Download Biodiversity, Species Interactions, and Population Control

Biodiversity, Species Interactions,
and Population Control
Chapter 5
Key Concepts
• Species interactions
• Responses to changes in environmental conditions
• Factors determining number of species in a
community
Species Diversity and Ecological Stability
 Many different species provide ecological stability
 Some exceptions
 Minimum threshold of species diversity (10 - 40 producer species?)
 Many unknowns
 Net primary productivity (NPP)
 Essential and nonessential species
Animation
Species diversity by latitude
Types of Species
 Native
 Nonnative (invasive or alien)
 Indicator Keystone  Foundation
Indicator Species
 Provide early warnings of ecosystem damage
 Indicator of water quality (trout)
 Birds as environmental indicators (affected by habitat
loss, chemicals)
 Butterflies
 Amphibians
Keystone Species
 What is a keystone?
 Keystone species play critical ecological roles
a. Pollination
b. Top predators
c. decomposition
 EXAMPLES: Dung beetles, Sharks, bees, bats, wolves,
alligators
Foundation Species
 Relationship to keystones species
 Play important roles in shaping communities
 Elephants
 Contributions of bats and birds
Species Interactions
 Interspecific competition
 Predation
 Symbiosis= close long term association 2 or more species
A. Parasitism + B. Mutualism + +
C. Commensalism + 0
Animation
Types of two species interactions animation.
Species Interactions: Competition
 Interspecific Competition
 Fundamental niches
 Fighting for limited resources
 Competition from humans
Reducing or Avoiding Competition
 Resource partitioning
 Role of natural selection
 Specialization and sharing of resources
 Resource partitioning of warblers
Number of individuals
Resource Partitioning and Niche
Specialization
Species 1
Species 2
Region
of
niche overlap
Number of individuals
Resource use
Species 1
Species 2
Resource use
Resource Partitioning of Warbler Species
How Do Predators Increase Their Chances of
Getting a Meal?
 Speed
 Senses
 Camouflage and ambush
 Chemical warfare (venom)
Avoiding and Defending Against Predators
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Escape
Senses
Armor
Camouflage
Chemical warfare
Warning coloration
Mimicry
Behavior strategies
Safety in numbers
How Species Avoid Predators
“If it is small and strikingly beautiful, it is probably poisonous. If it is strikingly beautiful and
easy to catch, it is probably deadly.” - E.O Wilson
Span worm
Wandering leaf insect
camouflage
Poison dart frog
Bombardier beetle
Foul-tasting monarch
butterfly
Chemical warfare / Warning
Viceroy butterfly mimics
monarch butterfly
mimicry
Hind wings of io moth
resemble eyes of a
much larger animal
Deceptive behavior
When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Parasites
 Parasitism +  Hosts
 Inside or outside of hosts
 Harmful effects on hosts
 Important ecological roles of parasites
Mutualism + +
 Both species benefit
 Pollination
 Benefits include nutrition and protection
 Mycorrhizae - fungi that helps plants extract nutrients
and water from soil
 Gut inhabitant mutualism
Examples of Mutualism
Oxpeckers and black rhinoceros
Mycorrhizae fungi on juniper
seedlings in normal soil
© 2006 Brooks/Cole - Thomson
Clown fish and sea anemone
Lack of mycorrhizae fungi on
juniper seedlings in sterilized soil
Fig. 6-7, p. 117
Commensalism + 0
 Species interaction that benefits one and has little
or no effect on the other
 Example: Small plants growing in shade of larger
plants
 Epiphytes
 Forehead mites
Bromeliad Commensalism
Ecological Succession: Communities in
Transition
 What is ecological succession?
(Gradual change in species composition)
 Primary succession = establishment of communities on
nearly lifeless ground (no soil) ex. glacier retreat, landslide, lava,
abandoned parking lot
 Secondary succession- community disturbed, soil
remains. Burned / cut forests, polluted stream, flood
Animation
Two types of ecological succession animation.
Limits on Population Growth
 Biotic potential
(capacity for growth)
 Intrinsic rate of increase (r) (assumes unlimited resources)
 No indefinite population growth
 Environmental resistance= all the factors that limit population growth
 Carrying capacity (K) - determined by biotic potential & enviro resistance
Population Growth Curves
Population size (N)
Environmental
resistance
Carrying capacity (K)
Biotic
potential
Exponential
growth
Time (t)
Exponential and Logistic Population
Growth
 Resources control population growth
 Exponential growth - J-shaped curve
 Logistic growth - S-shaped curve
Logistic Growth of Sheep Population
Number of sheep (millions)
2.0
Overshoot
Carrying Capacity
1.5
1.0
.5
1800
1825
1850
1875
Year
1900
1925
When Population Size Exceeds Carrying
Capacity
 Switch to new resources, move or die
 Overshoots
 Reproductive time lag
 Population dieback or crash
 Human Famines -
Irish potato famine 1845 - 1 million dead
 Factors controlling human carrying capacity- technology has
increased carrying capacity for humans
Number of sheep (millions)
Exponential Growth, Overshoot and Population
Crash of Reindeer
Population
Overshoots
Carrying
Capacity
2,000
Population
crashes
1,500
1,000
500
Carrying
capacity
0
1910
1920
1930
Year
1940
1950