came about a few years back when a young girl was raped and the punishment for her being ripped was that harappa she was gang-ripped and therapists were told to slash grass feminist organizations and young women organizations came back to the police and the police commissioner to ask and request that the people who are found to be perpetrators should be punished according to our constitution and according to the laws of the land and those are very big campaigns to get better justice so consequently they were jailed but also it was a sign that the system the police system had to be checked in terms of when someone reports a case any case of violence what happens and how is it followed through the maria pedra is another example of litigation that became a political mobilizer so this was a case from the inter-american commission that really galvanized a change in public policy a huge change because it was a case that addressed gender-based violence intimate partner violence it called on responsibility of brazil also for not having prevented this kind of violence the reality of a case that says you have the right to not be bruised you have the right to be free of physical psychological violence it's powerful it can change women's lives investing in autonomous women's movements has been one of the most important drivers of changes in laws and policies to address violence against women over the past 40 years according to data from over 70 countries women organizing to advance women's status define the very concept of violence against women raised awareness of the issue and put it on national and global policy agendas often we thought that it takes generations or centuries to change working intensely with the communities we can actually see change coming violence against women and girls is a violation of fundamental human rights to life and to physical and psychological integrity not to be tortured or treated in an inhuman and degrading way to respect for private and family life and the right not to be discriminated against this understanding is more than theoretical human rights-based tactics can offer a practical route to addressing systemic challenges across all the circumstances where violence against women and girls occurs including but not limited to at the hands of their partners at school and in the workplace by using evidence-informed prevention strategies addressing power relations and social norms community mobilizing and dialogue supporting health systems and professionals putting in place strong legal frameworks accessing justice and ending impunity feminist organizing and mobilizing every individual can help to deliver the 2030 agenda for sustainable development building a world in which women and girls are free from all forms of violence and discrimination [Music] you
Democratic Constitution in South Africa Struggle against Apartheid • Apartheid was the name of a system of racial discrimination unique to South Africa. • This system was particularly oppressive for the blacks. → They were forbidden from living in white areas. • Since 1950, the blacks, coloured and Indians fought against the apartheid system. • The African National Congress (ANC) was the umbrella organisation that led the struggle against the policies of segregation. • In 1964, Nelson Mandela and seven other leaders were sentenced to life imprisonment in 1964 for daring to oppose the apartheid regime in his country. Towards a New Constitution • As protests and struggles against apartheid had increased, the white regime changed its policies. • After 28 years of imprisonment, Nelson Mandela released from jail. • At the midnight of 26 April 1994, democracy was adopted as a form of government in South Africa. • After two years, a constitution came out which gave to its citizens the most extensive rights available in any country. Why do we need a Constitution? • A constitution is necessary because: → It generates a degree of trust and coordination that is necessary for different kind of people to live together. → It specifies how the government will be constituted, who will have power to take which decisions. → It lays down limits on the powers of the government and tells us what the rights of the citizens are. → It expresses the aspirations of the people about creating a good society. Making of the Indian Constitution • In 1928, Motilal Nehru and eight other Congress leaders drafted a constitution for India. • In 1931, the resolution at the Karachi session of the Indian National Congress dwelt on how independent India’s constitution should look like. • Factors contributed to the making of our Constitution. → Ideals of French Revolution → The practice of parliamentary democracy in Britain → The Bill of Rights in the US → The socialist revolution in Russia The Constituent Assembly • In July 1946, Elections to the Constituent Assembly were held. → The drafting of the document called the constitution was done Constituent Assembly. → Dr. Rajendra Prasad was the Chairman of the Constituent Assembly. → In December 1946, the first meeting was held. • After the country was divided into India and Pakistan, the Constituent Assembly also got divided. • The Assembly adopted the Constitution on 26 November 1949 but it came into effect on 26 January 1950. • To mark this day we celebrate January 26 as Republic Day every year. • The Constituent Assembly worked in a systematic, open and consensual manner. → First some basic principles were decided and agreed upon. → Then a Drafting Committee chaired by Dr. B.R. Ambedkar prepared a draft constitution for discussion. → More than two thousand amendments were considered. Philosophy of the Constitution • The Constitution begins with a short statement of its basic values which is called the Preamble to the constitution. The preamble focuses on: → Justice, social, economic and political. → Liberty of thoughts, expression, belief, faith and worship. → Equality of status and of opportunity. → Fraternity assuring the dignity of the individual and the unity and integrity of the nation.
The Columbian Exchange was the widespread exchange of animals, plants, culture, disease, people, and ideas that began between European countries and their colonies in North and South America. The Spanish came to the Americas in search of gold and other riches. The Europeans wanted to convert the Native Americans to Christianity/Roman Catholicism. Spain had the greatest impact on the culture of Latin America. Sugarcane was a crop that was grown in the Caribbean that required a lot of land and labor. Native populations died out largely due to diseases that they had no natural immunity to before the arrival of Europeans. When the Native populations died out, African slaves were brought over to work. Two cultural elements in Latin America that resulted from the Columbian Exchange were language - Spanish, and religion - Roman Catholicism/Christianity. Environmental Issues Deforestation is the clearing of forests for human demands such as farmland, timber, and mining. The Amazon Rainforest in Brazil is one area experiencing major deforestation. Hurricanes can damage the economies in the Caribbean and Central America by keeping tourists away. Economy The three economic indicators used to determine the Human Development Index (HDI) are: life expectancy, literacy rate, and GDP per capita. Higher literacy rates, GDP per capita, and life expectancy are associated with more developed countries, while lower literacy rates, GDP per capita, and life expectancy are associated with less developed countries. The three sectors of the economy are primary/agriculture (e.g. rancher), secondary/manufacturing (e.g. table factory), and tertiary/services (e.g. teacher). A single product economy is when a country depends on just one product for almost all of its jobs, like the Caribbean Islands depend on tourism. Three disadvantages of a single product economy are: having to import other goods/resources, facing competition from other countries for the same product, and if the product fails, the economy is ruined which could restrict access to goods/resources. A free enterprise/market economy is when individual people and businesses make all economic decisions. A command/communist economy is when the government makes all basic economic decisions. Cuba has a communist economy where the government controls all aspects of the economy.
The Invention of the Automobile An automobile, or car, is a wheeled vehicle that carries its own motor and transports passengers. The automobile as we know it was not invented in a single day by a single inventor. In 1769, the French engineer Nicolas-Joseph Cagnon devised the first self-propelled road vehicle, a military tractor powered by a steam engine. One year later, Cagnon built a steam-driven tricycle that could carry four passengers, but steam engines were very heavy and they proved a poor design for road vehicles. Around 1830, the Scotsman Robert Anderson built the first electric carriage. Both steam and electric road vehicles were soon abandoned in favour of petrol-powered vehicles. In 1876, Nicolaus August Otto built the first practical four-stroke internal combustion engine. In an internal combustion engine, the fuel is burnt inside the engine, while in a steam engine, the fuel is burnt outside. The most common internal combustion engine type is petrol-powered. The first petrol-powered vehicles were developed by Gottlieb Daimler and Karl Benz. In 1885, Karl Benz designed the first three-wheeler powered by an internal combustion engine. In 1891, Benz built the first four-wheeler. The first automobile to be mass-produced in the USA was the 1901 curved-dashed Oldsmobile built by Ransom L.E. Odds. Odds devised the basic concept of the assembly line and started the Detroit-area automobile industry. Henry Ford installed the first conveyor belt-based assembly line in his car factory in Michigan in 1913. The assembly line reduced production costs for cars by reducing assembling time. Ford's famous Model T was assembled in 93 minutes. The Ford Motor Company was launched in 1903, and by 1927, 15 million Model Ts have been manufactured. The modern era of automobiles had begun. The assembly line During the period known as the Industrial Revolution (1760-1850) machines changed people’s lives as well as their methods of manufacturing. Most products people in the industrialized nations use today are manufactured by the process of mass production, that is by people and robots that use power-driven machines. Through the use of mass pro-duction methods and the assembly line, a larger amount of goods can be produced in a given period of time, usually at a lower cost.The assembly line developed at the Ford Motor Com-pany in 1913 had immense influence on the automo-tive industry and on other industrial branches. Henry Ford, founder of the company, had built his first car in 1896 and was unique among automobile inventors. In Ford’s early assembly line, cars were pulled by rope from one worker to the next. This new technique allowed individual workers to stay in one place and perform the same task repeatedly on vehi-cles as they passed by. This reduced production timeby about one-half. Ford later employed the use of conveyor belts to move the parts down the line.
Translator: Joseph Geni Reviewer: Morton Bast Before March, 2011, I was a photographic retoucher based in New York City. We're pale, gray creatures. We hide in dark, windowless rooms, and generally avoid sunlight. We make skinny models skinnier, perfect skin more perfect, and the impossible possible, and we get criticized in the press all the time, but some of us are actually talented artists with years of experience and a real appreciation for images and photography. On March 11, 2011, I watched from home, as the rest of the world did, as the tragic events unfolded in Japan. Soon after, an organization I volunteer with, All Hands Volunteers, were on the ground, within days, working as part of the response efforts. I, along with hundreds of other volunteers, knew we couldn't just sit at home, so I decided to join them for three weeks. On May the 13th, I made my way to the town of Ōfunato. It's a small fishing town in Iwate Prefecture, about 50,000 people, one of the first that was hit by the wave. The waters here have been recorded at reaching over 24 meters in height, and traveled over two miles inland. As you can imagine, the town had been devastated. We pulled debris from canals and ditches. We cleaned schools. We de-mudded and gutted homes ready for renovation and rehabilitation. We cleared tons and tons of stinking, rotting fish carcasses from the local fish processing plant. We got dirty, and we loved it. For weeks, all the volunteers and locals alike had been finding similar things. They'd been finding photos and photo albums and cameras and SD cards. And everyone was doing the same. They were collecting them up, and handing them in to various places around the different towns for safekeeping. Now, it wasn't until this point that I realized that these photos were such a huge part of the personal loss these people had felt. As they had run from the wave, and for their lives, absolutely everything they had, everything had to be left behind. At the end of my first week there, I found myself helping out in an evacuation center in the town. I was helping clean the onsen, the communal onsen, the huge giant bathtubs. This happened to also be a place in the town where the evacuation center was collecting the photos. This is where people were handing them in, and I was honored that day that they actually trusted me to help them start hand-cleaning them. Now, it was emotional and it was inspiring, and I've always heard about thinking outside the box, but it wasn't until I had actually gotten outside of my box that something happened. As I looked through the photos, there were some were over a hundred years old, some still in the envelope from the processing lab, I couldn't help but think as a retoucher that I could fix that tear and mend that scratch, and I knew hundreds of people who could do the same. So that evening, I just reached out on Facebook and asked a few of them, and by morning the response had been so overwhelming and so positive, I knew we had to give it a go. So we started retouching photos. This was the very first. Not terribly damaged, but where the water had caused that discoloration on the girl's face had to be repaired with such accuracy and delicacy. Otherwise, that little girl isn't going to look like that little girl anymore, and surely that's as tragic as having the photo damaged. (Applause) Over time, more photos came in, thankfully, and more retouchers were needed, and so I reached out again on Facebook and LinkedIn, and within five days, 80 people wanted to help from 12 different countries. Within two weeks, I had 150 people wanting to join in. Within Japan, by July, we'd branched out to the neighboring town of Rikuzentakata, further north to a town called Yamada. Once a week, we would set up our scanning equipment in the temporary photo libraries that had been set up, where people were reclaiming their photos. The older ladies sometimes hadn't seen a scanner before, but within 10 minutes of them finding their lost photo, they could give it to us, have it scanned, uploaded to a cloud server, it would be downloaded by a gaijin, a stranger, somewhere on the other side of the globe, and it'd start being fixed. The time it took, however, to get it back is a completely different story, and it depended obviously on the damage involved. It could take an hour. It could take weeks. It could take months. The kimono in this shot pretty much had to be hand-drawn, or pieced together, picking out the remaining parts of color and detail that the water hadn't damaged. It was very time-consuming. Now, all these photos had been damaged by water, submerged in salt water, covered in bacteria, in sewage, sometimes even in oil, all of which over time is going to continue to damage them, so hand-cleaning them was a huge part of the project. We couldn't retouch the photo unless it was cleaned, dry and reclaimed. Now, we were lucky with our hand-cleaning. We had an amazing local woman who guided us. It's very easy to do more damage to those damaged photos. As my team leader Wynne once said, it's like doing a tattoo on someone. You don't get a chance to mess it up. The lady who brought us these photos was lucky, as far as the photos go. She had started hand-cleaning them herself and stopped when she realized she was doing more damage. She also had duplicates. Areas like her husband and her face, which otherwise would have been completely impossible to fix, we could just put them together in one good photo, and remake the whole photo. When she collected the photos from us, she shared a bit of her story with us. Her photos were found by her husband's colleagues at a local fire department in the debris a long way from where the home had once stood, and they'd recognized him. The day of the tsunami, he'd actually been in charge of making sure the tsunami gates were closed. He had to go towards the water as the sirens sounded. Her two little boys, not so little anymore, but her two boys were both at school, separate schools. One of them got caught up in the water. It took her a week to find them all again and find out that they had all survived. The day I gave her the photos also happened to be her youngest son's 14th birthday. For her, despite all of this, those photos were the perfect gift back to him, something he could look at again, something he remembered from before that wasn't still scarred from that day in March when absolutely everything else in his life had changed or been destroyed. After six months in Japan, 1,100 volunteers had passed through All Hands, hundreds of whom had helped us hand-clean over 135,000 photographs, the large majority — (Applause) — a large majority of which did actually find their home again, importantly. Over five hundred volunteers around the globe helped us get 90 families hundreds of photographs back, fully restored and retouched. During this time, we hadn't really spent more than about a thousand dollars in equipment and materials, most of which was printer inks. We take photos constantly. A photo is a reminder of someone or something, a place, a relationship, a loved one. They're our memory-keepers and our histories, the last thing we would grab and the first thing you'd go back to look for. That's all this project was about, about restoring those little bits of humanity, giving someone that connection back. When a photo like this can be returned to someone like this, it makes a huge difference in the lives of the person receiving it. The project's also made a big difference in the lives of the retouchers. For some of them, it's given them a connection to something bigger, giving something back, using their talents on something other than skinny models and perfect skin. I would like to conclude by reading an email I got from one of them, Cindy, the day I finally got back from Japan after six months. "As I worked, I couldn't help but think about the individuals and the stories represented in the images. One in particular, a photo of women of all ages, from grandmother to little girl, gathered around a baby, struck a chord, because a similar photo from my family, my grandmother and mother, myself, and newborn daughter, hangs on our wall. Across the globe, throughout the ages, our basic needs are just the same, aren't they?" Thank you. (Applause) (Applause)
Musical Texture Texture Musical texture is the element of music that analyzes musical layers in terms of number and function. The most basic texture is called monophonic. Oh mama, I'm in fear for my life from the long arm of the law. Monophonic texture has only one layer, a melody. With monophony, it doesn't matter how many instruments and or voices are present if they are all singing or playing the same thing at the same time. It also doesn't matter if the voices or instruments are on the exact same frequency, or if they are singing in octaves. An octave is the distance between two musical pitches that sound almost the same, but one is higher and one is lower. It also doesn't matter if drums are present or not. In most cases, drums, the rhythmic layer, are neither melody nor harmony, and therefore are generally not considered when determining texture type. Too much monophony can be boring, so most music has another kind of layer, harmony. When a melody is supported by a harmony, the texture is homophonic. No one may ever know the feelings inside my mind. All the lines I ever write are running out of time. One layer grabs your attention, and the other layer is just hanging out in the background. Most popular music is homophonic. Notice how there was only one instrument in the previous example, a piano, but there were two different things happening on that instrument, a melody, and a harmony. What if a piece of music has multiple independent layers happening at the same time, and you're not sure which one is the melody? This is called polyphony. Polyphony can occur if you take the same melody but start it at staggered intervals. This is called a round. ♪ The last texture is called heterophony. Heterophony is relatively rare in Western music but is very common in non-Western music. It occurs when there are two or more versions of the same melody happening at the same time. Usually, one of the melody lines has more notes than the other, a kind of musical decoration, and or a slightly different rhythmic pattern. Songs will often use a variety of textures to keep the piece interesting. Come on, I need you, I swear, at this moment, you need everything. Come on, I need you, I swear, at this moment, you need everything. Start trying to identify the musical textures in your favorite music.
Cell Theory The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. Despite the limitations of his now-ancient lenses, van Leeuwenhoek observed the movements of protista (a type of single-celled organism) and sperm, which he collectively termed “animalcules. ” In a 1665 publication called Micrographia, experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens. In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells. image Figure 4.3.1 : Structure of an Animal Cell: The cell is the basic unit of life and the study of the cell led to the development of the cell theory. By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory. Schleiden and Schwann proposed spontaneous generation as the method for cell origination, but spontaneous generation (also called abiogenesis) was later disproven. Rudolf Virchow famously stated “Omnis cellula e cellula”… “All cells only arise from pre-existing cells. “The parts of the theory that did not have to do with the origin of cells, however, held up to scientific scrutiny and are widely agreed upon by the scientific community today. The generally accepted portions of the modern Cell Theory are as follows: The cell is the fundamental unit of structure and function in living things. All organisms are made up of one or more cells. Cells arise from other cells through cellular division. The expanded version of the cell theory can also include: Cells carry genetic material passed to daughter cells during cellular division All cells are essentially the same in chemical composition Energy flow (metabolism and biochemistry) occurs within cells
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