Saltwater - open seas, estuaries and saltwater lakes.
Approximately 65% of the Earth's surface is covered
by oceans. Tides, currents, waves and wind
continuously move the water in the surface layers.
Freshwater - includes still water such as lakes and
ponds, swamps, and moving water such as springs
creeks and rivers.
Terrestrial environments vary as a result of
topography, climate, availability of water, and
Examples: rainforest, open forests, mountain
tops, deserts, grasslands, farms and cities.
A group of living organisms of the same kind
living in the same place at the same time.
Organisms living together in a particular place.
The habitat of an organism is the place where it lives.
These can vary in size e.g. desert, under tree bark,
within the digestive system of another organism.
Ecosystems will fail if they do not remain in
No community can carry more organisms than
its food, water and shelter can accommodate.
Food and territory are often balanced by
natural phenomena such as fire, disease, and
the number of predators.
Temperature (daily and seasonal)
Topography (altitude and depth)
Tides, currents and waves
Water (salinity, pH and availability)
Substrate (surface on which an organism grows or is
Space and shelter
Availability of food
Number of competitors
Availability of mates
Number of predators
Disease causing organisms
Limiting factors - anything that makes it
difficult for a species to live and grow, or
reproduce in its environment.
Organisms have roles in ecosystems:
Producers - organisms that make their own food
using the energy of sunlight - plants.
Consumers - obtain their food by consuming other
creatures - if they consume a producer then they are
primary consumers or herbivores - if they consume
herbivores they are secondary consumers or carnivores.
If they consume carnivores they are tertiary consumers or
carnivores. Some species eat both producers and other
consumers and they are called omnivores. Some
creatures eat dead producers or consumers and are called
Bacteria and fungi that
break down dead organic
have an important role in
ecosystems - they absorb
nutrients from dead
organisms or waste
materials and return
organic matter to the soil.
Food chains are simple ways of representing
feeding relationships among organisms.
Grass > insect > spider > bird
Food webs show the feeding relationship of all
organisms in a particular location (food web = many
food chains intertwined together).
Photosynthesis is the process by which plant cells
capture energy from sunlight and use it to combine
carbon dioxide and water to make sugars and oxygen.
Six molecules of water plus six molecules of carbon
dioxide produce one molecule of sugar plus six
molecules of oxygen.
All living things ultimately depend on this process -
Organisms that consume the plants gain nutrients
and energy, animals that eat the plant-eaters gain
energy from them, therefore the energy is passed on.
Respiration is the process by
which cells obtain energy.
Organic molecules (particularly
sugars) are broken down to
produce carbon dioxide and
water, and energy is released.
This is a feeding relationship
in which one animal
(predator) obtains its food by
killing another animal (prey).
This relationship increases
the predators chance of
survival and reproduction at
the expense of the preys.
The production by a plant of specific chemicals that can
be detrimental or beneficial to another plant.
These chemicals influence the growth and development
of neighboring plants by repelling predators and
parasites, or poisoning competitors.
E.g. Camphor produced in
leaves of the camphor
laurel tree accumulates in
the soil, preventing
germination or growth of
seedlings around each
A parasite obtains its food from a host. Although the host
is harmed in some way, it does not necessarily die. Most
free-living organisms have parasites. Many bacteria,
viruses and fungi which cause diseases are parasites.
Other relationships involve ticks, fleas and tapeworms.
A type of interaction between organisms where two
different species live together in a close association.
The association benefits at least one of them, and
the other is not disadvantaged. The two types of
symbiosis are commensalism and mutualism.
If two organisms are more
closely associated so that
A relationship that benefits one species and does not
harm the other. The organisms are not dependent on
this type of relationship: they could survive without each
Competition is the struggle between organisms for the
A particular ecosystem can support only a certain
number of each type of species. Competition may be
between members of the same species, or between
members of different species.
Short term - competition reduces the chance of
survival and restricts the abundance of all of the
Long term - one of the competitors will usually be
more successful and drive out or reduce the numbers
of other competitors.
How Ecosystems Respond to Change
• Wildfires are a relatively common event in
Australia. Many Australian plants have the
ability to survive regular burning.
• Banksias – this plants ripe seeds can stay on
the tree for years waiting for a fire to release
• Over time as Australia became warmer and
drier - both plants and animals evolved with
adaptations to enable them to survive this
• Australia’s vegetation is dominated by two
groups of flowering plants which have
successfully evolved to colonise a wide variety
of habitats – acacias (wattles) and eucalypts.