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Population Sampling

Population Sampling. Population Density. Measures the amount of population per unit area. Why Study population density?. Understanding the population size in an area allows ecologist to know if a population is healthy or not Review terms: carrying capacity and critical number

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Population Sampling

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  1. Population Sampling

  2. Population Density • Measures the amount of population per unit area

  3. Why Study population density? • Understanding the population size in an area allows ecologist to know if a population is healthy or not • Review terms: carrying capacity and critical number • Many factors affect population density of a species • Review limiting factors

  4. Population Sampling • Scientists use different sampling techniques to estimate the number of organisms in a given population

  5. Sampling Techniques • Direct Count- actually counting every organism; only works with certain organisms Examples: People- census Bacteria- colonies on a petri dish

  6. Indirect Counting- look for signs of an organisms presence Example- bird’s nest, burrows, scat (droppings) • Bird’s nest with eggs • Deer Scat 

  7. Quadrat Sampling- mapping out a grid of specific size and counting the organisms within that grid - Very common method

  8. Mark and Recapture- involves marking a number of individuals in a natural population, returning them to that population, and subsequently recapturing some of them as a basis for estimating the size of the population at the time of marking and release

  9. Population sampling allows for estimates of a population in a region • Using statistical analysis, scientists are able to get an idea of the amount of organisms for a specific species.

  10. The Horseshoe Crab Scientific Name: Limulus polyphemus

  11. Uses • Horseshoe crab blood is extremely important in the medical field • Every single intravenous drug is tested for contaminants using horseshoe crab blood • One quart of horseshoe crab blood costs around fifteen thousand dollars

  12. Population Decline • There is concern over the horseshoe crab population due to its over use as bait for eel and whelk

  13. Why is this a problem? • Besides its use in the medical community, horseshoe crabs play a key role in migratory bird patterns • When the horseshoe crabs spawn, its eggs provide a major food source for incoming shorebirds and other fish • If there are not enough eggs, the bird populations will begin to decline

  14. Horseshoe crab eggs Horseshoe crab spawning Shorebirds eating the eggs *first meal in 3-4weeks*

  15. Citizen Science • Project Limulus- uses everyday citizens to do population counts of horseshoe crabs along the Eastern Coast to determine population rate • Has led to laws in DE and NJ protecting and restricting the catching of horseshoe crabs for bait • Uses quadrat sampling technique

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