Population Studies

 Population- a group of individuals of a single species inhabiting a specific area  Why study populations? –Population Too high or low = unstable ecosystem –Low species diversity = unstable ecosystem Examples:  Endangered Species = low population due to human impact  Invasive Species = species introduced to a new ecosystem with no predators or competition allowing the population to increase rapidly

Examples of Invasive Species (Write the names of the two examples) European Gypsy Moth  Introduced from Europe in 1869  They were imported for silk production  They defoliate sections of forest Brown Marmorated Stink Bug  Native to Eastern Asia  1 st found in Allentown, PA in 1998  Possibly arrived in shipping crates from Asia  They feed on a variety of plants, including fruit trees, ornamental trees and shrubs, and some crops  Currently found in the northeast, mid- Atlantic region and the Pacific northwest

What keeps populations from growing out of control?  Limiting factors- A biotic or abiotic factor that a population needs as a resource. –Provide TWO or THREE Examples:  Carrying capacity- the number of individuals an ecosystem can support.

Population Growth = When the birth rate exceeds the death rate, due to an abundance of resources.

J-Curve Population Graph J curve- exponential growth of a population because of no natural predators and an abundance of resources. (Usually followed by a population crash after exceeding its carrying capacity).

S-Curve Population Graph  S curve- population increases to its carrying capacity & levels off due to predators or competition

Population Study Example  What kind of relationship does the graph show?  Which population seems to increase first before it drops?  Is the hare and lynx relationship a density dependent or density independent limiting factor?

How do ecologists determine population?  Counting- count the number in the population  Mark and Recapture- ex: bird banding, tagging, microchips  Random sampling- look at a part of the ecosystem and assume it is the same for the whole ecosystem

Which is the best method to determine each population?  Trout in the Delaware River  Diversity of trees in a state park  Eagle eggs in a nest  Deer in Bucks County  Dandelions in my neighbors yard  Trees on the school property

Random Sampling Method  Choose letter and number combinations first  A-J and 1-10  Count the number of dots in each letter and number combination square that you chose and place the numbers in the chart  When finished, add up these numbers for the total in the sample  Find the estimated total and then find the actual total  How well did this method work?

Table Set-up for Random Sampling Letter/Number Combination # of sunflower plants Ex: G34 Total # of sunflowers in 10 squares Estimated Total # of sunflowers in meadow= (Total/10) x 100 Count actual # of sunflowers in meadow

Mark & Recapture Method  Plug your numbers into the following equation for each trial. Solve for P. P = A (B/R)  P = estimated population  A = # caught and marked the first time  B = # caught the second time  R = # caught 2 nd time which were marked

Mark and Recapture  Choose a color  Count how many beads in your bowl are your color then release them back into the bowl. This number=A  A = # caught & marked during the first catch  Grab a small cup full and count the total number of beads in your hand. This number = B  B = # caught during the 2 nd catch)  Count how many are your color in your hand. This number = R  R = # caught during 2 nd catch that were already marked  (If Time) Repeat this method for 5 trials an record results

Table for Mark & Recapture Method Trial 1Trial 2Trial 3Trial 4Trial 5 A B R P= A(B/R)