People And The Earth's Ecosystem PDF

PEOPLE AND THE EARTH’S ECOSYSTEM  OVERVIEW This course emphasizes that life on Earth as we know it is an integrated and interdependent whole; its future is endangered by the impact of human development on natural resources; its survival for future generations will depend on concerted action...

PEOPLE AND THE EARTH’S ECOSYSTEM  OVERVIEW This course emphasizes that life on Earth as we know it is an integrated and interdependent whole; its future is endangered by the impact of human development on natural resources; its survival for future generations will depend on concerted action to conserve and manage the environment as a self-sustaining resource base. HUMAN POPULATIO N  CORE CASE STUDY Each week, about 1.6 million people are added to the world’s population. As a result, the number of people on the earth is projected to increase from 6.7 to 9.8 or more between 2008 and 2050, with most of this growth occurring in the world’s developing countries. This raises an important question: Can the world provide an adequate standard of living for a projected 3.1 billion more people by 2050 without causing widespread environmental damage?  CORE CASE STUDY According to one view, the planet already has too many people collectively degrading the earth’s natural capital. To some analysts, the problem is the sheer number of people in developing countries with 82% of the world’s population. To others, it is high per capita resource consumption rates in developed countries− and to an increasing extent in rapidly developing countries such as China and India− that magnify the environmental impact, or ecological footprint, of each person. Many argue that both population growth and resource consumption per person are important causes of the environmental problems we face.  CORE CASE STUDY Another view is that technological advances have allowed us to overcome the environmental resistance that all populations face and to increase the earth’s carrying capacity for our species. Some analysts argue there is no reason we cannot continue doing so, and they believe that the planet can support billions more people. They also see a growing population as our most valuable resource for solving environmental and other problems and for stimulating economic growth by increasing the number of consumers. As a result, they see no need to control the world’s population growth. Some people view any form of population regulation as a violation of their religious or moral beliefs. Others see it as an intrusion into their privacy and their freedom to have as many children as they want. These people also would argue against any form of population control.  CORE CASE STUDY Proponents of slowing and eventually stopping population growth have a different view. They point out that we are not providing the basic necessities for about one of every five people—a total of some 1.4 billion. They ask how we will be able to do so for the projected 2.6 billion more people by 2050. They also warn of two serious consequences we will face if we do not sharply lower birth rates. First, death rates may increase because of declining health and environmental conditions in some areas, as is already happening in parts of Africa.  CORE CASE STUDY Second, resource use and environmental degradation may intensify as more consumers increase their already large ecological footprints in developed countries and in rapidly developing countries, such as China and India. This could increase environmental stresses such as infectious disease, biodiversity losses, water shortages, traffic congestion, pollution of the seas, and climate change. This debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science LESSON 1: Population Growth  Population Each species is an ecosystem exist as a population. Members of a population rely on the same resources, BIG IDEA are influenced by similar environmental factors and are A population is a bred with one another. In other words, a population group of individuals (synonymous with biological population) consists of a of the same species group of interbreeding or potentially interbreeding that live together in organisms found in the same space or area at the a region. same time. The study of populations (especially population abundance) and how they change over time is called population ecology. It studies the spatial and temporal patterns in the abundance and distribution of organisms and of the mechanisms that produce those patterns. The study of population ecology includes understanding, explanation and prediction of population growth, regulation and dynamics or demography.  Population Characteristics A population has several characteristics or attributes which are a function of the whole group or not of the individual. Different populations cab be compared by measuring these attributes. These attributes are: population density, natality, mortality, population growth, age distribution. The study of the group characteristics of population, their changes over time and prediction of future changes is known as demography.  Population Characteristics I. Population Density The size of the population is represented by its fundamental property called density. It is generally expressed as the number of individuals or the population biomass per unit area or volume. Two Types of Densities 1. Crude Density – is the density per unit of total space. Generally, populations do not occupy all the space as whole because all area may not be habitable. 2. Specific (or Ecological) Density – is the density per unit of habitable space. It includes only that portion of total space that can actually be colonized by the population.  Population Characteristics Determining Population Size The size of the population can be measured in several ways, 1. Abundance – absolute number of individuals in population. 2. Numerical Density – number of individuals per unit area or volume. It is expressed when the size of individuals in the population is relatively uniform, as in mammals, insects and birds. 3. Biomass Density – is expressed in terms of wet weight, dry weight, volume, and carbon and nitrogen weight per unit area or volume. Population Characteristics Population Characteristics The city that has the highest population density in the world is Manila in the Philippines, which was found to have a population per square mile of 119,600. Cities in the Philippines dominated the list with six in the top 25, three of which landed in the top spots. Pateros and Mandaluyong came in second and third on the list, respectively, with population densities of 94,400 and 90,460. Density can also be used to refer to the number of plants or animals in a certain area. Sometimes, animal or plant populations are too dense. This leads to overpopulation. Population Characteristics  Population Characteristics ▪ The maximum number of births produced per individual under ideal conditions of environment is called potential natality. It is also called reproductive or biotic potential, absolute natality or maximum natality. ▪ If population density is unusually high, the birth rate may also below due to poor nutrition or physiological or psychological problems related to crowding. The maximum or absolute natality is observed when the species exists under ideal ecological and genetic conditions. The actual number of births occurring under the existing environment conditions is much less as compared to absolute natality. It is referred to as ecological natality or realized natality. It is not constant for population and may vary with the size of population as well as with the time. Population Characteristics  Population Characteristics ▪ Potential Mortality represents the minimum or theoretical loss of individuals under ideal or non-limiting conditions. Thus even under the best conditions individuals of a population would die of old age determined by their physiological longevity. So it is constant for a population. ▪ Ecological Mortality refers to the death of individuals of a population under existing environmental conditions. Since it varies with environmental conditions, it is never constant. The maximum mortality occurs at the egg, larval, seedling and old age. Mortality is affected by a number of factors, such as density, competition, disease, predation and environment. Death rates vary among the species and are correlated with birth rates. When the rate of natality is equal to the rate of mortality, the population is stationary.  Population Characteristics IV. Population Growth The growth is one of the dynamic features of species population. Population size increases in a characteristic way. When the number of individuals of population is plotted on the y-axis and the time on the x-axis, a curve is obtained that indicates the trend in the growth of population size in a given time. This curve is called population growth curve. There are two types of growth curves: 1) Sigmoid Curve (S-Curve) 2) J-Shaped Curve  Population Characteristics Sigmoid Curve (S-Curve) J-Shaped Curve ▪ A growth pattern in which, in a new ▪ A graph curve that depicts the situation in environment, an organism's population which an organism's population density density increases slowly at first, in a positive increases rapidly in an exponential or acceleration phase; then rapidly, logarithmic form in a new environment, but approaching an exponential growth rate. then abruptly stops.  Population Characteristics V. Age Distribution Age distribution is another important characteristic of population which influences natality and mortality. Mortality, usually varies with age, mas a chance of death are more in early and later periods of lifespan. Similarly, natality is restricted to certain age groups, as for example, in middle age-groups in higher animals. According to Bodenheimer (1958), the individuals of a population can be divided into pre-reproductive, reproductive, and post-reproductive groups. The individuals of pre-reproductive group are young, those of reproductive group are mature and those in post-reproductive group are old. Population Characteristics The distribution of ages may be constant or variable. It is directly related to the growth rate of the population. Depending upon the proportion of the three age-groups, populations can be said to be growing, mature or stable, and diminishing. In other words, the ratio of various age groups in a population determines the reproductive status of the population. Rapidly increasing population contains a large proportion of young individuals, a stable population shows even distribution of individuals in reproductive age-group and a declining population contains a large proportion of old individuals.  Population Characteristics VI. Population Fluctuations The size and density of natural population show a changing pattern over a period of time. This is called population fluctuation. There are three types of variations in the pattern of population change: (i) Non-fluctuating: When the population remains static over the years, it is said to be non-fluctuating. (ii) Cyclic: The cyclic variations may be (i) seasonal, and (ii) annual. Sometimes seasonal changes occur in the population and there are additions to the population at the time of maximum reproduction and losses under adverse climatic conditions. Population Characteristics Common examples of seasonal variations are met in mosquitoes and houseflies which are abundant in particular season and so also the weeds in the field during the rainy season. When the population of a species shows regular ups and downs over the years, it is called annual cyclic variation. It appears in the form of a sigmoid curve with regular drops in population after peaks. (iii) Irruptive: When the change in population density does not occur at regular intervals or in response to any obvious environmental factor, it is said to be irruptive fluctuation. In this there is a sudden exponential or logarithmic increase in population density in short time followed by equally quick drop in population density due to deaths, and final return to normal level or even below that level.  SELF CHECK Non-fluctuating Answer the following questions, choosemile 4 people/square your answer from the box below. Potential Note: You will answer this activity Natality on google classroom. Realized Natality Abundance Specific Density 12 people/square mile Realized Mortality S-curved J-curved 40 people/square mile  SELF CHECK Answer the following questions, choose your answer from the box below. 1. Density per unit of habitable space. 2. Absolute number of individuals in population. 3. The population in a 300 square mile area is 1200. What is the population density? 4. Maximum number of births produced per individual under ideal conditions of environment. 5. It refers to the death of individuals of a population under existing environment condition. 6. The study of populations and how they change over time. 7. A pattern of population change where the population remains static over the years. 8. Pattern of growth in which, in a new environment, the population density of an organism increases rapidly, approaching an exponential growth rate. 9. A ______ describe the tendency of a population’s growth rate to slow or stop as resources become unavailable. 10. There are 240 people living in a 20 square mile land. Calculate its population density.