1. Introduction to Ecology
What is Ecology?
Answer: The study of inter-relationships among living things
and the non-living environment:
Soil
Abiotic = Non-living factors:
Animals
Biotic = Living factors:
Water
Plants
Weather

2. Ecology - Increasing Levels of Complexity:
Introduction to Ecology
Ecology - Increasing Levels of Complexity:
Organism
Population: All members of a particular species living
within a defined area
Community: All interacting populations of species within a
defined area
Ecosystem: All living organisms and the non-living environment
within a defined area
Biosphere = Earth (multiple ecosystems)

3. Population Growth & Regulation
Chapter 38:
Population Growth & Regulation

4. Influences Affecting Population Sizes:
Chapter 38: Population Growth & Regulation
Influences Affecting Population Sizes:
1) Births
2) Deaths
3) Migration
Immigration = migration into a population
Emigration = migration out of a population
(minor factor)
(major factor - natural populations)
(major factor)
(Births - Deaths) + (Immigrants - Emigrants) 
Population
Size =

5. + - Ultimate size of population = balance between opposing forces
Chapter 38: Population Growth & Regulation
Ultimate size of population = balance between opposing forces
Biotic Potential: Maximum rate at which a population can
increase in size (ideal conditions)
(1st Force) +
Maximize
Births
Minimize
Deaths
Balance
(Births - Deaths) 
Population
Size =
Maximize
Deaths
Minimize
Births -
Environmental Resistance: Limits set by the environment
(e.g. food availability, competition, predation)
(2nd Force)

6. (10%) Biotic potential can produce Exponential Growth:
Chapter 38: Population Growth & Regulation
Biotic potential can produce Exponential Growth:
Continuously accelerating increase in population size
Growth Rate: Measure of  in population size / time
Growth Rate (r) = Birth Rate (b) - Death Rate (d)
1500 / 10,000
/ 10,000
(10%) =
increase / person / year
0.15
births / person / year
deaths / person / year
Population Growth: # of individuals added to population / time
Population Growth = Growth Rate (r) x Population Size (N)
0.10
increase / person / year
x ,000
People =
new individuals / year
New Population Size = 11,000

7. Biotic potential can produce Exponential Growth:
Chapter 38: Population Growth & Regulation
Biotic potential can produce Exponential Growth:
New Population Size = 11,000
2nd year: x = 1100
3rd year: x = 1210
4th year: x = 1331
5th year: x = 1464
Exponential
Growth
(ever-accelerating)
(Figure 38.1)
J curve

8. Factors Affecting Biotic Potential:
Chapter 38: Population Growth & Regulation
Factors Affecting Biotic Potential:
1) Age at which organism first reproduces ( age =  rate)
2) Frequency with which reproduction occurs ( freq. =  rate)
3) Average number of offspring / event ( # =  rate)
4) Length of organism’s life span ( lifespan =  rate)
5) Death rate of individuals (ideal condition -  rate =  rate)
(Figure 38.1)
(Figure 38.3)

9. Exponential growth cannot continue indefinitely:
Chapter 38: Population Growth & Regulation
Exponential growth cannot continue indefinitely:
Boom-and-Bust Cycles: Rapid population growth followed
by massive die-off (short-lived organisms)
(Environmental
Resistance
Predominates)
(Biotic Potential
Predominates)

10. Exponential growth cannot continue indefinitely:
Chapter 38: Population Growth & Regulation
Exponential growth cannot continue indefinitely:
Boom-and-Bust Cycles: Rapid population growth followed
by massive die-off (short-lived organisms)
Example: Lemmings

11. Environmental resistance stabilizes population growth for many
Chapter 38: Population Growth & Regulation
Environmental resistance stabilizes population growth for many
long-lived organisms (no boom-bust cycles):
S-curve
(Figure 35.8)
Growth
Rate
(= 0)
Carrying Capacity: The maximum population size that an
ecosystem can support indefinitely

12. Carrying Capacity Determined By:
Chapter 38: Population Growth & Regulation
Carrying Capacity Determined By:
1) Renewable Resources  Nutrients, water, light
Replenished by natural processes (can be damaged)
2) Non-renewable Resource  Space
Factors of Environmental Resistance Maintaining Populations
At / Near Carrying Capacity:
1) Density-Independent Factors: Limit pop. size regardless
of pop. density
2) Human
Activities
Pesticides /
pollutants
Habitat
destruction
1) Weather

13. (Pg. 798 - Scientific Inquiry)
Chapter 38: Population Growth & Regulation
Factors of Environmental Resistance Maintaining Populations
At / Near Carrying Capacity:
2) Density-dependent Factors: Factors more effective as
population size increases
** Most Important **
a) Predation: One organism (predator) kills another
organism (prey) to eat
More abundant prey = more chance of meeting
predator
Predator - Prey Cycles
(Pg Scientific Inquiry)

14. Factors of Environmental Resistance Maintaining Populations
Chapter 38: Population Growth & Regulation
Factors of Environmental Resistance Maintaining Populations
At / Near Carrying Capacity:
2) Density-dependent Factors: Factors more effective as
population size increases
b) Parasitism: One organism (parasite) feeds off another
organism (host) without killing it
More abundant hosts = easier for parasite to find
Malaria
Bark Beetle
Lamprey

15. Factors of Environmental Resistance Maintaining Populations
Chapter 38: Population Growth & Regulation
Factors of Environmental Resistance Maintaining Populations
At / Near Carrying Capacity:
2) Density-dependent Factors: Factors more effective as
population size increases
c) Competition: Organisms compete among each other
for limited resources (e.g. food)
Two types of competition:
1) Interspecific Competition: between species
2) Intraspecific Competition: within species
*More Intense*
Contest
Competition
Scramble
Competition

16. Types of Spatial Distribution:
Chapter 38: Population Growth & Regulation
Populations Exhibit Differing Spatial Distributions:
Distribution: Spatial pattern in which population members are
arranged in given area.
Types of Spatial Distribution:
1) Clumped: Population members live in defined groups
Family Groups (e.g. wolves)
Social Groups (e.g. Flamingos)

17. Types of Spatial Distribution:
Chapter 38: Population Growth & Regulation
Populations Exhibit Differing Spatial Distributions:
Distribution: Spatial pattern in which population members are
arranged in given area.
Types of Spatial Distribution:
2) Uniform: Relative constant distance between population
members
Territorial Groups (e.g. penguins)
(e.g. sage)

18. Types of Spatial Distribution:
Chapter 38: Population Growth & Regulation
Populations Exhibit Differing Spatial Distributions:
Distribution: Spatial pattern in which population members are
arranged in given area.
Types of Spatial Distribution:
3) Random: Members scattered haphazardly across
landscape
Many plants (e.g. trees)
Very rare in animals

19. Populations Show Characteristic Patterns of Survivorship:
Chapter 38: Population Growth & Regulation
Populations Show Characteristic Patterns of Survivorship:
Survivorship Curve: Graph depicting # of individuals in an age
class against their age
Late-loss (e.g. human)
1) Late-loss Populations:
Low infant death rates
Produce few offspring
Age of members
# of members surviving
3) Early-loss Populations:
Early-loss
(e.g. plants)
2) Constant-loss Populations:
Constant-loss
(e.g. birds)
Constant death rate
Produce variable offspring
High infant death rates
Produce many offspring

20. So How Do Humans Fit Into This?
Chapter 38: Population Growth & Regulation
So How Do Humans Fit Into This?
(Figure 38.11)
More hospitable
environment
More efficient
food gathering
 death rates

21. Doubling Time: 70 / growth rate (%) 70 / 1.4 = 50 years
Chapter 38: Population Growth & Regulation
Doubling Time:
70 / growth rate (%)
70 / 1.4 = 50 years
70 / 0.6 = 117 years
(Figure 38.13)

22. The human population will stop its exponential growth… either we will
Chapter 38: Population Growth & Regulation
The human population will stop its
exponential growth… either we will
voluntarily reduce our birth rate, or
various forces of environmental resistance
will dramatically increase our death
rates… the choice is ours...
- Earth Watch (pg. 809)