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Evolution
Ch 3, pgs 50-61
Evolution generates biodiversity
• Species = a population or group of populations
- Whose members share characteristics
- They can breed with one another and produce
fertile offspring
• Population = a group of individuals of a species that
live in the same area
• Evolution = means change over time
- Biological evolution: genetic change in
populations over time
- Genetic changes lead to changes in appearance,
functioning or behavior over generations
Natural selection
• Evolution may be random or directed by natural
selection
• Natural Selection = traits that enhance survival and
reproduction
- Are passed on more frequently to future generations
than those that do not
Evolution by natural selection
• It is one of the best-supported and most illuminating
concepts in all science
– It is the standpoint of modern biology
• We must understand it to appreciate environmental
science
– Key to knowing ecology and learning the history
of life
• Evolutionary processes influence pesticide
resistance, agriculture, medicine, health, etc.
• In 1858, both Darwin and Wallace proposed natural
selection as the mechanism of evolution
Natural selection shapes organisms
•
Premises of natural selection:
- Organisms struggle to survive
and reproduce
- Organisms produce more
offspring than can survive
- Individuals of a species vary in
their characteristics due to genes
and the environment
- Some individuals are better suited
to their environment and
reproduce more effectively
• Natural selection acts on genetic
variation
Genetic variation
• Adaptation = the process where, over time,
characteristics (traits) that lead to better reproductive
success
- Become more common in the population
• Adaptive trait (adaptation) = a trait that promotes
reproductive success
• Mutations = accidental changes in DNA that may be
passed on to the next generation
- Non-lethal mutations provide the genetic variation on
which natural selection acts
• Sexual reproduction also leads to variation
Micro vs. Macroevolution
• Micro: describes small genetic
changes that occur in a population
• Macro: describe long-term, largescale evolutionary changes in
which…
1. A new species is formed from
ancestral species
2. Other species are lost through
extinction
Natural selection acts on genetic variation
• Natural selection changes
characteristics through:
• Directional selection =
drives a feature in one
direction
• Stabilizing selection =
favors intermediate traits
- Preserving the status quo
• Disruptive selection = traits
diverge in two or more
directions
Environmental conditions affect selection
• Environmental conditions determine
the pressures natural selection exerts
- These pressures affect who
survives and reproduces
- Traits evolve that allow success in
that environment
• But traits that promote success at one
time or place may not do so at
another
• Natural selection weeds out unfit
individuals
- It also elaborates and diversifies
traits that may produce new
species
Selective pressures influence adaptation
• Related species in
different environments
- Experience different
pressures
- Evolve different traits
• Convergent evolution =
unrelated species may
evolve similar traits
- Because they live in
similar environments
Evidence of natural selection is everywhere
• It is evident in every adaptation of every organism
• Artificial Selection = the process of selection
conducted under human direction
- Producing the great variety of dog breeds and food
crops
Evolution generates biological diversity
• Biological diversity (biodiversity) = the variety of
life across all levels of biological organization
- Species
- Genes
- Populations
- Communities
• Scientists have described 1.8 million species
- Up to 100 million species may exist
- Tropical rainforests are rich in biodiversity
Speciation produces new types of organisms
• The process of generating new
species from a single species
• Allopatric speciation: species
formation due to physical
separation of populations
- The main mode of speciation
- Populations can be separated
by glaciers, rivers, mountains
- Each population gets its own
set of mutations
Another type of speciation
• Sympatric speciation = species
form from populations that
become reproductively isolated
within the same area
- Feed in different areas
- Mate in different seasons
- Hybridization between two
species
- Mutations
Speciation results in diverse life forms
• How do major groups diverge over time?
• Phylogenetic trees (cladograms) = show
relationships among species, groups, genes, etc.
- Scientists can trace how certain traits evolved
Misconceptions about evolution
• Two common misconceptions
- Survival of the fittest does not mean survival of the
strongest. Fittest means the measure of reproductive
success.
- Evolution does not involve some grand plan of nature
in which species become more perfectly adapted.
Final Thoughts
• Genetic engineering can’t
stop the loss of
biodiversity because there
are no new genes created
through genetic
engineering.
- Genetic engineers merely
transfer existing genes from
one organism to another.
We rely on biodiversity for
raw material.
Populations
Ch 3, pgs 61-72
Ecology is studied at several levels
• Ecology and evolution are
tightly intertwined
• Biosphere = the total living
things on Earth
- And the areas they inhabit
• Community = interacting
species living in the same
area
• Ecosystem = communities
and the nonliving material
and forces they interact with
Levels of ecological studies
• Population ecology = investigates the dynamics of
population change
- The factors affecting the distribution and abundance of
members of a population
- Why some populations increase and others decrease
• Community ecology = focuses on patterns of species
diversity and interactions
• Ecosystem ecology = studies living and nonliving
components of systems to reveal patterns
- Nutrient and energy flows
Habitats vary
• Habitats vary with the body size and needs of species
- A soil mite vs. an elephant
• Species have different habitat needs at different times
- Migratory birds use different habitats during
migration, summer and winter
• Species use different criteria to select habitat
- Soil, topography, vegetation, other species
- Water temperature, salinity, prey
• Species survival depends on having suitable habitat
A specialized frog
• Epiphytes grow on trees for support
- Obtaining water from the air
- They collect pools of rainwater and pockets of leaf
litter
- Frogs lay their eggs in
these rainwater pools
Organismal ecology: niche
• Niche = an organism’s use of resources, along with its
functional role in a community
- Habitat use, food selection, role in energy and nutrient
flow, interactions with other individuals
- Different from habitat, which is the physical location
where it lives
• Specialists = have narrow niches and specific needs
- Extremely good at what they do, but vulnerable when
conditions change
- Ex: giant panda (only eats bamboo)
• Generalists = species with broad niches
- They use a wide array of habitats and resources
- They can live in many different places
- Ex: cockroaches, mice, humans
Population characteristics
• All populations show
characteristics that help
scientists predict their
future dynamics
• Population size = the
number of individual
organisms present at a
given time
- Numbers can increase,
decrease, cycle or
remain the same
Population characteristics
• Population density = the number
of individuals in a population per
unit area
• Large organisms usually have low
densities
- They need many resources and
a large area to survive
• High densities make it easier to
find mates
- But increase competition and
vulnerability to predation
- Increased transmission of
diseases
• Low densities make it harder to
find mates
- But individuals enjoy plentiful
resources and space
Population characteristics
• Population distribution
(dispersion) = spatial
arrangement of organisms
• Random = haphazardly located
individuals, with no pattern
• Uniform = individuals are
evenly spaced
- Territoriality, competition
• Clumped = arranged according
to availability of resources
- Most common in nature
Population characteristics
• Sex ratio = proportion of males to females
- In monogamous species, a 1:1 sex ratio maximizes
population growth
• Age distribution (structure) = the relative numbers
of organisms of each age in a population
- Age structure diagrams (pyramids) = show the age
structure of populations
• In species that continue growing as they age
- Older individuals reproduce more (i.e. a tree)
- Experience makes older individuals better breeders
Birth and death rates
Survivorship curves = the likelihood of death varies with
age
• Type I: more deaths at older
ages
• Type II: equal number of
deaths at all ages
• Type III: more deaths at
young ages
Exponential population growth
• Exponential growth
- A population increases by a
fixed percent
- Graphed as a J-shaped
curve
• Exponential growth cannot
be sustained indefinitely
• It occurs in nature with a:
- Small population
- Low competition
- Ideal conditions
Reproductive strategies vary among species
• Biotic potential = an organism’s capacity to produce
offspring
• K-selected species = species with long gestation periods
and few offspring
- Have a low biotic potential
- Stabilize at or near carrying capacity
- Good competitors
- Examples: elephants, gorillas, humans
• r-selected species = species which reproduce quickly
- Have a high biotic potential
- Little parental care, populations fluctuate greatly
- Insects, rodents, grass
Limiting factors restrain population growth
• Limiting factors = physical, chemical and biological
attributes of the environment
- They restrain population growth
• Environmental resistance = all limiting factors taken
together
- Stabilizes the population size
- Space, food, water, mates, shelter, suitable breeding
sites, temperature, disease, predators
- Aquatic systems: salinity, sunlight, temperature, etc.
Carrying capacity
• Carrying capacity = the
maximum population size
of a species that its
environment can sustain
• Limiting factors slow and
stop exponential growth
- An S-shaped logistic
growth curve
Many factors contribute to environmental resistance and
influence a population’s growth rate and carrying capacity
Population curves
• K selected species are
usually associated with
s-curves
• R selected species are
generally associated with
j-curves (which then
crash)
Population density impacts limiting factors
• Density-dependent factors = limiting factors whose
influence is affected by population density
- Increased density increases the risk of predation and
competition for mates
- Results in the logistic growth curve
- Larger populations have stronger environmental
resistance
• Density-independent factors = limiting factors whose
influence is not affected by population density
- Events such as floods, fires, and landslides
Perfect logistic curves aren’t often found
Shannon-Weiner Diversity Index

The Shannon-Weiner Index is a common
way of showing that diversity involves not
only numbers of different species but also
how well each of these species is
represented in different habitats.
 It can range from no diversity at 0.0 to a
maximum diversity of 4.0
○ A large H value means if you randomly pick two
organisms in your test area, the odds are the
second individual will be different from the first
 The values have no real meaning by
themselves, but can be used to compare
different habitats
Shannon-Weiner Diversity
Index
H= - sum( pi ln pi )
 Where

 pi=the ratio of the number of organisms of a
species to the total number of organisms
 H= Shannon-Weiner Diversity Index
Example

You must first calculate pi for each species. Next, calculate ln pi.
Species
# of individuals
pi
ln pi
Beach
32
32/62= 0.52
-0.65
Oak
18
18/62= 0.29
-1.24
Maple
12
12/62= 0.19
-1.66
Total
62
We can now calculate diversity
 H = - [(0.52 X -0.65) + (0.29 X -1.24) + (0.19 X -1.66)]
 H = -[(-0.338) + (-0.360) + (-0.315)]
 H = -[(-1.01)] = 1.01
Biomes
Ch 4, pgs 96-103
Widely separated regions share similarities
• Biome = major
regional
complex of
similar
communities
Multiple factors determine a biome
• The type of biome
depends on abiotic
factors
- Temperature,
precipitation, soil
type, atmospheric
circulation
- Similar biomes
occupy similar
latitudes
Altitudes create “latitudinal patterns”
• Vegetative communities rapidly change along mountain
slopes
• The climate varies with altitude
• A mountain climber in the Andes
- Begins in the tropics and ends
on a glacier
• Rainshadow effect = air going
over a mountain releases
moisture
- Creating an arid region
on the other side
Hiking up a mountain in the southwest U.S. is like
walking from Mexico to Canada
Biomes
• Biome type is determined by precipitation, temperature
and soil type
Biomes and biodiversity
• Biomes are not uniform, but
patches of communities
- Climate and vegetation vary with
latitude (distance from equator)
and altitude (elevation above sea
level)
- Each biome contains many
ecosystems whose communities
have adapted to differences in
climate, soil, and other
environmental factors.
Vegetation Changes
• Parallel changes occur in vegetation type when we
travel from the equator to the poles or from lowlands
to mountaintops.
Plant Survival Strategies
• Desert – succulent plants, no leaves (no water loss),
store water in fleshy tissue, open stomata for CO2
only at night
• Tropical rainforest – broadleaf evergreens allow for
collection of sunlight and radiation of heat
• Cold/dry winters – broadleaf deciduous survive
drought and cold by shedding leaves and becoming
dormant
• Cool/short summer – coniferous evergreens – waxy
coating and shape of needles slow heat loss/evap
during cold winter
Aquatic systems have biome-like patterns
• Various aquatic systems make up 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, and dissolved nutrients
- Wave action, currents, depth, light levels
- Substrate type, and animal and plant life
Biomes on Earth
• Major biomes on Earth include forests, grasslands,
deserts, wetlands, and estuaries
- There’s more than that, but these are the ones most
likely to show up on the AP test!
Forests
• Characterized by the growth of mature
trees and a closed canopy. Rainfall must be
high enough to support the growth of large
trees
- Forest types largely determined by the
seasonal temperature range and the
length of the growing season
- Tropical forests: warm year-round
with large amounts of rain
- Temperate forests: deciduous with
four equal seasons, moderate rainfall
- Boreal forests (Taiga): evergreen
forests with short growing seasons,
moderate to high precipitation
Grasslands
• Characterized by a lack of trees and lots
of grasses and other non-woody plants.
Rainfall generally not high enough to
support large woody plants
- Grassland types determine largely on
seasonal temperature range
- Tropical grasslands: warm yearround, growing season is largely
determined by seasonal droughts
- Temperature grasslands: tend to
have cold winters and short
growing seasons. Soils tend to be
rich due to decomposing of dead
plant material
Deserts
• Driest of all biomes, usually with so
little rainfall there’s little diversity
of life
- Generally characterized as either
hot or cold
- Hot deserts: hot and dry with
sandy soils
- Cold deserts: very cold with
low precipitation and
permafrost or ice cover for
most of the year
Wetlands
• Characterized as an area where the
soils are flooded with water during
part of its natural cycle. Water plays
and important role in determining the
plant and animal life of the ecosystem
- Swamps and marshes have
standing or flowing water year
round
- Bogs and fens have saturated soil
and occasional standing water, but
generally have less water and
seasonal dryness
Estuaries
• An area where freshwater and
saltwater mixes. Known for
having high biodiversity
- Often found at the mouth of
a river where it flows into
the ocean
- The brackish (slightly
salty) water makes this a
valuable habitat for
shellfish, birds, fish and
other types of wildlife to
reproduce
Food Webs
Ch 4, pgs 83-90
Ecological communities
• Community = a collection of populations of organisms
living in the same place at the same time
- Members interact with each other
- Interactions determine the structure, function, and
species composition of the community
• Community ecologists are people interested in how:
- Species coexist and relate to one another
- Communities change, and why patterns exist
Energy passes through 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 (autotrophs)
- Consumers
- Detritivores and
decomposers
Producers: the first trophic level
• Producers, or autotrophs (“selffeeders”) = organisms capture
solar energy for photosynthesis to
produce sugars
- Green plants
- Cyanobacteria
- Algae
• Chemosynthetic bacteria use the
geothermal energy in hot springs
or deep-sea vents to produce their
food
Consumers: consume producers
• Primary consumers = second
trophic level
- Organisms that consume
producers
- Herbivores consume plants
- Deer, grasshoppers
• Secondary consumers = third
trophic level
- Organisms that prey on primary
consumers
- Carnivores consume meat
- Wolves, rodents
Consumers occur at higher trophic levels
• Tertiary Consumers = fourth
trophic level
- Predators at the highest trophic
level
- Consume secondary consumers
- Are also carnivores
- Hawks, owls
• Omnivores = consumers that eat
both plants and animals
Detritivores and decomposers
• Organisms that consume nonliving
organic matter
- Enrich soils and/or recycle
nutrients found in dead
organisms
• Detritivores = scavenge waste
products or dead bodies
- Millipedes, soil insects
• Decomposers = break down leaf
litter and other non-living material
- Fungi, bacteria
- Enhance topsoil and recycle
nutrients
Energy, biomass, and numbers decrease
• Most energy organisms use is lost as waste heat
through cellular respiration
- Less and less energy is available in each
successive trophic level
- Each 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
A human vegetarian’s ecological footprint is smaller
than a meat-eater’s footprint
QUESTION: Weighing the Issues
Would you be willing to decrease the amount of meat you
consume (e.g., eat lower on the food chain) to decrease
your ecological footprint?
a) Yes, if the extra food was sent to countries with
starving people.
b) Yes, because it would decrease environmental
degradation.
c) I don’t eat meat now.
d) No, I don’t see the need to eat lower on the food
chain.
Pyramids of energy, biomass, and numbers
Food webs show relationships and energy
flow
• Food chain = a series of feeding relationships
• Food web = a visual map of feeding relationships and
energy flow
- Includes many different
organisms at all various
levels
- Greatly simplified; leaves
out most species
Some organisms play big roles
• Community dynamics are
complex
- Species interactions differ in
strength and over time
• Keystone species = has a strong
or wide-reaching impact
- Far out of proportion to its
abundance
- Example: sea otters,
elephants, bees, prairie dogs
• Removal of a keystone species
has substantial ripple effects
- Alters the food chain
Species can change communities
• Trophic Cascade = predators at high trophic levels
indirectly affect 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 and changed
forest structure
• Ecosystem engineers = physically modify the
environment
- Beaver dams, prairie dogs, ants, zebra mussels
Species Interactions
Ch 4 pgs 77-83
Species interactions
• Species interactions are the backbone of communities
• Natural species interactions:
- Competition = both species are harmed
- Exploitative = one species benefits and the other is
harmed
- Predation, parasitism, and herbivory
- Mutualism = both species benefit
Competition
• Competition = multiple organisms seek the same limited
resources
- Food, space, water, shelter, mates, sunlight
• Intraspecific competition = between members of the
same species
- High population density = increased competition
• Interspecific competition = between members of 2 or
more species
- Strongly affects community composition
- Leads to competitive exclusion or species coexistence
Results of interspecific competition
• Competitive exclusion = one species completely
excludes another species from using the resource
- Zebra mussels displaced native mussels in the Great
Lakes
• Species coexistence = neither species fully excludes the
other from resources, so both live side by side
- This produces a stable point of equilibrium, with stable
population sizes
- Species minimize competition by using only a part of
the available resource (niche)
Niche: an individual’s ecological role
• Fundamental niche = the full niche of a species
• Realized niche = the portion of the fundamental
niche that is actually filled
- Due to competition or other species’ interactions
Resource partitioning
• Resource partitioning =
species use different
resources
- Or they use shared
resources in different
ways
- Ex: one species is
active at night, another
in the day
- Ex: one species eats
small seeds, another
eats large seeds
Character displacement
• Character displacement =
competing species diverge in their
physical characteristics
- Due to the evolution of traits best
suited to the resources they use
- Results from resource
partitioning
• Birds that eat larger seeds evolve
larger bills
- Birds that eat smaller seeds
evolve smaller bills
Competition is reduced when two species become more
different
Exploitation: predation
• Exploitation = one member
exploits another for its own
gain (+/- interactions)
- Predation, parasitism,
herbivory
• Predation = process by which individuals of one species
(predators) capture, kill, and consume individuals of
another species (prey)
- Structures food webs
- The number of predators and prey influences
community composition
Case Study: black and white and spread all
over
• In 1988, Zebra mussels were
accidentally introduced to
Lake St. Clair
- In discharged ballast
water
• By 2010, they had invaded
30 states
- No natural predators,
competitors, or parasites
• They cause millions of
dollars of damage to
property each year
Zebra mussel predation on phytoplankton
• Zebra mussels eat phytoplankton and zooplankton
- Both populations decrease in lakes with zebra mussels
• Zebra mussels don’t eat cyanobacteria
- Population increases in lakes with zebra mussels
• Zebra mussels are becoming prey for some North
American predators:
- Diving ducks, muskrats, crayfish, flounder, sturgeon,
eels, carp, and freshwater drum
Effects of predation on populations
• Increased prey populations increase predators
- Predators survive and reproduce
• Increased predator populations decrease prey
- Predators starve
• Decreased predator populations increase prey populations
Predation has evolutionary ramifications
• 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
Defenses against being eaten
Exploitation: parasitism
• Parasitism = a relationship in which one organism
(parasite) depends on another (host)
- For nourishment or some other benefit
- The parasite harms, but doesn’t kill, the host
• Some are free-living
- Infrequent contact with
their hosts
- Ticks, sea lampreys
• Some live within the host
- Disease, tapeworms
Parasites evolve in response to each other
• Parasitoids = insects that parasitize other insects
- Killing the host
• 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
Exploitation: herbivory
• Herbivory = animals feed on the tissues of plants
- Widely seen in insects
• May not kill the plant
- But affects its growth and survival
• Defenses against herbivory include:
- Chemicals: toxic or distasteful
- Thorns, spines, or irritating hairs
- Other animals: protect the plant
Mutualism
• Two or more species benefit from their interactions
• Symbiosis = mutualism in which the organisms live in
close physical contact
- Each partner provides a service the other needs (food,
protection, housing, etc.)
- Microbes within digestive tracts
- Mycorrhizae: plant roots and fungi
- Coral and algae (zooxanthellae)
• Pollination = bees, bats, birds and others transfer pollen
from one flower to another, fertilizing its eggs
Pollination
In exchange for the plant nectar, the animals pollinate
plants, which allows them to reproduce
Relationships with no effect on one member
• Amensalism = a relationship in which one organism is
harmed while the other is unaffected
- Difficult to confirm, because usually one organism
benefits from harming another
- Allelopathy = certain plants release harmful chemicals
- Or, is this a way to outcompete another for space?
• Commensalism = a relationship in which one organism
benefits, while the other remains unaffected
Succession
Ch 4, pgs 90-95
Communities respond to disturbances
• Communities experience many types of disturbance
- Removal of keystone species, spread of invasive
species, natural disturbances
- Human impacts cause major community changes
• Resistance = community of organisms resists change and
remains stable despite the disturbance
• Resilience = a community changes in response to a
disturbance, but later returns to its original state
• A disturbed community may never return to its original
state
Succession
• Succession = the predictable
series of changes in a community
following a disturbance that
removes all vegetation and/or soil
life
Primary succession
• Primary succession: Gradual
establishment on nearly lifeless ground
- Glaciers, drying lakes, volcanic lava
**No soil in terrestrial or no bottom
sediment in aquatic
• Before life can colonize, there must be
soil
- Takes several hundred to several
thousands
• Pioneer species = the first species to
arrive in a primary succession area (i.e.
lichens)
Secondary succession
• Secondary succession = a disturbance dramatically
alters, but does not destroy, all local organisms
- The remaining organisms form “building blocks”
which help shape the process of succession
- Fires, hurricanes, farming, logging
• Climax community = remains in place with few
changes
- Until another
disturbance restarts
succession
Ex: Piedmont region of NC
• Central region of NC, European settlers cleared mature
native oak and hickory forests to replant the land with
crops
- Later, abandoned land because of erosion and loss of
soil nutrients
- Area underwent secondary succession
Primary Succession
Secondary Succession
How do disturbance affect
succession and species diversity?
• Changes in environmental conditions that disrupt a community
can set back succession.
- Ex: Fire, drought, mining, plowing climate change can move
succession back to an earlier stage. Can be natural or man-made
• Not all disturbances are detrimental – some can create unfilled
niches or release nutrients.
• Communities that experience fairly frequent but moderate
disturbances have the greatest species diversity.
Communities may undergo shifts
• The dynamics of community change are more variable
and less predictable than thought
- 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
- i.e. overfishing and depletion of fish and turtles has
allowed algae to dominate corals
Invasive species threaten stability
• Invasive species = non-native (exotic) organisms that
spread widely and become dominant in a community
- Introduced deliberately or accidentally from
elsewhere
- Growth-limiting factors (predators, disease,
competitors, etc.) are removed or absent
- They have major ecological effects
- Chestnut blight from Asia wiped out American
chestnut trees
• Some species help people (i.e., European honeybees)
Top invasive species
•
•
•
•
•
•
•
•
•
•
Asian Carp
Rabbits (Australia, South Africa)
Cane Toads (Australia)
Kudzu
Gray Squirrel (Great Britain)
Killer Bees
Starlings
Northern Snakehead
Zebra Mussels
Burmese Python
Two invasive mussels
Controlling invasive species
• Techniques to control invasive species
- Removing them manually
- Applying toxic chemicals
- Drying them out
- Depriving them of oxygen
- 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
• Ecological restoration = efforts to restore communities
• Restoration is informed by restoration ecology = the
science of restoring an area to an earlier condition
- To restore the system’s functionality (i.e. filtering of
water by a wetland)
- It is difficult, time-consuming, and expensive
• It is best to protect natural systems from degradation in
the first place
Restoration efforts
• Prairie restoration = replanting native species,
controlling invasive species
• The world’s largest project = Florida Everglades
- Flood control and irrigation removed water
- Populations of wading birds dropped 90-95%
- It will take 30 years
and billions of dollars
to restore natural
water flow
QUESTION: Weighing the Issues
Although mustangs are not native to the United States, they
exist in several western states on federally owned land. As
an introduced species, what should be done with them?
a) As an exotic species, they should immediately be
removed and adopted or killed.
b) Although they are an exotic species, they are part
of our heritage, and should be allowed to stay.
c) They have been here so long, we should just
leave them alone.
d) Many countries eat horse flesh, so we should
round them up and export them to horse-eating
countries.