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This article explores the various factors that influence population size, including the number of births and deaths, immigration and emigration, as well as density-dependent and density-independent environmental factors. It also discusses the concept of carrying capacity and how human activity can impact population growth.
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Ch 5: Controlling Population Growth Notes #2
Factors affecting population size • Number of Births: Tracks the # of live births in an area • Number of Deaths: Tracks the # of deaths in an area • Number of individuals entering or leaving a population i. Immigration: entering an area ii. Emigration: leaving an area
Types of Population Growth Curves 1) Exponential Growth Curve: Population size grows extremely quickly over a short period of time, causing a population boom. Due to: Births > deaths Immigration > emigration
2) Logistic Growth Curve: Population size gradually increase and then fluctuates due to limited food, shelter, & mates. <--Carrying Capacity Carrying Capacity: The # of individuals that an area can support
What Controls Population Growth? (2 Types of Factors) • Density-dependent factors: Affects the population based on the number of individuals in an area a. Competition: Different populations fighting over resources (shelter, water, mates, food)
c. Parasitism: the parasite lives on or in another organism causing it some harm. Ex. Mosquito sucking blood from host, & possibly spreading diseases
d. Disease: Contagious illnesses that spread from one to another causing some harm to the population The Black Plague CHICKEN POX spreads if you are not immune to it.
2) Density-Independent Factors: Affects population size no matter of how small or big it is • Unusual weather: Strange and rare weather changes or occurrences Ex. Fire Tornado
b. Natural disasters: Natural destruction that changes the landscape of the habitat. Ex. Earthquakes, Volcano Eruptions, Hurricanes, Tornados
c. Seasonal Cycles: Changes of the 4 seasons (Ex. Fall, Winter, Spring & Summer)
D. Human activity: Human destroying natural habitats Ex. Deforestation Ex. Pollution