Environmental Science: A Study of Interrelationships (16th Edition) Chapter 7 - PDF

Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Populations: Characteristics and Issues Chapter 7 ENVIRONMENTAL SCIENCE A STUDY OF INTERRELATIONSHIPS, 16TH EDITION 1 © McGraw Hill Death Rate = Human deaths p...

Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Populations: Characteristics and Issues Chapter 7 ENVIRONMENTAL SCIENCE A STUDY OF INTERRELATIONSHIPS, 16TH EDITION 1 © McGraw Hill Death Rate = Human deaths per 1,000 individuals per year. Mortality: The number of deaths in a population over a particular time period. Birth Rate = Humans born per 1,000 individuals per year. Natality: The number of individuals added to a population through reproduction over a particular time period. Genetic differences commonly exist within different populations of a given species. A population is a group of individuals of the same species inhabiting the same area. 7.1 Population Characteristics 2 © McGraw Hill FIGURE 7.1 Genetic Differences between Black Bear Populations Genetic Differences between Black Bear Populations 3 2 © McGraw Hill Species with mortality high only in old age. Species with mortality equitable among age classes. Species with high mortality in young. Three types of survivorship curves can be recognized: A survivorship curve shows the proportion of individuals likely to survive to each age. 7.1 Population Characteristics 4 © McGraw Hill ©Getty Images RF, ©John W Bova/Science Source, ©Courtesy of Monika Al-Mufti Access the text alternative for slide images. Types of Survivorship Curves 5 © McGraw Hill 6 6 © McGraw Hill Age distribution greatly influences the population growth rate. Age distribution is the number of individuals of each age in the population. The number of females is important because females determine the number of offspring produced in sexually reproducing populations. Sex ratio refers to the relative number of males and females in a population. In human population studies it is often expressed as a percentage of the total population. Population growth rate is the birthrate minus the death rate. Population Characteristics 7 © McGraw Hill Access the text alternative for slide images. Source: Data from World Population Data Sheet 2016, Population Reference Bureau, Inc., Washington, D.C. Effect of Birth, Death Rates on Population Size 8 © McGraw Hill Access the text alternative for slide images. Source: Data from United States Census Bureau International Data Base. Age Distribution in Human Populations 9 © McGraw Hill Immigration: Movement into an area. Emigration: Movement from an area. Dispersal: Movement of individuals from densely populated locations to new areas. High population density injures all individuals within the population because they compete severely for necessary resources. Population density is the number of individuals per unit area. Population Density and Spatial Distribution 10 1 © McGraw Hill There is a natural tendency for increase. Biotic potential is the inherent reproductive capacity of a species (biological ability to produce offspring). Generally, biotic potential is much higher than the number needed to replace parents. 7.2 A Population Growth Curve 11 © McGraw Hill Access the text alternative for slide images. Lag Phase: This is the first portion of the curve; slow population growth. Exponential Growth Phase (Log Phase): More organisms are reproducing, causing accelerated growth. Deceleration Phase: The population growth rate slows as the death rate and birth rate come to equal one another. Stable Equilibrium Phase: The death rate and birth rate become equal and the population stops growing. Population growth follows a pattern consisting of a lag phase, an exponential growth phase, a deceleration phase, and a stable equilibrium phase. 7.2 A Population Growth Curve 2 12 1 © McGraw Hill Accidents of nature. Lack of sunlight. Loss of food source. Predators. Factors that prevent unlimited population growth are known as limiting factors. All of the different limiting factors that act on a population are collectively known as environmental resistance. Extrinsic limiting factors are those that come from outside the population. 7.3 Factors That Limit Population Size 13 2 © McGraw Hill Density-independent limiting factors are populationcontrolling influences that are not related to the density of the population. Density-dependent limiting factors are those that become more effective as the density of the population increases. Behavioral changes amongst the population cause lower birthrates and higher death rates. Intrinsic limiting factors are those factors that originate within the population and exercise control over it. 7.3 Factors That Limit Population Size 14 © McGraw Hill Interactions among organisms. Accumulation of waste products. Energy availability. Raw material availability. For most populations, limiting factors recognized as components of environmental resistance can be placed into four main categories: 7.4 Categories of Limiting Factors 15 © McGraw Hill Access the text alternative for slide images. Accumulation of waste products 7.4 Categories of Limiting Factors 16 © McGraw Hill Nutrient levels in aquatic ecosystems. Forest fires, floods, or natural disasters. Disease epidemics. Climate variations. Successional changes. It is not an inflexible number; it can be influenced by environmental differences such as: Carrying capacity is the maximum sustainable population for an area. 7.5 Carrying Capacity 17 © McGraw Hill Access the text alternative for slide images. Carrying Capacity 18 © McGraw Hill r-strategists: Typically, these are small organisms that have a short life, produce many offspring, exploit unstable environments, and do not reach a carrying capacity. K-strategists: Organisms that typically reach a stable population as the population reaches the carrying capacity. Species can be divided into two broad categories based on their reproductive strategies: 1 7.6 Reproductive Strategies and Population Fluctuations 19 © McGraw Hill K-strategists are controlled by density-dependent limiting factors. Reproductive strategy is to invest a great deal of energy in producing a few offspring that have a good chance of living to reproduce. Provide substantial parental care. Produce few offspring. Long-lived. Large organisms. Usually occupy relatively stable environments. K-strategist characteristics include: 2 7.6 Reproductive Strategies and Population Fluctuations 20 © McGraw Hill r-strategists are controlled by density-independent limiting factors. Reproductive strategy is to produce large numbers of offspring to overcome high mortality. Usually do not reach carrying capacity (boom-bust cycles). Exploit unstable environments. Little if any parental care. Produce many offspring. Small, short-lived organisms. r-strategist characteristics include: 3 7.6 Reproductive Strategies and Population Fluctuations 21 © McGraw Hill Access the text alternative for slide images. FIGURE 7.9 A Population Growth Curve for Short-Lived Organisms R-Strategist population cycle 22 Stable Large Long, most live to reproduce Small number produced, parental care provided Density-dependent limiting factors Exponential growth followed by a stable equilibrium stage at the carrying capacity Alligators, humans, redwood trees Environmental stability Size of organism Length of life Number of offspring Primary limiting factors Population growth pattern Examples © McGraw Hill K-Strategist Characteristic Protozoa, mosquitoes, annual plants 23 Exponential growth followed by a population crash Density-independent limiting factors Large number produced, no parental care Short, most die before reproducing Small Unstable r-Strategist Table 7.1 A Comparison of Life History Characteristics of Typical Kand r-Strategists A Comparison of Life History Characteristics of Typical K- and r-Strategists © McGraw Hill 24 © McGraw Hill Access the text alternative for slide images. Many kinds of animals show distinct population cyclesperiods of relatively large populations followed by periods of small populations. Population Cycles 25 1 © McGraw Hill A major reason for the increasing human population growth is a lowering of the death rate due control of disease and improved food production. The human population has been increasing rapidly. 7.7 Human Population Growth 26 © McGraw Hill https://worldpopulationreview.com/ In 1999, the world population passed the six billion mark. The world population has grown tremendously over the past two thousand years. World Population Growth 27 1500 450 million 1650 500 million 1750 700 million 1804 1 billion 1850 1.2 billion 1900 1.6 billion 1927 2 billion 1950 2.55 billion 1955 2.8 billion 1960 3 billion 1965 3.3 billion 1970 3.7 billion © McGraw Hill 1000 275 million 200 million 1 1980 4.5 billion 1985 4.85 billion 1990 5.3 billion 1995 5.7 billion 1999 6 billion 2006 6.5 billion 2009 6.8 billion 2083 10 billion 2043 9 billion 2025 8 billion 2011 7 billion 1975 4 billion World Population Growth 28 2 © McGraw Hill The doubling time for the human population is calculated by:70 / annual rate of increase (%) (70 / 2.0% = 35 years) 7.7 Human Population Growth 29 © McGraw Hill Access the text alternative for slide images. Source: Data from U.S. Census Bureau and the Population Reference Bureau The human population growth curve has a long lag phase followed by a sharply rising exponential growth phase that is still rapidly increasing. The Historical Human Population Curve 30 © McGraw Hill Expected to grow 3.5% between 2020 and 2050. Relatively stable populations. Combined population of 1.27 billion. Europe, Canada, the U.S., Japan, Australia, New Zealand. More-developed countries typically have per capita income exceeding $40,000. The world can be divided into two segments based on economic development. 1 7.8 Human Population Characteristics and Implications 32 © McGraw Hill Combined population of 6.5 billion. All other remaining countries of the world. Less-developed countries typically have a per capita income less than $20,000. 2 7.8 Human Population Characteristics and Implications 33 © McGraw Hill The degree of technological development and affluence is also significant; people in highly developed countries consume huge amounts of resources. Countries with abundant resources can sustain higher population densities than resource-poor countries. Population density relates the size of the population to available resources. Human population growth is tied to economic development and is a contributing factor to nearly all environmental problems. 4 7.8 Human Population Characteristics and Implications 35 © McGraw Hill Wind and solar energy lower environmental impact. Coal-fired power plants contribute to pollution. Firewood for heat can lead to deforestation. Technology: The technology used is an important contributor to environmental impact. Affluence: People in highly developed countries consume huge amounts of resources. 5 7.8 Human Population Characteristics and Implications 36 © McGraw Hill The ecological footprint of the U.S. is 1.5 times locally available resources. Japan is highly developed but has few resources; its ecological footprint is 5 times larger than its locally available resources. Most of the more-developed countries of the world have a much larger ecological footprint than is represented by their land area. The ecological footprint is a measure of the land area required to provide the resources and absorb the wastes of a population. 6 7.8 Human Population Characteristics and Implications 37 © McGraw Hill We can make conscious decisions based on the likely course of events and adjust our lives accordingly. Humans, unlike other kinds of organisms, are influenced by social, political, economic, and ethical factors. 1 7.9 Factors That Influence Human Population Growth 39 © McGraw Hill Zero population growth is when the birth rate equals death rate. proportion of young people leads to higher birth rates.) The age distribution of a population influence population growth (a high population growth. (high birth and low deaths results in large population growth.) The balance between the birth rate and death rate has a large influence on characteristics affect growth, and the consequences of that growth. Demography is the study of populations and their characteristics, how those Biological Factors: 2 7.9 Factors That Influence Human Population Growth 40 © McGraw Hill In male-dominated cultures, traditional role of women is to marry and raise children. The major social factors determining family size are the status and desires of women in the culture. Several factors (religious, traditional, social, and economic) influence the number of children a couple would like to have. Reducing fertility rates would be advantageous, especially in LD Cs, but not everyone agrees. Social Factors: 4 7.9 Factors That Influence Human Population Growth 42 © McGraw Hill During the months a woman is breast feeding, she is less likely to become pregnant again. Breast milk is an excellent source of nutrients and antibodies. In countries where breast feeding is practiced, several benefits accrue. Childrearing practices also influence population growth rates. Women are exposed to a high likelihood of pregnancy for longer. Early marriages foster high fertility rates. Social Factors: 5 7.9 Factors That Influence Human Population Growth 43 © McGraw Hill Parents are more secure when there are many children to look after their own needs in old age. In countries where infant mortality is high, it is traditional to have large families since several of a woman’s children may not live to adulthood. In some cultures women desire large families: Better-educated women are more likely to have access to and use birth control. Financial independence leads to marriage later in life. When level of education increases, fertility rates fall. Lack of education opportunities for women reduces their options. Social Factors: 6 7.9 Factors That Influence Human Population Growth 44 © McGraw Hill Source: Data from Population Reference Bureau, 2017 Data Sheet, and World Development Indicators 2019 from The World Bank. Female Literacy, Total Fertility Rate, and Economic Well-Being Access the text alternative for slide images. Early Marriage and Fertility Rate 7 7.9 Factors That Influence Human Population Growth 45 © McGraw Hill They consume large amounts of the family income. They must be sent to school at great expense. They are prevented from working. In the developed world, large numbers of children are an economic drain. Even young children can be given jobs that contribute to the family economy, such as protecting livestock, gathering firewood, or carrying water. In less developed countries, the economic benefits of children are extremely important. Economic Factors: 8 7.9 Factors That Influence Human Population Growth 46 © McGraw Hill Child tax deductions provide an indirect payment to families. Childcare facilities make it possible for both parents to work. Paid maternity leave and guaranteed job availability upon the mother’s return to work. Several European countries are concerned about low birth rates and have instituted policies to encourage couples to have more children. Governments can either reward or punish high fertility rates. Political Factors: 9 7.9 Factors That Influence Human Population Growth 47 © McGraw Hill One-child policy in China. Sometimes governments provide free or low-cost contraceptives. They provide information on family planning and maternal and child health. Most developing countries are concerned that population growth is too rapid and have instituted programs to limit growth: Political Factors: 10 7.9 Factors That Influence Human Population Growth 48 146.7 211.8 329.9 127.8 Russia Brazil United States Mexico 271.7 220.9 206.1 Indonesia Pakistan Nigeria 37 28 18 21 20 17 12 14 11 10 19 Births per 1,000 Individuals 12 6 7 5 6 6 9 6 13 7 7 5.3 3.6 2.3 2.3 2.2 2.1 1.7 1.7 1.6 1.5 2.3 Total Fertility Rate (Children per Woman per Lifetime) 44% 36% 27% 28% 27% 27% 18% 21% 18% 17% 26% % Population Less Than 15 Years Old © McGraw Hill Source: Population Reference Bureau, 2020 Population Data Sheet. 169.8 Bangladesh 1,400.1 1,402.4 China India 7,773 World Country Current Population (Millions) Deaths per 1,000 Individu als 0 0 0 0 +660,000 0 0 0 --- Migration Rate (Persons per Year) Table 7.2 Population Characteristics of the Ten Most Populous Countries, 2020 +43.1% +30% +13.3% +16% +12.6% +11% +9.7% +8.2% +1.5% +15% 49 Projected Population Change 2020–2035 (%) Population Characteristics of the Ten Most Populous Countries, 2013 © McGraw Hill The higher standard of living is a magnet for refugees or people who seek a better life than is possible where they currently live. Developed countries are under intense pressure to accept immigrants. Birthrates are so low in some countries that immigration is encouraged to offset a potential decline in the number of workingage citizens. Immigration Policies: 11 7.9 Factors That Influence Human Population Growth 50 © McGraw Hill Social status and mobility. Health conditions. Economic well-being. Factors usually included in an analysis of standard of living: Standard of living is a difficult concept to quantify since various cultures have different desires. There appears to be an inverse relationship between a country’s growth rate and its average standard of living. 1 7.10 Population Growth Rates and Standard of Living 51 © McGraw Hill Access the text alternative for slide images. Source: Data from Population Reference Bureau, 2020 Population Data Sheet; and United Nations Development Program Human Development Reports 2018. Standard of Living and Population Growth in Three Countries 53 © McGraw Hill 33% are obese. About 66% of North Americans are overweight or obese. Many people in more-developed countries suffer from overnutrition. A lack of protein in the diet can lead to malnutrition. People in less-developed countries must eat plants themselves instead of feeding the plants to animals and eating the animals. People in less-developed countries generally feed at lower trophic levels than those in the developed world. 2 7.11 Hunger, Food Production, and Environmental Degradation 55 © McGraw Hill Political activities such as war, repayment of foreign debt, corruption, and poor management often determine food availability. Improved plant varieties and agricultural techniques have dramatically increased food production in some parts of the world. Many more-developed countries are net food exporters. In countries where food is in short supply, agricultural land is already being exploited to its limit and there is still a need for more food. 3 7.11 Hunger, Food Production, and Environmental Degradation 56 © McGraw Hill The emphasis must be on selfsufficiency. It works against self-reliance. It provides a temporary relief of symptoms. Solving the problem of food distribution is not an easy question. 4 7.11 Hunger, Food Production, and Environmental Degradation 57 © McGraw Hill Eventually the birth rate falls to equal the death rate and the population stabilizes. (low birth rates and low death rates). Technological development and economic well-being improve and the birth rate falls. Improvements in food production, and healthier living conditions cause the death rate to fall while the birth rate remain high and the population grows. Initially, countries have a stable population with high birth and death rates. Demographic transition is a model that describes changes in population growth rates based on the historical, social, and economic development of Europe and North America. 7.12 The Demographic Transition Concept 1 59 © McGraw Hill Human population is growing much faster than before. Resources are no longer abundant. 7.12 The Demographic Transition Concept 2 60 © McGraw Hill Legal and illegal immigration significantly influences future population growth trends. As members of this group raised families, they had a significant influence on U.S. population growth and trends. This created a population bulge. 1947–1961: birthrates were much higher than today. United States population had a post-war baby boom period, significantly affecting population trends. 7.13 The U.S. Population Picture 62 © McGraw Hill Source: Data from U.S. Department of Commerce, U.S. Census Bureau, International Data Base. Source: Data from U.S. Department of Commerce, U.S. Census Bureau, International Data Base. Access the text alternative for slide images. Source: Data from U.S. Department of Commerce, U.S. Census Bureau, International Data Base. Source: Data from U.S. Department of Commerce, U.S. Census Bureau, International Data Base. Changing Age Distribution of U.S. Population (1980–2010) 63 5 © McGraw Hill Disagreement about exact size and primary limiting factors. The human population will ultimately reach a carrying capacity and stabilize. The human population is subject to same biological constraints as other species. If the world human population continues to grow at its current rate (1.1%), population will nearly 10 billion by 2050. 7.14 What Does the Future Hold? 68 1 © McGraw Hill The world’s population is growing rapidly. The causes of population growth are biological, social, political, philosophical, and theological. A typical population growth curve shows a lag phase followed by an exponential growth phase, a deceleration phase, and a stable equilibrium phase at the carrying capacity. The death rate is the number of deaths in a population in a certain period. The birth rate (natality) is the number of individuals entering the population by reproduction during a certain period. Summary 69 2 © McGraw Hill The demographic transition model suggests that as a country becomes industrialized, its population becomes stabilized. Population growth rates are determined by biological factors, but also by social and economic factors. Demography is the study of human populations and the things that affect them. Most of the growth is occurring in less-developed countries of the world. Summary 70