Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Population-Ecology Population Characteristics • Geographic Distribution/Range- describes area inhabited by population of organisms • Population Density- number of individuals per unit area; varies depending on species and its ecosystem • Growth rate- change in number of organisms/size of population over time • Age structure diagrams Factors affecting Population size • • • • Number of births Number of deaths Emigration-# leaving population Immigration-# entering population Growth Charts • Direct/Linear- rate of population growth constant over time • Exponential- (J-shape curve)- Rate of growth increases with time (note: ideal conditions/unlimited resources) • Logistic-(S-shaped curve)- realistic way of expressing growth-limiting factors – Carrying capacity- largest number of organisms a given environment can support Limits to growth • Limiting factors- factors causing population growth to decrease – Density-Dependent factors- affect population more strongly as population increases in size – Examples: Competition, Predation, Disease, Famine – Density-Independent- same impact no matter population size – Examples: Unusual weather, Natural disaster, Seasonal cycles, Human activities Age Structure Diagrams • Deals with human population growth • Size of human population tends to increase with time; Exponential growth • Demography- scientific study of human population; how human population changes with time • Birth rates, Death rates and age structure diagrams help predict why some countries have high growth rates and other countries grow more slowly Age Structure Diagrams • Demographic transition- dramatic changes in birth/death rates • Countries modernize and advances in nutrition, sanitation and medicine allow more children to survive to adulthood • First, graph shows a lowering of the death rate (begin transition) Age Structure Diagrams • Next, birthrates remain high (B>D) and population grows exponentially • Countries continue to modernize, families begin to have fewer children and birthrate begins to decrease/population begins to slow down and population growth stops (end of transition) Age Structure Diagrams • Predict future growth • How many people of different ages (and genders) make up population • U.S.- equal number of people across ages/gender; steady growth/slow • Nigeria- far higher number of young vs. old people; foresee large population growth/double over next 30 years