Stage 2 Biology – Ecosystems Notes
E3. Characteristics
of communities are determined by environmental conditions
·
Composition of a community is primarily
determined by the environmental conditions of the habitat
·
Regions with similar conditions on different
continents have similar types of producers
·
Adaptations:
o
Plants in Australia are adapted to variable
water levels, fire, high salinity and poor soil
o
Thick waxy cuticle
·
Determining survival of a particular species in
a given habitat
o
Interactions between other organisms (same or
different species)
o
Availability of resources
o
Climate
o
Impact of human activities
·
Sunlight
o
Competition for light in a rainforest, where
plants in the understory only receive low intensity light that filters through
the canopy – limits the types of species that can grow
o
In marine environments – plants do not grow
below 100m – insufficient light
o
Most producers are phytoplankton that live near
the surface that reach deeper into the water
·
Water
o
High temperatures and wind lead to evaporation
o
Only organisms that can survive are those that
can minimise water loss
o
Plants have evolved characteristics –
specialised leaves that store water, waxy cuticles to prevent water loss,
needle shaped leaves with a smaller surface area for evaporation
o
Mammals have specialised excretory systems –
excrete crystalline uric acid to reduce water loss
o
In marine environments, high solute
concentration = mechanisms to excrete salt from tissues
o
Where there is more rainfall, the communities
are higher density, with species that have high water requirements, lots of
leaf litter so many insects and decomposers which provide food for a variety of
consumers
·
Temperature
o
Temperature is critical for metabolism
o
Enzymes denature if the temperature is too high,
and work inefficiently if it is too low
o
Temperature links with water availability (due
to evaporation)
o
Higher temperatures generally are associated
with higher activity and growth of plants and animals
·
Nutrients
o
Plants obtain essential nutrients (phosphates,
nitrates, sulfates) from the soil to build organic materials
o
Plants in nutrient-poor soils must have
adaptations
§
Nitrogen-fixing bacteria in root nodules
§
Insectivorous plants that obtain nutrients from
insects
§
Relationship between roots and fungi
·
Wind
o
Tend to have deeper or more extensive root
systems to provide stability
·
Salinity
o
Need special adaptations to survive in elevated
solute concentrations to prevent dehydration
o
Excrete salts using active transport to maintain
correct salt-water balance
·
Wave action
o
Strong muscular tissue to clamp down on rock
substrate
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