community and population ecology chapter 6. good morning! place your portfolio containing your paper...
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Good Morning!
Place your portfolio containing your paper and sources on the front table and then sign in using the red pen.
Core Case Study: American Alligator
Highly adaptable
Only natural predator is humans
1967 – endangered species list
Successful environmental comeback
Keystone species
6-1 How Does Species Diversity Affect the Sustainability of a Community?
Concept 6-1 Species diversity is a major component of biodiversity and tends to increase the sustainability of communities and ecosystems.
Species Diversity
Species richness combined with species evenness
Niche structure
Varies with geographic location
Species richness declines towards poles
Science Focus: Community Sustainability
No certain definition of sustainability
Do communities need high inertia and high resilience?
Communities may have one but not the other
Equilibrium is rare
Richness and Sustainability
Hypotheses• Does a community with high species richness
have greater sustainability and productivity?
• Is a species-rich community better able to recover from a disturbance?
Research suggests “yes” to both
6-2 What Roles Do Species Play in a Community?
Concept 6-2 Based on certain ecological roles they play in communities, species are described as native, nonnative, indicator, keystone, or foundation species.
Ecological Niche
Species occupy unique niches
Native species – those normally found living and thriving in a particular community Spanish moss in the south
Nonnative species – plants, animals, fungi• Spread in new, suitable niches
Purple looselife European starling African honeybee(“Killer bee”)
Nutria Salt cedar(Tamarisk)
Marine toad Water hyacinth Japanese beetle Hydrilla European wild boar(Feral pig)
Fig. 9-11a, p. 193
Deliberately Introduced Species
http://dnr.wi.gov/invasiveS/fact/loosestrife.htm
http://www.npwrc.usgs.gov/resource/plants/loosstrf/index.htm
http://www.desertusa.com/mag98/sep/stories/kbees.html
http://www.invasivespeciesinfo.gov/animals/afrhonbee.shtml
http://aaabeeremoval.com/photogallery_africanbeeswarm.htm
Sea lamprey(attached to lake trout)
Argentina fire ant Eurasian muffleBrown tree snake Common pigeon(Rock dove)
Formosan termite Zebra mussel Asian long-hornedbeetle
Asian tiger mosquito Gypsy moth larvae
Fig. 9-11b, p. 193
Accidentally Introduced Species
Indicator Species
Early warning system – tell about harmful changes in biological communities
Birds – found everywhere; affected by habitat problems including pesticides
Butterflies – associate with various plant species becoming vulnerable to habitat loss
Amphibians – multiple reasons; complex and interacting
Case Study: Why Are Amphibians Vanishing? (1) – See latest article
Habitat loss and fragmentation
Prolonged drought
Pollution
Ultraviolet radiation
Parasites - chytrid fungi
sperm
Eggs
Sexualreproduction
Fertilized eggdevelopment Organ formation
Egg hatches
Tadpole
Tadpole develops into frog
Young frogAdult frog(3 years)
Fig. 6-3, p. 112
Life Cycle of a Frog
Case Study: Why Are Amphibians Vanishing? (2)
Viral and fungal diseases
Climate change
Overhunting
Nonnative predators and competition
Why we should care
Keystone Species
Significant role in their food web
Elimination may alter structure, function of community
Pollinators
Top predators
http://www.morning-earth.org/Graphic-E/Interliv-Two.html great overview
http://www.naturehaven.com/elephantbottom.html - Elephant site
Science Focus: Why Should WeProtect Sharks?
Remove injured, sick animals
Many are gentle giants
Provide potential insight into cures for human diseases
Keystone species
6-3 How Do Species Interact?
Concept 6-3A Five basic species interactions – competition, predation, parasitism, mutualism, and commensalism – affect the resource use and population sizes of the species in a community.
Concept 6-3B Some species develop adaptations that allow them to reduce or avoid competition for resources with other species.
Interspecific Competition
No two species can share vital limited resources for long
Resolved by:• Migration• Shift in feeding habits or behavior• Population drop• Extinction
Intense competition leads to resource partitioning
Fig. 6-4, p. 114
Nu
mb
er o
f in
div
idu
als
Nu
mb
er o
f in
div
idu
als
Resource use
Resource use
Species 1 Species 2
Regionof
niche overlap
Species 1 Species 2
Resource Partitioning and Niche Specialization
Predation
Predator-prey relationship
Predators and prey both benefit – individual vs. population
Predator strategies
Prey strategies
Span worm Bombardier beetle
Viceroy butterfly mimicsmonarch butterfly
Foul-tasting monarch butterfly
Poison dart frog When touched, the snake caterpillar changes shape to look like the head of a snake
Wandering leaf insect
Hind wings of io mothresemble eyes of a much larger animal
Fig. 6-6, p. 116
How Species Avoid Predators
Parasitism
Live in or on the host http://mybloatingrelief.com/parasites/
Parasite benefits, host harmed
Parasites promote biodiversity
http://www.youtube.com/watch?v=rLtUk-W5Gpk
Mutualism
Everybody benefit by unintentional exploitation
Nutrition and protection
Gut inhabitant mutualism
Oxpeckers and black rhinoceros
Clown fish and sea anemone
Lack of mycorrhizae fungi on juniper seedlings in sterilized soil
Examples of Mutualism
© 2006 Brooks/Cole - Thomson
Mycorrhizae fungi on juniper seedlings in normal soil
6-4 How Do Communities Respond to Changing Environmental Conditions?
Concept 6-4A The structure and species composition of communities change in response to changing environmental conditions through a process called ecological succession.
Concept 6-4B According to the precautionary principle, we should take measures to prevent or reduce harm to human health and natural systems even if some possible cause-and-effect relationships have not been fully established scientifically.
Ecological Succession
Primary succession
Secondary succession
Disturbances create new conditions
Intermediate disturbance hypothesis
Fig. 6-9, p. 119
Small herbs and shrubs
Jack pine,black spruce,
and aspen
Balsam fir, paper birch, and white spruce climax
communityExposedrocks
Lichensand mosses
Ecological Succession
Ecological succession
1. It is an orderly process of COMMUNITY development; it normally proceeds in a predictable, orderly direction; it represents the gradual replacement of populations by others that are better adapted to the existing conditions.
2. It results from modification of the physical environment by the populations that interact to makeup the community thus, succession is community controlled; the physical factors of the environment and climate determine the pattern and the rate of change; the climate and immediate environment often set the limit as to how far development can proceed
3. The end result of succession is a stabilized ecosystem which is in balance with the climate and environment of the area; under these conditions the maximum number of organisms (biomass) and their symbiotic (nutritional) interactions are balanced or maintained with the energy available to the system.
Thus, the strategy of succession as a short term process is very much like the strategy of long-term evolutionary development of the biosphere. It results in HOMEOSTATIC balance of organisms with the physical environment WITH THE BENEFIT of achieving a means of effectively dealing with the constant changes or pertubations presented by the environment.
The Strategy of Ecosystem Development, Eugene P. Odum Science 18 April 1969: Vol. 164. no. 3877, pp. 262 - 270
Fig. 6-9, p. 119
Time
Small herbsand shrubs
Heath mat
Jack pine,black spruce,
and aspen
Balsam fir, paper birch, and white spruce climax
community
Exposedrocks
Lichensand mosses
Primary Ecological Succession
Fig. 6-10, p. 120
Annualweeds
Perennialweeds and
grasses
Shrubs and pine seedlings
Young pine forest with developing understory
of oak and hickory trees
Mature oak-hickory forest
Secondary Ecological Succession
Time
Succession’s Unpredictable Path
Successional path not always predictable toward climax community
Communities are ever-changing mosaics of different stages of succession
Continual change, not permanent equilibrium
Precautionary Principle
Lack of predictable succession and equilibrium should not prevent conservation
Ecological degradation should be avoided
Better safe than sorry
6-5 What Limits the Growth of Populations?
Concept 6-5 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.
Population Distribution
Clumping – most populations Uniform dispersion Random dispersion
http://www.biology.iupui.edu/biocourses/n100/images/39dist.gif
Why Clumping?
Resources not uniformly distributed
Protection of the group
Pack living gives some predators greater success
Temporary mating or young-rearing groups
Populations Sizes Are Dynamic
Vary over timepopulation = (births + immigration) - (deaths + emigration)
Age structure• Pre-reproductive stage•Reproductive stage• Post-reproductive stage
Limits to Population Growth (1)
Biotic potential is idealized capacity for growth
Intrinsic rate of increase (r)
Nature limits population growth with resource limits and competition
Environmental resistance
Fig. 6-11, p. 121
Carrying capacity (K)
Environmentalresistance
Bioticpotential
Exponentialgrowth
Population Growth Curves
Time (t)
Po
pu
lati
on
siz
e (N
)
Limits to Population Growth (1)
Carrying capacity – biotic potential and
environmental resistance (Number of individuals of a given species that can be sustained indefinitely in a given area)
Exponential growth - logarithmic increase
Logistic growth – exponential growth followed by steady decrease over time until population size levels off. Due to population meeting environmental resistance and approaching carrying capacity
Fig. 6-12, p. 121
Logistic Growth of Sheep Population
Overshoot Carrying Capacity
Year
N
um
ber
of
shee
p (
mil
lio
ns) 2.0
1.5
1.0
.5
1800 1825 1850 1875 1900 1925
Overshoot and Dieback
Population does not transition smoothly from exponential to logistic growth
Overshoot carrying capacity of environment
Caused by reproductive time lag
Dieback, unless excess individuals switch to new resource
Exponential Growth, Overshoot and Population Crash of Reindeer
Fig. 6-13, p. 122
PopulationOvershootsCarrying Capacity
Populationcrashes
Carrying capacity
Year
Nu
mb
er o
f re
ind
eer
(mil
lio
ns)
2,000
1,500
1,000
500
01910 1920 1930 1940 1950
Different Reproductive Patterns
r-Selected species• High rate of population increase
• Opportunists
K-selected species• Competitors
• Slowly reproducing
Most species’ reproductive cycles between two extremes
Humans Not Exempt from Population Controls
Bubonic plague (14th century) – Ebola like symptoms
Famine in Ireland (1845) – led to emigration to the United States (through 1848)
AIDS – major player in population decline Technology, social, and cultural changes
extended earth’s carrying capacity for humans Expand indefinitely or reach carrying capacity?
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