A Local Ecosystem

Abiotic features of the environment

Abiotic features are the non-living

components of the environment. They

include, Physical features: temperature, rainfall,

wind, light intensity, humidity, soil type, water, landform

Chemical features: pH of soil or water, salinity, availability of gases

Biotic features of the environment

Biotic features are the living components of

the environment. This includes: Plants Animals Micro-organisms

Aquatic environments

Environments can be

classified as aquatic (water)

or terrestrial (land). Aquatic

environments can be either

freshwater or marine

(saltwater).

Terrestrial environments

Terrestrial environments are found in

different climates and range from deserts,

grasslands

and rainforests to

mountain regions.

Aquatic v’s terrestrial

Organisms living in aquatic and terrestrial

environments have to survive different abiotic

conditions. When comparing the difference

between the two it is necessary to look at

features such as: buoyancy, pressure,

temperature, availability of gases, light

penetration and viscosity.

Community and populationA community can be defined as the set of

interacting organisms within an ecosystem. A

population is a group

of individuals of the

same species

living in the

same area.

Distribution

Distribution refers to the region where an

organism is found.

Distribution of rabbits in AustraliaAdapted from: Clarke GM et al (2000). Environmental Pest Species in Australia. Internal report, Department of the Environment and Heritage, Canberra.

Transects

The distribution of plants can be determined

by marking out a straight line across an area,

noting the types of plants present, and plotting

their position along this line on a diagram. This

indicates the distribution of plants along a cross-

section of the ecosystem. This cross-section is

called a transect.

Transects

Georges River Environmental Education Centre http://www.georgesriv-e.schools.nsw.edu.au/Vegetation_study.htm

AbundanceAbundance is the number of individuals of the same species within an area. Abundance is usually found by taking small samples of a community and using the data to estimate the population in the

ecosystem as a whole.

Quadrats

The abundance of a plant species is often found

by marking out quadrats. Individuals within the

quadrats are counted and the average number

per area (density) is calculated. This information

can then be used to estimate the abundance in

the whole ecosystem. The more quadrats used,

the more accurate the estimate.

Quadrats

Capture – mark - recapture

This method of sampling involves: catching a number of individuals of a species marking or tagging them releasing them again at a later time catching another group and

counting the number of tagged individuals among them

This method is useful for mobile populations.

Trends in population estimates

Variable that can influence population size over time include, Birth rate Death rate Migration rate Environmental factors such as availability of

food, shelter and water, presence of predators

Photosynthesis

The initial source of energy in an ecosystem is light from the sun. Some of the light absorbed by plants is converted through photosynthesis into chemical energy in the form of carbohydrates such as glucose. Photosynthesis is summarised as:

lightcarbon dioxide + water glucose + oxygen

REACTANTS ENERGY PRODUCTSSOURCE

Respiration

Some of the glucose produced by

photosynthesis is broken down during the

process of respiration. Respiration can be

summarised as follows:

Glucose + oxygen water + carbon + energy

dioxide

The energy produced during respiration is then

used for cellular processes.

Energy transfer in an ecosystem

Light energy

Chlorophyll

Photosynthesis Glucose Transported through the plant

Respiration

Energy for cell processes

Converted into carbohydrates

Uses of energy by organisms

Living organisms need a constant supply of

energy to maintain cellular activities and stay

alive. In ecosystems the initial source of energy

is light from the sun. This is used by plants

during photosynthesis to produce carbohydrates.

Organisms (i.e. plants) that can manufacture their

own food from inorganic materials are called

autotrophs.

Producers and consumers

Green plants provide the entire input of energy to an ecosystem and are called producers. When animals (herbivores) eat plants, the carbohydrates stored in plants are converted back into glucose. The glucose is broken down during respiration to provide the animal’s energy requirements. Similarly, when carnivores eat other animals, this chemical energy is passed on.

Energy transfer in ecosystems

PlantEaten by

animal

Carbohydrates digested to

glucose

Respiration

Energy for animal cellular

process

Converted into other

substances

Food chains and websFood chains show the flow of energy through

ecosystems.

grass wallaby dingo

PRODUCER FIRST ORDER CONSUMER

SECOND ORDER CONSUMER

Trophic levels

Animals are consumers. An organism that feedson plants is a first-order consumer. An organism that feeds on a first-order consumer is called a second-order consumer, and so on. The level occupied by a consumer in a food chain is referred to as a feeding or TROPHIC level. First-order consumers occupy the first trophic level; second-order consumers occupy the second trophic level, and so on.

Food websThe interrelationship between many food chains

is called a

food web.

Biomass

Biomass is an estimate of the amount of matter

in a given population of organisms. Biomass

for different trophic levels is compared in a

biomass pyramid. A biomass pyramid shows

how the quantity of matter in living things

changes along a food chain.

Biomass pyramidThe base of the pyramid

represents the matter in

producers. The next level shows biomass of

1st order consumers

and so on.

Biomass pyramid

At each level in the pyramid biomass is smaller

than in the trophic level below. At each level

biomass is lost.

An energy pyramid shows the total energy in

trophic levels and how that energy is lost

along a food chain.

Energy pyramid

Decomposers

Organisms that use the organic matter of

dead plants and animals are called

decomposers. They release digestive enzymes

to break down organic matter and then absorb

the products of digestion. Decomposers include

fungi and bacteria. Decomposers do not fit

readily into one trophic level.

Competition for resources

Competition is a relationship in which two

organisms compete for a limited resource.

In the short term this results in a decrease in the

abundance of one of the species. In the long

term it can result in extinction of the less

successful species.

Competition for resources.

Competition is one pressure that influences the

evolution of organisms. For example,

competition is one of the factors that results in

organisms adapting to occupy distinct niches.

Adaptations

All organisms have adaptations that help them to survive. Organisms that are adapted to their environment are able to: obtain air, water, food and nutrients cope with physical conditions such as

temperature, light and heat defend themselves from their natural enemies reproduce respond to changes around them

Adaptations

Structural adaptations are the physical characteristics of an organism (e.g., skin color, shape, body covering).

Behavioral adaptations are the ways in which an organism behaves.

Physiological adaptations are those that allow an organism to perform certain biochemical reactions (e.g., making venom, secreting slime, being able to keep a constant body temperature).