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Populations

Populations. Chapter 5, Section 1 Pages 103-108. What is a population ? . Here’s a more specific definition: A population consists of a group of organisms of the same species that live in an area and interbreed

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Populations

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  1. Populations Chapter 5, Section 1 Pages 103-108

  2. What is a population? • Here’s a more specific definition: • A population consists of a group of organisms of the same species that live in an area and interbreed • Species—a group of organisms that can interbreed and produce fertile offspring

  3. Why is it important to study populations? • Populations affect other interacting populations, including human populations • How do populations grow? Or shrink? • Populations grow when pairs of individuals multiply and have offspring or new organisms immigrate from another area. • Populations shrink when organisms die or emigrate to another area.

  4. Mobility has an effect on population size • Immigration—movement of individuals into a population • Emigration—movement outof a population • Would movement within an area be (harder or easier) to track than movement into and out an area? • Movement within an area doesn’t really have too much of an effect on a population but movement in and out of an area makes it harder to track numbers of individuals.

  5. Exponential Growth (J-shaped) Two phases: Lag – little or no increase when population starts Exponential – very rapid increase; # of individuals doubles in time intervals

  6. Exponential Growth (J-shaped) • Population growth is not linear. They are more “J” shaped. • Examples: insect populations, bacteria • Populations unfortunately do not grow indefinitely and are hindered by a number of things. • What are some things that can hinder the growth of a population?

  7. Two types of factors that hinder population growth • Density-dependent factor—variables affected by the number of organisms present in a given area • Ex. Competition, parasites, space, mates, predators, and food • Dense populations are more prone to be effected by these factors

  8. Two types of factors that hinder population growth • Density-Independent factor—variables that affect population growth regardless of population size • Ex. Temperature, climate, storms, floods, drought, fires, and habitat disruption • Which factors are abiotic and which are biotic?

  9. Logistic Growth (S-shaped)

  10. Logistic Growth (S-shaped) • Limiting factors cause populations to reach carrying capacity • Population stabilizes where birth rate almost equals death rate • Carrying capacity—the maximum number of organisms of one species that an environment can support at any given time.

  11. Let’s talk about Human Population • In 1804, world population reached 1 billion • 1927: 2 billion (123 years later) • 1960: 3 billion (33 years) • 1974: 4 billion (13 years) • 1987: 5 billion (12 years) • 1999: 6 billion (12 years) • 2010: More than 6.5 billion and still increasing by about 9,000 people per hour!

  12. Industrial Revolution begins Agriculture begins Bubonic plague Plowing and irrigation

  13. Factors influence human population growth rates • Health care • Customs (value placed or large or small family) • Disease • Women’s roles • Government • Education • Economic stability • Religion • Nutrition • Pollution • Technology *To list a few…

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