Population Growth p 1033 1040 Population Growth Population

Population Growth p. 1033 -1040

Population Growth Population: a group of the same species living together in a given area Species: a group of organisms with shared characteristics capable of interbreeding & producing viable offspring Factors affecting population size: Birth (natality) Death (fatality) Immigration emigration

Three types of population growth: 1. Exponential Growth • When conditions are ideal for growth & reproduction, a population will increase rapidly, expanding forever unless it is stopped

* The larger the population gets, the faster it grows Exponential Growth Curve

2. Logistic Growth - When a population goes through a number of growth phases: A) B) C) D) To start, population grows slowly Population grows rapidly Population growth slows down (but is still growing) Population growth slows down even more - it is nearing carrying capacity E) Steady state = although small fluctuations occur, overall population size does not change significantly F) Carrying capacity = the size of the population during the steady state; limiting factors will prevent population growth

3. Cyclic Growth - when a population cycles up & down between a minimum & maximum population size; never staying at constant carrying capacity

Factors Affecting Population Growth 1. Density Dependent Limiting Factors: • Affect large populations more than small a) Competition: The struggle for resources between members of the same species & different species. REMEMBER: No two species can occupy the same niche in the same place at the same time!!

b) Predation: - predator-prey relationships can control the natural populations

c) Parasitism d) Crowding & stress

2. Density-Independent Limiting Factors a) Weather b) Natural disasters