Human Population Growth

History

1800 1 billion

1930 2 billion

1960 3 billion

1975 4 billion

1987 5 billion

1999 6 billion

2009 6.7 billion

History (cont)

Draw graph from Miller & Levine p.143 Most of human history, pop. grew slowly

Life was harsh – food was scarce, predators & diseases were common (limiting factors)

Industrial Revolution exponential growth Better nutrition, sanitation, medicine, &

healthcare lower death rates

Determining pop. growth

(Birthrate + Immigration rate (moving in)) – (Deathrate + Emmigration rate (moving out)) = Population growth rate (PGR)

**Unless growth rate becomes zero, pop. continues to grow

Birthrate - # live births per 1000 people / year Death rate - # deaths per 1000 people / year

Age Structure

Proportions of pop. in different age levels Rapid growth – wide base (many children

and teenagers) Stable growth – almost equal in each

category M & L p.144 fig 5-13 US: slow, steady growth rate Guatemala: rapid growth (double in 30

years)

What can you tell about this country based on its age structure graph?

Wide base = rapid growth

Skinny top = poor health care

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What can you tell about this country based on its age structure graph?

Base not much wider than middle = slow growth

Balanced fairly evenly throughout ages = good health care

# of females at top = females have longer life expectancy

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What can you tell about this country based on its age structure graph?

Base smaller than middle = population decline

Balanced fairly evenly throughout age groups = good health care

# females at top = live longer

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Biodiversity

Variety of species in a certain area Is there more biodiversity in …

A corn field or a tropical rain forest? A grassland or a coral reef? High Rock Lake or a lake in Brazil?

**Biodiversity is highest closer to the equator

Importance

Interdependence of food webs What would happen without insects or

decomposers? Brings stability

Monocultures vs. scattered population in a forest

Provides oxygen, carbon dioxide removal, food, genetic material for new crops (drought or pest-resistant), raw materials, medicines

Loss

Extinction – species dies, genetics are gone forever Passenger pigeon, Carolina parakeet,

dusky seaside sparrow Endangered – species numbers so low,

extinction is possible Threatened – likely to become

endangered

Threats

**Habitat loss** Habitat fragmentation Edge effects Habitat degradation (pollution) Exotic/invasive species

What can we do? – sustainable practices Recycling Conserve nonrenewable resources

Fossil fuels: oil, coal, natural gas, aluminum Use renewable resources sustainably

Solar power, wind, water, forests, crops Sustainable agriculture

Use fewer pesticides, avoid monocultures, drip irrigation, no-till drilling

Be a wise consumer! Vote with your money. Avoid products with excessive plastic packaging,

buy in bulk, watch for recycled products, reuse items until they wear out