Lesson 3 ecology human

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Lesson 3 ecology human

  1. 1. Population Growth Notes<br />Module 2 Ecology<br />
  2. 2. Growing rapidly<br />Tripled in size in about 70 years<br />Est. size to day 6 billion+ (approx. 2 billion in 1930)<br />Human Population<br />
  3. 3. Problems cause by humans<br />Thinning ozone layer – ozone layer protects living things from ultraviolet radiation form the sun<br />Climatic changes<br />Greenhouse effect: insulates earth from the deep freeze of space; keep Earth warm<br />Caused extinction of other species – extinction rate higher today than at any other time<br />Increased pop. requires increasing amts. of food, energy, space – greater share of Earth’s resources will be required<br />Burning Fossil Fuels for energy – releases carbon dioxide; excess CO2 traps too much heat in Earth’s atmosphere<br />
  4. 4. Human Population Growth<br />Improved by agricultural development, hygiene, diet, and economic conditions improved<br />Today, population growth is faster in less-developed countries and slower in more developed countries<br />
  5. 5. Population Dynamics<br />Changes in size and composition over time<br />Measure include:<br />birth rate - number of births over time (in US it is 4 million per year)<br />death or mortality rate – number of deaths in a period of time (in US it is 2.4 million per year)<br />life expectancy – how long an individual is expected to live (1996: in US it was 72 yrs. for a man and 79 for a woman)<br />
  6. 6. Population Growth Rates<br />Amount of change within a population’s size in a given time<br />Four factors that affect growth rates:<br />Birth<br />Death<br />Emigration – movement out of a population<br />Immigrations – movement into a population<br />Demographers – scientists who study populations dynamics<br />Birth rate – death rate = growth rate<br />
  7. 7. Carrying capacity of a population is the number if individuals the environment can support for an indefinite period of time.<br />Populations fluctuate over time do to environmental changes.<br />Small populations are less able to rebound from environmental changes. They are more likely to experience inbreeding and their genetic diversity is low.<br />
  8. 8. Population Growth Curves<br />Linear – growth occurs along a straight line<br /> NOT what we see w/ populations of organisms<br />
  9. 9. Population Growth Curves<br />Exponential – as population gets larger, it grows faster (population explosion)<br /> “J shaped”<br />
  10. 10. Predator-Prey<br />Predator-Prey – (predation is density dependent limiting factor)<br /> When population grows beyond carrying capacity of environment, density-dependent Limiting Factors reduce population  population grows/shrinks cycles<br />
  11. 11. Carrying Capacity<br /> What is seen in most populations of organisms. Population growth is limited by factors in the environment such as food supply or habitat.<br />

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