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