Chapter 6
Population and Community Ecology
Part 1
Prior to lecture:
• Case study
• Gause’s experiment
• Answer questions – Slide 12, 13
Case Study
New England Forests Come Full Circle
1.
Describe the temperate forest as seen by the
Pilgrims.
2.
What happened to the temperate forest
between 1620 and 1800s? Explain why this
happened.
3.
What happened to the temperate forest
between 1850 and 1950. Explain why this
happened.
4.
What caused the appearance of the leaf
beetle?
4.
What did the “outbreak” of the leaf
beetle cause to happen?
5.
What was the first tree species to
dominate and why?
6.
What led to the rise of the broadleaf
deciduous trees?
7.
What does this process demonstrate?
Levels of Complexity
Population Ecology



Population ecology
 Study of the factors that cause populations to
increase or decrease.
 Populations are dynamic
Value of a population study
5 basic population characteristics.
 Size
 Density
 Distribution
 Sex
Ratio
 Age Structure
Population Size

Definition:

Factors that determine population
size

Effects of these factors.
Population Density
Definition:
Endangered species
Threatened species
Population Distribution
Definition:
3 types of distribution:
Population Sex Ratio


Definition:
Value of knowing the population
sex ratio:
Population Age Structure
Information from the two
sides of the graphs:
 Dark green –
 Medium green –
 Light green –
India –
 U.S. –
 Germany –
 China –

Factors that Influence
Population Size

Density-Dependent factors

Density-Independent factors
Gause’s Experiments
1.
2.
3.
4.
5.
What type
conditions were
ideal?
What condition
was manipulated?
What were the
results?
Define limiting
resource.
Define carrying
capacity.
6.
What was changed in this experiment?
7.
What result was the same? Different?
Growth Models

Purpose:

Name of this growth model

Shape of the curve

Explain how the population
changes over time.
This model shows intrinsic
growth rate (maximum
potential growth) in ideal
conditions.
r = intrinsic growth
N0 = # of individuals
Nt = population’s future size
t = time
e = base of the natural
logarithms
•
•
•
•
Name of this type of
growth model.
Populations do not
experience exponential
growth indefinitely.
Initially:
Environmental limits –
density dependent
constraints.
• Biotic
• Abiotic
More realistic model.
• Describe the growth.
• Shape of the curve
•
Variations on the Logistic
Growth Model



Explain overshoot.
Explain die-off.
Populations fluctuate
around the carrying
capacity.
Growth and Decline of a
Reindeer Population

1910 – 25

1938 – 2,000

1950 – 8

What happened?
Predation

Predation as
limiting
factor.

What causes
the hares to
peak?

What causes
the lynx to
peak?
Reproductive Strategies
Characteristics of K-selected species.
•
Slower growth
•
Fewer
Reproductive Strategies
Characteristics of r-selected species.
•
Faster growth
•
More organisms
Survivorship Curves
Patterns of survival over
time.
• Description of each with
examples.
•
•
Type I
•
•
Type III
•
•
K-selected species
R-selected species
Type II
•
Others
Metapopulations
•
A group of spatially distinct
populations that are connected by
occasional movement of individuals
between them.
•
Corridors
•
Reason for connections
End Part 1
Chapter 6
Part 2
There
Species Interactions
•
Factors that determine distributions of
species:
•
Three factors.
•
Community ecology
•
Four categories of interactions with
other species.
Competition
•
Struggle of organisms
to obtain a limiting
resource.
•
Identify information
from this graph.
•
Define Competitive
Exclusion Principle
Resource Partitioning
From the Graph:
•
What was the
competition over?
•
Which is the strongest
competitor?
•
How were the
resources shared?
Types of Resource
Partitioning
Three types of resource partitioning.:
Predation
•
Definition:
•
Types:
•
True predators
•
Herbivores
•
Parasites
Pathogens and Parasoids
Difference between a pathogen and a
parasitoid:
Prey Defenses
•
To avoid being eaten or harmed
by a predator.
10.
Types of defenses:
•
Behavioral
•
Morphological
•
Chemical
•
Mimicry
• Chemical
Defenses
• Mimicry
Which one is the
poison dart frog?
Symbiotic Relationships
Definition:
Three types:
•
Mutualism
Lichens and Coral Reef
Mutualism
•
Lichen:
•
Coral reef:
Cattle Egrets and Cows
Commensalism
•
One organism
benefits and the
other is not affected.
•
How is the cow
affected?
•
How is the egret
affected?
Keystone Species
Definition:
 May
be predators, sources of food,
mutualistic species or providers of an
essential service.
Keystone Predator – Sea Stars
What information do you get from the
graph?
Foundation Species
Definition:
•
A species that plays a major role in shaping
communities by creating and enhancing
habitats in ways other species benefit.
•
•
Elephant and alligator
Foundation and Keystone species are similar.
•
Foundation species create habitats.
•
Keystone species do this and more.
Ecological Succession
•
Definition:
•
Two Types:
•
•
Primary succession
•
Secondary succession
What is the MAIN difference in
these two types of succession?
Primary Succession
Describe primary succession including the
progression of species.
•
Exposed rock
•
Organisms with their own food
•
Opportunistic weeds
•
Long lasting grasses/weeds
•
Shrubs
•
Fast growing trees
•
Slow growing forest
Secondary Succession

Describe secondary
succession including the
progression of species.

Soil is already in place
•
Opportunistic weeks
•
Long lasting grasses/weeds
•
Shrubs
•
Fast growing trees
•
Slow growing forest

Define pioneer species.

Which type of succession is
faster and why?
Aquatic Succession
Description of primary
marine aquatic succession.
Description of succession in a
freshwater lake.
Factors Influencing Species Richness
Three processes that determine the number and
types of species present.
•
Colonization by new species
•
Speciation
•
Losses by extinction

How does latitude affect species richness?

How does time affect species richness?
Theory of Island
Biogeography

Two processes affecting species
richness forming the Theory or
Island Biogeography?

How does the size of the island
affect species richness?

What do larger islands have that
promotes more species richness?
Theory of Island
Biogeography

What aspect of
the Theory of
Island
Biogeography is
shown by this
graph.

What information
about species
richness do you
get from this