1. Biology 3A Biodiversity

2. 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

3. 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)

4. 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

5. 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

6. 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

7. 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

8. 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)

9. 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 out-compete 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

10. 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

11. 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

12. 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

13. 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
Eutrophication
Pollution
Biodiversity
More land is cleared for farming  desertification
More fertilizers are used  eutrophication
More people  more pollution (sewage, combustion, industrial pollution)
Changes in species as some native species are removed and others added (introduced species)

14. 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
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
Corellas, cockatoos
Compete for resources – especially nesting sites
Prickly pear, brambles, arum lilies
Competition, reduces native species
Duckweed, water hyacinth
Chokes water ways

15. 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 be danger to livestock)
Extinct native species
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

16. Pollution Examples of pollution Causes of pollution
Effects of pollution
Carbon dioxide
Combustion –eg cars, factories, etc
Greenhouse gas  global warming
Carbon monoxide
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
Poisons
Sewage
Human waste
Algal blooms, disease