Download - Catalyst

TESC 211
The Science of Environmental Sustainability
Autumn 2011UWT
What about non-feeding relationships between species?
Mutually supportive relationships
•Symbiosis
•Pollinator-plant
Competitive relationships
•Habitat
•Niche
•Resource Partitioning
•Competitive exclusion principle
The concept that relationships between species may be of mutual
benefit is known as mutualism.
e.g. Honey bees and flowering plants
In some cases the mutualistic relationship has become so close
that one species cannot survive without the other.
e.g. lichens are composed of an algae (producer) living in
symbiosis (close union) with a fungus (consumer)
In parasite-host relationships the symbiotic relationship may not
be beneficial to both species.
These non-feeding relationships may improve the overall
functioning of the ecosystem.
e.g. Worms aerate and return nutrients to soil which is of benefit
to plants.
Predators targeting weaker or sick members of a species may
benefit the population as a whole by keeping it healthy.
Competition between species is limited as a result of each
species being specialized and adapted to its own habitat and
niche.
Habitat refers to the place a species is adapted to live. Different
habitats support different species.
e.g. we don’t get every species in every place
Even within a given habitat competition is limited as each
species occupies its own niche.
A species ecological niche describes amongst other things:
• what it consumes
• grubs versus nectar
•where it feeds
• Different species of warblers have different foraging
heights
(Warblers live in the spruce forests of Maine)
•When it feeds
• nocturnal versus diurnal
By adapting to particular ecological niches species that occupy
the same habitat limit competition.
This adaptation to each others presence is an example of
resource partitioning and is of benefit to all species present in
an ecosystem.
However, some competition is unavoidable.
e.g. All green plants require sunlight, water and nutrients
If two species compete directly in many respects (often occurs
with introduced species) one of the two generally perishes.
“competitive exclusion principle” also known as Gause’s Law.
This was formulated by Georgii Gause by studying species of
Paramecium.
He observed that under constant conditions one species of
Paramecium would always exclude another.
We can divide abiotic factors into conditions and resources.
Conditions can be defined as:
“abiotic factors that vary in space and time but are not used
up or made unavailable to other species”
e.g. temperature, salinity, wind etc
Abiotic resources can be defined as:
“any abiotic factors that are consumed by organisims”
e.g. Water, nutrients, oxygen, space
When we grow organisms in the lab in such away that we keep all
factors constant except one that we vary we discover that for
every factor there is an optimum value.
The range of the factor over which any growth occurs is called
the “range of tolerance” for that factor.
The values at the extreme ends of the range of tolerance are
referred to as the limits of tolerance.
Between the optimal range and the limits of tolerance are
zones of stress where growth is poor.
Often this is referred to as “Law of limiting factors” or “Liebig’s
Law of minimums” (Justus von Liebig)
The population of a species will be greatest where all factors are
optimal and will decrease when one or more are not.
The previous discussion does not describe the possibility of
synergistic effects.
i.e. what happens when we have several factors at suboptimal
values?
Often we find the synergistic effect can be greater than the sum
of the parts.
An additional factor that may constrain a species is a physical
barrier.
Examples include:
• Ocean
• Desert
• Mountain range
These physical barriers limit the range in which we will find
certain species.
Physical barriers are overcome when Human’s transport a
species.
The introduced species may disrupt the ecosystem into which
it is introduced.
e.g. Starlings, rabbits, cane toads
Alternatively Human’s may create artificial barriers which restrict
normal movement of a population.
e.g. dams (migratory fish), roads, forest clearings
Sequim WA
We have explained in great detail how matter is cycled through
food chains and webs.
What other processes are occurring to cycle materials in
ecosystems?
How have humans impacted these processes (if at all)?
Elements and compounds in ecosystems are continually cycled
the biosphere, lithosphere, atmosphere and hydrosphere through
“biogeochemical cycles”.
These cycles are driving either by gravity or solar energy.
Of particular importance are the:
• carbon cycle
• nitrogen cycle
• phosphorus cycle
• sulfur cycle
• hydrological (water) cycle
The Earth has a fixed supply of water. This supply is collected,
transported and purified by the hydrological cycle.
The are large reservoirs of water in the atmosphere and the
hydrosphere, predominantly the oceans.
Transportation of water is driven by gravity and solar energy
and involves by three major processes.
• Evaporation
• Precipitation
• Transpiration
Evaporation is the transformation of liquid water into the vapor
phase. It is the mechanism by which water is transported from
the hydrosphere to the atmosphere.
Does this process require in input of energy? If so where
does this energy come from?
Over land 90% of evaporation occurs from the surfaces of
plants (transpiration) and from the soil.
Gravity draws some of the water back from the atmosphere to
the Earth’s surface as rain, snow, sleet and dew. This process is
called precipitation.
• This is a release of gravitational potential energy
Most precipitation falling on terrestrial ecosystems becomes
surface runoff which eventually flows back into the
hydrosphere.
Some water falling on terrestrial ecosystems is converted to ice
and stored in Glaciers, some sinks through permeable rock and
soil and is stored as ground water in aquifers.
Through out the hydrological cycle many processes purify
water.
• Evaporation and precipitation as a natural distillation
process.
• Water flowing above ground is filtered and partially purified
by natural chemical and biological processes.
The hydrological cycle can be considered as:
“a cycle of natural renewal of water quality”
It is worth noting that water is a powerful solvent.
• Agent for transporting nutrients and pollutants
Human activities have seriously modified the hydrological cycle.
• Clearing of vegetation for agricultural, industrial and
residential use.
• Increases run-off (transportation of matter)
• Reduces ground water recharge
• Accelerates erosion
• Increases risk of flooding
Human activities have seriously modified the hydrological cycle.
• Withdrawal of large amounts of freshwater from streams,
lakes and underground sources
• Only ~0.024% of the Earth’s water is accessible to
humans and other species as liquid freshwater.
• The rest is too salty, stored as ice or too deep
underground.
Carbon is the basic building block of the lipids, carbohydrates,
DNA , proteins and other organic molecules common to all
organisms.
The carbon cycle serves to circulate carbon through the
biosphere, atmosphere, lithosphere and hydrosphere.
The carbon cycle is based upon the circulation of inorganic
carbon dioxide. Carbon dioxide is a minor component of our
atmosphere (0.038%) and is also dissolved in water.
Terrestrial producers remove carbon from the atmosphere.
Aquatic producers remove carbon from water.
The producers use carbon dioxide to produce glucose via
photosynthesis which is then further converted to the desired
organic molecules.
Consumers and decomposers (as well as some oxygen
consuming producers) carry out respiration.
Respiration breaks down complex organic molecules producing
water and carbon dioxide
Humans affect the carbon cycle by adding carbon dioxide to the
atmosphere.
• Through clearing of vegetation faster than it can grow back
•Through the burning of “biomass” and fossil fuels