1. POPULATIONS & CARRYING CAPACITY
02 June 2010
Populations.ppt

2. Population: all the individuals of a species that live together in an area
Demography: the statistical study of populations, make predictions about how a population will change
02 June 2010
Populations.ppt

3. Three Key Characteristics of Populations
Size, number of individuals (N)
Density (N/ area)
Dispersion,
Random, uniform, clumped,
(appropriate scale)
02 June 2010
Populations.ppt

4. Three Key Characteristics of Populations
1. Size: number of individuals in an area
Characterized by (N)
Growth Rate:
Birth Rate (natality) - Death Rate (mortality)
(How many individuals are born vs. how many die)
02 June 2010
Populations.ppt

5. Three Key Characteristics of Populations
2. Density: measurement of population per unit area or unit volume
Pop. Density =
# of individuals ÷ unit of space
02 June 2010
Populations.ppt

6. 4 Factors that affect density
1. Immigration- movement of individuals into a population
2. Emigration- movement of individuals out of a population
02 June 2010
Populations.ppt

7. 4 Factors that affect density
3. Density-dependent factors- Biotic factors in the environment that have an increasing effect as population size increases
  Ex. disease
competition
parasites
4. Density-independent factors- Abiotic factors in the environment that affect populations regardless of their density
  Ex. temperature
storms
habitat destruction
drought
02 June 2010
Populations.ppt

8. Three Key Characteristics of Populations
Dispersion: describes their spacing relative to each other
02 June 2010
Populations.ppt

9. Dynamic characteristics of populations
Age distribution,
proportions of young, middle-aged, old
Differs in growing, stable, decreasing populations
02 June 2010
Populations.ppt

10. Factors That Affect Future Population Growth
Immigration + + -
Population
Mortality
Natality -
Emigration

11. Changes in populations
Growth
Expansion of species’ populations may lead to evolution of new species
Decline
Shrinking species’ populations may lead to extinction
Small populations
Narrowly specialized species
02 June 2010
Populations.ppt

12. Changes in populations
ΔN = +B +I –D –E
+B = births (birth rate)
+I = immigrants (immigration rate)
– D = deaths (death rate)
– E = emigrants (emigration rate)
(For many [most] natural populations I and E are minimal.)
02 June 2010
Populations.ppt

13. Other factors that affect population growth
Limiting factor- any biotic or abiotic factor that restricts the existence of organisms in a specific environment.
EX.- Amount of water
Amount of food
Temperature
02 June 2010
Populations.ppt

14. Other factors that affect population growth
Carrying Capacity- the maximum population size that can be supported by the available resources
There can only be as many organisms as the environmental resources can support
02 June 2010
Populations.ppt

15. J-shaped curve (exponential growth)
Carrying Capacity Nu m b e r
J-shaped curve (exponential growth)
Carrying Capacity (k)
S-shaped curve (logistic growth)
Ok so
Time

16. 02 June 2010
Populations.ppt

17. Logistic model Logistic model works, to a point.
Real organisms have time lags for growth, time to develop eggs, flowers, etc.
seasonality, longevity
Real populations may exceed carrying capacity.
Easter Island
Pribloff Reindeer
Kaibab Deer
02 June 2010
Populations.ppt

18. Easter Island Discovered by Polynesians ~ A.D. 1000
Population grew to several thousand
Used trees for canoes to hunt dolphins
Used wood for cooking
Also ate birds, eggs, vegetables
Resources (trees) depleted
No canoes, no dolphins
Warfare over land, food resources
Population fell to ~ 100 when discovered by Dutch, Easter Sunday 1722.
02 June 2010
Populations.ppt

19. 2 Life History Patterns 1. “R” Strategists short life span
small body size
reproduce quickly
have many young
little parental care
Ex: cockroaches, weeds, bacteria

20. 2 Life History Patterns 2. “K” Strategists long life span
large body size
reproduce slowly
have few young
provides parental care
Ex: humans, elephants

21. Two general types of Life History Strategies
Life History trait
r-adapted, Opportunistic
K-adapted, Equilibrium
Offspring
Many, small (high r)
Fewer, large (low r)
Offspring survival
Low
High
Parental care
Rare
Common
Reproductive age
Early
Later
Reprod. “seasons”
1-few
Many
Habitat
Unstable, temporary
Stable, permanent
Competitiveness
Population regulation
Density independent
Density dependent
Population fluctuation
Irruptive
Stable near K

22. Survivorship curves 3 types: Type 1 Type 2 Type 3 02 June 2010
Populations.ppt

23. Survivorship curves Type 1
Most individuals survive childhood and middle age
rapidly decline in old age
Example: humans
02 June 2010
Populations.ppt

24. Survivorship curves Type 2 Example: birds
Roughly a constant mortality rate throughout individual’s life span
Example: birds
02 June 2010
Populations.ppt

25. Survivorship curves Type 3
Most individuals will die early in life and not make it to adulthood
Example: frogs, plants
02 June 2010
Populations.ppt

26. Life History Strategies
Fluctuating populations of two interacting populations
Based on pelts sold by Canadian trappers to the Hudson Bay Company, ~
02 June 2010
Populations.ppt