Transcript Year 12 Biology

Biology 3A Biodiversity
Biodiversity
• ecosystem biodiversity – a range of
different habitats and complex ecosystems
are available around the world or within an
area
• species biodiversity – different species
exist within each ecosystem
• genetic biodiversity – variations exist
within a species within an ecosystem
Diversity and change
Ecosystems change –
Abiotic factors may vary –
eg light, water, temperature, salinity, tides
These may vary cyclically eg day/night; monthly,
seasonally, over longer periods, or
catastrophically (eg fire, flood, volcanic
eruption, ice age, etc)
Biotic factors may vary –
Numbers of
• Producers
• Prey species (1st order consumers)
• Predators (high order consumers)
Everything in an ecosystem is linked
• A change in one factor can lead to changes in other
factors – domino effect
eg decreased rainfall  decrease in vegetation 
decrease in herbivores (prey species)  decrease in
predators
eg removal of predators (hunting or biomagnification) 
increase prey species (plague)  decrease vegetation
 decrease in herbivores due to no food
• Key species a species whose removal negatively
affects an entire ecosystem eg otters in kelp forests –
when hunted to extinction, sea urchin numbers
increased so much that they destroyed the kelp 
decrease in the other species depending on kelp for
food or shelter
Changes in ecosystems - water
• Damschanges distribution of populations in ecosystems –
can get animals accumulating around dams  over grazing
near the water source; loss of original ecosystem in flooded
area
• Presence of bores  lowers water table; increases number of
animals around bore  over grazing near the water source
• Tailing dams  kills wildlife that tries to use it as water
• Removing water for human use  lowers amount of water in
river/streams eg Murray  not enough water to maintain
ecosystem
• Filling in wetlands  destroys ecosystem; loss of habitat for
migrating birds; damage to neighbouring ecosystems as
wetlands act as filters to remove pollutants and excess
nutrients
Changes in ecosystems - clearing
Loss of trees  loss of habitat & nesting places as well as
the following
• Loss of topsoil  (= erosion) loss of fertility  decreased
producers  decreased biomass in the whole ecosystem
• Rise of water table  water logging in low lying areas,
increased soil salinity as salts are brought up with the
water
• Increased soil salinity  loss of fertility  decreased
producers  decreased biomass in the whole ecosystem
• Increased water salinity  loss of fertility  decreased
producers  decreased biomass in the whole ecosystem;
poisoning of consumers, loss of aquatic life
Changes in ecosystems – climate change
Climate change  changes in temperature, rainfall & humidity
– also affects water availability
• Increased temperature  increased water loss  higher
water needs; may cause death of organisms if temperature
too high; rising sea levels (thermal expansion of water) and
melting of glaciers and polar icecaps may also impact on
ecosystems
• Decreased rainfall  reduced water availability 
decreased biomass (less plants  less animals)
• Reduced water table  dries out seasonal water sources
(eg swamps, small creeks) and cave systems, less water 
decreased biomass (less plants  less animals)
• Change in seasons  organisms may not be able to find
enough food to survive & raise offspring eg birds breed as
light levels change, insects breed as temperature rises
Changes in ecosystems -agriculture
Farming  agricultural practices include
• Monoculture  presence of only one species in the crop,
decreases biodiversity, encourages population explosions or
plagues of pest species eg mice, locusts, in the long term
reduces soil fertility
• Killing insects (eg pesticides)  disrupts ecosystems by
destroying food source of higher order species (eg owls,
wattle birds); can lead to ecological magnification
• Loss of dead/decaying matter  loss of fertility, loss of
decomposers  soil problems  reduction in producers 
reduction in consumers
• Fertilisers  chemical poisoning of plants or animals (eg
high phosphate fertilisers kill many native trees; run-off into
rivers can cause eutrophication (algal blooms)
Changes in ecosystems – human
interference
Human presence  disrupts ecosystems in many ways
including:
• Loss of predators  removal of predators (sg spiders,
wolves) can lead to population explosions of prey species
• Introduction of new carnivore  eg foxes, cats, dogs  loss
of native wildlife
• Introduction of new herbivore  eg rabbit, sheep, may outcompete natives  loss of native species; may cause over
grazing as no native predators erosion
• Introduction of new producer  eg brambles, prickly pear,
may out compete natives (as often not edible to consumers)
 loss of native plant and animal species (now not enough
food for them); aquatic plants eg duckweed may block rivers
Succession
• Succession change in an ecosystem over time as
organisms change the abiotic features (eg soil, humidity)
so it becomes more suitable for other organisms to survive
• Colonisers hardy organisms that first invade an area and
establish themselves. They must be able to cope with
harsh conditions eg no soil, low soil fertility, salinity, low
humidity, etc
• Climax community final community. This is the most
diverse and stable, and usually consists of forest
Primary succession
Occurs when the soil is totally
destroyed or absent, or
extremely infertile, organisms
must invade from neighbouring
ecosystems
eg after a volcanic eruption, a
glacier retreats or at the beach
http://www.micro.utexas.edu/courses/levin/bio304/ecosystems/ecology.html
Secondary succession
Occurs when a disruption
occurs that kills organisms,
but the soil remains
relatively fertile, organisms
may still survive or seeds
may still be present
eg after a fire, clearing or
logging, abandoned land
http://www.scienceclarified.com/Sp-Th/Succession.html
Effects of increased human population
Settlement
patterns
More people living in cities, cities become larger.
Resource use:
Energy
Water
Food
Increases – leading to scarcity in fuel, water & food supply
 more land cleared for farming, increased use of
pesticides & fertilizers
The environment:
Desertification
More land is cleared for farming  desertification
Eutrophication
More fertilizers are used  eutrophication
Pollution
More people  more pollution (sewage, combustion, industrial
pollution)
Biodiversity
Changes in species as some native species are removed and
others added (introduced species)
Introduction of new species
Examples of
introduced species
Reasons for introduction
Effects of introduction
Fox
For hunting
Predation of native species
Cat, dog
Escaped from houses, dumped
Predation of native species
Rabbits
Brought in as food source
Competition for feed, overgrazing &
burrows cause erosion
Goats, sheep, cattle,
horses, camels,
water buffalo
Escaped from farms, dumped
Competition for feed, overgrazing
causes erosion, hooves damage river
banks
Carp
Escaped, dumped
Competition for food sources,
predation, reduces native species
Cane toad
Brought in to control cane
beetle
Predation of native species
Corellas, cockatoos
Escaped, dumped
Compete for resources – especially
nesting sites
Prickly pear,
brambles, arum lilies
Escaped, dumped
Competition, reduces native species
Duckweed, water
hyacinth
Escaped, dumped
Chokes water ways
Removal of organisms
Examples of
removed organisms
Reasons for removal
Effects of removal
Wolf, puma
Removal of predators so there
would be more deer to hunt
Overpopulation of deer, ate out the
food supply, ecosystem destruction
Tasmanian tiger
Hunted to extinction (thought to Extinct native species
be danger to livestock)
Trees
Clearing for mining, farming,
housing
Salinity, erosion, loss of habitat for
native species
Hollow logs & dead
wood
Firewood, aesthetics, clearing
for mining, farming, housing
No nesting sites for native birds,
especially cockatoos
Wetland organisms
Filling in for housing or landfill
Salinity, erosion, loss of habitat,
downstream pollution
Elephant, rhino,
orang utan, etc
Poaching for tusks, horns, fur,
pet trade
Disrupts ecosystems, threat of
extinction for some hunted species
Pollution
Examples of pollution
Causes of pollution
Effects of pollution
Carbon dioxide
Combustion –eg cars, factories,
etc
Greenhouse gas  global
warming
Carbon monoxide
Combustion –eg cars, factories,
etc
Poison
Nitrogen dioxide, sulfur
dioxide
Factories, mining
Combines with water in the air
to produce nitric & sulfuric acid
 acid rain
Methane
Ruminants (eg sheep & cattle),
rotting garbage (land fill)
Green house gas global
warming
Fertilizers
Farming, gardens
Algal bloom (eutrophication)
Pesticides
Farming, urban spraying
Ecological magnification
Heavy metals eg
mercury, lead, cadmium
Factories, mining
Poisons
Sewage
Human waste
Algal blooms, disease