AP Environmental Science
Ecosystems: Relationship - chapter 5
text web site | main class page | Gonzaga page
I. Community structure refers to the physical appearance, species diversity and abundance, and
ecological relationships in an ecosystem (p. 144)
A. biodiversity varies across different ecosystems
1. types of biodiversity: ecological, species, genetic, functional
(Miller p.91)
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2014 Bioblitz at Kenilworth gardens in DC
2. in general, diversity increases as you move toward the equator
3. diversity also varies with depth in water
4. pollution has a significant effect on diversity in aquatic systems
(such as streams and the Chesapeake)
5. Alpha, beta, and gamma diversity
6. Diversity indeces | richness vs. evenness
B. island biodiversity varies with island size and distance to the mainland
1. number of species on an island depends on rates of immigration
and extinction
2. larger islands have more species
3. nearer island have more species
4. research supports these theoretical projections
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90% - 50% rule
C. types of species – ecological roles
1. species can be described by their mode of obtaining energy
(predator, decomposer, etc) – see chap 3
2. non-native species cause problems (more on this later)
3. indicator species are particularly sensitive to environmental
problems (amphibians are a good example; also certain stream
insects)
4. umbrella species: A recent article in National Parks calls the
Greater Prairie Chicken an umbrella species , because each type of
habitat required by this bird also serves as important habitat for
many other species, including deer and other prairie birds
5. are all species vitally important? Compare the rivet and
redundancy models
6. keystone species have a disproportionate effect on the rest of
the ecosystem
a. top predators such as wolves, cougars, or grizzly
bears
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Do cougars still exist in the eastern
US? check out these sites: Michigan cougar
| save the cougar | Eastern Cougar
study suggests that predators exert "topdown control" on ecosystem structure
learn more about the "top-down control"
from Where the Wild Things Were
the effects of wolves in Yellowstone |
Spring 2010 Nat Geo article
Ecological effects of cougars
Lords of Nature video explores this
phenomenon
b. ecosystem engineers such as elephants, beavers,
buffalo, prairie dogs, and even ants | more on
buffalo as keystones
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beavers causing problems in suburban areas
c. providers of important services, such as
pollinators | more here - match pollinators with their
flowers | Another pollinators page
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the starfish Pisaster is a classic example
from rocky tidal zones of the western North
America coast
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more on wolves
American Chestnuts
d. Miller suggests that the term "Foundation Species" is
broader
D. competition
1. intraspecific competition (within the same species) leads to
natural selection, but does not affect community structure
2. interspecific competition refers to competition between different
species for resources such as food and habitat
3. interference competition – individuals chase each other away or
otherwise physically exclude them
4. exploitation competition – individual vary in how efficiently
they use a resource
5. the competitive exclusion principle states that two species
cannot occupy the same niche (classic experiment with mussels described in class)
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lynx and bobcats in North America
6. species reduce competition through resource partitioning - fig.
5-2 and also 4-16: they use different parts of the same habitat or
forage at different times
E. predator-prey relationships – fig. 5-6
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deer have become a major pest in suburban areas because of lost
predators.
simulation of predator-prey relationships using wolves and rabbits
Oak trees, mice, ticks, and deer have complex relationships (explore with
this interactive)
F. non-predatory ecological relationships
1. interactions between species can be positive, negative, or neutral
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overview of the types
these relationships are examples of co-evolution | more
here on co-evolution
2. parasitism is a relationship in which one species benefits and the
other is harmed
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parasites and the red queen hypothesis -- running just to
stand still
derive nutrients and energy from the blood/body fluids of
another organism (note examples)
Can have very complicated life cycles – often two or more
hosts (example – deer ticks)
Cryptosporidium and Giardia are parasites found in water -even in the wilderness!!
slide show of parasites that take over their host bodies
3. mutualism is a relationship in which both species benefit (fig. 59)
a. symbiosis – organisms living on or in each other
i. lichens
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a professor in Wisconsen has
created a list of fungi of the
month
ii. myccorhizal fungi
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pictures from the microbe
zoo
iii. termites
b. non-symbiotic
i. herbivores and grasses
ii. dispersal of fruits by birds and
small mammals
iii. pollination
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flowers display many
interesting designs adapted to
pollination
the forgotten pollinators -many are going extinct or
getting rare!
iv. cleaner fish
v. animals that are normally enemies
will sometimes form mutual
relationships
4. commensalism - one organism benefits and the other is not
harmed. (fig 5-10)
a. ephiphytes (distinguish from parasitic plants)
b. barnacles
c. remora and shark
II. Ecological succession
A. Primary succession
1. Occurs in an area previously unoccupied by organisms
2. Examples – volcanic islands, places exposed by retreating
glaciers, etc.
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Glacier Bay National Park has glaciers that have retreated
dramatically in the past 200 years (more on Glacier Bay)
vegetation at Mt. St. Helens is growing back after the 1980
eruption
occasionally a flood can be severe enough to expose
rock. One example is found at the spillway of a dam near
DeMoines, Iowa |
3. example of typical progression shown for Isle Royale in fig. 511
B. Secondary Succession
1. Occurs in areas that have been disturbed by some natural
phenomenon
2. examples of disturbances: fire, storms, floods, agriculture
C. Examples:
1. field to forest (fig. 5-12)
2. pond to bog to meadow
3. fire-disturbed areas
4. sand dunes
D. Climax communities
1. type of climax community is determined by local climate, soil,
rainfall, etc.
2. Succession is not necessarily a predictable event, and some
ecologists prefer the term “mature” to “climax” – see discussion p.
110
E. The ecological importance of fire
1. In many ecosystems, regular fires are
an important part of the community
structure
2. benefits of fires (see also links on right)
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3. history of fire management in the US
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Healthy Forest Initiative
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Ecosystems adapted to fire
fire management on US public lands including a map o
current fires and National Fire Plan | Incident Fire
Management - an interactive list of current fires
US Forest Service fire-fighting page
fire-fighting jobs
how to conduct a prescribed burn | more on prescribed
fire
Yellowstone fires of 1988: Yellowstone NP page on fir
Fire Wars - NOVA special on fire
o global maps of fires in 2000
o how plants are adapted to fire
Global Fire Monitoring Center
Fire ecology - plants and ecosystems that benefit from
fire
2007 California wildfires and more on wildfire in
general
Ashes to Wildflowers - before and after photos and text
describing ecological succession after a fire
Southern California Chaparral | more here
Google Earth view of current fires
Life returns to the blast zone (Mt. St. Helens)
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Chaparral
Southeastern coastal pine forest
Grasslands