Environmental Science Chapter 3: Population Ecology

ENVIRONMENTAL SCIENCE CHAPTER 3: POPULATION ECOLOGY POPULATION MARK AND RECAPTURE Refers to the group of individuals of the It is a method in which animals are same species inhabi...

ENVIRONMENTAL SCIENCE CHAPTER 3: POPULATION ECOLOGY POPULATION MARK AND RECAPTURE Refers to the group of individuals of the It is a method in which animals are same species inhabiting the same area. captured, marked, and released back into the environment to mix with the rest of the It is characterized by the total numbers of population. individuals and the space they occupy per unit area. Later, a new sample is captured and counts how many of these marked animals are in Are dynamic entities that are characterized the new sample. by their size and composition. The population size (N) can be determined The prompt growth of the human population using the equation: has raised concerns about our existence as a species due to limited resources available N = (number marked first catch x total number of second catch) on Earth. number of marked second catch Widespread environmental damage caused EX: If 50 frogs are captured, marked, and released in a by human actions may lead to a population lagoon, then in a second trapping, 70 frogs are captured catastrophe.. with 10 of them as marked. 50 𝑓𝑟𝑜𝑔𝑠 × 70 𝑓𝑟𝑜𝑔𝑠 𝑁 = 10 𝑓𝑟𝑜𝑔𝑠 = 350 𝑓𝑟𝑜𝑔𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑙𝑎𝑔𝑜𝑜𝑛 (𝑒𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑) PROPERTIES OF POPULATION Capture & Tag: 200 1 Capture & Tag: 500 Recapture: 22 out of 40 Capture & Tag: 80 Recapture: 4% tagged Recapture: 5 tagged Population = x Population = x Population = x 1. Population Size Capture & Tag: 20 Capture & Tag: 120 Capture & Tag: 40 2. Population Density Recapture 3 out of 50 Recapture x out of 250 Recapture: 8 out of x Population = x Population = 15, 000 Population = 500 3. Dispersion Capture & Tag: 50 Capture & Tag: x Capture & Tag: 150 Recapture: 7% tagged Recapture: 4 out of 25 2 Recapture: 7 tagged Population = x Population = 900 Population = x POPULATION SIZE Is the precise number of individuals in an area. POPULATION DENSITY It may have a large or small number of Indicates how crowded a population is. individuals that are distributed densely or sparingly in a local area. It is a measurement of population per unit area or unit volume. SAMPLING METHOD Dp = N (number of individuals) Is used to make inferences about the S (space/area/volume) population as a whole. EX:10,400 mice are living in a 1000m x 1000m field. Two Methods: What is the density of this population? ○ Quadrat – used for immobile or 𝐷𝑝 = 𝑁 = 10, 400 𝑚𝑖𝑐𝑒 = 0.0104/𝑚 2 𝑆 2 slow-moving organisms like plants. 1000000 𝑚 ○ Mark and recapture – used for smaller mobile organisms such as DISPERSION mammals. It is the distribution of the individuals throughout their range in an area. QUADRAT Individuals within a population can be Is a square structure that must be placed at distributed into different patterns. random locations within the habitat enough times and count the number of individuals within its boundaries.  When the population size, N, is plotted over time, it forms a J-shaped growth curve. DISTRIBUTION PATTERNS ○ The reproduction of bacteria, which CLUMPED DISTRIBUTION produces offspring every successive generation. Occurs when individuals aggregate in patches like wolf packs attack prey, mushroom on a rotting log, and so on. UNIFORM DISTRIBUTION Occurs when individuals are evenly distributed and usually seen in territorial animal species like penguins that maintain a defined territory for nesting. RANDOM DISTRIBUTION It is a unique pattern where each individual’s position is independent of other individuals–for example, plants established LOGISTIC GROWTH by windblown seeds in the forest. Is a more realistic model of population growth in which it introduces limits to POPULATION GROWTH reproduce growth. Populations are affected by many factors As the population size increases, resources that affect the level of (increase or will be depleted, and the growth rate will decrease) within the population. slow down due to limited resources. The four fundamental factors are: Populations do not exist in isolation and share the environment with other species, ○ Birth rate = natality rate competing with them for the same resources. ○ Immigration = permanent arrival of new individuals into the population ○ Death rate = mortality rate ○ Emigration = movement of individuals out of a population Population growth rate = (birth rate + immigration) - (death rate + emigration) TWO SIMPLEST MODELS OF POPULATION GROWTH CARRYING CAPACITY (K) 1. Exponential Growth The maximum population size that a 2. Logistic Growth particular environment can sustain. Most populations usually fluctuate around the carrying capacity, where the death rate EXPONENTIAL GROWTH increases beyond the birth rate. Describes populations that increase in An S-shaped curve was produced when numbers without any limits to their plotted. resources or encounter some other limitation. The important concept of this growth rate model is that the population size is increasing at a greater rate.  This shows that the logistic model of distribution, structure, and changes in the population growth is a simplification of population that occur over time. real-world population dynamics. Population structure is the proportion of Moreover, limiting factors in regulating the people by age, sex, ethnicity, education,and population is very important: other parameters. Demographic processes that affect the increase or decrease in population growth DENSITY-INDEPENDENT FACTORS are fertility/natality, mortality, and This growth is not dependent on the density migration. of the population. Demography is the study of human The population increases at a rate populations, focusing on their size, determined by its biotic potential. structure, and distribution. Many factors influence the death rate It examines factors such as birth rates, regardless of its density and may only be death rates, migration patterns, and age slowed down by severe environmental demographics to understand population catastrophes such as drought, storm, dynamics. earthquakes, and the like. Demographic analysis provides insights As a result, it reduces the population into societal trends, resource allocation, and regardless of population size. policy making. It helps forecast population changes and their impacts on areas like healthcare, DENSITY-DEPENDENT FACTORS education, and economics. This is a growth influenced by the density of By studying demographic shifts, societies the population. can make informed decisions to address As the density of the population increases, challenges such as aging populations, the resources become limited. urbanization, and disparities in population growth. Thus, it affects the availability of specific resources to other species and can influence population size further. FERTILITY RATE Examples of this are food supply, nesting sites, mating partners, and so on. Fertility refers to the actual production of offspring. It depends on various factors like physical HUMAN POPULATION health and nutrition, sexual behavior, culture, emotions, economics, way of life, The world’s human population is growing etc. rapidly, and so is their use of resources. Thus, fertility rates vary among countries Many human activities alter the ecosystem and cultures. to the point of harming it. The birth rate is an issue of concern for Overexploitation of natural resources, many government and policy makers. human technology, exploitation of fossil fuels, and other factors have caused Earth’s Some seek to increase the national birth environment unprecedented changes. rate while other countries have policies to reduce the birth rate. Different demographic measures are used to study the population. The scientific study of populations is called MORTALITY RATE demography. It is a measure of the number of deaths in a particular population depending on various factors like age and gender distribution. DEMOGRAPHY A life table is a statistical tool that It is the statistical analysis of the human summarizes the number of deaths of a population, which encompasses the size, population.  It yields information about longevity and Some of these measures are useful and gives a reasonable estimate of life provide a baseline for monitoring population expectancy. health and offer insight into the mechanisms driving population declines. Life expectancy refers to the average survival time for an individual. Mortality refers to the incidence of death AGE-SEX STRUCTURE within a population during a specific period, often expressed as the number of deaths It is a population parameter that refers to per 1,000 individuals. the number of individuals of each sex and age group and is often represented by a bar It is a crucial measure in demography and graph called a population pyramid. public health, providing insights into population health, disease prevalence, and ○ For example, the facts from the PSA life expectancy. Census 2015 of Central Luzon showed that children aged 5 to 9 Mortality rates can vary due to factors such years have the largest age group, as age, gender, socio-economic status, with 10.12 percent of the household access to healthcare, and environmental population. conditions. ○ This was followed by those in the Understanding mortality patterns help age groups 0 to 4 years and 10 to 14 policymakers develop interventions to years, which contributed 9.93 improve healthcare systems, prevent percent share. diseases, and enhance overall well-being. ○ Moreover, males outnumbered females in the age group 0 to 54 years, while females outnumbered MIGRATION / IMMIGRATION their male counterparts in the older It is the physical movement of people from age group (55 years old and over). one place to another. It is divided into two groups: push and pull. The push factors are things that an immigrant is unfavorable about the area he is coming from. The pull factors interest the immigrant in the new place. DEMOGRAPHY DATA These are important data from sources like SEX RATIO statistics registries (Philippine Statistics The sex ratio refers to the rate of males to Office/PSA) and censuses. females in a population. Statistics registries track all status on births, Based on the 2015 Census of Population, deaths, marriages, migrations, and the like. Central Luzon had a total population of The national government usually conducts 11,218,177 persons, and Bulacan had an censuses. immense population size. Its main goal is to count every person in the Of the total population, 50.5 percent was country and collect information on such male, while 49.5 percent was female, which variables as age, sex, marital status, yields a sex ratio of 102 males for every 100 education, employment status, and females. occupation. We can determine the status of a population by measuring and calculating different variables common to all populations such as size, age structure, etc.