Environmental Factors and their Influence
Environmental change happens in almost all places on earth. Consequently, all life forms (biota) have to be able to
must adapt to their environmental conditions in order to survive. Organisms adapt in three main ways: structurally,
physiologically (body functioning) and behaviourally.
The biosphere is the layer of the Earth that includes the water, lower atmosphere and soil. The biosphere is made up
of biomes, areas that contain common features. Examples of biomes include terrestrial and aquatic.
Environmental Factors
Environmental factors can be classified as ‘abiotic’ or ‘biotic’.
Abiotic factors are physical or chemical factors. They include things like soil pH, soil texture, temperature, light
intensity, concentration of nutrients in air or water and the availability of water. The nutrient and water cycles play
a significant part in the abiotic factors of an environment.
Biotic factors are to do with other living things that affect an organism.
Tolerance limits
Most species have a tolerance range and a tolerance limit in their abiotic factors. The tolerance range is the
conditions in which a species functions best. Outside that range, the species becomes stressed and its functioning is
affected. This is called its tolerance limit.
The optimum range is referred to as the ‘preferred niche’ of an organism. The more an organism can adapt, the
wider its optimum range and the wider its geographic range.
Ecosystems
An ecosystem consists of a habitat and the community of organisms living within it. Ecosystems usually have a
degree of cycling or exchange within them e.g. water and nutrient cycling. Ecosystems are often described by their
climate and vegetation types e.g. tropical, desert, grassland, temperate or rainforest, woodland, heath, grassland.
Scientists often look at the tree height and % cover they provide in an area to determine the type of vegetation. A
transect (cross-section across an area) is usually used in determination, as are soil factors and the gradient of the
landscape.
Transect across an area
Living on Land and Living in Water
Plants are photosynthetic. They utilise sunlight, water and carbon dioxide from their environment to produce
oxygen and glucose for energy.
Photosynthesis:
Carbon dioxide + water  glucose + oxygen + water
6CO2 (g) + 12H2O (g)  C6H12O6 (l) + 6O2 (g) + 6H2O (g)
Note: This is a biological equation. The process involves both the absorption of water and production of water. The
water is not at the start is not the same as the water at the end as all the elements mix up. In a chemical equation,
the process is simplified to have water only as a reactant.
Many plants have to cope with extremes in their environment. A plant living in a terrestrial environment, has to
cope with significant temperature changes. In an aquatic environment, the temperature is considerably more stable
as the water absorbs heat during the day and releases it during the night. This is called latent heat transfer (latent
means hidden). It is also the reason why coastal areas or those near large bodies of water do not experience such
extremes of temperature. The water regulates the environment. Temperature also affects how much oxygen
dissolves in the water. The colder or deeper the water, the less oxygen it contains.
Plants need to exchange gases from their environment in order to photosynthesise. This mostly occurs on their
leaves. The cells in plant leaves contain chloroplasts: green cells that absorb light energy for photosynthesis. Many
plants have adapted their leaves to suit their environment: in very hot areas, the leaves dangle to reduce the area
exposed to the sun, they can also be shiny to reflect excess heat and light. Stomata cells in the leaves are in charge of
regulating gas exchange and water loss. Underwater absorption of gases is more difficult than on land. One example
of a difficult environment is mangroves. Mangroves grow in waterlogged soils in tropical regions. When soil
becomes waterlogged, it contain very little dissolved oxygen. Mangrove plants grow pneumatophores or peg roots
(roots growing straight up out of the water into the air) which link into their underground root systems. In this way,
they can exchange their gases in the air where it is easier.
Availability of light is also a concern for plants, especially those living in water. The deeper the body of water, the
less light penetrates. Consequently, those organisms living deep below the water surface have to adapt and find
alternate ways to generate energy.
Other concerns for plants are water balance (ensuring sufficient water remains within the cells) and support systems
(making sure they stay in their environments e.g. root systems).
How do plants survive bushfires?
Many Australian plants have adapted to the occurrence of bushfires by utilising the fires heat in order to regenerate.
Some species produce huge numbers of seeds in the surrounding soils that germinate after a fire has been through
the area. Germination is often a combination of the high heat cracking the seed casings and the increased
availability of light that encourages growth.
Other species develop thick bark to protect growth buds underneath. These are called epicormic buds. Growth is
once again stimulated by an increase in light availability.
Others again develop lignotubers: bulbous root systems at the base of a plant. The lignotubers contain huge
numbers of growth buds and because they are so dense and chunky, they are not as affected by fire as the thinner
trees they produce.
Ecosystems: Relationships and Populations
Ecologists study the relationships between living things and their surroundings. An ecosystem is not really a place,
although we tend to use the word in that way. An ecosystem is a framework for studying the interactions between
living things and their non-living surroundings (i.e. their environment). E.g. a forest ecosystem includes not only all
the organisms that make up the community living there, but also aspects of the physical environment such as
rainfall, nutrient levels, sunlight, oxygen and carbon dioxide. All these factors interact with each other in a system we
call an ecosystem.
Habitat + community = ecosystem
Draw a concept map that shows the relationship between the following:
- Biosphere
- Habitat
- Ecosystem
- Community
- Biome
- Environmental factors
As mentioned previously, ecosystems are mostly named after the dominant species in the community, together
with its overall layout. E.g. river red gum woodland, mangrove swamp, alpine herb field. All ecosystems are relatively
self-contained. It tends to support itself by cycling or exchanging materials within the ecosystem. E.g. in a forest, the
leaves of trees fall and decompose, returning nutrients to the soil which later may be reabsorbed if they combine
with water and get taken in by the tree roots and utilised for the trees growth. Although cycling does occur, we
generally refer to ecosystems as being open as opposed to closed. Animals are able to move between different
ecosystems and communities, so not everything is recycled.
Indicator species: Frogs in Decline
Research task: Cane Toads
Write a couple of paragraphs summarising what you find out. Make sure you include the following.
What is their life cycle and niche environment? Why were they introduced? Was the introduction successful? Why
are they now considered a problem? What is currently being done about them?