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Microsoft PowerPoint - Chapter52

Microsoft PowerPoint - Chapter52 - Ecology Population...

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Unformatted text preview: Ecology: Population Growth is a feature common to all Growth populations of living organisms of Outline 1. Key concepts 2. Population growth 3. Limiting factors on growth 4. What contributes to the growth of a population 5. Population density 6. Regulation of population size 7. Human population growth 8. Key terms 9. Conclusions Key Concepts: 1. Natural populations have the potential to grow exponentially. 2. Both density dependent and density independent factors affect population growth. 3. Human population growth has accelerated in the last century. 1 Population growth Population: individuals of a given species that occur together at one place and time • Population change: growth rate = births - deaths • Exponential growth: rapid, requires ideal conditions • Carrying capacity: the number of individuals an environment can support • Population growth Growth is a feature common to all populations Growth of living organisms. of While we have a perception that growth While implies an increase, populations may exhibit positive growth and grow larger, or... positive they may show negative growth and grow they negative smaller. smaller. Populations may even remain the same size and exhibit what is known as zero growth. zero Populations which experience Populations positive growth exhibit one of two growth patterns. two Exponential: In exponential growth, the time required to In double the size of the population becomes shorter and shorter. When plotted as a graph of numbers vs. time, this produces a characteristic J-shaped growth curve. 2 Exponential Growth Logistical Growth Obviously, there is some limit to the growth Obviously, of a natural population. Some combination of factors which will limit a population’s size. population This set of factors represents the carrying This capacity of a given environment and the capacity of affects are illustrated with a S-curve. S-curve Growth 3 Limiting Factors on Growth • Limiting factor – Essential resources • Food • Minerals • Water • Space – Carrying capacity What contributes to the growth What of a population? of Growth is the result of the difference Growth between the number of births and deaths for a population during a given period of time. time. Mortality and survivorship Mortality and Mortality survivorship survivorship Population growth rate depends on the ages of the organisms in it ·Mortality: death rate Survivorship: proportion of an original population that survives to a certain age Survival curves: shapes vary with type of population, number of young, sexual or asexual reproduction, level of care for young 4 Survivorship What contributes to What the growth of a population? population? Also contributing to growth are the new individuals joining the population from Other populations. This is immigration. Other immigration Just as immigration can have an impact Just on the size of a population, so can on individuals leaving the population, or emigration. Population density Population density (the number of organisms per unit of area) influences its survival 5 Regulation of Regulation population size population Density-independent limiting factors: soil nutrients, weather, physical features Density-dependent limiting factors: · competition for resources · accumulation of poisonous wastes Demography Demography • Statistical study of human populations · predicts how population size will change • Age stucture: bar graph · shows current composition of population by age and gender · can be used to predict future size based on number of females and birth rate Age Structure Diagram U.S. http://www.census.gov/ipc/www/idbpyr.html 6 Green - Pre-reproductive years Dark Blue- Reproductive years Light blue - Post- reproductive years Population of the U.S. The human population The explosion explosion • Exponential increase began in 19th Century: industrial revolution, better nutrition, advances in medicine, etc. · lowered death rate, increased birth rate Carrying capacity has been increased by human technology • Current increases in population are higher in developing countries • 7 Estimating Earth’s carrying carrying capacity for humans is a complex problem complex Predictions of the human population vary from 7.3 to 10.7 billion people by the year 2050. Will the earth be overpopulated by this time? http://www.mnsu.edu/emuseum/information/population/ http://www.ibiblio.org/lunarbin/worldpop Population density Survivorship curve Exponential population growth Logistic population growth Density-dependent factor Density-independent factor Birth rate Death rate Age structure Demography In Conclusion • A population is a group of individuals of the same species occupying a given area • The growth rate can be determined by calculating the rate of birth, death, immigration, and emigration • Carrying capacity is the maximum number of individuals in a population that can be sustained in an environment 8 In Conclusion • The availability of sustainable resources dictates population size • Limiting factors such as competition for resources, disease and predation are densitydependent • Patterns of reproduction, death, and migration vary over the life span for a species In Conclusion • The availability of sustainable resources dictates population size • The human population growth rate varies in various parts of the world • Rapid growth of human population occurred • We have the unique opportunity (responsibility?) to decide our fate and the fate of the rest of the biosphere 9 ...
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