Population Properties PDF

PROPERTIES OF POPULATION  POPULATION ECOLOGY is the study of populations in relation to the environment. It includes environmental influences on population density and distribution, age structure, and variations in population size. ...

PROPERTIES OF POPULATION  POPULATION ECOLOGY is the study of populations in relation to the environment. It includes environmental influences on population density and distribution, age structure, and variations in population size.  POPULATION Group of organisms of the same species living together at a particular place  PROPERTIES OF POPULATION  - size of the population to a definite unit of space. Crude density includes all the land within the organism's range whereas Ecological density includes only that portion of land that can actually be colonized by the species.  Population dispersion- describes how organisms are arranged in a given area. Random- when the position of each individuals in a population is independent of the others Uniform- it results as a form of some negative interactions Clumped- where individuals occur in groups due to suitable habitat or the resources are distributed in patches  Population Dispersal- The process by which groups of living organisms expand the space or range within which they live. Dispersal operates when individual organisms leave the space that they have occupied previously, or in which they were born, and settle in new areas. It includes emigration, immigration and migration.  Natality- the birthrate, which is the ration of total live births to total population in a particular area over a specified period of time.  Mortality- the death rate, which is the ration of the total number of deaths to the total population.  Age structure-is the proportion of a population in different age classes. - Pre-reproductive age - Reproductive age - Post-reproductive age  Biotic potential- refers to the organism’ s maximum capacity to reproduce. Biological organisms can produce enormous number of offspring if their reproductive capacity is unrestrained. Constraints include: scarcity of resources, competition, predation, disease  Population Growth- refers to how the number of individuals in a population increases or decreases with time (N, t)  HUMAN POPULATION  The human pop ulation has gr own faster in the 20th century t han it has ev er before.  Demographers stud y t he historic al size and makeup o f the populations of d ifferent co untries to make comparisons and predi ctions.  The c ountrie s c an be d ivided into 2 groups- develo ped co untries and d evelop ing countr ies. Developed countries have higher average i nco me s, slow population growth, diverse industrial economies, and stronger so cial suppo rt systems. Developing countries have lower average incomes, simple and agric ult ural eco no mie s, and higher population growth.  After growing slowly for thousands of years, the human population began to grow more rapidly in the 1800s.The human population underwent exponential growth.  FORECASTING POPULATION SIZE  Age Structure C ountri es with high rates of growth tend to have more yo unger people than older people. In contrast, countries with a sl ow growth rat e usually have an equal dist ribution of age s in the population. Survi vorship It refers to the pe rcentag e of members of a g roup that are likely to surv ive to any given age. Factor s such as numbe r of offspring pro duced, fre que nc y of rep roduction, amount of care and r eso urc es d edicated t o offspring and what kind of surviv orship cur ve the org anism exhibits can influe nc e the population growth.  Type I survivorship curve has a high percentage of offspring survive their early and middle years— death occurs predominantly in older individuals. These types of species usually have small numbers of offspring at one time, and they give a high amount of parental care to them to ensure their survival.  Type II survivorship curve are organisms who die more or less equally at each age interval. These organisms also may have relatively few offspring and provide significant parental care.  Type III survivorship curve are those with very few of these organisms survive their younger years; however, those that make it to an old age are more likely to survive for a relatively long period of time. SURVIVORSHIP CURVE  Fe rtility Rates The number o f babie s bo rn eac h year per 1000 women in a population is called the fertilit y rate. Historically, in 19 72, the total fe rtility rate dro pped b elow the replacement lev el for the first time. Migration In 2 019, 270 milli on people in t he wor ld were migrants— defined as p eople not living in the ir country of b irth. The migrant population has increased by 120 mil lion since 1990. However, the share of migrants i n the world ’ s population has hovered aro und 3 per cent over t he p ast 60 years. Striking ly, the share o f immigrants in the t otal population of ad vanced economies has risen fro m 7 perce nt t o 12 p ercent, while the share of immigrants in emergi ng market and develo ping economies has remained at around 2 perce nt.  Declining Death Rates They have declined due to more people now having access to adequate food, clean water, and safe sewage disposal. The discovery of vaccines in the 20th century also contributed to declining death rates, especially among infants and children.  Life Expectancy The average number of years a person is likely to live. This longevity is due to better health care and hygiene, healthier lifestyles, diet, and improved medical care.  THE DEMOGRAPHIC TRANSITION  The demographic transition is a model t hat describes h ow t he changes of popula tion growth can occur. Four sta ges of Transit ion: Stage 1- Prei ndust ria l condit ion The bi rth rat e and death ra te are bot h at hi gh l evel s a nd the popul ation si ze is st abl e. Stage 2- Popul ation expl osion occurs Death rat es decl ine due to better hygi ene, nut rit ion, and edu ca tion.Birt h ra tes a re stil l high. Stage 3- Popul ation growth sl ows beca use of t he birt h rate decreasi ng. As t he birt h rate becomes cl oser to t he death rat e, the popul ation si ze sta bi li zes. Stage 4- t he birt h rate drops below repl acement level , so the size of t he popul ation begins t o decrease. RAPID POPULATION GROWTH Pros Cons Increase human capital Increased pressures on natural environment More scope for innovation, Water shortages invention and creative genius Enables specialization Increases pollution Increase economic growth of Exacerbates global warming the country More wastes Congestion  SOLUTIONS  Population Commission, also known as PopCom or CPD- tasked with coordinating and implementing policies and programs concerning population development, including addressing issues related to population growth, family planning and reproductive health in the country.  Reproductive Health Act No. 10354, commonly known as the Responsible Parenthood and Reproductive Health Act of 2012- includes provision on access to family planning services and population education  National Demographic and Health Survey- which conducts regular demographic and health surveys to gather data on population trends, health indicators and family planning practices.