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is our surroundings or external factors and forces (conditions) that affect an organism or a group of organisms
Physical (air, water, soil)
- Biological (biosphere: plants; animals)
Societal (our culture; political system)
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Earth’s Spheres
ATMOSPHERE Air
Contains all the air in Earth’s system.
BIOSPHERE Living Things
Contains all of Earth’s living things— microorganisms, plants, and animals .
LITHOSPHERE Land
Contains all the cold, hard, solid land of Earth’s crust (surface), the semi-solid land underneath the crust, and the liquid land near the center.
HYDROSPHERE Water
Contains all the solid, liquid, and gaseous water of Earth.
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Atmosphere
Mt. Pinatubo
Eruption
Biosphere
Lithosphere Hydrosphere
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• The study of interactions that take place between organisms and their environment.
• It explains how living organisms affect each other and the world they live in.
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– In an ecosystem, there are various factors that affect the survival and welfare of a population.
– These factors are classified as:
• abiotic
• biotic.

– In an ecosystem, there are various factors that affect the survival and welfare of a population.
– These factors are classified as:
• abiotic
• biotic.

Abiotic factors : involve all those factors that are non-living .
• For example-
– Soil pH
– Soil Humidity
– Soil Temperature
– Air Temperature
– Wind Speed
– Sunlight Intensity
– Soil Nutrients

Biotic factors : involve all those factors that are living.
• For example-
– Competitors
– Predators
– Decomposers
– Population Density
– Disease

• Some abiotic and biotic factors affect the organisms sufficiently to limit population growth.
• These are known as limiting factors.
• The factor may be too little in quantity or too much.
• For example, the limiting factor for a plant population near a chemical factory may be the soil pH.

• The success of an organism depends on several requirements, if one of these is present in minimal quantities this will limit the organism regardless of the abundance of the others.

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P Fe K N Ca Mg
Minerals in the
Soil

– No matter how much of the other minerals you have once you run out of nitrogen plants can not grow.
– So nitrogen in this example is the limiting factor.

• Oxygen in a billabong
• Water in a desert
• Light in the ocean depths
• Nutrients in the upper layers of the sea

Organisms have an ecological maximum and minimum, with a range in between which represents the “limits of tolerance”.

• Every population thrives in an optimal range of abiotic factors.
• Beyond this range, one finds less and less numbers of these organisms.
• In an ecosystem, it is harder to represent what this optimal range is, since a host of factors affect the survivability of this population.
• Often, the range is shown for each factor, and this is known as the range of tolerance.

Too dry
Just right
Too wet

Just Right
Too Cold!
Too Hot!

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• A habitat : is an ecological or environmental area that is inhabited by a particular species of animal, plant, or other type of organism.
eg
– an ocean,
– a lake,
– a tree,
– a rotting log,
– the alimentary tract etc
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• The Ecological Niche of an organism describes how that particular individual "fits" into its ecosystem.
• Within its habitat, it must make use of available resources, withstand abiotic and biotic factors, with the help of adaptations
• the role that the individual organism plays in its nonliving and living environment.
Habitat and Niche

An investigation into the niche of two species of barnacles
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Describe what happened to the distribution/realised niche of Cthamalus once Balanus was removed.
Why might this change have occurred?
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The wider the species range of tolerance the greater the potential geographic range or distribution
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• Species that have relatively tightly defined niches and have a narrow range of tolerance .
• Such species are better off when their preferred environment remains stable.
• Pandas are considered to be a specialist species.

• Species that have broad niches and tolerate larger changes in the environment.
• Such species can survive in a variety of different conditions.
• Humans are considered to be a generalist species.

• The description of a niche may include descriptions of the organism's life history , habitat , and place in the food chain .
A ringtailed possum is a nocturnal marsupial herbivore that inhabits a range of forests , woodlands, shrublands and is adapted to urban gardens.

• The external surroundings including all of the biotic and abiotic factors that surround and affect the survival and development of an organism or population .
• Eg Rocks, minerals, soil, water, air, mountains, rivers , oceans, plants , animals etc

• Populations: the number of a specific species of organisms living in a specific habitat at a specific time.
• eg: population of dolphins in Port Phillip bay
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Community: A group of interdependent organisms living and interacting with each other in the same habitat .
eg the Port Phillip Bay Community includes populations of algae. microorganisms, invertebrates, fish , birds, mammals including humans
Dolphins hunting fish using sea snakes!!!!!!
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• is a natural system consisting of all plants, animals and microorganisms (biotic factors) in an area functioning together with all the non-living physical
(abiotic factors) of the environment .
• Ecosystem = habitat + community
Eg
• a billabong ecosystem
• a river ecosystem
• a desert ecosystem,
• Port Phillip Bay etc

• In order to systematically study and understand ecosystems- we make both:
– Qualitative observations
• (eg the water temperature is mild )
– Quantitative observations
• ( eg the water temperature range is 12 0 C – 22 0 C with an average temperature of 16 0 C etc….)
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• Systematic quantitative measurements or monitoring enable us to determine…
• Within habitats there are: microhabitats = small scale differences in abiotic factors
• These variations affect the biotic factors such as type and distribution of species
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• Some methods of monitoring and categorisation of abiotic and biotic factors are very specific or narrow
• These can give us important information about potential effects on the environment and ecosystems
– eg rainfall is a narrow measure however it is a critically important factor which determines what flora and fauna may inhabit an environment

• Climatic factors: individually and together are important descriptors of environment and determinants of the presence and pattern of life in an environment .

• Climate encompasses the statistics of:
– temperature ,
– humidity ,
– atmospheric pressure ,
– wind ,
– rainfall ,
– atmospheric particle count and
– numerous other meteorological elements in a given region over long periods of time.

Mapping individual abiotic climatic factors can reflect biotic patterns

Combining several climatic factors we can classify the Australian environment in to the following major classification zones

Geomophological factors such as:
• altitude
• topology - lay of the land
(flatness/steepness)
• geology rocks- minerals soils
• etc
Are all abiotic factors that are important determinants of biotic distribution.
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• Botanists seeking to understand our vegetation look for patterns in the distribution of identifiable vegetation communities.
• The type of plants and their distribution reflect the underlying geomorphology and climate of the area and in turn affect the distribution of animals and other life.

• Specht developed a system which has become widely used both in Australia and overseas.
• It is based on three elements:
– Identification of the lifeform of the tallest stratum (or layer) of plants in an area (e.g., trees, shrubs, hummock grasses or other herbs).
– Determination of the height and/or type of vegetation in the tallest stratum (e.g., ‘trees over 30m’, or ‘shrubs, non-sclerophyllous’, etc.).
– Determination of the projective foliage cover of the tallest stratum.
This is the percentage of area which is covered by that foliage (leaves).

Closed > 70%
Open 30-70%
< 10%
Open 10-30%

Tall Open
Forest
Tall closed forest
Tall Closed
Forest
Tall
Woodland