1. CHAPTER 5: Populations
Mrs. Yanac
Biology 1B

2. CHARACTERISTICS OF A POPULATION
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

3. FACTORS THAT AFFECT POPULATION SIZE
# of BIRTHS (Birth rate)
# of DEATHS (Death rate)
# of individuals that ENTER (Immigration) a population
# of individuals that LEAVE (Emigration) a population

4. POPULATION GROWTH

5. EXPONENTIAL GROWTH
Under IDEAL conditions with UNLIMITED resources, a population will grow & grow (exponentially)

6. LOGISTIC GROWTH
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)

7. CARRYING CAPACITY 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

8. Comparison

9. LIMITS TO GROWTH

10. LIMITING FACTOR
Any factor that causes the population to decrease

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

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

13. Heavy Snow
(-) 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

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

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

16. Over-Population
(-) Crowding and trampling of vegetation (-) Disease spreads easily (-) Vegetation is stripped

17. Density-Dependent Limiting Factors
Factors that depend on the size of a population
Examples:
Competition
Predation
Parasitism
Disease

18. Density-Independent Limiting Factors
Affect all populations regardless of size.
Examples
Natural disasters
Weather
Human activities

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

20. 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?