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unit 7 Are they teachers?
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Unit 7 Are they teachers? The advantage of direct method is that the teacher can control the class and fit in a lot of activity into a short class period. This leaves plenty of opportunities for the students to hone their skills, especially new ones. On the other hand, because the class is centered around the teacher, some students may not receive proper feedback, and creativity is limited. Also, the lesser talented athletes often tend to get lost in the shuffle while the great athletes shine. However, there are now a multitude of various teaching strategies that can be employed in addition to that method. Ex: Announcements, Module/Unit introductions, Descriptions/modeling of assignments and learning activities, Written or video lectures, Demonstration videos, Presentations, Discussions moderated by instructors, Interactive tutorials. Indirect Method The Indirect Teaching Style allows students to be involved in their own learning through experience and other peer’s knowledge. Students can use critical thinking to expand their learning capabilities by seeing what others may be doing correct and adjusting this to their own knowledge. The Indirect approach is the opposite of what the direct style suggests, but they are both strictly related, meaning you can’t have one without the other. Direct teaching: The instructor stands in front of the class or group and lectures or advises. Indirect teaching: The instructor assumes a more passive role and guides the student interactions. Movement exploration: Incorporates the use of equipment that involves movement. Movement Exploration The movement exploration class is founded on developing a strong, positive association to physical activity. Classes are aimed at developing movement skills and foundational strength through fun and engaging activities. The activities are age appropriate and include games, challenges, and exploration that positively challenge children’s competency while improving their physical capabilities. Skills such as the ability to climb, hold animal shapes, gymnastic style activities, and the introduction to athletic motor skill competencies are the foundations to youth training. This class provides the introduction to strength training to give children the opportunity to learn the skills required to safely and confidently engage in resistance training. Cooperative Skills Cooperative activities teach students to work together for their group's common good. By participating in these activities, students can learn the skills of listening, discussing, thinking as a group, group decision making, and sacrificing individual wants for the common good. There are two primary objectives guiding the teaching of cooperative activities. First, cooperative activities allow students to apply a variety of fundamental motor skills in a unique setting. Students are typically asked to perform motor skills in a specific way, such as “skip in general space” or “balance on one foot and one elbow.” Cooperative activities ask students to perform different activities such as skip with their hands on the shoulders of someone in front of them, walk with big steps while placing their feet on small spots, or walk across an area blindfolded while someone directs their moves. Due to the uniqueness of such experiences, students often find cooperative activities exciting and motivating. Second, cooperative activities are a wonderful medium for teaching social and emotional learning (SEL). SEL offers students an opportunity to understand and manage their emotions. In addition, such activities offer an opportunity to show empathy for others and develop positive relationships. Cooperative activities demand that all students play a role in completing the task or solving the movement problem. Every student, regardless of ability level, is important and contributes to group goals. 9 traits a PE teacher often needs Here are nine essential traits of an effective PE teacher: 1. Athletic ability Athletic ability is an essential trait for a PE teacher because they're often showing kids how to perform exercises. To demonstrate proper form and encourage the kids to continue their fitness education, it's important they can perform the exercises themselves. Having experience with fitness training can enhance a PE teacher's lesson planning because they're familiar with how each exercise affects a person's body. Athletic ability can also refer to an aptitude for sports and games. PE teachers can instruct students on how to play these games or lead after-school activities involving them, like soccer or basketball. An aptitude for sports and games can help a PE teacher encourage students to participate in the activities during class. If the PE teacher enjoys physical activity, they may make the lessons more enjoyable for the student. 2. Teaching ability A PE teacher is a member of a school faculty, so it's essential they have the teaching ability that allows them to communicate lessons to students. There are various skills involved in teaching, including the technical capabilities associated with each professional's particular field. Learning these skills can help PE teacher plan their lessons effectively and connect with their students, meaning they can encourage students to practice fitness skills in optimal ways for their health. Here are some important teaching skills for PE teachers: Having an engaging classroom presence Real-world learning Project building Lesson planning Technology 3. Interpersonal skills PE coaches are part of faculty teams, so working alongside other teachers is an essential part of their job. They often collaborate with a student's general education teacher to address any behavioral issues that arise. They can also team up with other classes to plan activities for students, like field days and special field trips. Communicating with peers can ensure these interactions remain productive and create opportunities for more fulfilling lessons. Teachers can also model emotional skills for their students by displaying positive social interactions. Interpersonal skills can also help PE teachers interact with students and their families. If a student can make a student feel comfortable expressing their needs and preferences, they can often perform physical exercises or play games to the best of their individual capacities. Understanding how to soothe nerves and support students' emotional needs are important examples of interpersonal skills. When interacting with family members, you may use some of these same techniques to communicate effectively and best uplift students. 4. Written and verbal communication Both verbal and written communication is important for PE teachers because they often communicate with students, families and various personnel on a day-to-day basis. For example, a PE teacher uses their communication skills in a lesson plan to describe any student assignments or expectations accurately. They may also write instructions in a document, then explain them in a classroom lecture. They also use communication skills to share their lesson plans with other PE teachers during conferences or classroom development exercises. Many teachers continue to learn their trade even after working as a teacher for many years. They may share tips with each other or special lessons they've developed if they feel another teacher may benefit from it. Creating a community can help PE teachers continue to expand their teaching methodology and receive feedback on their lessons. 5. Patience and adaptability Working with children can require patience and adaptability because they're encountering many new concepts at the same time and learning how to regulate their emotions. As a result, it's important to treat them with patience and care while they're in your class so they can feel comfortable and feel motivated to complete assignments. As children become teenagers, they may require patience and adaptability to account for their changing bodies and attention spans. Like any job where you perform tasks in real-time, certain circumstances may occur that require you to adapt lesson plans. For example, if the weather turns from sunshine to rain on a day you planned for students to run a mile outside, you may need to adapt the lesson plan so they can practice endurance sports inside a gymnasium instead. 6. Organization PE teachers can use organization skills to improve their lesson planning sessions. For example, they can keep their plans in one place, and determine which parts of a semester or quarter to introduce new concepts. Throughout the year, these objectives may change because of unforeseen setbacks, but organizational skills can help PE teachers control the trajectory of their class curriculum. PE teachers can also use organizational skills to maintain their classroom space. Physical education frequently requires balls, equipment and tools to play games that may be on a lesson plan. They also organize equipment and decide where to store it within their classroom or storage space. 7. Creativity Creativity can help a PE teacher develop fun ways to introduce new material to their students or reinforce previous lessons. They can teach new games or devise interesting ideas to change the rules of a game to help keep students engaged. To find inspiration for their lesson plans, they can turn to personal hobbies or media aspects they enjoy, like movie scenes, songs or dances. A varied lesson plan can foster more engagement among students who prefer action- based learning activities, rather than lectures. 8. Focus Focus is an essential trait of a PE teacher because students often require their full attention during class, especially if they're learning a complicated physical task. You can focus your lesson plans around specific elements of physical education you believe are essential for students of a certain age group or skill level. If students require mentorship, you can also focus on each student's needs to supply them with a steady support system. Focusing on your students can help guide your career purpose. It can give you a core value system that informs your lesson plans and mentorship activities. This passion for your student's well-being can also help you become an advocate for each student in your class. You can also help organize funding for different field trips or establish after-school activities to support their interests. 9. Enthusiasm for teaching sports and fitness Enthusiasm is essential for a PE teacher. Many physical education activities require high energy and may suit someone who enjoys teaching them to others. Being an effective PE teacher also requires an enthusiasm for working with kids and making a positive impact on their lives.Owls, such as the young snowy owls on the previous page, have for centuries been symbols of both wisdom and mystery. To many cultures their piercing eyes have conveyed a look of intelligence. Their silent flight through darkened landscapes in search of prey has projected an air of power or wonder. For this chapter and this book, owls are an engaging example of a living organism from the world of biology—the study of life. BIOLOGY AND YOU Living in a small town, in the country, or at the edge of the suburbs, one may be lucky enough to hear an owl's hooting. This experience can lead to questions about where the bird lives, what it hunts, and how it finds its prey on dark, moonless nights. Biology, or the study of life, offers an organized and scientific framework for posing and answering such questions about the natural world. Biologists study questions about how living things work, how they interact with the environment, and how they change over time. Biologists study many different kinds of living things ranging from tiny organisms, such as bacteria, to very large organisms, such as elephants. Each day, biologists investigate subjects that affect you and the way you live. For example, biologists determine which foods are healthy. As shown in Figure 1-1, everyone is affected by this impor- tant topic. Biologists also study how much a person should exer- cise and how one can avoid getting sick. Biologists also study what CHARACTERISTICS OF LIFE The world is filled with familiar objects, such as tables, rocks, plants, pets, and automobiles. Which of these objects are living or were once living? What are the criteria for assigning something to the living world or the nonliving world? Biologists have established that living things share seven characteristics of life. These characteristics are organization and the presence of one or more cells, response to a stimulus (plural, stimuli), homeostasis, metabolism, growth and development, reproduction, and change through time. Organization and Cells Organization is the high degree of order within an organism’s internal and external parts and in its interactions with the living world. For example, compare an owl to a rock. The rock has a spe- cific shape, but that shape is usually irregular. Furthermore, differ- ent rocks, even rocks of the same type, are likely to have different shapes and sizes. In contrast, the owl is an amazingly organized individual, as shown in Figure 1-2. Owls of the same species have the same body parts arranged in nearly the same way and interact with the environment in the same way. Copyright © by Holt, Rinehart and Winston. All rights reserved. ORGANISM (Barn Owl) ORGAN (Owl’s Ear) TISSUE (Nervous Tissue Within the Ear) CELL (Nerve Cell) your air, land, and fAll living organisms, whether made up of one cell or many cells, have some degree of organization. A cell is the smallest unit that can perform all life’s processes. Some organisms, such as bacteria, are made up of one cell and are called unicellular (YOON-uh-SEL-yoo-luhr) organisms. Other organisms, such as humans or trees, are made up of multiple cells and are called multicellular (MUHL-ti-SEL-yoo-luhr) organisms. Complex multicellular organisms have the level of orga- nization shown in Figure 1-2. In the highest level, the organism is made up of organ systems, or groups of specialized parts that carry out a certain function in the organism. For example, an owl’s ner- vous system is made up of a brain, sense organs, nerve cells, and other parts that sense and respond to the owl’s surroundings. Organ systems are made up of organs. Organs are structures that carry out specialized jobs within an organ system. An owl’s ear is an organ that allows the owl to hear. All organs are made up of tissues. Tissues are groups of cells that have similar abilities and that allow the organ to function. For example, nervous tissue in the ear allows the ear to detect sound. Tissues are made up of cells. A cell must be covered by a membrane, contain all genetic information necessary for replication, and be able to carry out all cell functions. Within each cell are organelles. Organelles are tiny structures that carry out functions necessary for the cell to stay alive. Organelles contain biological molecules, the chemical compounds that provide physical structure and that bring about movement, energy use, and other cellular functions. All biological molecules are made up of atoms. Atoms are the simplest particle of an ele- ment that retains all the properties of a certain element. Response to Stimuli Another characteristic of life is that an organism can respond to a stimulus—a physical or chemical change in the internal or external environment. For example, an owl dilates its pupils to keep the level of light entering the eye constant. Organisms must be able to respond and react to changes in their environment to stay alive. ORGANELLE (Mitochondrion) BIOLOGICAL MOLECULE (Phospholipid) ATOM (Oxygen) cell from the Latin, cella meaning “small room,” or “hut” Word Roots and Origins www.scilinks.org Topic: Characteristics of Life Keyword: HM60257 mb06se_bios01.qxd 5/18/07 10:37 AM Page 7 8 CHAPTER 1 Homeostasis All living things, from single cells to entire organisms, have mecha- nisms that allow them to maintain stable internal conditions. Without these mechanisms, organisms can die. For example, a cell’s water content is closely controlled by the taking in or releas- ing of water. A cell that takes in too much water will rupture and die. A cell that doesn’t get enough water will also shrivel and die. Homeostasis (HOH-mee-OH-STAY-sis) is the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. Organisms have regulatory systems that maintain internal conditions, such as temperature, water content, and uptake of nutrients by the cell. In fact, multi- cellular organisms usually have more than one way of maintain- ing important aspects of their internal environment. For example, an owl’s temperature is maintained at about 40°C (104°F). To keep a constant temperature, an owl’s cells burn fuel to produce body heat. In addition, an owl’s feathers can fluff up in cold weather. In this way, they trap an insulating layer of air next to the bird’s body to maintain its body temperature. Metabolism Living organisms use energy to power all the life processes, such as repair, movement, and growth. This energy use depends on metabolism (muh-TAB-uh-LIZ-uhm). Metabolism is the sum of all the chemical reactions that take in and transform energy and materials from the environment. For example, plants, algae, and some bacteria use the sun’s energy to generate sugar molecules during a process called photosynthesis. Some organisms depend on obtaining food energy from other organisms. For instance, an owl’s metabolism allows the owl to extract and modify the chemi- cals trapped in its nightly prey and use them as energy to fuel activities and growth. Growth and Development All living things grow and increase in size. Some nonliving things, such as crystals or icicles, grow by accumulating more of the same material of which they are made. In contrast, the growth of living things results from the division and enlargement of cells. Cell division is the formation of two new cells from an existing cell, as shown in Figure 1-3. In unicellular organisms, the primary change that occurs following cell division is cell enlargement. In multi- cellular life, however, organisms mature through cell division, cell enlargement, and development. Development is the process by which an organism becomes a mature adult. Development involves cell division and cell differen- tiation, or specialization. As a result of development, an adult organism is composed of many cells specialized for different func- tions, such as carrying oxygen in the blood or hearing. In fact, the human body is composed of trillions of specialized cells, all of which originated from a single cell, the fertilized egg. This unicellular organism, Escherichia coli, inhabits the human intestines. E. coli reproduces by means of cell division, during which the original cell splits into two identical offspring cells. FIGURE 1-3 Observing Homeostasis Materials 500 mL beakers (3), wax pen, tap water, thermometer, ice, hot water, goldfish, small dip net, watch or clock with a second hand Procedure 1. Use a wax pen to label three 500 mL beakers as follows: 27°C (80°F), 20°C (68°F), 10°C (50°F). Put 250 mL of tap water in each beaker. Use hot water or ice to adjust the tem- perature of the water in each beaker to match the temperature on the label. 2. Put the goldfish in the beaker of 27°C water. Record the number of times the gills move in 1 minute. 3. Move the goldfish to the beaker of 20°C water. Repeat observations. Move the goldfish to the beaker of 10°C. Repeat observations. Analysis What happens to the rate at which gills move when the temp- erature changes? Why? How do gills help fish maintain homeostasis? Quick Lab mb06se_bios01.qxd 5/18/07 10:37 AM Page 8 THE SCIENCE OF LIFE 9 Reproduction All organisms produce new organisms like themselves in a process called reproduction. Reproduction, unlike other characteristics, is not essential to the survival of an individual organism. However, because no organism lives forever, reproduction is essential for the continuation of a species. Glass frogs, as shown in Figure 1-4, lay many eggs in their lifetime. However, only a few of the frogs’ off- spring reach adulthood and successfully reproduce. During reproduction, organisms transmit hereditary informa- tion to their offspring. Hereditary information is encoded in a large molecule called deoxyribonucleic acid, or DNA. A short segment of DNA that contains the instructions for a single trait of an organism is called a gene. DNA is like a large library. It contains all the books—genes—that the cell will ever need for making all the struc- tures and chemicals necessary for life. Hereditary information is transferred to offspring during two kinds of reproduction. In sexual reproduction, hereditary information recombines from two organisms of the same species. The resulting offspring are similar but not identical to their parents. For example, a male frog’s sperm can fertilize a female’s egg and form a single fer- tilized egg cell. The fertilized egg then develops into a new frog. In asexual reproduction, hereditary information from different organisms is not combined; thus the original organism and the new organism are genetically the same. A bacterium, for example, reproduces asexually when it splits into two identical cells. Change Through Time Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of living organisms evolve or change through time. The ability of populations of organisms to change over time is important for survival in a changing world. This factor is also impor- tant in explaining the diversity of life-forms we see on Earth today. 1. How does biology affect a person’s daily life? 2. How does biology affect society? 3. Name the characteristics shared by living things. 4. Summarize the hierarchy of organization found in complex multicellular organisms. 5. What are the different functions of homeostasis and metabolism in living organisms? 6. How does the growth among living and nonliv- ing things differ? 7. Why is reproduction an important characteristic of life? CRITICAL THINKING 8. Applying Information Crystals of salt grow and are highly organized. Why don’t biologists con- sider them to be alive? 9. Analyzing Models When a scientist designs a space probe to detect life on a distant planet, what kinds of things should it measure? 10. Making Comparisons Both cells and organisms share the characteristics of life. How are cells and organismsood supply will be like in the near future.EVOLUTION OF LIFE Individual organisms change during their lifetime, but their basic genetic characteristics do not change. However, populations of liv- ing organisms do change through time, or evolve. Evolution, or descent with modification, is the process in which the inherited characteristics within populations change over generations, such that genetically distinct populations and new species can develop. Evolution as a theme in biology helps us understand how the various branches of the “tree of life” came into existence and have changed over time. It also explains how organisms alive today are related to those that lived in the past. Finally, it helps us understand the mechanisms that underlie the way organisms look and behave. Natural Selection The ability of populations of organisms to change over time is important for survival in a changing world. According to the theory of evolution by natural selection, organisms that have certain favorable traits are better able to survive and reproduce success- fully than organisms that lack these traits. One product of natural selection is the adaptation of organisms to their environment. Adaptations are traits that improve an indi- vidual’s ability to survive and reproduce. For example, rabbits with white fur and short ears in a snowy place, such as the one in Figure 1-7a, may avoid predators and frostbitten ears more often than those with dark fur and long ears. Thus, the next generation of rabbits will have a greater percentage of animals carrying the genes for white fur and short ears. In contrast, the brown, long- eared rabbit, as shown in Figure 1-7b, would survive and reproduce more successfully in a hot desert environment. The survival and reproductive success of organisms with favor- able traits cause a change in populations of organisms over gener- ations. This descent with modification is an important factor in explaining the diversity of organisms we see on Earth today. 1. Name three unifying themes found in biology. 2. How is the unity and diversity in the living world represented? 3. Identify the three domains and the kingdoms found in each domain. 4. How are organisms interdependent? 5. Describe why evolution is important in explain- ing the diversity of life. 6. Distinguish between evolution and natural selection. CRITICAL THINKING 7. Applying Information Assign the various top- pings you put on pizza to the appropriate domains and kingdoms of life. 8. Analyzing Graphics According to the “tree” in Figure 1-5, which of these pairs are more closely related: Archaea:Bacteria or Archaea:Eukarya? 9. Making Hypotheses Fossil evidence shows that bats descended from shrewlike organisms that could not fly. Write a hypothesis for how natural selection might have led to flying bats. SECTION 2 REVIEW (a) This short-eared arctic hare, Lepus arcticus, is hidden from predators and protected from frostbite in a snowy environment. (b) The mottled brown coats of desert rabbits blend in with the dirt and dry grasses, and their long ears help them radiate excess heat and thus avoid overheating. FIGURE 1-7 (a) (b) Copyright © by Holt, Rinehart and Winston. All rights reserved. THE SCIENCE OF LIFE 13 TH E STUDY OF BIOLOGY Curiosity leads us to ask questions about life. Science provides a way of answering such questions about the natural world. Science is a systematic method that involves forming and testing hypotheses. More importantly, science relies on evidence, not beliefs, for drawing conclusions. SCIENCE AS A PROCESS Science is characterized by an organized approach, called the scientific method, to learn how the natural world works. The methods of science are based on two important principles. The first principle is that events in the natural world have natural causes. For example, the ancient Greeks believed that lightning and thunder occurred because a supernatural god Zeus hurled thunderbolts from the heavens. By contrast, a scientist considers lightning and thunder to result from electric charges in the atmos- phere. When trying to solve a puzzle from nature, all scientists, such as the one in Figure 1-8, accept that there is a natural cause to solve that puzzle. A second principle of science is uniformity. Uniformity is the idea that the fundamental laws of nature operate the same way at all places and at all times. For example, scientists assume that the law of gravity works the same way on Mars as it does on Earth. Steps of the Scientific Method Although there is no single method for doing science, scientific studies involve a series of common steps. 1. The process of science begins with an observation. An observation is the act of perceiving a natural occurrence that causes someone to pose a question. 2. One tries to answer the question by forming hypotheses (singular, hypothesis). A hypothesis is a proposed explanation for the way a particular aspect of the natural world functions. 3. A prediction is a statement that forecasts what would happen in a test situation if the hypothesis were true. A prediction is recorded for each hypothesis. 4. An experiment is used to test a hypothesis and its predictions. 5. Once the experiment has been concluded, the data are analyzed and used to draw conclusions. 6. After the data have been analyzed, the data and conclusions are communicated to scientific peers and to the public. This way oth- ers can verify, reject, or modify the researcher’s conclusions. SECTION 3 OBJECTIVES ● Outline the main steps in the scientific method. ● Summarize how observations are used to form hypotheses. ● List the elements of a controlled experiment. ● Describe how scientists use data to draw conclusions. ● Compare a scientific hypothesis and a scientific theory. ● State how communication in science helps prevent dishonesty and bias. VOCABULARY scientific method observation hypothesis prediction experiment control group experimental group independent variable dependent variable theory peer review All researchers, such as the one releasing an owl above, use the scientific method to answer the questions they have about nature. FIGURE 1-8 Copyright © by Holt, Rinehart and Winston. All rights reserved. 14 CHAPTER 1 OBSERVING AND ASKING QUESTIONS The scientific method generally begins with an unexplained observa- tion about nature. For example, people have noticed for thousands of years that owls can catch prey in near total darkness. As shown in steps and of Figure 1-9, an observation may then raise ques- tions. The owl observation raises the question: How does an owl detect prey in the dark? FORMING A HYPOTHESIS After stating a question, a biologist lists possible answers to a sci- entific question—hypotheses. Good hypotheses answer a question and are testable in the natural world. For example, as shown in step Figure 1-9, there are several possible hypotheses for the question of how owls hunt at night: (a) owls hunt by keen vision in the dark; (b) owls hunt by superb hearing; or (c) owls hunt by detecting the prey’s body heat. Predicting To test a hypothesis, scientists make a prediction that logically fol- lows from the hypothesis. A prediction is what is expected to hap- pen if each hypothesis were true. For example, if hypothesis (a) is true, (owls hunt by keen night vision) then one can predict that the owl will pounce only on the mouse in either a light or a dark room. If hypothesis (b) is true (owls hunt by hearing), then one can pre- dict that in a lighted room, the owl will pounce closer to the mouse’s head. But, in a dark room, the owl should pounce closer to a rustling leaf attached to the mouse. Finally, if hypothesis (c) is true (owls hunt by sensing body heat), then an owl would strike only the prey no matter the room conditions, because owls hunt by detecting the prey’s body heat. 3 1 2 Copyright © by Holt, Rinehart and Winston. All rights reserved. A scientific study includes observations, questions, hypotheses, predictions, experiments, data analysis, and conclu- sions. A biologist can use the scientific method to set up an experiment to learn how an owl captures prey at night. FIGURE 1-9 1 OBSERVATION Owls capture prey on dark nights. 2 QUESTION How do owls detect prey on dark nights? 3 HYPOTHESES a) Owls hunt in the dark by vision. b) Owls hunt in the dark by hearing. c) Owls hunt in the dark by sensing body heat. THE SCIENCE OF LIFE 15 Notice that these predictions make it difficult to distinguish be- tween the vision and body heat hypotheses. The reason is that both hypotheses predict that the owl could grab the mouse in a dark room. Also, these three hypotheses do not eliminate all other factors that could influence how the owl finds its prey. However, testing predictions can allow one to begin rejecting hypotheses and thus to get closer to determining the answer(s) to a question. DESIGNING AN EXPERIMENT Biologists often test hypotheses by setting up an experiment. Step in Figure 1-9 outlines an experiment to test the hypotheses about how an owl hunts at night. First, experimenters set up a room with an owl perch high on one side and a small trap door on the other side for releasing mice. Then, they tied a leaf to each mouse’s tail with a string and released each mouse into the room. Next, each mouse ran silently across the room, but the leaf trailed behind, making a rustling noise. During half of the trials, the lights were on. During the other half, the room was dark. Technicians videotaped all the action in the chamber with an infrared light, which owls cannot see. The researchers then viewed the videos and measured the position of the owl’s strike relative to each mouse’s head. Performing the Experiment Many scientists use a controlled experiment to test their hypotheses. A controlled experiment compares an experimental group and a control group and only has one variable. The control group pro- vides a normal standard against which the biologist can compare results of the experimental group. The experimental group is iden- tical to the control group except for one factor, the independent variable. The experimenter manipulates the independent variable, sometimes called the manipulated variable. 4 4 EXPERIMENT 5 DATA COLLECTION AND ANALYSIS Measure and compare the distance from the owl’s strike to the mouse and to the leaf in light and dark. 6 CONCLUSION Data supported the hearing hypothesis: Owls hunt in the dark by hearing. prey Test predictions of the three hypotheses. Control: In the light Experimental: In the dark 1 2 3 4 5 6 7 8 9 10 11 Predicting Results Materials 2 Petri dishes with agar, cellophane tape, wax pen Procedure 1. Open one of the Petri dishes, and streak your finger across the surface of the agar. 2. Replace the lid, and seal it with the tape. Label this Petri dish with your name and a number 1. 3. Seal the second Petri dish with- out removing the lid. Label this Petri dish with your name and the number 2. 4. Write a prediction about what will happen in each dish. Store your dishes as your teacher directs. Record your observations. Follow your teacher’s directions for disposal of your dishes. Analysis Was your prediction accurate? What evidence can you cite to support your prediction? If you did not obtain the results you predicted, would you change your testing method or your prediction? Explain. Evaluate the importance of obtaining a result that does not support your prediction. Quick Lab mb06se_bios03.qxd 5/18/07 10:40 AM Page 15 16 CHAPTER 1 The independent variable in the owl experiment is the presence or absence of light. In the owl experiment, the control group hunts in the light, and the experimental group hunts in the dark. In addi- tion to varying the independent variable, a scientist observes or measures another factor called the dependent variable, or respond- ing variable, because it is affected by the independent variable. In the owl experiment, the dependent variable is distance from the owl’s strike to the mouse’s head. Testing the Experiment Some controlled experiments are conducted “blind.” In other words, the biologist who scores the results is unaware of whether a given subject is part of the experimental or control group. This factor helps eliminate experimenter bias. Experiments should also be repeated, because living systems are variable. Moreover, scien- tists must collect enough data to find meaningful results. COLLECTING AND ANALYZING DATA Most experiments measure a variable—the dependent variable. This measurement provides quantitative data, data measured in numbers. For example, in the experiment above, scientists mea- sured the distance of an owl’s strike from the prey’s head in cen- timeters, as shown in step of Figure 1-9. An event’s duration in milliseconds is also an example of quantitative data. Biologists usually score the results of an experiment by using one of their senses. They might see or hear the results of an experiment. Scientists also extend their senses with a micro- scope for tiny objects or a microphone for soft sounds. In the owl experiment, biologists extended their vision with infrared cameras. Analyzing and Comparing Data After collecting data from a field study or an experiment and then organizing it, biologists then analyze the data. In analyzing data, the goal is to determine whether the data are reliable, and whether they support or fail to support the predictions of the hypothesis. To do so, scientists may use statistics to help determine relation- ships between the variables involved. They can then compare their data with other data that were obtained in other similar studies. It is also important at this time to determine possible sources of error in the experiment just per- formed. Scientists usually display their data in tables or graphs when analyzing it. For the owl study, biologists could have made a bar graph such as the one in Figure 1-10, which shows the average distance from the owl’s strike relative to the mouse’s head or the leaf in the light and in the dark. 5 5 0 10 15 20 25 In the light In the dark Average distance from strike (cm) Distance Between Owl Strike and a Mouse or From a Leaf Attached to Mouse 30 Mouse Leaf Mouse Leaf The data below are hypothetical results that might occur from the described owl experiment.The independent variable is the darkness of the room, and the dependent variable is how far the owl struck from the mouse’s head.The data show that the owl strikes more accurately at the mouse in the light but strikes more accurately at the leaf in the dark. FIGURE 1-10 Copyright © by Holt, Rinehart and Winston. All rights reserved. THE SCIENCE OF LIFE 17 DRAWING CONCLUSIONS Biologists analyze their tables, graphs, and charts to draw conclu- sions about whether or not a hypothesis is supported, as shown in step of Figure 1-9. The hypothetical owl data show that in the light, owls struck with greater accuracy at the mouse than at the leaf, but in the dark, owls struck with greater accuracy at the leaf than the mouse. Thus, the findings support the hearing hypothe- sis, but not the vision hypothesis. An experiment can only disprove, not prove, a hypothesis. For example, one cannot conclude from the results that the hearing hypothesis is proven to be true. Perhaps the owl uses an unknown smell to strike at the mouse. One can only reject the vision hypothe- sis because it did not predict the results of the experiment correctly. Acceptance of a hypothesis is always tentative in science. The scientific community revises its understanding of phenomena, based on new data. Having ruled out one hypothesis, a biologist will devise more tests to try to rule out any remaining hypotheses. Making Inferences Scientists often draw inferences from data gathered during a field study or experiment. An inference (IN-fuhr-uhns) is a conclusion made on the basis of facts and previous knowledge rather than on direct observations. Unlike a hypothesis, an inference is not directly testable. In the owl study, it is inferred that the owl detects prey from a distance rather than by direct touch. Applying Results and Building Models As shown in Figure 1-11, scientists often apply their findings to solve practical problems. They also build models to represent or describe things. For example in 1953, James Watson and Francis Crick used cardboard balls and wire bars to build physical models of atoms in an attempt to understand the structure of DNA. Mathematical models are sets of equations that describe how dif- ferent measurable items interact in a system. The experimenter can adjust variables to better model the real-world data. CONSTRUCTING A THEORY When a set of related hypotheses is confirmed to be true many times, and it can explain a great amount of data, scientists often reclassify it as a theory. Some examples include the quantum the- ory, the cell theory, or the theory of evolution. People commonly use the word “theory” in a different way than scientists use the word. People may say “It’s just a theory” suggesting that an idea is untested, but scientists view a theory as a highly tested, generally accepted principle that explains a vast number of observations and experimental data. 6 Copyright © by Holt, Rinehart and Winston. All rights reserved. Biologists often apply their knowledge of the natural world to practical problems. Studies on the owl’s keen ability to locate sounds in space despite background noise are helping biotechnologists and bioengineers develop better solutions for people with impaired hearing, such as the people shown in this picture. FIGURE 1-11 18 CHAPTER 1 COMMUNICATING IDEAS An essential aspect of scientific research is scientists working together. Scientists often work together in research teams or sim- ply share research results with other scientists. This is done by publishing findings in scientific journals or presenting them at sci- entific meetings, as shown in Figure 1-12. Sharing information allows others working independently to verify findings or to con- tinue work on established results. For example, Roger Payne pub- lished the results of his owl experiments in a journal in 1971. Then, other biologists could repeat it for verification or use it to study the mechanisms introduced by the paper. With the growing impor- tance of science in solving societal issues, it is becoming increas- ingly vital for scientists to be able to communicate with the public at large. Publishing a Paper Scientists submit research papers to scientific journals for publica- tion. A typical research paper has four sections. First, the Introduction poses the problem and hypotheses to be investigated. Next, the Materials and Methods describe how researchers proceeded with the experiment. Third, the Results state the findings the experiment presented, and finally, the Discussion gives the significance of the experiment and future directions the scientists will take. Job Description Forensic biolo- gists are scientists who study biological materials to investigate potential crimes and other legal issues against humans and animals. Forensic scientists have knowledge in areas of biology, such as DNA and blood pattern analysis, and work in private sector and public laboratories. Focus On a Forensic Biologist As a law enforcement forensic specialist for the Texas Parks and Wildlife Department, Beverly Villarreal assists the game warden in investigations of fish and wildlife violations, such as illegal hunting and fishing. Villarreal analyzes blood and tissue samples to identify species of animals such as fish, birds, and reptiles. Her work helps game wardens as they enforce state laws regarding hunting and fishing. Most people think of forensic scientists as the glamorous crime investigators on TV, but according to Villarreal real forensic scientists “spend a great deal of time at a lab bench running analysis after analysis.” Many of the methods used in animal forensics, such as DNA sequenc- ing, are also used in human forensics. Education and Skills • High school—three years of science courses and four years of math courses. • College—bachelor of science in biol- ogy, including course work in zoology and genetics, plus experience in per- forming DNA analyses. • Skills—patience, attention to detail, and ability to use fine tools. Careers in BIOLOGY Forensic Biologist For more about careers, visit go.hrw.com and type in the keyword HM6 Careers. www.scilinks.org Topic: Scientific Investigations Keyword: HM61358 mb06se_bios03.qxd 5/18/07 10:40 AM Page 18 THE SCIENCE OF LIFE 19 1. What two principles make the scientific method a unique process? 2. Define the roles of observations and hypotheses in science. 3. Summarize the parts of a controlled experiment. 4. Summarize how we make conclusions about the results of an experiment. 5. Why is the phrase, “it’s just a theory” misleading? 6. Give another example of a conflict of interest. CRITICAL THINKING 7. Making Hypotheses On a nocturnal owl’s skull, one ear points up, and the other ear points down. Suggest a hypothesis for this observation. 8. Designing Experiments Design an experiment to establish if owls hunt by keen sight or hunt by heat seeking. 9. Calculating Information What was the average distance between the owl’s strike and the mouse if the recorded differences in this experiment were 25, 22, 19, 19, and 15? SECTION 3 REVIEW After scientists submit their papers to a scientific journal, the editors of that journal will send the paper out for peer review. In a peer review, scientists who are experts in the field anonymously read and critique that research paper. They determine if a paper pro- vides enough information so that the experiment can be duplicated and if the author used good experimental controls and reached an accurate conclusion. They also check if the paper is written clearly enough for broad understanding. Careful analysis of each other’s research by fellow scientists is essential to making scientific progress and preventing scientific dishonesty. HONESTY AND BIAS The scientific community depends on both honesty and good sci- ence. While designing new studies, experimenters must be very careful to prevent previous ideas and biases from tainting both the experimental process and the conclusions. Scientists have to keep in mind that they are always trying to disprove their favorite ideas. Scientists repeat experiments to verify previous findings. This allows for science to have a method for self-correction and it also keeps researchers honest and credible to their peers in the field. Conflict of Interest For most scientists, maintaining a good reputation for collecting and presenting valid data is more important than temporary prestige or income. So, scientists try to avoid any potential conflicts of interest. For example, a scientist who owns a biotechnology company and manufactures a drug would not be the best researcher to critically test that drug’s safety and effectiveness. To avoid this potential con- flict of interest, the scientist allows an unaffected party, such as a research group, to test the drug’s effectiveness. The threat of a potential scandal based on misleading data or conclusions is a pow- erful force in science that helps keep scientists honest and fair. Scientists present their experiments in various forms. The scientists above are presenting their work in the form of a poster at a scientific meeting. FIGURE 1-12 Copyright © by Holt, Rinehart and Winston. All rights reserved. The Internet can provide a wealth of scientific information for a report, but the information may not always be credible or accurate. You can use the methods above to check the accuracy and credibility of your sources. SCIENCE TECHNOLOGY SOCIETY SCIENCE ON THE INTERNET: A New Information Age I n the past, students research- ing a science topic would typ- ically begin their research by visiting a library to use printed reference materials, such as encyclopedias. Today, most stu- dents research topics by using a computer and searching for information on the Internet. The Internet can provide students with a wealth of infor- mation. But which Web sites have accurate information, and which Web sites do not? Checking Web Addresses Students should use the Web address, or URL, to establish the Web site’s credibility. Usually, the domain name can suggest who has published the Web site. Web sites can be pub- lished by governmental agen- cies (ends in “dot gov” or .gov), by educational institutions (ends in “dot edu” or .edu), by organizations (ends in “dot org” or .org), or by commercial businesses (ends in “dot com” or .com). Government Web sites are usually reliable. Examples of credible governmental Web sites are the National Institutes of Health (NIH) and the Food and Drug Administration (FDA). University and medical school sites are also reliable sources of information. Many organiza- tions that research and teach the public about specific diseases and conditions can also provide reliable information. Examples of such organizations are the American Cancer Society and the American Heart Association. Evaluating Web Sites The credibility of the author of the Web site should also be checked. Make sure the author is not trying to sell anything and is established in his or her field. For example, a health Web site’s author should be a med- ical professional. It is also important to check the date that the information was posted on the Web to ensure that the information is current. Also, the Web site should provide ref- erences from valid sources, such as scientific journals or govern- ment publications. Finally, the student should always double-check informa- tion between several reliable Web sites. If two or three reliable sites provide the same informa- tion, the student can feel confi- dent in using that information. Web Sites for Students The Internet Connect boxes in this textbook have all been reviewed by professionals at the National Science Teachers Association (NSTA). Students can trust that these sites are reliable sources for science- or health-related topics. REVIEW 1. Which types of Web addresses are the most reliable? 2. List four important features to evaluate when using a Web site for research. 3. Supporting Reasoned Opinions Why do you think a Web site that is advertising a product may not offer accurate information? REVIEW 20 www.scilinks.org Topic: Using the Internet Keyword: HM61589 mb06se_biosts.qxd 5/18/07 10:42 AM Page 20 TOOLS AND TECHNIQUES With proper equipment and good methods, biologists can see, manipulate, and understand the natural world in new ways. Microscopes are one of many useful tools used to unlock nature’s biological secrets. MICROSCOPES AS TOOLS Tools are objects used to improve the performance of a task. Microscopes are tools that extend human vision by making enlarged images of objects. Biologists use microscopes to study organisms, cells, cell parts, and molecules. Microscopes reveal details that otherwise might be difficult or impossible to see. Light Microscopes To see small organisms and cells, biologists typically use a light microscope, such as the one shown in Figure 1-13. A compound light microscope is a microscope that shines light through a spec- imen and has two lenses to magnify an image. To use this micro- scope, one first mounts the specimen to be viewed on a glass slide. The specimen must be thin enough for light to pass through it. For tiny pond organisms, such as the single-celled paramecium, light passing through the organism is not a problem. For thick objects, such as plant stems, biologists must cut thin slices for viewing. There are four major parts of a compound light microscope. For further description of the parts of a micro- scope, see the Appendix. 1. Eyepiece The eyepiece (ocular (AHK-yoo-luhr) lens) magnifies the image, usually 10 times. 2. Objective Lens Light passes through the specimen and then through the objective lens, which is located directly above the specimen. The objective lens enlarges the image of the specimen. Scientists sometimes use stains to make the image easier to see. 3. Stage The stage is a platform that supports a slide holding the specimen. The slide is placed over the opening in the stage of the microscope. 4. Light Source The light source is a light bulb that provides light for viewing the image. It can be either light reflected with a mirror or an incandescent light from a small lamp. SECTION 4 OBJECTIVES ● List the function of each of the major parts of a compound light microscope. ● Compare two kinds of electron microscopes. ● Describe the importance of having the SI system of measurement. ● State some examples of good laboratory practice. VOCABULARY compound light microscope eyepiece (ocular lens) objective lens stage light source magnification nosepiece resolution scanning electron microscope transmission electron microscope metric system base unit Compound light microscopes open the human eye to an interesting world including tiny pond organisms, healthy and diseased cells, and the functioning of cell parts. FIGURE 1-13 Objective lens Eyepiece (ocular lens) Stage Light THE SCIENCE OF LIFE 21 Copyright © by Holt, Rinehart and Winston. All rights reserved. 22 CHAPTER 1 Magnification and Resolution Microscopes vary in powers of magnification and resolution. Magnification is the increase of an object’s apparent size. Revolving the nosepiece, the structure that holds the set of objective lens, rotates these lenses into place above the specimen. In a typical com- pound light microscope, the most powerful objective lens produces an image up to 100 times (100) the specimen’s actual size. The degree of enlargement is called the power of magnification of the lens. The standard ocular lens magnifies a specimen 10 times (10). To compute the power of magnification of a microscope, the power of magnification of the strongest objective lens (in this case, 100) is multiplied by the power of magnification of the ocular lens (10). The result is a total power of magnification of 1000. Resolution (REZ-uh-LOO-shuhn) is the power to show details clearly in an image. The physical properties of light limit the ability of light microscopes to resolve images, as shown in Figure 1-14a. At pow- ers of magnification beyond about 2,000, the image of the speci- men becomes fuzzy. For this reason, scientists use other microscopes to view very small cellsHealth 11/12 Review for Final Exam Core Concepts - Mental and Emotional Health, Substance Abuse Prevention, Safety and Violence Prevention, Family Life and Human Sexuality, Disease Prevention and Control, Healthy Eating Health Education Skills - goal setting, decision making, accessing information/resources, analyzing influences, communication, self-management, advocacy DIMENSIONS of Wellness - social, spiritual, emotional/mental, environmental, financial, intellectual, multicultural, occupational, physical, sexual RISK factors - anything that increases the risk of disease, injury, or illness. PROTECTIVE factors - anything that decreases the risk of disease, injury, or illness. INTERNAL health factors - health factors that can be either hereditary and genetic or acquired elements -- include smoking and personal diet or eating habits. Example – a genetic predisposition to an illness. EXTERNAL health factors - health factors that are part of the direct outer environment, the geographical location, micro-organisms, socio-economic elements that could affect an individual's health. Example – being unable to afford mental health services. Unit 1- Managing Personal and Community Wellness Explain Maslow’s Hierarchy of Needs in your own words using the image provided. Explain how each Social Determinant of Health may impact a person’s health. Levels of Disease Prevention • PRIMARY The goal is to avoid conditions altogether. • SECONDARY The goal is early detection. • TERTIARY The goal is to minimize the damage (manage). Define the following terms. Fads/Trends Sleep hygiene Driver safety Unit 2- Investigating Social Ecological Factors on Well-Being Socio-Ecological Model – The SEM examines how health behaviors form based on characteristics of individuals, communities, nations and levels in between. Each level overlaps with other levels signifying how the best public health strategies are those that encompass and target a wide range of perspectives. Interpersonal (personal) health vs. intrapersonal (relationship) health Health INEQUITY - systemic, ingrained and unjust barriers that prevent segments of the population from having the opportunity of health leading to health disparity. IMPLICIT BIAS - a form of bias that occurs automatically and unintentionally, that nevertheless affects judgments, decisions, and behaviors. Research has shown implicit bias can contribute to unequal access to quality healthcare, negative patient-provider relationships and interactions; and create mistrust in the healthcare system and practitioners among patients. This can contribute to health disparities. Health DISPARITY - represents a difference in health between populations. It is often used to describe disease burden and other negative health outcomes socially disadvantaged groups may face. Health EQUITY - The opposite of health inequity. It describes a system that supports a high standard of health and healthcare for all people. Racism - Beliefs, attitudes, institutional arrangements, and acts that tend to denigrate individuals or groups because of phenotypic characteristics or ethnic group affiliation. DISCRIMINATION - An unjust differential treatment of a person or a group. PRIVILEGE- The unearned access to resources and social power that are only available to some because of their membership within certain social groups. OPPRESSION is the act of taking away choices from others and can be defined as a system that maintains advantage and disadvantage based on social identities and that acts on multiple levels from interpersonal to institutional and societal. (internalized, interpersonal, institutional, structural) Systematic Oppression - Intentional disadvantage of groups of people based on their identity while advantaging members of dominant group (race, gender, sexual orientation, language, size, ability, etc.). Intersectionality - The complex, cumulative way in which the effects of multiple forms of discrimination (such as racism, sexism, and classism) combine, overlap, or intersect especially in the experiences of marginalized individuals or groups Unit 3- Accessing Resources and Communicating to Support Mental and Emotional Health What is anger? What is anxiety? What is stress? STRESSORS are the things that cause stress. Stressors can be internal and external. A stressor may be a one-time or short-term occurrence, or it can happen repeatedly over a long time. INTERNAL Stressors - are made by your belief system and the way you evaluate yourself. Examples include pessimistic attitude, negative self-talk, deep need to be perfect, low self-esteem or body image, unhealthy standards for self. EXTERNAL Stressors - are stressful things that happen in your surroundings and/or in your environment. Examples include busy schedules, work problems, family issues, financial trouble, social problems, injury, unforeseen circumstances. Socio-economic issues are also a part of external stressors such as poverty, violence, and racism. Define the following mental health conditions. Depression Eating disorders NSSI Non-suicidal self-injury Grief/Loss Suicide prevention A.C.T. • ACKNOWLEDGE- Tell them in a caring way that you recognize that they are having a problem • CARE- You can show you care by actively listening - put away anything else you are doing, make eye contact, sit down, ask questions. • TELL-(call 988 for additional help and support) - Tell them it is important that they speak with a trusted adult. Help them figure out who this may be and offer to go with your friend. A social norm is an unwritten, informal rule meant to guide behavior among the of society. It distinguishes between acceptable and unacceptable, good and bad, and so on. Social norms can influence a person with emotional or mental health disorders, access to care and stigmatize their situation. STIGMA- a mark of disgrace associated with a particular circumstance, quality, or person. • Self-stigma - This describes the internalized stigma that people with mental health conditions feel about themselves. • Public stigma - This refers to the negative attitudes around mental health from people in society. • Institutional stigma - This is a type of systemic stigma that arises from corporations, governments, and other institutions. Unit 4- Evaluating Risks of Substance Use and Abuse Harm Reduction - a set of practical strategies and ideas aimed at reducing negative consequences associated with drug use. Explain how each level of the Social Ecological Model is impacted by addiction. Individual Relationship Community Society SEM Level Contributing/Risk Factors to substance use Preventative/Protective Factors for substance use Individual Interpersonal/Relationship Community Society Unit 5- Analyzing Influences to Examine Ways to Increase Safety and Reduce Violence HATE CRIME - a crime, usually violent, motivated by prejudice or intolerance toward an individual’s national origin, ethnicity, color, religion, gender, gender identity, sexual orientation, or disability. Explain how the media influences violence in society. The Pyramid of Hate Explain the escalation of hate using the Pyramid of Hate visual. List several hate crime motivators. Example: age HEALTHY Relationship Signs - comfortable pace, trust, honesty, independence, respect, equality, kindness, taking responsibility, healthy conflict, fun UNHEALTHY Relationship Signs - intensity, possessiveness, manipulation, isolation, sabotage, belittling, guilting, volatility, deflecting responsibility, betrayal Sexual Assault is a sexual behavior WITHOUT consent. Human trafficking - the recruitment, harboring, transportation, provision, or obtaining of a person for labor or services, using force, fraud, or coercion for the purpose of subjection to involuntary servitude, peonage, debt bondage, or slavery. Sex trafficking - commercial sex act induced by force, fraud, or coercion, or in which the person induced to perform such an act has not attained 18 years of age. Trafficking happens using… • Force - using violence to control someone. • Fraud - using lies to control someone. • Coercion - using threats to control someone. Unit 6- Family Life and Human Sexuality Agency - A belief about yourself and the extent to which you can act on that belief. • The ability to choose freely one’s own narrative. • To embrace the idea that I am the cause (or agent) of my own thoughts and actions. • Personal agency is a personal responsibility for who we are, what we experience, what we do about that experience, and how we shape our world to give us more of the experiences we want. SEXUAL Agency • The ability to choose your own interests and desires vs. what we see in the media or others’ perceptions • The ability to identify, communicate, and negotiate one’s sexual needs • The ability to initiate behaviors that allow for the satisfaction of those needs Sexually Explicit Material - photographs, videos, films, magazines, and books whose primary themes, topics, or depictions involve sexuality that may cause sexual arousal. Sexual scripts - thoughts, patterns, or behavior that a person has about themselves in a romantic or sexual context. It is how people picture themselves or want to project themselves in front of others. Reproductive Rights of Teens - In Maryland, teens have the right to an abortion, keep their child, obtain and use birth control, paternity tests, adoption, give up custody of their child within 10 days of birth (Safe Haven Law). • REPRODUCTIVE RIGHTS- legal rights and the freedom of the individual to control decisions regarding contraception, abortion, sterilization and childbirth. • SAFE HAVEN LAW- a distressed parent who is unable or unwilling to care for their infant can safely give up custody of their baby, no questions asked. CONSENT is an agreement between participants to engage in sexual activity. • It is clearly and freely communicated, verbal, and affirmative. Consent CANNOT be given if… • A person is underage, one or both partners is intoxicated or incapacitated by drugs or alcohol, one partner is asleep or unconscious, one partner feels pressured, threatened or intimidated, or one partner holds a position of power or authority over the other. Unit 7- Advocating for Enhanced Nutrition, Food Systems, and Health Outcomes Dietary Guidelines for Americans Guideline 1: Follow a Healthy Dietary Pattern at Every Life Stage Guideline 2: Customize and Enjoy Food and Beverage Choices to Reflect Personal Preferences, Cultural Traditions, and Budgetary Considerations Guideline 3: Focus on Meeting Food Group Needs with Nutrient-Dense Foods and Beverages, and Stay Within Calorie Limits Guideline 4: Limit Foods and Beverages Higher in Added Sugars, Saturated Fat, and Sodium, and Limit Alcoholic Beverages FOOD DESERT- a neighborhood where there is little or limited access to healthy and affordable food such as fruits, vegetables, whole grains, low-fat milk and other foods that make up the full range of a healthy diet. FOOD INSEQURITY lack of access to a sufficient amount of food because of limited funds. More than 49 million American households are considered food insecure and are vulnerable to poor health as a result. PROCCESED FOODS- any raw agricultural commodities that have been washed, cleaned, milled, cut, chopped, heated, pasteurized, blanched, cooked, canned, frozen, dried, dehydrated, mixed or packaged — anything done to them that alters their natural state.Sc.8.p.8.5 Students will be able to: • Recognize that there are a finite number of elements and that their atoms combine in a multitude of ways to produce compounds that make up all the living and nonliving things that we encounter. • Distinguish among mixtures (including solutions) and pure substances. • Recognize that elements are grouped in the periodic table according to similarities of their properties • Recognize that atoms are the smallest unit of an element and they are composed of sub-atomic particles (electrons surrounding a nucleus containing protons and neutrons) • Explain why theories may be modified but are rarely discarded Advanced Benchmarks: • Write chemical formulas for simple covalent (HCl, SO2, CO2, and CH4) and ionic (Na+ + Cl- + NaCl) and molecular (O2, H2O ) compounds. Predict the formulas of ionic compounds based on the number of valence electrons and the charges on the ions (912.P.8.7) • Use the periodic table and electron configuration to determine an element’s number of valence electrons and its chemical and physical properties. Explain how chemical properties depend almost entirely on the configuration of the outer electron shell (912.P.8.5) • Explain that electrons, protons, and neutrons are parts of the atoms and the nuclei of atoms are composed of protons and neutrons, which experience forces of attraction and repulsion consistent with their charges and masses (912.P.8.4)Electrostatics The section of CBSE Class 12 Physics electrostatic potential and capacitance notes mainly deals with the in-depth analysis of electromagnetic phenomena when they are not performing any movements. Additionally, it is divided into ten further sub-topics to study the companion processes of reaching the state. These are - 1. Electric charge In this section of Physics ch 2 Class 12 notes, you get to learn about the basic features of electric charge and its expression in Physics. Along with its basics, the sections help to understand the full potential of charge. Different aspects of Charge included in Class 12 Physics Chapter 2 notes are - Definition Type: Positive and Negative Charge Unit and dimensional formula Point Charge Properties of Charge Comparison of Charge and Mass Methods of Charging Electroscope 2. Coulomb's Law Force is created when charges of opposite signs attract each other, and they repulse if the signs are the same. Coulomb's law tries to define this phenomenon through a mathematical formula, explicitly mentioned in Physics Class 12 notes Chapter 2. Moreover, there is key information about the variation of the constant k and its effect on a medium. Coulomb's law's vector form and the principle of superimposition are also explained in ch 2 Physics Class 12 notes. (Image will be uploaded soon) 3. Electric Field As stated in Class 12 Physics Chapter 2 notes, every positively or negatively charged particle has their respective electric fields. It feels a force at the time of interaction which might be attraction or repulsion. As it arises from electric charge, it is crucial to know about its different parts like - Electric field intensity Relation between electric force and electric field Super imposition of electric field Point charge Continuous charge distributions Properties of Electric Field Lines Motion of Charged Particles in an Electric field Learning more about the electric field from electric potential and capacitance notes Class 12 helps a student to get a grasp of upcoming chapters. 4. Electric Potential Energy When energy helps a charge to move from an electric field, it is known as the Electric Potential Energy. This section of electrostatic chapter Class 12 notes requires a student to study the Electron volt (eV), and the potential energy that an n number of charges can hold. 5. Electric Potential This section of Class 12 Physics Chapter 2 notes focuses on in-depth learning of Electric Potential or Voltage. Basically, it defines the potential movement of energy. 6. Relation between Electric Field and Potential Apart from knowing more about the relationship between the two values, Physics Class 12 Chapter 2 notes also discuss equipotential surfaces. 7. Electric Dipole Essentially, 'Dipoles' are two opposite points of charge represented with q and –q, with their distance between each other being 2a. Electric Dipoles are crucial in your study of Physics Class 12 Chapter 2 notes to learn more about electric fields and their potential. Additionally, Class 12 Physics Chapter 2 notes focus on the influence of electric dipoles on a uniform electric field mainly through Force and Torque, Work, and Potential Energy. In the last part of Electrostatics, further focus is on using the formulas to their fullest potential. It includes subsections of Electric Field, Electric Potential Energy, Electric Potential, and Electric Dipole. In the notes for electrostatic potential and capacitance, you will find proper solutions accompanied by clear and crisp diagrams for better understanding. 8. Gauss's Law Apart from just discussing the Gauss's Law, in Physics Class 12 ch 2 notes there is a thorough explanation of its properties and applications. The Gauss' Law states that net electric flux passing through a hypothetical closed surface is equal to the net electric charge present within the same closed surface. Being a broad part of the whole chapter, you may need to spend a little more time on it. Moving forward, it starts discussing the properties of conductors in relation to Gauss's Law. The Class 12 Physics notes Chapter 2 perfectly defines the journey to Gauss' Law from Coulomb's Law. Here is the Gauss's Law present in the Class 12 Physics ch 2 notes, (image will be uploaded soon) 9. Capacitors There is a dedicated section about Capacitors in the Class 12 Physics Chapter 2 notes elucidating its functions and importance as storage of potential electric energy. After explaining the structure of a capacitor, it points out the different types, parallel plate, spherical and cylindrical. The section of Chapter 2 notes of Physics Class 12 is further divided into subheads like: Properties of an ideal battery Grouping of capacitors Simple circuits (Series and Parallel) Dielectric Van de Graaff generator Combination of drops Charge distribution method Wheatstone Bridge-based circuit Extended Wheatstone Bridge Infinite network of capacitors Redistribution of charge between two capacitors Vedantu prepares the Class 12 Physics Chapter 2 notes with help from subject matter experts. In the PDF, you get a comprehensive idea of the topic along with potential answers to the most asked questions. Furthermore, the detailed explanation on each section and subsections are written in a simple language allows a student to ace their exams with wholesome knowledge. These Physics Chapter 2 Class 12 notes are going to be one of the best supplementary study materials besides a student’s textbooks. Visit the Vedantu website or download the app to get your hands on all important notes! Important Questions A charge of 4 × 10–8C is uniformly distributed on the surface of a spherical conductor, having a radius of 15 cm. Determine the electric field just outside this sphere at a point that is 15 cm from the centre of this sphere. Determine the capacitance given that the distance between the two plates has been reduced by half and the parallel plate capacitor holds a capacitance of 20 pF (where 1pF = 10-12 F) having air between the two plates. What will be the total capacitance of a combination where three capacitors, each having a capacitance of 20 pF, are connected in series. A square having a side of 10 cm has a 500 µC charge at its centre. Determine the work done to move a charge of 10 µC between two points that are diagonally opposite each other on the square. At an equatorial point, what will be the electrostatic potential because of an electric dipole? Calculate the work done to move a test charge, q, through a length of 1 cm along the equatorial axis of an electric dipole? Polarisation A capacitor has its plates enclosed in a medium that can be filled by insulating substances. A net dipole moment is then induced by an electric field in the dielectric. This event causes the field in an opposite direction. Equipotential Surface An equipotential surface is a type of surface where the potential always has a constant value. If considered as a point charge, the concentric spheres that are centred at a particular area of this charge are basically equipotential surfaces. Advantages of Vedantu's Revision Notes: A Comprehensive Resource for Effective Learning There are several reasons why one may refer to Vedantu's revision notes for studying a subject like Electrostatic Potential and Capacitance. Here are some key points: Comprehensive Coverage: Vedantu's revision notes provide a comprehensive coverage of the entire topic, ensuring that all important concepts and subtopics are included. Concise and Organized: The notes are designed to be concise, focusing on the key points and core ideas. They are organized in a structured manner, making it easy for students to navigate and revise the content. Simplified Explanation: The revision notes offer simplified explanations of complex concepts, making them more accessible and easier to understand. This helps students grasp the material more effectively. Key Formulas and Equations: The notes highlight the key formulas and equations relevant to the topic, ensuring that students have a clear understanding of the mathematical aspects of Electrostatic Potential and Capacitance. Examples and Illustrations: Vedantu's revision notes often include examples and illustrations that help clarify concepts and provide practical applications, enabling students to better relate theory to real-world scenarios. Quick Recap: The revision notes serve as a quick recap of the important points, allowing students to review the material efficiently before exams or assessments. Exam-Oriented Approach: Vedantu's revision notes are designed with an exam-oriented approach, focusing on the topics and concepts that are frequently asked in examinations. This helps students prepare effectively and increase their chances of scoring well. Accessible Anytime: Vedantu's revision notes are easily accessible online, allowing students to study at their convenience and revise the material anytime, anywhere.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, areMake mcq quiz with 4 option in which one is correct -'10 Basis of Material Science • .....;;;";;;"~~;;,,;;,,,,;.;.,,;;,,,;,,;.;,.,------------ 6. Temporary materials: Some materials are meant to be placed in the oral cavity for a short period of time for different reasons. • Temporary crowns: While a permanent crown is prepared in the dental laboratory, the patient must wait for few days before it can be fabricated and cemented into place. Does patient experience any problems during this time period? If the tooth is vital (the pulp is alive), the patient is likely to experience pain and sensitivity while eating and drinking, also it looks unesthetic. What can be done to solve this problem? A temporary crown is placed before the patient leaves the clinic. It is constructed and luted in the same appointment in which the crown preparation is done. Temporary crowns are not very strong or esthetic but they serve adequately till the permanent crown is ready to be cemented. • Temporary restorations: Sometimes it is difficult to decide immediately the best line of treatment for a particular tooth. The exact condition of the pulp may not be obvious to the dentist from the patient's symptoms. A dentist removes all or part of the decay and then places a temporary restoration to have time to observe the behaviour of the pulp or to give the pilip time to heal before deciding the further treatment required. Classification based on Location of Fabrication 4,9 Materials can be classified based on the location of fabrication into: • Direct restorative materials. • Indirect restorative materials Direct restorative materials: They include those materials which are used to restore cavity preparations directly in the oral cavity (Box 1.5). Box 1.5: Examples of direct restorative materials Amalgam, composites, glass ionomer and other materials, which set by chemical reactions in the mouth. Indirect restorative materials: It includes those restorations which must be fabricated outside the mouth, indirectly on a cast/ model/ die, because their processing condition would harm oral tissues. Materials used in the construction of such prosthesis are called indirect restorative materials (Box 1.6). Box 1.6: Examples of indirect restorative materials Gold inlays, crowns of metal, ceramic and polymers, which are processed at elevated temperatures. Some indirect composite restorations can be processed under specific wavelength of light, e.g. Ceramage. Classification based on Longevity of Use 1. Permanent restorations: These restorations are not planned to be replaced for a particular time period. Though they are referred to as permanent, actually they are not, e.g. fillings, crowns, bridges and dentures do not last forever (Fig. 1.5). 2. Temporary restorations: These restorations are planned to be replaced in a short period of time, such as few days to weeks. For ~ Permanent C/) c c -.2 0 c- :;::; Cll co Interim ~ Q; 0 .8ll::1iJ C/) o~ Cll a:: c:=:J Temporary Time period Fig. 1.5: Diagram depicting the time period of use of a restoration. (Arrow in permanent restoration depicts that such restorations are not planned to be replaced for a long period of time.) Introducton to Dental Materials Dental materials Box 1.7: Characteristics of metals 1. High thermal and electrical conductivity 2. Ductility (pure metals are very soft and they can be bent without breaking) 3. Opacity (they do not transmit light) 4. Luster (they have a surface that strongly reflects light and appears bright and shiny) 5. They tend to dissolve to some extent in water or other aqueous solutions, producing cations. 6. All metals are white (actually gray) except for gold, which is yellow, and copper, which is reddish. 7. All metals are solid at room temperature except mercury, which is liquid at room temperature and is used with silver alloys as amalgam. 8. All metals have high melting temperatures because of high strength of the metallic bond that holds the atoms together. 3. Polymers 4. Composites Composites are mixtures of two or more of the first three classes in which the different components remain distinct from one another in the final structure. A common example is composite resin. Fig. 1.7a: Three-dimensional structure of iron (metal) Metals Metals are the oldest of the three classes of materials that have been used as dental materials. Metals are characterized by metallic bonds (Box 1.7) which will be discussed in the next chapter. Metals solidify with their atoms in a regular or crystalline arrangement (see Chapter 2), often in the form of a cube (Fig. 1.7a). example, temporary fillings done in a tooth during root canal treatment, which have to be replaced within 2-4 days during subsequent visits. They are used to protect the tooth and provide function till the final restoration is done. 3. Interim restoration: At times, dental treatment requires "long-term" definite temporary restorations or "interim" restorations. For examle, a 7-year-old child, met with trauma and fractured one of his central incisors. A large composite build- up may serve his immediate requirement until the root formation is completed and a permanent crown is placed. 5 Classification based on the Chemical Nature of the Material These are the atoms that make up a material and the way they are bonded together determine the properties of that materiaLS Weak bonds make for weak materials and vice versa (Table 1.4). Materials can be classified into different categories based on their primary atomic bonds (Fig. 1.6): 1. Metals 2. Ceramics Fig. 1.6: Classification of dental materials based on chemical nature 12 Basis of Material Science Box 1.9: Benefits of ceramics in dentistry 1. Many ceramic oxides are used as pigmenting agents. These oxides produce good range of colors. Due to this characteristic, we are able to match almost any tooth color with good esthetic results. 2. They are inert, i.e. not chemically reactive. This quality provides ceramics with good bio- compatibility. 3. Ceramic materials are translucent, like natural teeth. This translucency gives the ceramic crown a more natural appearance than any other dental material. Fig. 1.7b: Internal arrangement of tetrahedral structure of ceramic (silica) four large oxygen atoms surround smaller silicon atom Ceramics A ceramic is a compound formed by the union of a metallic and a non-metallic element (Box 1.8). Most of these materials are oxides, formed by the union of oxygen with metals such as silicon, aluminum, calcium and magnesium (Fig.1.7b). Ceramics may be simple or complex. Examples of simple ceramics are alumina and silica. Examples of complex ceramics are feldspar (potassium aluminum silicate) and kaolin (hydrated aluminum silicate). Ceramics may be crystalline or non- crystalline (i.e. amorphous). Porcelain is a specific type of ceramic used extensively in dentistry (Box 1.9). Box 1.8: Characteristics of ceramics 1. High melting points. 2. Brittleness, which means they cannot be bent or deformed (no sliding) to any extent without actually cracking and breaking. 3. They are poor conductor of heat and electricity. 4. They are chemically inert. 5. They have excellent esthetic result in terms of matching natural teeth. Fig. 1.8: Stucture of synthetic polymer Polymers They are the latest addition (early to mid- 1900s) to dental materials. Most of the polymers are nowadays synthesized by humans. Polymers are giant, long-chain organic molecules (Fig. 1.8). Polymers are characterized by covalent bonds within each molecule, giving them tremendous strength in a single direction. Try to break a nylon rope by pulling it! They are poor conductors of heat and electri- city. Most polymers have a structure containing thousands of carbon atoms linked together like beads on a string. Others, such as silicone polymers are formed with silicon-oxygen bonds. Introducton to Dental Materials Table 1.4: Characteristics of different materials 13 Characteristics Bond Properties Crystal structure Metals Metallic bonding High strength and hardness, high electrical and thermal conductivity BCC, FCC, or HCP unit cells Ceramics Ionic or covalent bonding, or both High hardness and stiffness, electrically insulating, refractory, and chemically inert Crystalline or amorphous Polymers Covalent bonding Low sensitivity, high electrical resistivity, and low thermal conductivity, strength and stiffness vary widely Amorphous and crystalline Composites Composites are combinations of any of the basic ceramic, metallic and polymeric materials (Box 1.10). Each material that makes up composites is called a phase. Their properties tend to be somewhere between those of their basic constituents and are used to enhance their performance, longevity and handling chracterstics. Box 1.10: Types of composites in dentistry 1. Ceramic - metallic composite: Tungsten carbide bur. 2. Metal - polymer composite: Die materials in dental laboratory. 3. Ceramic - polymer composite: Enamel, dentin, bone and restorative composites. A composite is a kind of "combination" of materials, which compliment each other. The properties lacking in one material are compensated by those of the other material. For example, restorative composite has two phases, namely resin and fillers. Teeth and bones are examples of natural composites. Enamel is a composite of hydroxyapatite (which is a ceramic material) and protein (which is a polymer). EVALUATION OF DENTAL MATERIALS Most manufacturers of dental materials maintain a quality assurance programme (As per international standard like ADA specifications) and materials are thoroughly tested before being released into the market for dental practitioner (Fig. 1.9). Laboratory Evaluations Most ADA/ ANSI specifications involve laboratory tests. The tests performed as per these specifications are useful but they all are performed in vitro, (carried out in the laboratory away from the clinical conditions) which have a lot of limitations in clinical practice.lO Clinical Notes 1. For example, most of the direct restorative materials are tested for their compressive strength but ultimately the material is subjected to a combination of compressive, tensile and shear stresses, which may decide the final success or failure of the material under masticatory load. 2. Similarly upper dentures mostly fracture along the midline because of bending. Hence a bending or transverse strength ~B-a-s-is-o-f-M-a-t-e-ria-I-S~c-ie-n-c-e-------------- ---------. test is far more meaningful for denture base materials than a compression test. Clinical Trials The majority of new materials are subjected to extensive clinical trials normally in co-operation with a dental college or hospital departments prior to their release. CONCLUSION As the number of available materials is going up, it is important that the dentist remains more aware about new products so that their judgement about the selection of material remains successful. Materials which have not been thoroughly evaluated should be avoided, specially with clinical dentistry falling under Consumer Protection Act (CPA). I Research and development I iI Manufacturer/analysis Ideal requirements for clinical use: Thermal, optical, mechanical, chemical, biological Available materials and their properties are evaluated Launch of new I product Choice and selection of material by the dentist Critical assessment based on clinical performance I I H feedback to I