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Ecology
We share the earth with all of the other
creatures; removing any organism from an
environment can have many diverse
consequences - not always predictable ones.
Ecology is the study of the interactions of
organisms with the living and nonliving parts of
their environment.
An interacting group of organisms and their
environment constitute an ecosystem.
Habitat - place where a particular population of
organisms live.
Community - all the populations (of different
species living together in the same habitat.
Species diversity - the number of species
living within an ecosystem. Ecosystems are
made up of representatives of at least 5 of the
6 kingdoms.
For example - there may be up to 100 species of
trees living in just 1 hectare (2.5 acres) of a tropical
rain forest.
No ecosystems are completely isolated
although the physical boundaries are not
always obvious.
Natural changes in the physical environment of
an ecosystem happen all the time. Ex. volcanic
eruption forms a new island - sets off a process
of colonization and ecosystem development.
How Organisms Interact in Communities
Interactions
Interspecific Interactions
Interaction
Effects on Population Density
Competition (-/-)
Both species are harmed
Predation (+/-)
(includes parasitism)
One species is harmed the
other is benefitted.
Mutualism (+/+)
Both species benefit.
Commensulism (+/0)
One species benefits, the other
is not affected.
Mutualism: Both Species Benefit
Facultative: Helpful to both species
• Rhinos and oxpeckers
• Trees and fungi
• Ants and Acacia
• Pollination
Commensalism
• One member is helped, the other
neither benefits or is harmed
• Epiphytes and forest trees
• Clown Fish and Anemone
Parasitism
• + and - relationship
• parasite benefits, host loses
• parasite usually smaller than host
What is Predation?
Predation - one organism feeds upon the other.
How would coevolution of
predator-prey happen?
* Predator benefits from
relationship
* Prey is always harmed ∴
they evolve ways to protect
themselves
*in response predator
evolves way to counteract
defenses of prey and so
on…
Predator Strategies
Structural advantages
* Natural Weapons - Fangs, claws
* Flexible bodies
*Larger Size
Predator Strategies
Ambush* Stalk a victim
* Venom
* Gape & Suck (fish)
* Keen eyesight
Predator Strategies
SPEED & CUNNING
• More intelligent than prey
• Run faster than prey
•Hunt in packs
Prey Strategies
Defense Techniques
*Inflate
*Flee
*Fight Back
*Stab
*Poison
Prey Strategies
Structural advantages
*Hard Body Coverings
*Thorns or Spines
*Break away body parts
*Natural Weapons
Prey Strategies
Chemical Warfare
*Blinding ink
*Poison
*Offensive Smells and tastes
Prey Strategies
Camouflage
•Cryptic (camouflage) coloration
•Aposematic (warning) coloration
Mimicry
• Mostly a prey technique
* Optical and sonic illusions
* LOOKS like a predator:
•School of fish;
false eyes; frilled
neck and
inflation
Mimicry
Batesian
Mullerian
Plant-herbivore interactions
How do plants defend themselves from
herbivores?
* obvious ways - thorns, spines, etc.
* most contain defensive secondary compounds
ex. include poison ivy and oak - produce a gummy oil
mustard family - produce oils toxic to most insects
* for each group of plants there is usually a type of
herbivore that can feed upon - often as their
exclusive diet
* cabbage worms feed on mustard plants.
Competition
* When two species use the same resources,
they are said to compete and their interaction =
competition.
ex. lions and hyenas compete for food in Africa
* Competition does not necessarily involve
contact; interaction may be only by means of
effects on the resources.
* No two organisms can occupy the same
niche at the same time
Principle of Competitive Exclusion
*If two species try to occupy the same niche
at the same time, one species will outcompete
the other
Example:
Paramecium aurelia and Paramecium caudatum compete for the same
resources
When introduced to a petri dish separately, each each grows well
If grown together - P. aurelia will win (more resistant to bacterial waste
products)
Competition evidence
Resource partitioning~
sympatric species consume
slightly different foods or use
other resources in slightly
different ways
Ex: Anolis lizard sp. perching sites in the
Dominican Republic
Character Displacement~
sympatric species tend to diverge
in those characteristics that overlap
Ex: Darwin’s finch beak size on the
Galapagos Islands
The Niche
•Ecological niche: the sum total of an organism’s use of biotic and abiotic
•resources in its environment; its “ecological role”
* Fundamental: the set of resources a population is theoretically capable of
using under ideal conditions
* Realized: the resources a population actually uses
* Thus, 2 species cannot coexist in a community if their niches are identical
Relationships
* Trophic structure / levels~
feeding relationships in an ecosystem
* Primary producers~ the
trophic level that supports all others;
autotrophs
* Primary consumers~
herbivores
* Secondary and tertiary
consumers~ carnivores
* Detrivores/detritus~ special
consumers that derive nutrition from
non-living organic matter
* Food chain~ trophic level food
pathway
Relationships
* The path of energy through
trophic levels of an ecosystem
is called a food chain. Food
chains interconnect to form
food webs.
* Energy is lost as heat at any
energy transfer in a food web generally not useful energy for
biological systems.
* From a biological point of view,
amount of energy decreases as
energy passes through an
ecosystem.
Heat
Abiotic chemicals
(carbon dioxide,
oxygen, nitrogen,
minerals)
Heat
Solar
energy
Heat
Producers
(plants)
Decomposers
(bacteria, fungi)
Heat
Consumers
(herbivores,
carnivores)
Heat
Fig. 3-14, p. 61
Energy Flow
Energy pyramid
* Ecological efficiency: % of
E transferred from one
trophic level to the next (520% - rule of 10%)
* Pyramid of productivity:
multiplicative loss of
energy in trophic levels
* Biomass pyramid: trophic
representation of biomass
in ecosystems
* Pyramid of numbers:
trophic representation of
the number of organisms
in an ecosystem
Numbers pyramid
Biomass pyramid
*There
is limit to the number of trophic levels
in an ecosystem - maximum 3 or 4 because
of this energy loss - a consequence of the
2nd law of thermodynamics.
* For example it takes a large population of
zebras and wildebeests to support a small
population of lions (1000 to 1!!!)
* Humans eat steak and hamburger at a great
cost in energy.
* Cattle Ranching vs Agriculture – Third World
Pyramid of numbers based on the number of organisms in each trophic level
Ecosystem Changes
* No ecosystems are completely isolated
although the physical boundaries are not
always obvious.
* Natural changes in the physical
environment of an ecosystem happen all the
time. Ex. volcanic eruption forms a new island
sets off a process of colonization and
ecosystem development. -
* Ecosystems change through the process of
succession
* Succession on newly formed habitat is called
primary succession .
It can take 1000+ years from sand dune to
forest.
No remaining organisms or soil
Examples, lava flow, sand dune, glacier
retreat succession. .
*Small, fast growing plants move in first pioneer
organisms , such as moss, lichens. These species
are r selected organisms.
•These do not persist because their pioneering
efforts make the area more hospitable for other
organisms to invade.
* This process continues with each group of
inhabitants paving the way for a new group to
better compete in the environment .
•Succession in a previously inhabited area is called
secondary succession . Succession
Much shorter period of time 100 years or so. –
Some organisms and soil remain
examples are fires, abandoned fields
* During succession, one set of species replaces
another until a community is reached that is self
sustaining and persists over time climax
community self- - .
Primary succession example
exposed rocks
lichens and mosses
small herbs and shrubs
heath mat
jack pine, spruce, aspen
white spruce, climax
Secondary Succession Example
annual weeds
perennial weeds
and grasses
shrubs
young pine forest
mature oakhickory forest
Is there only one climax community possible per
location?
•Originally, it was thought -- > YES –
•Now, we think -- > No think—
•There are many possible climax communities in an area
it depends upon original pioneer species, climate and
interaction among later species. –
* No two succession sequences are exactly alike but will
tend toward similar communities in similar physical
environments. > >
HUMAN IMPACT ON THE
ENVIRONMENT
Global Change
•The Earth faces unprecedented environmental
problems ranging from global changes in the
atmosphere to loss of topsoil.
* Human induced environmental changes that affect
ecosystems worldwide are referred to as global
change Humanchange.
ACID RAIN
* Burning high sulfur coal creates acid precipitation.
* Sulfur introduced into air combines with water vapor to
form H2SO4; precipitation carries acid back to earth.
* Acid rain is any precipitation with higher than normal
acidity. Acid rain is caused by the interaction between
pollutants and water in the atmosphere.
Acid Rain Concentrations in the U.S.
* High smoke stacks are supposed to release gases
high into the atmosphere where wind will dilute
and disperse them
* In the 1970’s, scientists began to report that these
stacks were not eliminating the problem only
shifting it. -
In Northern Europe
decrease in species diversity
trees in Black Forest is dying
In North America -eastern U.S. and Canadian forests also
damaged
Acid Rain breaks down limestone buildings
and sculpture
* Average pH of precipitation in U.S. in 1989 was 5.6
except in New England where it is 3.6 (100x higher!!)
•Possible solutions
capture emission with “scrubbers”; very expensive
Clean Air Act of 1990 helped in US
•Polluters and recipients of pollution are far apart on
the issue no one wants to pay for “another’s problem” –
tragedy of the commons
OZONE LAYER
•The ozone layer of the upper atmosphere (11 16
miles above sea level) absorbs 99% of the UV
radiation that reaches the earth (good ozone) 11* Ozone also forms in the lower atmosphere when
emissions from cars and factories react with sunlight
where the ozone then becomes a corrosive reactive
substance (bad ozone)
•In the past, CFCs, an ideal heat exchanger, were
used as coolants in air conditioners and propellants
in aerosol containers
*In 1985, it was noticed that the ozone layer over
Antarctica had decreased 30% over 10 years
satellite images revealed a “hole” –
* Destruction of the ozone layer is caused by
chlorofluorocarbons (CFCs) and several other kinds
of chemicals.
Ozone Depletion
High ozone values are yellow-red in color, while low total ozone values
are blue-purple in color. Note the distinct differences in ozone between
the earlier years and later years in the Arctic region.
CFC’s stick to frozen water vapor and catalyze
the conversion of O3→O2
•One chlorine atom can destroy 100,000 ozone
molecules!
•As ozone levels , amount of UV radiation leading to
an increase in skin cancer rates, cataracts and
malignant melanomas. ↓, ↑
•Every 1% in ozone levels a 6% in skin cancer rates ↓
→ 6%↑
* Ozone depletion affects crops such as soybeans,
rice, corn
* Many marine algae are very sensitive to UV levels production levels∴O2
* Ozone levels in lower atmosphere irritates and damages lungs & eyes,
suppresses the immune system and aggravates respiratory and heart
diseases ↑ ↓
* In 1996, 93 nations agreed to stop
production of CFCs but those already in
atmosphere can remain for the next
century!
*The good news is that CFC levels
should have begun to decrease in 1998
and should be close to normal by 2045
GLOBAL WARMING
* The Greenhouse Effect
Much of the light that hits the surface of the earth and is
reflected as heat is
trapped by gases in the upper
atmosphere (water vapor, methane carbon dioxide & nitrous
oxide).
*This results in an earth that is habitable
•Global Warming
Humans are increasing the concentrations of greenhouse
gases such as carbon dioxide with the burning of cheap fossil
fuels.
*This is resulting in a higher surface temperature Effect:
Warming:
Energy in = Energy out
Solar
radiation
Reflected by
atmosphere (34% )
UV radiation
Lower Stratosphere
(ozone layer)
Absorbed
by ozone
Visible
Light
Absorbed
by the earth
Troposphere
Radiated by
atmosphere as heat
(66%)
Greenhouse
effect
Heat
Heat radiated
by the earth
Temperature records of the last 50 years support this fear that
temperatures are ↑
Ecosystem Damage
*Two serious environmental problems are a)pollution
b)destruction of non--replaceable resources.
*Unlike other organisms, the human population has
the capacity to increase the carrying capacity of the
Earth.
*Since the Industrial Revolution, people have thought
that the environment could absorb unlimited
pollution.
Many types of pollution involve toxic or
carcinogenic chemicals --ex. mercury, pesticides,
oil (Exxon Valdez leaked 11 M gallons of oil in
1989 --effects still being felt)
Three non renewable resources in particular danger are top
soil, ground water and species.
TOP SOIL
* Soil has three layers the top has the most layersorganic material (a.k.a.
humus)
* Originally the prairie had
top soil to a depth of >1M
* Now it is much less
GROUND WATER
•Ground water = water trapped beneath soil (much of
it in porous rock) in reservoirs called aquifers
•Much of this water is polluted by run off from
fertilizers, chemical wastes, etc..
•It is being wasted on lawns, washing cars, fountains,
etc..
* Once pollution enters ground water there is no
effective way to remove it.
EXTINCTION OF SPECIES
•During the last 50 years, 50% of the world’s
tropical rain forests have been destroyed.
*As they disappear, so do their inhabitants
the most species diverse biome on the
earth –
* It is estimated that 1M species (20% of
world total) will become extinct during the
next 50 years.
Extinction
•In addition to the problems of pollution
and consumption, a more fundamental
problem is the rapid growth in the
human population.The number of people
the Earth can support is unknown.
•World population now over 7B
* Expected to double every 40 years (or
less)
Solving Environmental Problems
•One of the most encouraging developments in the 1990’s has been a
world wide effort to reduce pollution.
International agreements to stop CFC production
Restriction of DDT, dioxin and asbestos in the U.S.
Emissions of SO , CO and soot 30% SO2, ↓
Number of secondary sewage treatment plants 72% ↑
Businesses spending approximately 100B/yr on pollution controls
•In our economy, pollution can be profitable
because the environmental damage caused by
pollution and/or health consequences are not
usually not factored into the price of products.
*There are two ways to factor the costs of
environmental damage into the prices of goods
and services. One way is to require pollution
devices. The other is to tax products or services
that create pollution.
* Environmental problems must be
documented and understood before they
can be solved. There are five
components to solving environmental
problems: assessment, risk analysis,
public education, political action and
follow through. follow-
Biomes
*A major terrestrial community that is found in
different areas with similar climates is called a
biome. A biome’s structure and appearance are
similar throughout its distribution.
*The world’s biomes are tropical rain forest,
savanna, desert, temperate grassland, temperate
deciduous forest, taiga and tundra.
*Terrestrial biomes: most important factors in determining wildlife =
precipitation / temperature
–Tropical rain forest:
*where -tropics; 20N-20S
*temp. -warm all year; av. = 25-27°C; little daily fluctuation
*precipitation -200-400cm/year
* species -high diversity (50% of all species!)
*other -high primary productivity; bad soil; in jeopardy
*Grassland
–Savanna-between tropical rain forest
& desert
–Temperate grasslands/prairies-U.S.
Midwest
*precipitation -25-75cm/year;
rain and snow
*temperature -more fluctuation
than rain forest, moderate climate; 025 °C,hot,dry summers
*species -grasses; herds of large
grazing animals
*other -two seasons; prolonged
dry & rain, fertile soil
*Desert
*where -interior of continents:Sahara and Mojave, at 30°N and S
*temperature -24-34°C,hot days; cold nights; greatest daily fluctuation
*precipitation -<25cm/year
*species -sparse vegetation, shrubs, coyotes, hares, rodents, reptiles
*Temperate deciduous forests:
*where -east coast US
*temperature -warm summers; cold winters;. 6-28°C
*precipitation - 75-125cm/yr, well distributed through year
*species -oak, maple, hickories, some conifers, deer, beavers, bear, raccoon
*Coniferous forest/taiga:
*where -north of temp.deciduous.forest; south of tundra
*temperature -colder winters(short growing season); 10-14 °C
*precipitation - 35-75cm/yr, mostly in summer
*species -pine, spruce, elk, moose; low species diversity
*Tundra -arctic and alpine:
*where -near poles (or top of high mountains)
*temp -extremely cold, high winds;-26-4 °C
*precipitation -low (<25cm); polar desert; permafrost
*species -low shrubs, mosses, caribou, reindeer