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Population Ecology Basic ecological principles govern the growth and sustainability of all populations 1.

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Presentation on theme: "Population Ecology Basic ecological principles govern the growth and sustainability of all populations 1."— Presentation transcript:

1 Population Ecology Basic ecological principles govern the growth and sustainability of all populations 1

2 Population Characteristics (Demographics) Population Size Population Density Population Distribution Age Structure = number of individuals in age categories Pre-reproductive, reproductive, post-reproductive Reproductive Base POPULATION SIZE = Number of individuals that contribute to populations gene pool within the same geographic area Birth rate vs. Death rate Immigration vs. emigration 2

3 Population Density Number of individuals per specified area or habitat 2011 World Population density (individuals per square km) 3

4 General pattern in which individuals are distributed Population Distribution Clumping is MOST COMMON, due to ??? environmental conditions behavioral issues reproductive concerns Random Sampling Capture/ recapture 4

5 Population Growth Immigration Emigration Migration Birth/death rate With NO limiting factors J-Shaped curve = exponential curve Doubling TimeBiotic Potential 5

6 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 6

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9 Limiting Factors In nature, most populations are never able to reach biotic potential Density-dependent Density-independent Abiotic factors Biotic factors Predator Competition Parasitism Weather Elevation 9

10 Typical biotic carrying capacity relationship 10

11 World Population Growth What differentiates humans from other species found in nature? How does this impact population growth? 11

12 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. Doubling Time 12

13 World Population Distribution by Region, 1800–2050 13

14 Age Structure Diagrams 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 Fertility Rate Replacement Levels 14

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16 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 16


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