* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Population Ecology and Ecosystems Ecology Human Population
Source–sink dynamics wikipedia , lookup
Soundscape ecology wikipedia , lookup
Deep ecology wikipedia , lookup
The Population Bomb wikipedia , lookup
Human overpopulation wikipedia , lookup
Two-child policy wikipedia , lookup
World population wikipedia , lookup
Cultural ecology wikipedia , lookup
Molecular ecology wikipedia , lookup
Population Ecology Population Ecology and Ecosystems Ecology Ecology: The study of how organisms interact with one another and with their environment Concepts and Applications: Chapters 40 & 43 • Certain ecological principles govern the growth and sustainability of all populations • Human populations are no exception Basic Concepts: Chapters 27 & 30 http://darwin.bio.uci.edu/~sustain/bio65/lec16/b65lec16.htm Population Ecology Human Population Problems Population Ecology Population • Over 6 billion people alive • A group of individuals of the same species occupying a given area • About 2 billion live in poverty • Can be described by demographics • Most resources are consumed by the relatively few people in developed countries – Vital statistics such as size, density, distribution, and age structure Population Ecology Population Age Structure • Divide population into age categories • Population’s reproductive base includes members of the reproductive and prereproductive age categories Population Ecology Density & Distribution • Number of individuals in some specified area of habitat • Crude density information is more useful if combined with distribution data Fig 40.2 1 Population Ecology Assumptions in Capture-Recapture Determining Population Size • Direct counts are most accurate but seldom feasible • Can sample an area, then extrapolate Mark and Recapture # marked Captured Total Captured Population Ecology • Marking has no effect on mortality = Number released Total Pop • Marking has no effect on likelihood to being captured • There is no immigration or emigration between sampling times • Capture-recapture method is used for mobile species Population Ecology Changes in Population Size Population Ecology Zero Population Growth- ZPG • Immigration adds individuals • Interval in which number of births is balanced by • Emigration subtracts individuals number of deaths • Births add individuals • Assume no change as a result of migration • Deaths subtract individuals • Population size remains stable Population Ecology Per Capita Rates • Rates per individual • Total number of events in a time interval divided by the number of individuals • Per capita birth rate per month = Number of births per month Population size Population Ecology Exponential GrowthFig 40.4 • Population size expands by ever increasing increments during successive intervals • The larger the population gets, the more individuals there are to reproduce 2 Population Ecology Population Ecology r Exponential Growth Equation • Net reproduction per individual per unit time G = rN • Variable combines per capita birth and death rates (assuming both constant) • Can be used to calculate rate of growth of a population • G is population growth per unit time • r is net reproduction per individual per unit time • N is population size Population Ecology Population Ecology Biotic Potential Limiting Factors • Maximum rate of increase per individual • Any essential resource Space under ideal conditions that is in short supply Food • Varies between species • All limiting factors acting • In nature, biotic potential is rarely reached Shelter on a population dictate Temperature sustainable population Mates Pollution size Disease Population Ecology Carrying Capacity (K) Population Ecology Logistic Growth Equation • Maximum number of individuals that can be sustained in a particular habitat • Logistic growth occurs when population size is limited by carrying capacity G = rmax N (K-N/K) • G = population growth per unit time • rmax = maximum population growth rate per unit time • N = number of individuals • K = carrying capacity 3 Population Ecology Logistic Growth Population Ecology Overshooting Capacity • As size of the population increases, rate of reproduction decreases • Population may temporarily increase above carrying capacity • When the population reaches carrying capacity, population growth ceases • Overshoot is usually followed by a crash; dramatic increase in deaths Fig 40.7 Population Ecology Resetting the Carrying Capacity Population Ecology Density-Dependent Controls • Major changes in environment can change the carrying capacity of a local system • Logistic growth equation deals with density-dependent controls • Limiting factors become more intense as population size increases • Disease, competition, parasites, toxic effects of waste products Fig 40.6 Population Ecology Density-Independent Controls • Factors unaffected by population density • Natural disasters or climate changes affect large and small populations alike Population Ecology Life History Patterns • Patterns of timing of reproduction and survivorship • Vary among species • Summarized in survivorship curves and life tables 4 Population Ecology Population Ecology Life Table Survivorship Curves • Tracks age-specific patterns • Population is divided into age categories • Birth rates and mortality risks are calculated for each age category Fig 40.8 Population Ecology Human Population Growth Population Ecology Human Population Growth • Population now exceeds 6 billion • Rates of increase vary among countries • Average annual increase is 1.26 percent • Population continues to increase exponentially Fig. 40.9, p. 695 Population Ecology How Humans have Side-Stepped density dependent controls • Expanded into new habitats • Agriculture increased carrying capacity; use of fossil fuels aided increase • Hygiene and medicine lessened effects of density-dependent controls Population Ecology Future Growth • Exponential growth cannot continue forever • Breakthroughs in technology may further increase carrying capacity • Eventually, densitydependent factors will slow growth Population Momentum • Lowering fertility rates cannot immediately slow population growth rate. Why? • If every couple had just two children, population would still keep growing for another 60 years 5 Population Ecology Resource Consumption Population Ecology Effects of Economic Development • United States has 4.7 percent of the world’s population • Americans have a disproportionately large effect on the world’s resources • Per capita, Americans consume more resources and create more pollution than citizens of less developed nations • Total fertility rates (TFRs) are highest in developing countries, lowest in developed countries • When individuals are economically secure, they are under less pressure to have large families Population Ecology Slowing Growth in China Community Ecology Community Ecology • World’s most extensive family planning program • Government rewards small family size, penalizes larger families, provides free birth • Community: Populations of all species in a habitat. • Niche: Sum total of all a species activities and relationships as species do what they do. – Fundamental, Realized control, abortion, sterilization • Since 1972, TFR down to 1.8 from 5.7 Community Ecology Types of Interactions Community Ecology Competition Who benefits? • • • • • • Neutral Commensalism Mutualism Competition Predation Parasitism Spp 1 0 Y Y N Y Y Spp 2 0 0 Y N N N • Competitive Exclusion – Paramecium • Resource Partitioning – Fruit eating birds, Barnacles 6 Community Ecology Predator-Prey Interactions Ecosystems Ecosystems • The Classic Lynx / Hare system • Energy is transferred from the SUN to all organisms • Primary Producers • Consumers • Decomposers • Energy is LOST with each transition Ecosystems Food Webs Ecosystems Food Webs can be Disrupted • A composite picture of an ecosystem’s membership and their interaction • Natural Disasters • External inputs – Pesticides, Pollution Do not post photos on Internet Fig. 43.6, p. 740 Ecosystems Ecosystems Other Cycles • Carbon • Nitrogen • Phosphorus The Hydrologic Cycle Fig. 43.14, p. 746 7 Quiz 8