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Shaping an Ecosystem
C-4-2
Ecosystems are influenced by a combination of
biotic (living organisms) and abiotic (physical)
factors.
The area in which an org. lives is a habitat - this
includes both factors.
Niche - all conditions in which an org. lives and how
it uses those conditions
~ type of food eaten
~ place in the food web
~ temp. in which they survive
~ reproduction style
No two species will share the same niche in the
same habitat!
However, there are many different ways species
can interact with each other within their
communities...
1.) Competition - species have similar needs and
compete for survival
* Competitive exclusion principle  no 2
species can occupy the same niche in the same
habitat at the same time
~ this would result in the elimination of one of
the species
2.) Predation - one org. eats another
3.) Symbiosis - relat. where 2 species live closely
together.
3 types:
a.) Mutualism - both species benefit
ex: flowers and insects
b.) Commensalism - one benefits, the other is
neither helped or harmed
ex: barnacles on a whale
c.) Parasitism - one org. lives on another and
the host is harmed
ex: tapeworms in mammals
Ecosystems are constantly changing
* human interference
* natural disturbances
As these changes occur, old species die out and are
replaced by new.
~ called ecological succession
Primary succession = occurs on surfaces where no
soil exists
ex: bare rock eventually gets covered by
vegetation
~ pioneer species are the first ones to
populate the area - usually lichen
Secondary succession = the rebound of an
ecosystem after a disturbance
ex: forest fire or clearing land by humans
~ eventually, the plants will re-grow and
restore the land
Extension - EXTRA CREDIT!!!
Read through section 3 of chapter 4. Pick any biome and
make a travel brochure that makes me want to go there!
~ worth 20 bonus points!
~ see me for guidelines!
Limits to growth
C-5-2
Populations can grow exponentially if not kept in
check.
~ for instance: one bacteria will become 2,
then 4 then 8,then 64, then 512,then at the end of
one day, there will be 4.72 x1021
* Called Exponential Growth!
However, this only happens when populations have
every offspring survive to reproduce.
As resources become less available, offspring
don't live as well. This stops population growth.
~ This happens when the population has
reached carrying capacity. - max # org. an
ecosystem can support
There are several limiting factors that keep pop's
in check...
1.) Competition - more org. = less resources
2.) Predation - predator-prey relationships
keep each other in balance
3.) Parasitism and Disease - keeps pops. down
by killing host
4.) Drought / Climate extremes - extreme
heat or cold, lack of or too much
water...all can kill
5.) Human disturbances - changing the
ecosystem ~ deforestation, waste
dumping, killing off predators
1-3 are density-dependent factors, 4-5 are
density-independent
DDF - only become limiting when the pop. density
reaches a certain level
DIF - affect all pops. similarly regardless of pop.
size
Through a combination of all of these factors,
populations can vary from being in balance, to being
way out of balance.
The most influential? US!!
Biodiversity
C-6-3
Biodiversity - the sum of all genetically based org.
in the biosphere
Along with this, there are several other types of
diversity...
~ Ecosystem diversity - includes habitats,
communities, and processes
~ Species diversity - # of dif. species in
biosphere
~ Genetic diversity - all dif. forms of genetic
info for all life forms on the planet!
We benefit from this diversity in many ways:
* food
* medicine - pain killers, antibiotics, heart
drugs, anticancer drugs etc.
* industrial products
However, there are many threats to biodiversity:
~ We are the # 1 threat!
1.) Habitat
alteration
* land development splits habitats and
destroys others
*this makes the species that live there more
fragile and open to harm from further change
2.) Demand
for wildlife products
* hunting has made some species extinct!
* fur, meat, body parts thought to have
medicinal qualities
* most endangered species are now protected
from hunting - but poaching continues to
be huge problem
3.) Pollution - major factor is toxic compound
accumulation - Biological magnification - fig. 6-16
4.) Invasive
species - non-native species that
reproduce rapidly due to lack of predators.
~ often overcrowd native species and overtake
the habitat thus destroying or changing the
ecosystem
ex: zebra mussles - in Lake Erie - have pushed
some species to near extinction!
So how do we make sure the biosphere is
maintained?
Conservation!
Strategies:
*captive breeding programs at zoos
*set aside land to protect certain
ecosystems - parks/reserves
* limiting hunting and fishing to certain
seasons
* imposing stricter laws against pollution
and mining for natural resources
Challenges... implementing these strategies may
infringe on some ways of life but it must be done!
ex: fishing industry - loss of habitat = loss of jobs
Charting a Course for the Future!
C-6-4
Before we can make a plan, we need research and
evidence to help us come up with a strategy.
2 biggest problems for our future...
1.) Depletion of the ozone layer
2.) Global climate system
Ozone depletion:
* Ozone layer resides bet. 20-50km above earth
* absorbs UV rays - like sunscreen!
* without it, we receive too much UV which can
lead to tissue damage in plants and animals
* holes are over the poles and thought to be
caused by CFCs - we have since banned use of CFCs
in aerosol cans and refrigerators - holes should
shrink in about 50 years
Global climate change:
~ there is strong evidence that the climate is
changing!
ex: from 1980, the avg. world temp has
increased approx. .3o Celsius and about .6o C over
the last 100 years
~ the ice caps on both poles are significantly
smaller from what they were 30 years ago
~ thought to be due to possible natural
fluctuations in the earth's climate change along
with our influence of burning fossil fuels
magnifying the greenhouse effect
*greenhouse effect is like this:
Possible effects:
1.) Avg. global temps. likely to increase by between
1.4 and 5.8 degrees Celsius (2.5 and 10.4
degrees Fahrenheit) by the year 2100.
2.) Sea levels may rise enough to flood coastal
areas
3.) More severe weather - storms, drought
4.) Ecosystems may not be able to adapt fast
enough leading to extinction or take over
where they once did not live
Do your part to conserve Ohio and the world's ecosystems!