Population Ecology Chapter 39 – Certain ecological prinicples govern ALL populations Basic ecological principles govern the growth and sustainability of all populations

Population Characteristics (Demographics) Population Size Population Density Population Distribution POPULATION SIZE = Number of individuals that contribute to population’s gene pool within the same geographic area Age Structure = number of individuals in age categories Pre-reproductive, reproductive, post-reproductive Reproductive Base 39.1 - Demographics = “vital statistics” Birth rate vs. Death rate Immigration vs. emigration

Population Density Number of individuals per specified area or habitat 2011 World Population density (individuals per square km)

Population Distribution General pattern in which individuals are distributed Covers 39.2 Clumping is MOST COMMON, due to ??? environmental conditions behavioral issues reproductive concerns Random Sampling Capture/ recapture

Population Growth Immigration Emigration Migration Birth/death rate With NO limiting factors J-Shaped curve = exponential curve 39.3 Doubling Time Biotic Potential

Population Growth Limits Reality Limiting Factors Short supply of any essential resource = ? Carrying capacity Maximum number of individuals that an environment can sustain NATURAL SELECTION? S-shaped curve = logistic curve

Typical population growth

Limiting Factors In nature, most populations are never able to reach biotic potential Density-dependent Biotic factors Predator Parasitism Competition 39.4 Limits Density-independent Abiotic factors Weather Elevation

Typical biotic carrying capacity relationship

World Population Growth What differentiates humans from other species found in nature? How does this impact population growth? Skip 39.5& 39.6, this is 39.7

Doubling Time The rate of national population growth is expressed as a percentage for each country, commonly between about 0.1% and 3% annually. You'll find two percentages associated with population - natural growth and overall growth. Natural growth represents the births and deaths in a country's population and does not take into account migration. The overall growth rate takes migration into account. In the U.S., the natural growth rate is 0.6% and overall growth is 0.9%. The growth rate of a country provides demographers and geographers with a good contemporary variable for current growth and for comparison between countries or regions. For most purposes, the overall growth rate is the more frequently utilized. The world's current growth rate is about 1.3%, representing a doubling time of 54 years. We can expect the world's population of approximately 6 billion (2000) to become 12 billion by 2054 if the current rate of growth continues. The world's growth rate peaked in the 1960s at 2% and a doubling time of 35 years.

World Population Distribution by Region, 1800–2050

Age Structure Diagrams Fertility Rate Replacement Levels Rapid Growth High pre-reproductive and productive population Slow Growth Steady declining population with age Zero Growth Equal distribution of ages Negative Growth Low pre-reproductive and productive population 39.8

Demographic Transition Relates economic conditions to population growth Stages: Pre-Industrial High birth & death rates Transitional Declining death rates Industrial Declining birth rates Post-Industrial Low birth & death rates