Module 1 of People and the Earth\'s Ecosystem PDF

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People and theEarth's EcosystemModule inModule1P R E P A R E D B Y : J E M U E L B. L A G A R T O , L P TPrefaceWelcome to People and the Earth’s Ecosystem , an interdisciplinary study of how the earth works, how humans interact with it, and how we can address the world's environmental issues. The c...

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PREPARED BY: JEMUEL B. LAGARTO, LPT

Welcome to People and the Earth’s Ecosystem, an interdisciplinary study of how the earth works, how humans interact with it, and how we can address the world's environmental issues. The concepts, facts, and issues presented in this module and the course you are taking will be beneficial to you now and in the future since environmental issues touch every aspect of your life. This module is designed to enhance students understanding of basic ecology concepts in three major areas: (1) Population, (2) Ecosystem, and (3) The Anthropogenic Impact to Environment. This module comprises of three series, module 1, module 2, and module 3 and it is divided based on the grading period during the school term, prelim, midterm, and finals. This module is centered in addressing the concern of the changing environment due to climate change and what can we do about it. Varied activities are provided in each chapter to help the students to develop important 21st century skills such as effective communications skills; learning and innovation skills; and information, media, and technological skills despite the pandemic. The components found in this module are as follows: Core Case Study - This presents article or research or case study for additional information.

Key Questions & Concepts - These are essential questions that students need to answer and understand. Big Idea - These are pop-up sections placed in the discussions to so that the students can easily identify essential concepts. Wordstorm - This is a vocabulary section to help the students to understand difficult terms.

Gear Up - This is a set of enrichment activities.

Self-Check - This is a 10-20 items test that includes formative and summative questions.

As the students go through the pages of this module, may it be their desire to explore the world around them, observe the changes, and realize their role in protecting and conserving our ecosystem.

The Author

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As you go through this chapter, you will be able to: Define what population is; Enumerate the different characteristics of population; Calculate the birth rate, mortality rate and natality rate of a population; Differentiate the two types of population growth curve, the S-curve and the J-curve; and Identify the two factors affecting the birth rate of a population.

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CORE CASE STU DY 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 9.3 billion 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 2.6 billion more people by 2050 without causing widespread environmental damage? There is disagreement over the answer to this question.

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. 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.

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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. 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. 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.

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1. What is population? 2. What factors influence the size of the human population? 3. How does a population’s age distribution affect natality and mortality? 4. How can we slow human population growth?

Each species in an ecosystem exist as a population. Members of a population rely on the same resources, are influenced by similar environmental factors and are bred with one another. In other words, a population (synonymous with biological population) consists of a group of interbreeding or potentially interbreeding organisms found in the same space or area same area at the same time. The study of populations (especially population abundance) and how they change over time is called population ecology. It A population is a group of individuals studies the spatial and temporal patterns in the of the same species that live together in abundance and distribution of organisms and of the a region. mechanisms that produce those patterns. The study of population ecology includes understanding, explanation and prediction of population growth, regulation and dynamics or demography. Multicellular organisms are of two kinds, unitary organisms and modular organisms. Most animal populations are made up of unitary organisms. In unitary organisms, the form is highly determinate consisting usually of a strictly defined number of parts (such as legs or wings) established only during embryogenesis. Their pattern of development and final form are predictable. For example, all dogs have four legs, all squid have two eyes, etc. In modular organisms, on the other hand, neither timing nor form is predictable. These organisms grow by the repeated iteration of modules, usually to yield a branching pattern. Examples of modular organisms include plants and many sessile benthic invertebrates. In modular organisms, a single genetic individual (or genet) can consist of many modules (or ramets) capable of existence as individuals. In plants, a genet is an individual that has arisen from a seed. A ramet is a new plant which has arisen through vegetative propagation and is now a completely independent plant with its own roots and shoots. For example, a population of grasses may consist of several genets, each of which has several ramets.

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POPULATION CHARACTERISTICS A population has several characteristics or attributes which are a function of the whole group and not of the individual. Different populations can be compared by measuring these attributes. These attributes are population density, natality, mortality, distributions, etc. The study of the group characteristics of a population, their changes over time and prediction of future changes is known as demography. 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 - 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 - Specific 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. Determining Population Size Population size can be measured by several methods: 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 - Biomass density is expressed in terms of wet weight, dry weight, volume, and carbon and nitrogen weight per unit area or volume.

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Population density can be calculated by the following equation: Dp = N

A In this equation, Dp is the density of population, N is the total population as a number of people, and A is the land area covered by that population. A is usually expressed in terms of either square miles or square kilometers, especially when looking at human population. However, we could use smaller units as well. For example, if we're looking at the population density of a type of insect on a tree, we would use square feet or square meters, because kilometers would be far too large. We might also use acres if we're looking at the population density of cattle on a ranch. The same population density formula applies to both human and non-human populations. II. Natality Natality refers to the rate of reproduction or birth per unit time. It is an expression of the production of new individuals in the population by birth, hatching, germination or fission.

Birth rate or Natality (B) =

Number of births per year Number population per year

x 1,000

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. Natality varies from organism to organism. It depends upon the population density and environmental factors. It is a general rule that if the population density is usually low, the birth rate is also low. This is so because the chances of mating between males and females are low. 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 environmental 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. III. Mortality Mortality refers to the number of deaths for every 1,000 people per year. The death rate is correlated with the conditions of country, for example, with the levels of prosperity, health, or the occurrence of war.

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Mortality rate =

Number of birth per year Number of population per year

x 1,0000

Mortality can be expressed in the following two ways: 1. Minimum or Specific or Potential Mortality: - It represents the minimum of theoretical loss of individuals under ideal or nonlimiting condition. 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. 2. Ecological or Realized Mortality: - It 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. A birth death ratio (Births/death x 100) is called vital index. For a population, the survival of individuals is more important than the death. The number of births in relation to the carrying capacity of the habitat is a fundamental factor influencing the mortality rate. When more young’s are born than the habitat can support, the surplus must either die or leave the area. Because the number of survivors is more important than the number of dying individuals, mortality is better expressed as survival or as life expectancy. The life expectancy refers to the average number of years the members of a population have left to live. 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 times 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) When a few organisms are introduced in an area, the population increase is very slow

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slow in the beginning (positive acceleration phase or lag phase), in the middle phase, the population increase becomes very rapid(logarithmic phase) and finally in the last phase population increase is slowed down (negative acceleration phase) until an equilibrium is attained and which the population size fluctuates according to variability of environment. The level beyond which no major increase can occur is referred to as saturation level or carrying capacity. In the last phase the new organisms are almost equal to the number of dying individuals and thus there is no increase in population size. In this way, one gets sigmoid or 5-shaped growth curve (Fig. 1). 2. J-Shaped Curve The second type of growth curve is J-shaped. Here in the first phase there is no increase in population size because it needs some time for adjustment in the new environment. Soon after the population is established in the new environment, it starts multiplying rapidly. This increase in population is continued till large amount of food materials exist in the habitat. After some time, due to increase in population size, food supply in the habitat becomes limited which ultimately results in decrease in population size. This will result in J-shaped growth curve rather than S-shaped (Fig. 1).

J- Curve

S- Curve

Figure 1, J-curved and S-curved population growth curves.

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V. Age Distribution Age distribution is another important characteristic of population which influences natality and mortality. Mortality, usually varies with age, as chances 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 postreproductive groups. The individuals of pre-reproductive group are young, those of reproductive group are mature and those in postreproductive group are old. 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. VI. Population Fluctuations

Young

Mature

Old

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: 1. Non-fluctuating: - When the population remains static over the years, it is said to be non-fluctuating. 2. Cyclic: - The cyclic variations may be (a) seasonal, and (b) 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. Common examples of seasonal variations are met in mosquitoes and houseflies which area abundant in particular season

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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. 3. 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.

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Answer the following questions , choose your answer from the box below. Note: You will answer this activity on google form. Non-fluctuating

12 people/square mile

4 people/square mile

Realized mortality

Potential Natality

S-curved

Abundance

J-curved

Specific density

40 people/square mile

1. Density per unit of habitable space. 2.Absolute number of individual 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 environmental condition. described the tendency of a population to grow without limit to its 6. A size. 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 slowly initially, in a positive acceleration phase; then increases rapidly, approaching an exponential growth rate. describe the tendency of a population's growth rate to slow or stop 9. A as resources become unavailable. 10. There are 240 people living in a 20 square mile land. Calculate its population density.

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As you go through this chapter, you will be able to: Cite factors that can affect the birth rate of a population; Compare the changes of population's number added every eleven years in the world using a table; Identify the major causes of human population change; and Enumerate different ways on how can we slow the growth of population.

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Factors that Cause Populations to Change Population Ecologists classify factors causing changes in populations as either densitydependent or density in dependent factors. Density refers to the number of animals per unit area (usually measured in animals/hectare or animals/square kilometer). Density-dependent factors As the density of a popula...