1 / 28

Limits to Growth

Limits to Growth. 5-2. Limiting Factors. Remember, primary productivity of an ecosystem can be reduced by limiting nutrients @Limiting factors can cause population size to decrease@. A resource base that is limited can also affect the long-term survival of a species Ex: pandas and bamboo.

ulema
Download Presentation

Limits to Growth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Limits to Growth 5-2

  2. Limiting Factors • Remember, primary productivity of an ecosystem can be reduced by limiting nutrients • @Limiting factors can cause population size to decrease@

  3. A resource base that is limited can also affect the long-term survival of a species • Ex: pandas and bamboo

  4. Density-Dependant Factors • Limiting factors that depend on population size • @Density-dependent factors become limiting only when population density reaches a certain level@ • Do not affect small, scattered populations

  5. Examples of density-dependent limiting factors: • @Competition • Predation • Parasitism • Disease@

  6. Competition • Occurs when populations become crowded • All organisms in a population need sunlight, food, water, space, etc. • Competition among members of the same species is density dependent

  7. The more members in the population, the faster the resources are used up • Competition also happens between members of different species • Major force behind evolutionary change • When 2 species compete for same resource, they are under pressure to change • Over time, evolve to occupy diff. niches

  8. Predation • Populations in nature are controlled by predation • Known as predator-prey relationship • Ex: • sea otters and urchins • Sea otters and whales

  9. Isle Royale • Well known example of predator-prey relationship is the moose/wolf populations on Isle Royale in Lake Superior • When moose numbers are high, wolf #’s increase • As wolves feed on moose, moose #’s decrease, causing a decrease in wolves • With fewer wolves, moose #’s can increase again

  10. Parasitism & Disease • Parasites can also limit population growth • Parasites are similar to predators – weaken and kill hosts • Large populations can be under stress making them more susceptible to diseases • More members = easier to pass “things” around

  11. Density-Independent Factors • @Factors that affect populations regardless of their size@ • Examples: • Unusual weather • Season cycles • Human activities (damming rivers, clear cutting)

  12. Populations usually respond to such factors with a crash in population size • After crash, numbers may increase quickly, or stay low for awhile • Storms and hurricanes can wipe out populations of insects

  13. Extreme cold or hot weather can also take a toll on populations • Droughts can affect entire populations of vegetation, which can affect populations of consumers

  14. Environments are always changing • Most populations can adapt to a certain amount of change (grow or shrink) • @Major upsets in ecosystems can lead to long-term decline in certain populations@ • Human activities have caused some of these upsets

  15. 5-3 Human Population Growth • Like the populations of many other living organisms, the size of the human population tends to increase with time. • For most of human existence, the population grew slowly • Until fairly recently, only half the children in the world survived to adulthood.

  16. What caused human populations to suddenly grow rapidly?

  17. @About 500 years ago, the human population began growing more rapidlybecause of agriculture and industry.@ • The world's food supply became more reliable, and essential goods could be shipped around the globe. • Improved sanitation, medicine, and health care dramatically reduced the death rate and increased longevity. • With these advances, the human population experienced exponential growth, as shown in the figure at right.

  18. Patterns of Population Growth • English economist Thomas Malthus observed that human populations were growing rapidly. • Malthus predicted that such growth would not continue indefinitely. • @Instead, according to Malthus, war, famine, and disease would limit human population growth.@

  19. The scientific study of human populations is called demography •   Birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly.

  20. Demographic Transition • Over the past century, population growth in the United States, Japan, and much of Europe has slowed dramatically. • According to this hypothesis, these countries have completed the demographic transition, a dramatic change in birth and death rates.

  21. Age Structure Diagram • Demographers can predict future growth using models called age-structure diagrams, or population profiles. • @Age-structure diagrams show the population of a country broken down by gender and age group.@

  22. What are the 4 density-dependent limiting factors? • Predation • Disease • Competition • Parasitism

  23. What are examples density independent limiting factors? • Storms • Natural Disasters • Human activity

  24. What caused the human population to grow rapidly? • Agriculture • Industry • Medicine

More Related