2.  Population  group of individuals of same species in same general area
 rely on same resources
 interact
 interbreed

3. Populations repond to variation on a scale… or “grain”.
Grain be either:
Spatial (size/location) or
Temporal (daily vs seasonal)
Course Grained environment: Patches are large ; organism can select
Fine Grained Environment: Patches are small ; organism cannot select.

4. Changes to population size
 Adding & removing individuals from a population
 birth
 death
 immigration
 emigration

5. Demography  Factors that affect growth & decline of populations.
 vital statistics & how they change over time
Life table
What does this tell you
about the population?

6. Factors that affect birth/death rates:
AGE STRUCTURE: relative numbers of individuals at each age. In general,
older populations grow more slowly than younger populations.
GENERATION TIME: span of time between birth and first reproductive event.
Often directly related to body size.
Other factors being equal, shorter generation time = faster population growth
SEX RATIO: proportion of each sex in population.
number of females more significant except for monogamous species.
CLUTCH SIZE: number of offspring per episode. Smaller clutches usually larger kids.
Tends to increase with latitude. Trade off between number & quality.

7. Survivorship curves
 What does this tell about survival & strategy of a species?

8. Population growth change in population = births – deaths dN = rmaxN dt
N = # of individuals
r = rate of growth
t = time period
maximum rate =
intrinsic rate of increase

9. Exponential growth rate
 Characteristic of populations introduced to a new environment or rebounding from a catastrophe.
Whooping crane
coming back from near extinction
African elephant
protected from hunting

10. Carrying Capacity  Carrying Capacity (K)  Can populations continue
grow exponentially?
 Of course NOT!
What sets limit?
 Carrying Capacity (K)
maximum population size that environment can support with no degradation of habitat.
 not fixed; varies with changes in resources

11. Logistic model of growth
Or….
Let’s just practice this
on the board.

12. Life history traits
r-selection = maximize reproductive success
Populations fluctuate, shorter maturation time/lifespan, higher mortality rates, lager clutch sizes, less parental care, reproductive events.
K-selection = density dependent
Populations remain more constant, (near carrying capacity). Characteristics opposite those of r-selected.
Iteroparity- life history in which adults produce offspring over many years.
Semelparity- life history in which adults have only a single reproductive opportunity to produce
one large number of offspring.

13. Trade offs Principle of Allocation: Number & size of offspring vs.
survival of offspring or parent
Principle of Allocation:
-Natural Selection has resulted in
different budgeting strategies for each
organism’s limited amount of energy.

14. Regulation of population size
 Limiting factors
 density independent
 environmental disturbances
 density dependent
 food supply
 competition
 predators
 Population cycles
 population fluctuations
ocean currents & cannibalism

15. Predator – prey interactions
 Population cycles

16. Human population

17. Total population (in billions) Annual increase (in millions)
Figure 36.9a
100 10
Population increase 80 8
Total population (in billions)
Annual increase (in millions) 60 6 40 4
Total population size 20 2
Year
Adapted from The World at Six Billion, United Nations Publications (1999).

18. Age structure  Relative number of individuals of each age
What do the data imply about population growth in these countries?

19. Impact: Ecological Footprint
youtube
Is the human population near carrying capacity?
Based on land & water area
appropriated to produce all
resources it consumes & to
absorb all wastes it generates
Is the human population
near carrying capacity?
2008 = ~6.5 billion
K = 10–15 billion?