Download Species Interactions and Biomes

2/2/2015
AFTER THIS LECTURE, YOU WILL BE
ABLE TO:
Compare and contrast the major types of
species interactions
Characterize feeding relationships and
energy flow, using them to construct trophic
levels and food webs
Distinguish characteristics of a keystone
species
Characterize succession and notions of
community change
Perceive and predict the potential impacts of
invasive species in communities
Explain the goals and methods of restoration
ecology
Describe the terrestrial biomes of the world
Species
Interactions
and Biomes
Chapter 4
CENTRAL CASE STUDY: BLACK AND
WHITE AND SPREAD ALL OVER
TYPES OF SPECIES INTERACTIONS
In 1988, ballast water
discharged from a ship
accidentally released zebra
mussels into Lake St. Clair
By 2010, they had spread to
30 states
They cause millions of dollars
of property damage each
year
COMPETITION OCCURS WITH
LIMITED RESOURCES
Competition: multiple organisms seek the same
limited resource
Food, water, space, shelter, mates, sunlight,
etc.
Intraspecific competition: between members of
the same species
High population density: increased
competition
Interspecific competition: between members of
different species
Strongly affects community composition
Leads to competitive exclusion or species
coexistence
RESULTS OF INTERSPECIFIC
COMPETITION
Competition is usually subtle and indirect
One species may exclude another from using the resource
Zebra mussels displaced native mussels in the Great Lakes
Quagga mussels are now displacing zebra mussels
Or, competing species may be able to coexist
Natural selection favors individuals that use different
resources or shared resources in different ways
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RESOURCE PARTITIONING
Resource partitioning:
competing species coexist by
specializing
By using different resources
(small vs. large seeds)
Or using shared resources
differently (active during day
vs. night)
AN EXPLOITATIVE INTERACTION:
PREDATION
• Exploitation: one
member benefits
while the other is
harmed (+/interactions)
– Predation,
parasitism,
herbivory
Predation: process by which
individuals of one species
(predators) capture, kill, and
consume individuals of
another species (prey)
PREDATION CAN DRIVE
POPULATION DYNAMICS
Interactions between predators and prey structure
food webs
The number of predators and prey influences
community composition
Predators can, themselves, become prey
PREDATION AFFECTS THE
COMMUNITY
PREDATION HAS EVOLUTIONARY
RAMIFICATIONS
Increased prey populations
increase food for predators
Predators survive and
reproduce
Increased predator populations
decrease prey
Predators starve and their
populations decrease
Decreased predator
populations increase prey
populations
PREY DEVELOP DEFENSES AGAINST
BEING EATEN
Natural selection leads to evolution of adaptations that
make predators better hunters
Individuals who are better at catching prey:
Live longer, healthier lives
Take better care of offspring
Prey face strong selection pressures—they are at risk of
immediate death
Prey develop elaborate defenses against being eaten
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AN EXPLOITATIVE INTERACTION:
PARASITISM
PARASITE – HOST RELATIONSHIPS
Parasitoids: insects that parasitize other insects
Kill the host
Parasitism: a relationship in
which one organism (parasite)
depends on another (host)
For nourishment or some
other benefit
Coevolution: hosts and parasites become locked in a duel
of escalating adaptations
Has been called an evolutionary arms race
Each evolves new responses to the other
It may not be beneficial to the parasite to kill its host
The parasite harms, but
doesn’t kill, the host
AN EXPLOITATIVE INTERACTION:
HERBIVORY
Herbivory: animals feed on the
tissues of plants
Widely seen in insects
May not kill the plant
But affects its growth and
reproduction
Defenses against herbivory
include:
Chemicals: toxic or distasteful
Thorns, spines, or irritating
hairs
Herbivores may overcome
these defenses
Two or more species benefit from their interactions
Each partner provides a service the other needs (food,
protection, housing, etc.)
Symbiosis: a relationship in which the organisms live in close
physical contact (mutualism and parasitism)
Microbes within digestive tracts
Mycorrhizae: plant roots and fungi
Coral and algae (zooxanthellae)
MUTUALISTS HELP ONE ANOTHER
Pollination: bees, bats, birds, and others transfer pollen from
one flower to another, fertilizing its eggs
POLLINATION
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ECOLOGICAL COMMUNITIES
Community: an assemblage of populations of organisms
living in the same area at the same time
Members interact with each other
Interactions determine the structure, function, and species
composition of the community
Community ecologists are interested in how:
MYCORRHIZAE
Species coexist and interact with one another
Communities change, and why these patterns exist
ENERGY PASSES AMONG TROPHIC
LEVELS
One of the most important
species interactions
Who eats whom?
Matter and energy move
through the community
Trophic levels: rank in the
feeding hierarchy
PRODUCERS: THE FIRST TROPHIC
LEVEL
Producers, or autotrophs (“self-feeders”): organisms capture
solar energy for photosynthesis to produce sugars
Green plants
Cyanobacteria
Algae
They capture solar energy and use photosynthesis to produce
sugars
Producers (autotrophs)
Consumers
Detritivores and
decomposers
CONSUMERS: CONSUME
PRODUCERS
•Primary consumers: second trophic level
Organisms that consume producers
Herbivorous grazing animals
Deer, grasshoppers
Secondary consumers: third trophic level
Organisms that prey on primary consumers
Wolves, rodents, birds
Tertiary consumers: fourth trophic level
Predators
Hawks, owls
DETRITIVORES AND DECOMPOSERS
Organisms that consume
nonliving organic matter
Detritivores: scavenge waste
products or dead bodies
Millipedes, soil insects
Decomposers: break down leaf
litter and other nonliving
material
Fungi, bacteria
Enhance topsoil and recycle
nutrients
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ENERGY, BIOMASS, AND NUMBERS
PYRAMIDS OF ENERGY, BIOMASS,
AND NUMBERS
Most energy that organisms use in cellular respiration is
lost as waste heat
Less and less energy is available in each successive trophic
level
Each trophic level contains only 10% of the energy of the
trophic level below it
There are also far fewer organisms and less biomass (mass
of living matter) at the higher trophic levels
FOOD WEBS SHOW RELATIONSHIPS &
ENERGY FLOW
SOME ORGANISMS PLAY BIG ROLES
Food chain: a series of
feeding relationships
Food web: a visual map of
feeding relationships and
energy flow among
organisms
Keystone species: has a strong
or wide-reaching impact
Far out of proportion to its
abundance
Removing a keystone species
has substantial ripple effects
Alters the food web
Large-bodied secondary or
tertiary consumers
SPECIES CAN CHANGE
COMMUNITIES
TROPHIC CASCADE
Trophic cascade: predators at high trophic levels indirectly
promote populations at low trophic levels
By keeping species at intermediate trophic levels in check
Extermination of wolves led to increased deer populations …
Which overgrazed vegetation …
Which changed forest structure
Ecosystem engineers: physically modify the environment
Beaver dams, prairie dogs, ants
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PRIMARY SUCCESSION
Communities experience many types of disturbance
Removal of keystone species, natural disturbances (fires,
floods, etc.)
Human impacts cause major community changes
Resistance: a community resists change and remains
stable despite the disturbance
Resilience: a community changes in response to a
disturbance, but later returns to its original state
Or, a disturbed community may never return to its
original state
COMMUNITIES RESPOND TO
DISTURBANCES
Succession: the predictable
series of changes in a
community
After a severe disturbance
Primary succession:
disturbance removes all
vegetation and/or soil life
Glaciers, drying lakes,
volcanic lava covering the
land
Pioneer species: the first
species to arrive in a primary
succession area
Lichens: fungi + algae
SECONDARY SUCCESSION
Secondary succession: a
disturbance has removed
much, but not all, of the biotic
community
Fires, hurricanes, logging,
farming
Aquatic systems can also
undergo succession
Ponds eventually fill in to
become terrestrial systems
Climax community: remains in
place with few changes
Until another
disturbance restarts
succession
COMMUNITIES MAY UNDERGO
SHIFTS
Community changes are more variable and less
predictable than early models of succession suggested
Conditions at one stage may promote another stage
Competition may inhibit progression to another stage
Chance factors also affect changes
Phase (regime) shift: the overall character of the
community fundamentally changes
Some crucial threshold is passed, a keystone species is
lost, or an exotic species invades
Example: overfishing and depletion of fish and turtles
has allowed algae to dominate coral reef communities
INVASIVE SPECIES THREATEN
STABILITY
Alien (exotic) species: non-native species from
somewhere else enters a new community
Invasive species: non-native species that spreads
widely and become dominant in a community
Introduced deliberately or accidentally
Growth-limiting factors (predators, disease,
competitors, etc.) are absent
Major ecological effects
Pigs, goats, and rats have destroyed island species
But some invasive species (e.g., honeybees) help
people
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INVASIVE MUSSELS MODIFY
COMMUNITIES
CONTROLLING INVASIVE SPECIES
Techniques to control invasive species
include:
Removing them manually
Applying toxic chemicals
Drying them out, depriving them of
oxygen
Introducing predators or diseases
Stressing them with heat, sound,
electricity, carbon dioxide, or ultraviolet
light
Control and eradication are hard and
expensive
Prevention, rather than control, is the
best policy
ALTERED COMMUNITIES CAN BE
RESTORED
Humans have dramatically changed ecological systems
Severely degraded systems cease to function
Restoration ecology: the science of restoring an area to an
earlier (pre-settlement) condition
Tries to restore the system’s functionality (e.g., filtering of
water by a wetland)
Ecological restoration: actual efforts to restore an area
Difficult, time-consuming, and expensive
WIDELY SEPARATED REGIONS SHARE
SIMILARITIES
Biome: major regional complex of similar communities recognized by:
Plant type
Vegetation
structure
EXAMPLES OF RESTORATION
EFFORTS
Prairie restoration: replanting
native species, controlling
invasive species, controlled fire
to mimic natural fires
The world’s largest project:
Florida Everglades
Flood control and irrigation
removed its water
Populations of wading
birds dropped 90–95%
It will take 30 years
and billions of dollars
to restore natural
water flow
ABIOTIC FACTORS INFLUENCE BIOME
LOCATIONS
The type of biome depends on
temperature, precipitation
Also air and ocean circulation,
soil type
Climatographs: a climate
diagram showing an area’s
mean monthly temperature
and precipitation
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AQUATIC SYSTEMS HAVE BIOME-LIKE
PATTERNS
Various aquatic systems comprise distinct communities
Coastlines, continental shelves, open ocean, deep sea
Coral reefs, kelp forests
Some coastal systems (estuaries, marshes, etc.) have both
aquatic and terrestrial components
Aquatic systems are shaped by
Water temperature, salinity, dissolved nutrients
Wave action, currents, depth, light levels
Substrate type
Animals, not plants, delineate marine communities
TEMPERATE DECIDUOUS FOREST
Deciduous trees lose their
broad leaves each fall
They remain dormant during
winter
Mid-latitude forests in Europe,
east China, eastern North
America
Even, year-round precipitation
Fertile soils
Forests: oak, beech, maple
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TEMPERATE GRASSLANDS
More temperature difference
Between winter and summer
Less precipitation supports
grasses, not trees
Also called steppe or prairie
Once widespread, but has been
converted to agriculture
Bison, prairie dogs, groundnesting birds, pronghorn
TEMPERATE RAINFOREST
U.S. coastal Pacific Northwest
Heavy rainfall
Coniferous trees: cedar,
spruce, hemlock, fir
Moisture-loving animals
Banana slug
Erosion and landslides affect
the fertile soil
Most old-growth is gone as a
result of logging
TEMPERATE RAIN FOREST
TROPICAL RAINFOREST
Southeast Asia, west Africa
Central and South America
Year-round rain and warm
temperatures
Dark and damp
Lush vegetation
Diverse species
But in low densities
Very poor, acidic soils
Nutrients are in the plants
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TROPICAL DRY FOREST
Also called tropical deciduous
forest
Plants drop leaves during the
dry season
India, Africa, South America,
north Australia
Wet and dry seasons
Warm, but less rainfall
Converted to agriculture
Severe soil erosion
SAVANNA
Tropical grassland interspersed with trees
Africa, South America, Australia, India
Precipitation occurs only during the rainy season
Animals gather near water holes
Zebras, gazelles, giraffes, lions, hyenas
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DESERT
Minimal precipitation
Sahara: bare, with sand dunes
Sonoran: heavily vegetated
Temperatures vary widely
Day vs. night, seasonally
Soils (lithosols): high mineral
content, low organic matter
Animals: nocturnal, nomadic
Plants: thick skins, spines
TUNDRA
Russia, Canada, Scandinavia
Minimal rain, very cold winters
Permafrost: permanently
frozen soil
Residents: polar bears, musk
oxen
Migratory birds, caribou
Lichens, low vegetation, no
trees
Alpine tundra: on
mountaintops
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BOREAL FOREST (TAIGA)
Canada, Alaska, Russia,
Scandinavia
A few evergreen tree species
Cool and dry climate
Long, cold winters
Short, cool summers
Nutrient poor, acidic soil
Moose, wolves, bears, lynx,
migratory birds
CHAPARRAL
Occurs in small patches around
the globe
Mediterranean Sea, Chile,
California, south Australia
Densely thicketed, evergreen
shrubs
Highly seasonal biome
Mild, wet winters
Warm, dry summers
Fire-resistant plants
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COMPETITION IS A FORM OF
SPECIES INTERACTION WHERE:
20%
20%
20%
20%
20%
20%
1.
2.
3.
4.
5.
Both species are harmed
One species benefits, but
the other is harmed
Both species benefit
One species invites
another to enter a
particular area
Neither species is
particularly affected
1.
2.
3.
20%
20%
20%
20%
4.
WHICH
STATEMENT IS FALSE ABOUT
TROPHIC LEVELS?
5.
1
20%
1.
2.
3.
4.
5.
Autotrophs (plants) occupy the
first trophic level
Detritivores consume waste
products or dead bodies
Biomass and energy increase
going up the food chain
There are fewer predator
species than prey species in an
area
Food webs leave out many
species interactions
2
3
20%
20%
4
20%
1.
2.
3.
WHICH OF THE FOLLOWING IS NOT AN
EXPLOITATIVE
INTERACTION?
2
3
4
2
3
4
5
20%
Predation
Herbivory
Parasitism
Competition
All of these are
exploitative interactions
1
1
5
One species preys on mice
during the day, another species
preys on mice during the night
One species is chased out of an
area by another species
A prey species becomes more
vulnerable to a predator
A pine tree evolves thicker
pinecones to reduce
consumption by squirrels
A host becomes resistant to a
parasite
20%
20%
20%
WHICH
OF THE FOLLOWING IS AN
4.
EXAMPLE OF RESOURCE
PARTITIONING?
5.
1
2
3
20%
4
20%
5
5
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20%
1.
20%
1.
2.
3.
4.
The slopes of a newly
formed volcanic island
Wetlands in Texas,
following Hurricane Rita
A receding glacier
Vegetation growing in a
newly exposed lake bed
Secondary succession
would not occur in any of
these areas
20%
20%
20%
20%
2.
3.
SECONDARY SUCCESSION WOULD TAKE
PLACE5. ON WHICH OF THE FOLLOWING?
1
2
3
4
20%
2.
3.
4.
5.
20%
20%
5.
5
20%
20%
Remove exotic species
from an area
Introduce native species
to a newly reforested area
Plant trees in a logged
forest
Replace topsoil and plant
grasses on an old coal
mining site
A restoration ecologist
would do all of these
1
20%
3
4
2
2.
3.
4.
5.
3
4
4
5
20%
b)
c)
20%
20%
d)
e)
WOULD YOU BE WILLING TO DECREASE THE
AMOUNT OF MEAT YOU CONSUME (I.E.,
EAT LOWER ON THE FOOD CHAIN) TO SAVE
ENERGY AND DECREASE YOUR ECOLOGICAL
FOOTPRINT?
1.
2
3
20%
20%
Tropical rainforest
Temperate grasslands
Temperate rainforest
Taiga
Tundra
1
20%
5
WHICH BIOME IS FOUND IN THE COASTAL
PACIFIC NW OF THE U.S., HAS HEAVY
RAINFALL; CEDAR, SPRUCE, AND HEMLOCK
20%
20%
20%
20%
20%
TREES; AND MOISTURE-LOVING ANIMALS?
1.
2.
3.
4.
5.
20%
Tropical rainforest
Temperate grassland
Chaparral
Taiga
Tundra
a)
2
20%
WHICH BIOME DOES NOT HAVE ENOUGH
PRECIPITATION TO SUPPORT TREES, IS
ALSO CALLED STEPPE OR PRAIRIE, AND
HAS BEEN CONVERTED TO AGRICULTURE?
a)
b)
c)
d)
e)
1
20%
WHAT4. IS THE BEST DEFINITION OF
INVASIVE SPECIES?
WHICH OF THE FOLLOWING ACTIVITIES
WOULD A RESTORATION ECOLOGIST
DO?
1.
Any species that occurs
naturally in an area
Any species that arrives in
an area from somewhere
else
An exotic species that
spreads widely and
changes a community
A native species that
spreads widely and
changes a community
A species that is not alien
or exotic to an area
5
Yes, if the extra food were
sent to countries with
starving people
Yes, because it would help
protect the environment
I don’t eat meat now
No, I don’t see the need
to eat lower on the food
chain
No, I won’t get enough
protein if I don’t eat meat
1
20%
20%
2
3
20%
4
20%
5
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ALTHOUGH MUSTANGS ARE NOT NATIVE
TO THE UNITED STATES, THEY EXIST IN
SEVERAL WESTERN STATES ON FEDERALLY
1. AsLAND.
an exotic species,
they should
OWNED
AS AN
INTRODUCED
immediately be removed and adopted
SPECIES,orWHAT
SHOULD BE DONE WITH
killed
2. Although they are an exotic species,
THEM?
they are part of our heritage and
20%
should be allowed to stay
They have been here so long that we
should just leave
them alone
Many countries eat horseflesh, so we
should round them
up and export them to horse-eating
countries
It doesn’t matter; it’s not that
important
3.
4.
5.
1
20%
2
20%
3
20%
WHAT DOES THIS FIGURE
ILLUSTRATE?
20%
4
1. A predator–prey
cycle
2. Competitive
exclusion
3. Resource
partitioning
4. Succession
5. Mutualism
20%
20%
20%
20%
20%
5
1
2
3
4
5
In this climatograph for Odessa,
Ukraine, in the grassland biome,
certain months are depicted in yellow.
These show:
1.
2.
3.
4.
5.
20%
1
Cold winters
Hot winters
Dry seasons
Wet seasons
Cool summers
20%
2
20%
3
20%
4
20%
5
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