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Unit 1: Body
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Health 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 â 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 â being unable to afford mental health services. Unit 1- Managing Personal and Community Wellness Explain Maslowâs Hierarchy of Needs in your own words using the image provided. Explain how each Social Determinant of Health may impact a personâs 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 â 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 individualâs 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 oneâs 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 othersâ perceptions ⢠The ability to identify, communicate, and negotiate oneâs 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 â anything done to them that alters their natural state.
Make a test, with answers best on the following: Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells. Supporting Content LS1.A: Structure and Function ⢠All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different numbers and types of cells (multicellular). (MS-LS-1.1) Further Explanation: Emphasis is on developing evidence that living things are made of cells, distinguishing between living and non-living things, and understanding that living things may be made of one cell or many and varied cells. In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions. (MS-LS-1.3) Further Explanation: Emphasis is on the conceptual understanding that cells form tissues and tissues form organs specialized for particular body functions. Examples could include the interaction of subsystems within a system and the normal functioning of those systems. Organisms reproduce, either sexually or asexually, and transfer their genetic information to their offspring. (MS-LS-1.4) ⢠Living things share certain characteristics. (These include response to environment, reproduction, energy use, growth and development, life cycles, made of cells, etc.) (MS-LS1.4) Further Explanation: Examples should include both biotic and abiotic items, and should be defended using accepted characteristics of life. Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use. (MS-LS-1.5) Further Explanation: Emphasis is on tracing movement of matter and flow of energy. Supporting Content LS1.C: Organization for Matter and Energy Flow in Organisms ⢠Within individual organisms, food moves through a series of chemical reactions (cellular respiration) in which it is broken down and rearranged to form new molecules, to support growth, or to release energy. (MS-LS-1.6) Further Explanation: Emphasis is on describing that molecules are broken apart and put back together and that in this process, energy is released and on understanding that the elements in the products are the same as the elements in the reactants. Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors. (MS-LS-2.1) ⢠In any ecosystem, organisms and populations with similar requirements for food, water, oxygen, or other resources may compete with each other for limited resources, access to which consequently constrains their growth and reproduction. (MS-LS-2.1) ⢠Growth of organisms and population increases are limited by access to resources. (MS-LS-2.1) Further Explanation: Emphasis is on cause and effect relationships between resources and growth of individual organisms and the numbers of organisms in ecosystems during periods of abundant and scarce resources. Similarly, predatory interactions may reduce the number of organisms or eliminate whole populations of organisms. Mutually beneficial interactions, in contrast, may become so interdependent that each organism requires the other for survival. Although the species involved in these competitive, predatory, and mutually beneficial interactions vary across ecosystems, the patterns of interactions of organisms with their environments, both living and nonliving, are shared. (MS-LS-2.2) Further Explanation: Emphasis is on predicting consistent patterns of interactions in different ecosystems in terms of the relationships among and between organisms and abiotic components of ecosystems. Examples of types of interactions could include competitive, predatory, and mutually beneficial. Food webs are models that demonstrate how matter and energy is transferred between producers, consumers, and decomposers as the three groups interact within an ecosystem. Transfers of matter into and out of the physical environment occur at every level. Decomposers recycle nutrients from dead plant or animal matter back to the soil in terrestrial environments or to the water in aquatic environments. The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem. (MS-LS-2.3) Further Explanation: Emphasis is on describing the conservation of matter and flow of energy into and out of various ecosystems, and on defining the boundaries of the system. Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions to any physical or biological component of an ecosystem can lead to shifts in all its populations. (MSLS-2.5) Further Explanation: Emphasis is on recognizing patterns in data and making warranted inferences about changes in populations, and on evaluating empirical evidence supporting arguments about changes to ecosystems. Biodiversity describes the variety of species found in Earthâs terrestrial and oceanic ecosystems. The completeness or integrity of an ecosystemâs biodiversity is often used as a measure of its health. (MS-LS-2.6) Supporting Content LS4.D: Biodiversity ⢠Changes in biodiversity can influence humansâ resources, such as food, energy, and medicines, as well as ecosystem services that humans rely onâfor example, water purification and recycling. (MS-LS-2.6) Supporting Content ETS1.B: Developing Possible Solutions ⢠There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem. (MS-LS-2.6) Further Explanation: Examples of ecosystem services could include water purification, nutrient recycling, and prevention of soil erosion. Examples of design solution constraints could include scientific, economic, and social considerations. Genes are located in the chromosomes of cells, with each chromosome pair containing two variants of each of many distinct genes. Each distinct gene chiefly controls the production of specific proteins, which in turn affects the traits of the individual. Structural changes to genes (mutations) can result in changes to proteins, which can affect the structures and functions of the organism and thereby change traits. (MS-LS-3.1) Supporting Content LS3.B: Variation of Traits ⢠In addition to variations that arise from sexual reproduction, genetic information can be altered because of mutations. Though rare, mutations may result in significant changes to the structure and function of proteins. Changes can be beneficial, harmful, or neutral to the organism. (MS-LS-3.1) Further Explanation: Emphasis is on conceptual understanding that changes in genetic material may result in making different proteins. Organisms reproduce, either sexually or asexually, and transfer their genetic information to their offspring. (MS-LS-3.2) Supporting Content LS3.A: Inheritance of Traits ⢠Variations of inherited traits between parent and offspring arise from genetic differences that result from the subset of chromosomes (and therefore genes) inherited. (MS-LS-3.2) Supporting Content LS3.B: Variation of Traits ⢠In sexually reproducing organisms, each parent contributes half of the genes acquired (at random) by the offspring. Individuals have two of each chromosome and hence two alleles of each gene, one acquired from each parent. These versions may be identical or may differ from each other. (MS-LS-3.2) Further Explanation: Emphasis is on using models such as simple Punnett squares and pedigrees, diagrams, and simulations to describe the cause and effect relationship of gene transmission from parent(s) to offspring and resulting genetic variation. The collection of fossils and their placement in chronological order is known as the fossil record and documents the change of many life forms throughout the history of the Earth. Anatomical similarities and differences between various organisms living today and between living and once living organisms in the fossil record enable the classification of living things. (MS-LS-4.1, MS-LS-4.2) Further Explanation: Emphasis is on finding patterns of changes in the level of complexity of anatomical structures in organisms and the chronological order of fossil appearance in the rock layers. The collection of fossils and their placement in chronological order is known as the fossil record and documents the change of many life forms throughout the history of the Earth. Anatomical similarities and differences between various organisms living today and between living and once living organisms in the fossil record enable the classification of living things. (MS-LS-4.1, MS-LS-4.2) Further Explanation: Emphasis is on explanations of the relationships among organisms in terms of similarity or differences of the gross appearance of anatomical structures. Scientific genus and species level names indicate a degree of relationship. (MS-LS-4.3) Further Explanation: Emphasis is on inferring general patterns of relatedness among structures of different organisms by comparing diagrams, pictures, specimens, or fossils. Natural selection leads to the predominance of certain traits in a population, and the suppression of others. (MS-LS-4.4) Further Explanation: Emphasis is on using concepts of natural selection, including overproduction of offspring, passage of time, variation in a population, selection of favorable traits, and heritability of traits. In artificial selection, humans have the capacity to influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed to offspring. (MS-LS-4.5) Further Explanation: Emphasis is on identifying and communicating information from reliable sources about the influence of humans on genetic outcomes in artificial selection (such as genetic modification, animal husbandry, gene therapy), and on the influence these technologies have on society as well as the technologies leading to these scientific discoveries. Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes. (MS-LS-4.6) Further Explanation: Emphasis is on using mathematical models, probability statements, and proportional reasoning to support explanations of trends in changes to populations over time. Examples could include Peppered Moth population changes before and after the industrial revolution.
Land warfare is a complex domain that involves the application of military power on the ground to achieve political and strategic objectives. Modern military doctrine, such as that used by the U.S. Army and the Indian Army, categorizes these elements into Combat Power and the Principles of War. 1. The 8 Elements of Combat Power Combat power is the total means of destructive, constructive, and information capabilities that a military unit can apply. It is typically broken down into eight key elements: ElementDescriptionLeadershipThe "multiplier" of all other elements. It provides purpose, direction, and motivation to soldiers.InformationEnables commanders to make informed decisions and creates opportunities to achieve results.Mission CommandThe system used to integrate the other elements. It focuses on decentralized execution based on the commander's intent.Movement & ManeuverThe movement of forces to gain a positional advantage over the enemy to deliver lethal or non-lethal effects.IntelligenceThe understanding of the enemy, terrain, weather, and civil considerations.FiresThe use of weapon systems (artillery, mortars, air support) to create specific lethal or non-lethal effects.SustainmentThe logistics required to maintain operations, including ammunition, fuel, food, and medical support.ProtectionThe preservation of the force so that the commander can apply maximum combat power.2. The Principles of War These are the enduring "rules of thumb" that guide how land forces are employed strategically and tactically: Objective: Direct every operation toward a clearly defined and attainable goal. Offensive: Seize, retain, and exploit the initiative. You cannot win by defending alone. Mass: Concentrate the effects of combat power at the most advantageous place and time. Economy of Force: Allocate the minimum essential combat power to secondary efforts so you can "mass" elsewhere. Maneuver: Place the enemy in a position of disadvantage through flexible movement. Unity of Command: Ensure all forces operate under a single responsible commander toward a common objective. Security: Prevent the enemy from gaining an unexpected advantage. Surprise: Strike the enemy at a time, place, or in a manner for which they are unprepared. Simplicity: Prepare clear, uncomplicated plans to minimize confusion in the "fog of war." 3. The Modern Legal Framework Land warfare is also governed by the Law of Land Warfare (International Humanitarian Law), which rests on four pillars: Military Necessity: Actions must be necessary to achieve a legitimate military goal. Distinction: Forces must distinguish between combatants and non-combatants (civilians). Proportionality: The anticipated harm to civilians must not be excessive in relation to the concrete military advantage gained. Unnecessary Suffering: Weapons and methods must not cause gratuitous or superfluous injury. Note: Contemporary land warfare is increasingly "Multi-Domain," meaning land forces must now integrate with cyber, space, and electronic warfare to be effective. , While land warfare uses many tools, the two primary "philosophies" of how to win a war are Attrition and Maneuver. Most modern conflicts are a spectrum of both, but understanding the pure form of each helps explain military strategy. 1. Attrition Warfare: The "Sledgehammer" Attrition warfare is a strategy where one side attempts to win by wearing down the enemy to the point of collapse through continuous losses in personnel, equipment, and supplies. Core Logic: "I have more than you." It assumes that if you can destroy the enemyâs resources faster than they can replace them, you will eventually win. Focus: Firepower and mass. Success is measured by "body counts," equipment destroyed, and the steady seizing of terrain. Command Style: Usually centralized and methodical. It requires strict synchronization of massive resources (artillery, logistics, manpower). Historical Example: The Battle of Verdun (WWI). German Chief of Staff Erich von Falkenhayn famously stated his goal was to "bleed France white" by forcing them to defend a position they could not afford to lose, regardless of the cost in lives. 2. Maneuver Warfare: The "Scalpel" Maneuver warfare seeks to shatter the enemyâs moral and physical cohesionâtheir ability to act as a unified forceârather than simply destroying every soldier. Core Logic: "I am faster and more unpredictable than you." It aims to create a state of chaos where the enemy's leadership can no longer make effective decisions. Focus: Speed, surprise, and dislocation (forcing the enemy to be in the wrong place at the wrong time). The OODA Loop: Developed by Col. John Boyd, this is the heart of maneuver theory. It stands for Observe, Orient, Decide, Act. The goal is to cycle through these steps faster than the enemy, essentially "getting inside" their decision-making process until they collapse from confusion. Historical Example: The 1940 Invasion of France (Blitzkrieg). Instead of fighting a line-by-line battle of attrition, German forces used speed and concentrated armor to bypass strongpoints, cut communication lines, and cause a total systemic collapse of the French military in weeks. 3. Key Differences at a Glance FeatureAttrition WarfareManeuver WarfareObjectivePhysical destruction of the enemy army.Functional/Psychological collapse of the enemy.TargetThe enemy's strength (mass).The enemy's weakness (vulnerability).Primary ToolMassed Firepower.Movement and Tempo.Command"Command Push" (Top-down, rigid)."Recon Pull" (Decentralized, flexible).Success MetricExchange ratios (Kill counts).Disruption and loss of enemy control.4. The Modern Synthesis: "Schwerpunkt" In practice, no army is purely "maneuver" or "attrition." To maneuver successfully, you often need a period of attrition to punch a hole in the enemy's line. A critical concept here is the Schwerpunkt (Center of Gravity/Focus of Effort). A commander identifies the single most important place to strike and concentrates all available "elements of power" there. While the rest of the front might look like attrition, the Schwerpunkt is where the maneuver happens to achieve a breakthrough. Modern Reality: In high-intensity conflicts today (like the war in Ukraine), we see a "return to attrition" because modern sensors (drones, satellites) make it very difficult to achieve the surprise needed for pure maneuver warfare. When you can see everything, it's hard to be "unexpected."
Figure 18-11 represents the amount of energy stored as organic material in each trophic level in an ecosystem. The pyramid shape of the diagram indicates the low percentage of energy transfer from one level to the next. On average, 10 percent of the total energy consumed in one trophic level is incor- porated into the organisms in the next. Why is the percentage of energy transfer so low? One reason is that some of the organisms in a trophic level escape being eaten. They eventually die and become food for decomposers, but the energy contained in their bodies does not pass to a higher trophic level. Even when an organism is eaten, some of the molecules in its body will be in a form that the consumer cannot break down and use. For example, a cougar cannot extract energy from the antlers, hooves, and hair of a deer. Also, the energy used by prey for cellu- lar respiration cannot be used by predators to synthesize new bio- mass. Finally, no transformation or transfer of energy is 100 percent efficient. Every time energy is transformed, such as during the reactions of metabolism, some energy is lost as heat. Limitations of Trophic Levels The low rate of energy transfer between trophic levels explains why ecosystems rarely contain more than a few trophic levels. Because only about 10 percent of the energy available at one trophic level is transferred to the next trophic level, there is not enough energy in the top trophic level to support more levels. Organisms at the lowest trophic level are usually much more abundant than organisms at the highest level. In Africa, for exam- ple, you will see about 1,000 zebras, gazelles, and other herbivores for every lion or leopard you see, and there are far more grasses and shrubs than there are herbivores. Higher trophic levels con- tain less energy, so, they can support fewer individuals.A population is a group of organisms that belong to the same species and live in a particular place at the same time. All of the bass living in a pond during a certain period of time make up a pop- ulation because they are isolated in the pond and do not interact with bass living in other ponds. The boundaries of a population may be imposed by a feature of the environment, such as a lake shore, or they can be arbitrarily chosen to simplify a study of the population. The humans shown in Figure 19-1 are part of the pop- ulation of a city. The properties of populations differ from those of individuals. An individual may be born, it may reproduce, or it may die. A population study focuses on a population as a wholeâhow many individuals are born, how many die, and so on. Population Size A populationâs size is the number of individuals that the population contains. Size is a fundamental and important population property but can be difficult to measure directly. If a population is small and composed of immobile organisms, such as plants, its size can be determined simply by counting individuals. Often, though, individ- uals are too abundant, too widespread, or too mobile to be counted easily, and scientists must estimate the number of individuals in the population. Suppose that a scientist wants to know how many oak trees live in a 10 km2 patch of forest. Instead of searching the entire patch of forest and counting all the oak trees, the scientist could count the trees in a smaller section of the forest, such as a 1 km2 area. The scientist could then use this value to estimate the population of the larger area. SECTION 1 OBJECTIVES â Describe the main properties that scientists measure when they study populations. â Compare the three general patterns of population dispersion. â Identify the measurements used to describe changing populations. â Compare the three general types of survivorship curves. VOCABULARY population population density dispersion birth rate death rate life expectancy age structure survivorship curve FIGURE 19-1 A population can be widely distributed, as Earthâs human population is, or confined to a small area, as species of fish in a lake are. Copyright Š by Holt, Rinehart and Winston. All rights reserved. 382 CHAPTER 19 If the small patch contains 25 oaks, an area 10 times larger would likely contain 10 times as many oak trees. A similar kind of sampling technique might be used to estimate the size of the pop- ulation shown in Figure 19-2. To use this kind of estimate, the sci- entist must assume that the distribution of individuals in the entire population is the same as that in the sampled group. Estimates of population size are based on many such assumptions, so all esti- mates have the potential for error. Population Density Population density measures how crowded a population is. This measurement is always expressed as the number of individuals per unit of area or volume. For example, the population density of humans in the United States is about 30 people per square kilome- ter. Table 19-1 shows the population sizes and densities of humans in several countries in 2003. These estimates are calculated for the total land area. Some areas of a country may be sparsely popu- lated, while other areas are very densely populated. Dispersion A third population property is dispersion (di-SPUHR-zhuhn). Dispersion is the spatial distribution of individuals within the popu- lation. In a clumped distribution, individuals are clustered together. In a uniform distribution, individuals are separated by a fairly con- sistent distance. In a random distribution, each individualâs location is independent of the locations of other individuals in the popula- tion. Figure 19-3 illustrates the three possible patterns of dispersion. Clumped distributions often occur when resources such as food or living space are clumped. Clumped distributions may also occur because of a speciesâ social behavior, such as when animals gather into herds or flocks. Uniform distributions may result from social behavior in which individuals within the same habitat stay as far away from each other as possible. For example, a bird may locate its nest so as to maximize the distance from the nests of other birds. These migrating wildebeests in East Africa are too numerous and mobile to be counted. Scientists must use sampling methods at several locations to monitor changes in the population size of the animals. FIGURE 19-2 TABLE 19-1 Population Size and Density of Some Countries Population size Population density Country (in millions) (in individuals/km2) China 1,289 135 India 1,069 325 United States 292 30 Russia 146 8 Japan 128 337 Mexico 105 54 Kenya 32 54 Australia 20 3 dispersion from the Latin dis-, meaning âout,â and spargere, meaning âto scatterâ Word Roots and Origins Copyright Š by Holt, Rinehart and Winston. All rights reserved. POPULATIONS 383 The social interactions of birds called gannets, which are shown in Figure 19-3b, result in a uniform distribution. Each gannet chooses a small nesting area on the coast and defends it from other gannets. In this way, each gannet tries to maximize its distance from all of its neighbors, which causes a uniform distribution of individuals. Few populations are truly randomly dispersed. Rather, they show degrees of clumping or uniformity. The dispersion pattern of a population sometimes depends on the scale at which the popu- lation is observed. The gannets shown in Figure 19-3b are uni- formly distributed on a scale of a few meters. However, if the entire island on which the gannets live is observed, the distribution appears clumped because the birds live only near the shore. POPULATION DYNAMICS All populations are dynamicâthey change in size and composition over time. To understand these changes, scientists must know more than the populationâs size, density, and dispersion. One important measure is the birth rate, the number of births occur- ring in a period of time. In the United States, for example, there are about 4 million births per year. A second important measure is the death rate, or mortality rate, which is the number of deaths in a