1. What is ecology?
The study of interactions between
organisms and their environment.

2. Ecology? Biology?
 Biology is simply the “study of life.”
 Ecology involves the interactions of living
and nonliving aspects of the environment.
 Both biotic and abiotic factors are
interconnected – a change in one,
changes all the others over time.

3. Factors
 Biotic Factors
 Living factors
 Humans, plants, insects
 Abiotic Factors
 Nonliving factors
 Physical & chemical characteristics
 Temperature, pH, O concentration,
2
sunlight, H2O, soil

4. Abiotic? Biotic?
 Exploding human population
 Biotic
 Species endangerment/extinction
 Biotic
 Thinning of the ozone layer
 Abiotic
 Greenhouse effect
 Abiotic

5. Interactions at Levels
 Organism
 A single species
 Example: one blue gill
 Note: Since no organism is isolated,
ecologists must use MODELS to study
the environment and to make
predictions about the future

6. Interactions at Levels
 Population
 Members of a single species
 Example: population of blue gills in a
lake

7. Interactions at Levels
 Community
 A group of different populations that
live in the same area
 Only living factors in an area interacting
with each other
 Example: fish, turtles, algae

8. Interactions at Levels
 Ecosystem
 The interactions among living things
and the nonliving things in an area
 Example: lake
 NOTE: Biomes are large ecosystems

9. Interactions at Levels
 Biosphere
 Broadest category
 The part of Earth
where living things
exist
 Example:
atmosphere,
lithosphere

10. Organisms
 Habitat
 Where an organism lives
 Niche
 What an organism does (its job or role) in
its environment
 Role in the food chain & nutrient cycling
 Interactions with other species
 Two types of niches
 Fundamental niche
 Realized niche

12. Fundamental Niche
 The potential range of conditions and
resources that an organism can assume
 Total range of environmental conditions
that are suitable for a species existence
 Example:
 We can live anywhere in U.S. (tolerance)

13. Realized Niche
 The actual range of conditions and
resources that an organism assumes
 Example:
 We live and do our “jobs” in
Northbrook.

14. Ecological Roles
 Generalists
 Organisms with very broad niches
 Can live in many habitats, many
conditions
 “Jack of all trades, master of none”
 Example:
 Opossum
 Cockroaches
 Mice
 Humans

15. Ecological Roles
 Specialists
 Organisms with very narrow and
specific niches
 Live in one or few habitats, narrow
range of conditions
 Out compete generalists in preferred
habitats
 Example:
 Koala can only live and survive on
Eucalyptus trees in Australia

16. Ecological Roles
 In a changing environment, it is better to
be a generalist.
 In a stable environment, it is better to be a
specialist.

17. What is a population?
All the individuals of a single
species living in an area

18. Rabbits in Australia

19. Population Size? Density?
 Population Size
 Number of individuals
 Population Density
 Number of individuals in an area
 Persons/square mile

20. Limiting Factors
 Density dependent limiting factors
 Factors that limit a population only
when a population reaches a certain
density
 Examples:
 Competition, predation, parasitism,
disease, water availability

21. Limiting Factors
 Density independent limiting factors
 Factors that affect all population in the
same way regardless of density
 Examples:
 Weather, natural disasters, seasonal
cycles, pollution

22. Growth Rate
 Change in population size over time
 Depends on births, deaths, immigration
(in), and emigration(out).

23. Growth Rate
 Populations grow exponentially until they
reach carrying capacity (the maximum
number of organisms that an area can
support)
 Example:
 1, 2, 4, 8, 16, 32….

24. Population Growth Models
 Exponential (J-shaped) Growth Curve
 Logistic (S-shaped) Model
 Boom and Bust Model

25. Exponential (J-shaped) Growth
Curve
 Ideal Model
 Under ideal conditions:
plenty of resources, no
competition, no parasites,
no predators, etc.
 Because of limiting
factors, populations rarely
exhibit J-shaped growth
curves

26. Logistic (S-shaped) Model
 Realistic model
 Rapid growth, then slowing of growth and
leveling off
 Regulated by carrying capacity (# of individuals
which can be supported by resources of
environment without damage to environment)
 Generally density dependent
 Growth is affected by the density of
individuals

28. Boom and Bust Model
 Example:
 26 reindeer were introduced onto an
island off the coast of Alaska in 1910.
 Within 30 years the herd increased to
2,000.
 However, overgrazing reduced the food
supply and the population crashed to 8
animals by 1950.

29. Boom and Bust Model
 Realistic Model
 Growth occur exponentially, but crash due
to…
 Disturbance, such as weather
 Overexploitation of environment