Mrs. Yanac Biology 1B

 DENSITY – The number of individuals in particular area  GROWTH RATE – The rate at which the population increases  GEOGRAPHIC DISTRIBUTION – The area inhabited by the population

 # of BIRTHS (Birth rate)  # of DEATHS (Death rate)  # of individuals that ENTER (Immigration) a population  # of individuals that LEAVE (Emigration) a population

 Under IDEAL conditions with UNLIMITED resources, a population will grow & grow (exponentially)

 As resources become LESS available, the growth of a population SLOWS or STOPS  Leveling off is known as carrying capacity ( total # of individuals a population can support)

 EX: White-Tailed Deer Habitat  Food Source = 10 deer  Carrying Capacity = 10 deer  Although the water, cover & space are sufficient for more deer, the limiting factor of the food supply determines what this habitat will support.  Carrying capacity does not exceed the number that the most limiting factor will allow

 Any factor that causes the population to decrease

Younger or weaker animals die (-) There may be fewer animals born (-) Takes more energy just to survive

Animals could get burned (-) Food & cover burned (-) Water source may evaporate (+) Re-growth of nutritional vegetation (+) Encourages grass cover (+) Cleans out debris

(-) Movement is difficult, requires more energy (-) Food is difficult, often impossible, to find (-) Thermal cover is difficult to reach & often ineffective (+) Insulates plants & animals from extreme cold

(-) Vegetation withers, food disappears (-) Water sources dry up (-) Cover thins

(-) Habitat & wildlife washed away or inundated. (-) Vegetation drowns (+) Disperse seeds & soil

(-) Crowding and trampling of vegetation (-) Disease spreads easily (-) Vegetation is stripped

 Factors that depend on the size of a population  Examples:  Competition  Predation  Parasitism  Disease

 Affect all populations regardless of size.  Examples  Natural disasters  Weather  Human activities

RECAP: 1. What are 4 factors that affect population growth? 2. What are 3 characteristics of a population? 3. What type of growth goes through a period of rapid growth, then slows down or stops?

4. What is the term for the largest # of individuals a population can hold? 5. What type of growth grows at a constant rate? 6. What are some density- dependent limiting factors? 7. What are some density- independent limiting factors?