Populations

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Populations

  1. 1. Population Biology
  2. 2. Rainforest Movie Questions <ul><li>Describe what happens in the rainforest when a large tree falls. </li></ul><ul><li>Describe the mating rituals of jungle birds. </li></ul><ul><li>Explain why some of the earth’s largest rivers are found in rainforests. </li></ul><ul><li>Describe the importance of decomposers in the rainforest. </li></ul><ul><li>Explain how the “pitcher plant” gets its nutrients in very nutrient poor soil. </li></ul><ul><li>Explain why most animals in the rainforest are small. </li></ul>
  3. 3. Population Growth <ul><li>Population growth is the change in the size of a population over time. </li></ul><ul><li>Populations of organisms do not experience linear growth, instead they grow exponentially , when the number of organisms rise at an ever-increasing rate. </li></ul><ul><li>It results in a population explosion and a J-shaped curve on a graph. </li></ul>
  4. 4. Graph of Exponential Growth P O P U L A T I O N S I Z E TIME
  5. 5. Environmental Limits <ul><li>Populations can not grow forever. </li></ul><ul><li>There are limiting factors, such as food availability and space, that limit the size of a population. </li></ul><ul><li>Eventually, all populations will level off then they reach carrying capacity- the number of organisms of a population that a particular environment can support over an indefinite period of time. </li></ul><ul><li>The leveling off of the population results in a s-shaped graph. </li></ul>
  6. 6. Population growth when carrying capacity is reached Carrying capacity TIME P O P U L A T I O N S I Z E
  7. 7. Estimating populations <ul><li>Scientists find that obtaining an exact number for a population of organisms is very difficult if not impossible. </li></ul><ul><li>Why? </li></ul><ul><li>Most animals do not just line up and wait to be counted!!! They wander or migrate. </li></ul><ul><li>Plants and non-mobile species are easier. </li></ul><ul><li>Scientists use 2 different techniques to help them to estimate the size of a population……. </li></ul>
  8. 8. Sampling <ul><li>Sampling - organisms in a few small areas are counted and projected for the entire area. </li></ul><ul><li>Ex. If there are 5 deer living in a 200 square foot area, how many would there probably be living in the surrounding 2000 square foot area? </li></ul>
  9. 9. Mark and recapture <ul><li>Mark and recapture - animals are captured alive, marked or tagged, and then returned unharmed into their natural environment. </li></ul><ul><li>Over time, the animals from the population are continued to be trapped and data is recorded on how many are captured with tags. </li></ul><ul><li>Then the population size is estimated mathematically…….. </li></ul><ul><li>Total # captured X Total # marked/tagged = Estimate of Total Population </li></ul><ul><li>Total # recaptured with mark/tag </li></ul>
  10. 10. Bellwork <ul><li>Describe what type of growth do populations exhibit. </li></ul><ul><li>Explain carrying capacity. How do you know when a population exceeds the carrying capacity? </li></ul><ul><li>Explain why is it difficult to find out an exact number of a population. </li></ul><ul><li>Describe the 2 techniques that scientists use to estimate population size. </li></ul>
  11. 11. Patterns of Population Growth <ul><li>All population levels do not reach carrying capacity and remain stable. </li></ul><ul><li>It depends on the most important factor that determines how a population grows- the organisms reproductive pattern. </li></ul><ul><li>There are 2 growth patterns….. </li></ul><ul><li>Rapid reproduction pattern- Some species reproduce rapidly, produce many offspring, have a small body size, mature rapidly, and have a short life span. </li></ul><ul><li>These organisms are successful in environments that are unpredictable. </li></ul>
  12. 12. <ul><li>These populations increase rapidly and then decline rapidly as environmental conditions suddenly change and become unsuitable. </li></ul><ul><li>Ex. Mice, insects, rabbits…… </li></ul><ul><li>Slow reproduction pattern- Some species have a slow rate of reproduction, have relatively few young over their lifetimes, live in stable environments, are large in size, reproduce and mature slowly. </li></ul><ul><li>Ex. Elephants, whales, California Redwood….. </li></ul>
  13. 13. Environmental Limits to Population Growth <ul><li>Limiting factors (last chapter) can also regulate the size of a population. </li></ul><ul><li>There are 2 main kinds…… </li></ul><ul><li>Density-dependent factors - have an increasing effect as the population size increases. </li></ul><ul><li>Ex. Disease, competition for food/shelter/space, parasites…… </li></ul>
  14. 14. <ul><li>Density-independent factors- have the same affect on all populations, regardless of the density or size. </li></ul><ul><li>Ex. Temperature, floods, storms, drought, habitat destruction…….. </li></ul>
  15. 15. Other influences on population growth and size <ul><li>Predator and prey relationships will affect population size. </li></ul><ul><li>Competition for resources can affect a population’s size. </li></ul><ul><li>Crowding and stress can negatively affect a population and cause a decrease in population size. </li></ul>
  16. 16. Bell Work <ul><li>Explain why insects need to mature quickly. </li></ul><ul><li>Explain in your own words how disease can be a density -dependent factor. </li></ul><ul><li>Explain in your own words how cutting down a forest is a density-independent factor. </li></ul><ul><li>Compare the care given by the mothers who fall into a rapid reproductive pattern and care given by mothers who fall into a slow reproductive pattern. </li></ul>
  17. 17. Bell Work <ul><li>Describe the pattern of population growth of a predator and prey relationship. You can use a fox/rabbit example if necessary. </li></ul><ul><li>Explain why a flood is a density-independent factor. </li></ul><ul><li>Describe an environmental factor that might have an effect on a population of individuals who reproduce rapidly. What effect will it have on the population? </li></ul>
  18. 18. Human Population Growth <ul><li>Demography is the study of population growth characteristics. </li></ul><ul><li>Scientists can study…… </li></ul><ul><li>Birth rates- the amount of children being born into a population in a period of time </li></ul><ul><li>Fertility rates- number of offspring a female produces during her reproductive years </li></ul><ul><li>Death rates- the amount of individuals dying in a population in a period of time. </li></ul><ul><li>Immigration- movement of individuals into a population. </li></ul><ul><li>Emigration- movement of individuals out of a population </li></ul>
  19. 19. YEARS POPULATION IN BILLIONS
  20. 20. <ul><li>The birth rates, fertility rates, and death rates are directly linked to….. </li></ul><ul><li>Education </li></ul><ul><li>Health care </li></ul><ul><li>Sanitation </li></ul><ul><li>Births and immigration add to a population’s size. </li></ul><ul><li>Deaths and emigration subtract from a population’s size. </li></ul>
  21. 21. Bell Work <ul><li>Compare immigration and emigration. </li></ul><ul><li>Describe what can increase the size of a population. </li></ul><ul><li>Explain why Kenya has higher birth rates and death rates than the Unites States does. </li></ul><ul><li>Describe the type of population growth that humans have had in the past 150 years. </li></ul>
  22. 22. Age Structures <ul><li>An age structure is a type of graph that shows the proportion of a population that is in a certain age range. </li></ul><ul><li>By looking at an age structure, you can tell if a population is growing rapidly, growing slowly, or not growing at all. </li></ul>
  23. 24. Answer the following questions for each age structure, making sure to label the countries. <ul><li>Calculate the total population for this country. </li></ul><ul><li>Describe the type of growth that this country is currently experiencing. Explain why!! </li></ul><ul><li>Using your answer to number 2, describe the education, health care and sanitation likely in this country. </li></ul>

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