Transcript BASICS OF ECOSYSTEMS

BASICS OF ECOSYSTEMS
• Simplistic view
• Can divide ecosystems into two parts
– abiotic (never living) and biotic (living)
• Abiotic examples
– temperature, dissolved oxygen in water
– Amount of abiotic materials at any one time in
an ecosystem is called the standing state
• Biotic material
– could conceive of three structural parts
• Producer organisms (autotrophic)
• Consumer organisms (heterotrophic)
– Primary, Secondary, Tertiary
• Decomposer organisms
• Leads into a discussion of trophic structure
– food webs, food pyramids, food chains
• The total amount of living material in a
tropic structure is termed the biomass
• Theoretical structure
• More realistic picture
PROBLEMS FROM THE
STRUCTURE OF
ECOSYSTEMS
Interdependence
• Each level within the structure is called a
trophic level
• relationships between species and trophic
levels
– what impacts on one will be spread to others
– systems interlink as well
PROBLEM
• Island of Mauritius
• Calvaria Tree - valuable as a hardwood and
linked to exports
• Number of trees diminishing in the system
• Assumption of overcutting
• Last 13 trees protected but would not
reproduce (youngest tree 300 yrs old)
• Seed hulls too thick for plant to germinate
NORTH BORNEO 1955
Spray with Dieldrin to kill mosquitoes carrying malaria
Malaria declines
Roofs
fall in
Caterpillars
increase and
eat through
thatched roofs
Spray kills wasps
and insects which
feed on
caterpillars
Cats eat dead
lizards
and die
Rat population
increases
Plague declines
Insect eating
lizards die
Spray also
kills flies and
cockroaches
Sylvatic plague
carried by fleas
on rats increases
Rat population
declines
WHO
parachutes
in cats
Canadian Forests
threatened by
spruce budworm
spray
Kills other species
ie bees
Spread to water
systems
Possible
link to
Reye’s
Syndrome
NOTE: TEMPORAL & SPATIAL SEPARATION
Decreasing Biomass with
Pyramid Shape
• Amount of biomass at higher trophic levels
is less than that below it
• The conversion of energy uses energy
(feeding, digestion, movement, etc)
• On average there is a 90% loss when
energy is transferred from one level to the
next
• Theoretical pyramid
Note: At higher levels could be 99%+ loss
Consequences
• If a lower level is affected it will have a
more significant effect (%) on the lesser
biomass above
• Species at the top are more vulnerable to
change as the populations are smaller
Biomagnification
• Sometimes referred to as ‘funneling’
• If materials added to the system do not break down
into their component parts they will ‘move up’ the
pyramid
• Because of energy loss there is less biomass to
absorb the material
• This means that the concentration levels increase in
the members of species further up the food chain
• ddd
CONSEQUENCES
• Humans are at the top of some food chains
• Mercury, for example, can be found in
Minimata, Japan or in the English River in
Ontario
• The Minamata Disease got its name from Minamata Bay in
Southwestern Japan where it was first observed in nearby
communities. It was officially discovered in 1956, and a
few years later it was known to be caused by ingestion of
fish that had been contaminated by mercury let off from a
chemical manufacturing plant. Levels of methylmercury
chloride were very high: up to 50 ppm in fish and 85 ppm
in shellfish from the contaminated areas. 121 people were
poisoned from eating the contaminated fish, 46 of
which died. Dogs, cats, pigs, rats, and birds that were
living around the bay also showed the signs of mercury
poisoning, and many died.
•
• The initial symptoms were numbness of the limbs and the
area around the mouth, sensory disturbance, and difficulty
with everyday hand movements. Also there occurred a lack
of coordination, weakness and tremor, slowed and slurred
speech, and altered vision and hearing. These symptoms
worsened and led to general paralysis, involuntary
movements, difficulty in swallowing, convulsions, brain
damage, and death.
• Between 1962 and 1970, a pulp mill operated by
Dryden Chemicals dumped about 9,000 kilograms
of mercury into the English-Wabigoon river
system. Both communities sit along the 480kilometre system, which runs across the OntarioManitoba border.
• Testing showed people had high levels of mercury
in their blood, which was blamed for birth defects
in children.
• In the mid-1980s, the bands received a
compensation package of almost $17 million from
the company and provincial and federal
governments.
• They're still advised not to eat fish from the
river.