Unit 2 Ecology Ch. 5 Populations Characteristics of Populations R3 important characteristics of a population are its geographic distribution, density, & growth rate RGeographic distribution refers to the area inhabited by a population R3 important characteristics of a population are its geographic distribution, density, & growth rate RGeographic distribution refers to the area inhabited by a population Characteristics of Populations RPopulation density - the # of individuals per unit area RGrowth rate refers to the speed of a population increasing or decreasing in size RPopulation density - the # of individuals per unit area RGrowth rate refers to the speed of a population increasing or decreasing in size Population Growth R3 factors affect population size: the # of births, the # of deaths, & the # of individuals that enter or leave the population RBasically, a population will increase or decrease in size depending on the amount of individuals added to or removed from it R3 factors affect population size: the # of births, the # of deaths, & the # of individuals that enter or leave the population RBasically, a population will increase or decrease in size depending on the amount of individuals added to or removed from it Population Growth RA population can grow when its birth rate is greater than its death rate RIf the birth rate = death rate, the population will stay the same RIf the death rate is greater than the birth rate, the population will decrease RA population can grow when its birth rate is greater than its death rate RIf the birth rate = death rate, the population will stay the same RIf the death rate is greater than the birth rate, the population will decrease Population Growth RImmigration - movement of individuals into an area, can cause a population to grow REmigration - movement of individuals out of an area, can cause a population to decrease RImmigration - movement of individuals into an area, can cause a population to grow REmigration - movement of individuals out of an area, can cause a population to decrease Exponential Growth RIf a population has plenty of space & food, & is protected from predators & disease, then organisms in that population will multiply & it will increase in size RExponential growth - occurs when the individuals in a population reproduce at a constant rate RIf a population has plenty of space & food, & is protected from predators & disease, then organisms in that population will multiply & it will increase in size RExponential growth - occurs when the individuals in a population reproduce at a constant rate Logistic Growth RAs resources become less available, the growth of a population slows or stops RLogistic growth - occurs when a populations growth slows or stops, after a period of exponential growth, S-shaped curve RAs resources become less available, the growth of a population slows or stops RLogistic growth - occurs when a populations growth slows or stops, after a period of exponential growth, S-shaped curve Logistic Growth RCarrying capacity - the # of individuals in a population, that an environment can support RShown in a graph, when a population levels off RCarrying capacity - the # of individuals in a population, that an environment can support RShown in a graph, when a population levels off Limits to Growth RLimiting factor - a factor that causes population growth to decrease RDensity-dependent factor - a limiting factor that depends on population size RIncludes: competition, predation, parasitism, & disease RLimiting factor - a factor that causes population growth to decrease RDensity-dependent factor - a limiting factor that depends on population size RIncludes: competition, predation, parasitism, & disease Limits to Growth RCompetition: RWhen populations become crowded, organisms compete with each other for food, water, space, sunlight, etc. RCompetition will cause 2 different species to evolve over time, to occupy separate niches, therefore, less competition RCompetition: RWhen populations become crowded, organisms compete with each other for food, water, space, sunlight, etc. RCompetition will cause 2 different species to evolve over time, to occupy separate niches, therefore, less competition Limits to Growth RPredation: RThe regulation of a population by predation takes place within a predator-prey relationship RPredation: RThe regulation of a population by predation takes place within a predator-prey relationship Limits to Growth RParasitism & Disease: RParasites can limit the growth of a population, by acting as predators RMany take the nourishment of their hosts, some cause disease & even death RParasitism & Disease: RParasites can limit the growth of a population, by acting as predators RMany take the nourishment of their hosts, some cause disease & even death Limits to Growth RDensity-independent factors - affect all populations in similar ways, regardless of population size RExamples include: unusual weather, natural disasters, seasonal changes, & certain human activities (damming rivers, clear-cutting forests) RDensity-independent factors - affect all populations in similar ways, regardless of population size RExamples include: unusual weather, natural disasters, seasonal changes, & certain human activities (damming rivers, clear-cutting forests) Limits to Growth Human Population Growth RIn the US & other developed countries, the current growth rate is very low RIn some developing countries, the population growth rate is nearly 3 people per second RBecause of this, the human population is on its way to reaching 9 billion people within your lifetime RIn the US & other developed countries, the current growth rate is very low RIn some developing countries, the population growth rate is nearly 3 people per second RBecause of this, the human population is on its way to reaching 9 billion people within your lifetime Historical Overview RLike the populations of many other living organisms, the size of the human population tends to increase with time Patterns of Population Growth RThe human population cannot keep growing exponentially forever, because Earth & its resources are limited RExperts have predicted that war, famine, & disease would limit human population growth RThe human population cannot keep growing exponentially forever, because Earth & its resources are limited RExperts have predicted that war, famine, & disease would limit human population growth Patterns of Population Growth RDemography - the scientific study of human populations RIt examines the characteristics of human populations & attempts to explain how those populations will change over time RBirthrates, death rates, & the age structure of a population help predict why some countries have high growth rates, while others grow more slowly RDemography - the scientific study of human populations RIt examines the characteristics of human populations & attempts to explain how those populations will change over time RBirthrates, death rates, & the age structure of a population help predict why some countries have high growth rates, while others grow more slowly Patterns of Population Growth RPopulation growth depends on how many people of different ages make up a given population RAge-structure diagrams - population profiles that demographers can use to predict future growth RPopulation growth depends on how many people of different ages make up a given population RAge-structure diagrams - population profiles that demographers can use to predict future growth Patterns of Population Growth Future Population Growth RDemographers predict that the human population will be growing more slowly over the next 50 years