7: Environmental Factors & Their Influence

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The Environment: 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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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.

ATMOSPHERE AirContains all the air in Earth’s system.

BIOSPHERE Living ThingsContains all of Earth’s living things—microorganisms, plants, and

animals.

HYDROSPHERE WaterContains all the solid, liquid, andgaseous water of Earth.

Earth’s Spheres

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Atmosphere

EVENT

Biosphere

Lithosphere Hydrosphere

Mt. PinatuboEruption

EcologyEcology• The study of interactions that take The study of interactions that take

place between organisms and their place between organisms and their environment.environment.

• It explains how living organisms It explains how living organisms affect each other and the world they affect each other and the world they live in.live in.

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Abiotic/Biotic factors

– In an ecosystem, there are various factors that affect the survival and welfare of a population.

– These factors are classified as:• abiotic • biotic.

Abiotic/Biotic factors

– 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

Limiting Factors

• 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.

Liebigs Law of the Minimum

• 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 theSoil

Limiting Factor = Nitrogen

–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.

Some further examples of limiting factors:

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

sea

Shelford’s Law of Tolerance

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

Too Much or Too Little!

Range 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 Too wetJust right

Just Right

Too Cold!

Too Hot!

Tolerance Limits

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Tolerance to heavy metals

Variation in ranges of tolerance

Habitat• 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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Ecological Niche

• 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

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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

Specialist species

• 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.

Generalist 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.

Feeding Niches for Wading Birds

Environment:

• 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!!!!!!

An ecosystem:• 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 120C – 220C with an

average temperature of 16 0C 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

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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.

Australian Elevation Map

Soil Distribution in Australia

• 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’s Classification of Australian Vegetation

 • 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).

Foliage cover

Closed > 70% < 10%

Open 30-70%

Open 10-30%

Tall closed forest

Tall Closed Forest

Tall Open Forest

Tall Woodla

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Low closed forest & Tall closed shrublands

Grasslands

Low closed herbfield