1. POPULATIONS
DEFINITION: GROUP OF ORGANISMS OF THE SAME SPECIES LIVING IN A GIVEN GEOGRAPHIC REGION EXAMPLES: HONEY BEE HIVE, FIRE ANT HILL, FLOCK OF CANADA GEESE, DANDILIONS IN A LAWN, POD OF KILLER WHALES, PEOPLE!

2. LIMITING FACTORS
AS WE HAVE DISCUSSED THE ABIOTIC LIMITING FACTORS DETERMINE THE NATURE OF ADAPTATION WITHIN A SPECIES…
ENVIRONMENT SELECTS THOSE ORGANISMS THAT CAN BEST ADAPT TO THE TEMPERATURE, WATER, SOIL, SUNLIGHT, pH, SALINITY, NUTRIENTS, AND PRESSURE DEMANDS OF THEIR HABITATS
IN ADDITION TO THESE ABIOTIC FACTORS THERE ARE ALSO BIOTIC LIMITING FACTORS; THOSE BENEFICIAL OR HARMFUL FACTORS THAT DIRECTLY INFLUENCE A SPECIES POPULATION, SIZE, OR DISTRIBUTION ONCE ADAPTED

3. BIOTIC LIMITING FACTORS
BENEFICIAL
HARMFUL
EASE OF REPRODUCTION
FIND FOOD
PROTECTION
DISEASES SPREAD EASIER AND FASTER
COMPETITION AND CONSUMPTION OF RESOURSES
HUMAN
INFLUENCES

4. POPULATIONS GROW EXPONENTIALLY IF FEW LIMITING FACTORS ARE PRESENT
WHAT DO YOU NOTICE ABOUT THESE TWO GRAPHS?
THIS GRAPH ILLUSTRATES A POPULATION
WHRE THERE ARE FEW LIMITING FACTORS
CONTROLLING GROWTH
THIS GRAPH ILLUSTRATES A POPULATION
WHRE LIMITING FACTORS ARE CONTROLLING
GROWTH
‘J’ CURVE
‘S’ CURVE

5. CARRYING CAPACITY
The maximum population of a given species that can survive indefinitely in a given environment.
WHAT IS THE CARRYING CAPACITY OF HARES? OF LYNX?
around 40,000
around 2800

6. How would you count members of the following populations?
Large mouth bass in Lake Lanier
Bacteria E. coli growing on a petri dish
Blue jays in Smokey Mtn National Park
Periwinkle snails on marsh grass
Live oak trees in South Georgia
Which were easiest?
More difficult?
What influenced your method of counting the most?
TREES, SNAILS
BASS, JAYS, BACTERIA
MOVING? VISIBLE? NEED INSTRUMENTS?

7. HOW ARE POPULATIONS COUNTED?
METHODS DEPEND UPON WHETHER OR NOT THE POPULATIONS ARE MOBILE OR STATIONARY; EASY TO SEE OR DIFFICULT TO ACCESS. RANDOM SAMPLING: METHOD USED FOR POPULATIONS THAT ARE STATIONARY/SLOW MOVING. AN AVERAGE OF THE POPULATION SIZE IS MADE USING A GRID AND SELECTION OF SECTIONS AT RANDOM.
PROCESS
1. SELECT BOXES AT RANDOM
2. COUNT NUMBER OF ORGANISMS IN EACH
3. TOTAL COUNT AND DIVIDE BY THE NUMBER
OF BOXES SELECTED
4. MULTIPLY BY TOTAL NUMBER OF BOXES 6 7 7 7
35 WORMS/5 BOXES= 7
More accurate estimates with populations
that are evenly distributed within the grid
Organisms that move must be marked
Controls must be in place for counting organisms that overlap
7 X 16 BOXES=112 WORMS 8

8. Random Sampling: Sunflowers
BOX
COUNT A2 1 D7 F7 B8 2 H5 I8 4 E2 3 F5 E9 J3
Total 19
19 flowers / 10 boxes = 1.9 flowers per box
1.9 x 100 boxes = 190 sunflowers
ACTUAL # = 194

9. MARK AND RECAPTURE
METHOD USED FOR POPULATIONS THAT ARE NOT STATIONARY, OR ARE HIDDEN FROM VIEW. SAMPLE OF THE POPULATION IS CAPTURED, MARKED AND RETURNED. THEN THOSE RECAPTURED WITH MARK ARE COUNTED THOSE THAT AREN’T ARE MARKED.