Posts Tagged ‘system’

  • Outline the concept and characteristics of systems.
System: Assemblage of parts and relationships between them, which together make up a whole.
The components are connected together through the transfer of energy and matter, with all parts linking and effecting eachother.
Examples of these are:
  • atoms
  • molecules
  • cells
  • organs
  • organ systems
  • communities
  • ecosystems
  • biomes
  • earth
  • solar systems
  • galaxies
  • universes
Systems consist of:
  • storages ( of matter and energy )
  • flows ( inputs into the system, output from the system )
  • processes (which transfer or transform energy or matter )
  • feedback mechanisms that maintain stability and equilibrium
System diagrams consist of: 
  • boxes show storages
  • arrows show flows (inputs/outputs)
Diagram can be labelled with the processes on each arrow:
  • Photosynthesis – transformation of CO2, H2o and light into biomass and oxygen O2
  • Respiration – transformation of biomass into CO2 and water
  • Diffusion – movement of nutrients and water
  • Consumption – tissue transfer from trophic level to another
  • Apply the systems concept on a range of scales.
There are different scales of systems; there can be small-scale local ecosystem, large ecosystem as a biome, and global ecosystems.
For example: Forests contain many small-scale ecosystems.
  • Define the terms open system, closed system and isolated system.
Open: exchanges matter and energy between the system. They are organic and must interact with environment to obtain new matter and energy. Ex: People are open systems.
Closed: exchanges energy but not matter. Ex: the earth can be seen as a closed system.
Isolated: Neither energy or matter is exchanged. But these systems do not seem to exist. However the universe could be looked at as an isolated system,
  • Describe how the first and second laws of thermodynamics are relevant to environmental systems.
First law:
  • Energy is not created nor destroyed
  • Energy can only change from one to another
  • Ex: solar radiation -> sugars -> chemical energy -> chemical energy again
  • Energy has only moved and changed form
Second law:
  • not efficient energy (the more processes/transfers the less energy)
  • transformations lead to energy loss
  • living systems are only maintained through constant input of new energy from the sun
  • energy= work+heat
  • Explain the nature of equilibria.
Steady-state equilibrium:
Is the common property of most open systems in nature. There is a tendency in natural systems for the equilibrium to return after the disturbances, but some systems (succession) may go through long-term changes to keep their equilibrium while keeping their integrity.
Open systems have steady-state equilibrium, where any change to a stable system returns to the original equilibrium after the disturbance.
Stable changes then goes back to the normal state.
Unstable changes and does not go back to the normal state.
  • Define and explain the principles of positive and negative feedback.
Negative feedback: tends to damp down, neutralize or counteract any deviation from an equilibrium, and promotes stability.
Positive feedback: increases change in a system and deviation away from a equilibrium.
A system may include both feedbacks.
  • Describe transfer and transformation processes.
Both material and energy move or flow throw ecosystems.
Transfers: normally flow through a system and involve a change in location. When the flow does not involve a change in form just location.
Ex: Material through biomass, and energy movement.
Transformations: lead to an interaction within a system in the formation of a new and product, or involve a change of state. A flow involving a change in form.
Ex: Matter and energy transformations, energy to matter transformations.
  • Distinguish between flows (inputs and outputs) and storages (stock in relations to systems)
Inputs and outputs from systems are called flows and represented by arrows in system diagrams. The stock held within a system is called the storage and is represented through boxes.
  • Construct and analyse  quantitative models involving flows and storages in a system.

  • Evaluate the strengths and limitations of models.
  • allow scientist to predict/simplify complex systems
  • inputs can be changed and outcomes examined without having to wait for real events.
  • results can be shown to scientists and the public
  • might not be totally accurate
  • rely on the expertise of people making them
  • different people may interpret them in different ways
  • vested interests might hijack them politically
  • any model is only as good as the data goes in and these may be suspect
  • different models may show different effects using the same data

  • Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem along an environmental gradient.
Ecological gradients are often found where two ecosystems meet. Biotic and abiotic factors change and form gradients in which then can be recorded. All parts of the gradient needs to be sampled, so a transect is used. The simplest one is when a line of tape is layed down across the area wanted to be measured then to take samples of all the organisms touching the tape. Many transects should be taken to obtain quantitative data. A belt transect is used for bigger samples.
  • Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem due to a specific human activity.
Chernobyl 1986, Russia:
Nuclear reactor blew up
  • design drawback
  • human errors due to poor supervision
The cause:
This caused an increase in thermal power which lead to more explosions. This contaminated soil, plants and animals.
  • Fire fighters tried to turn it off, it took 5000 tonnes of sand, lead and clay.
  • The UN gave £75 million to make it safe and it was fixed by an international team ten years later.
  • People had to evacuate 30km away
  • The town was cleared of everything
  • 15cm of soil depth was removed
  • land washed away and dams were built
  • wall built around it
  • food was contaminated
  • Describe and evaluate the use of environmental impact assessment (EIA).
EIA: Environmental Impact Assessment
Process for identifying the likely consequence for the biophysical environment and for man’s health and welfare of implementing particular activities and for conveying information at a stage where it can materially affect the decision, to those for sanctioning the proposals. (long definition)
Purpose of the EIA:
Helps the decision making process by providing information about the consequences of the environment. Promotes sustainable development by identifying environmentally sound practice and migration measures for development.
Used for: 
Planning process that governments set out in law when large developments are considered. They provide a documented way of examining environmental impacts that can be used as evidence in the decision making process of any new development.
What developments used in the EIA:
  • Major new road networks
  • Airport/port developments
  • Building power stations
  • Building dams and reservoirs
  • Quarrying
  • Large scale housing projects.
  • Explain the role of producers, consumers and decomposers in the ecosystem.
Producer: can make their own food, as they use sunlight to make food and are called  the basis of every ecosystem which helps the rest of the species through input of energy and new biomass. This all happens through photosynthesis which is the process when the producer uses the sun for energy.
Consumer: feed on other organisms, they do not contain photosynthesis pigments so they cannot make their own food. They have to get energy, minerals and nutrients by eating other organisms. This makes the heterotrophs. Herbivores feed on autotrophs, carnivores on other heterotrophs and omnivores on both.
Decomposer: get their food from the breakdown of a dead organism matter. They break down tissue and release nutrients for absorption by other producers. Decomposers also improve the nutrient capacity in the soil by breaking down the organic material.
  • Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.
Photosynthesis: needs carbon dioxide, water, chlorofyll and certain visible wave lengths of light to produce organic matter and oxygen.
  • inputs: sunlight as energy resource, carbon dioxide and water
  • processes: chlorofyll traps sunlight; energy is used to split water molecules; hydrogen from water is combined with carbon dioxide to produce glucose.
  • outputs: glucose used as an energy source for the plant and as a building block for other organic molecules; oxygen is released to the atmosphere through stomata.
  • transformations: light energy is transformed to store chemical energy.
Respiration: needs organic matter and oxygen to produce carbon dioxide and water.
  • inputs: glucose and oxygen
  • processes: oxidation processes inside cells
  • outputs: release of energy for work and heat
  • transformations: stored chemical energy to kinetic energy and heat
  • Describe and explain the transfer and transformation of energy as it flows through an ecosystem.
Not all solar radiation ends up being stored as biomass. Losses include_
  • reflection from leaves
  • light not hitting chloroplasts
  • light of the wrong wavelengths (not absorbed by chloroplast pigments)
  • transmission of light through the leaf
  • inefficiency of photosynthesis
In this diagram we can see the energy flow through an ecosystem.
  • Describe and explain transfer and transformation of materials such as they cycle within an ecosystem.
The Carbon Cycle:
The Hydrological cycle:

The nitrogen cycle:
  • Define the terms gross productivity, net productivity, primary productivity, and secondary productivity.
*Productivity is production per unit time.
Primary productivity is the gain by producers (autotrophs) in energy or biomass per unit area per unit time. It is when solar energy is converted, it depends on the amount of sunlight the ability of the producers to use energy to synthesize organic compounds and the availability of other things needed for growth, like minerals and nutrients.
Primary production is highest were conditions for growth are optimal, where there are high levels of insolation, good water supply, warm temperatures and high nutrient levels.
You can then divide primary productivity into gross and net profits.
*GROSS is the income
*NET is the incomes minus costs
Secondary productivity depends on the amount of food there is and the efficiency of the consumers turning this into new biomass. Unlike the primary productivity net productivity involves feeding or absorption.
Gross productivity (GP): The total gain in energy or biomass per unit area per unit time.
Net productivity (NP): The gain of energy or biomass per unit area per unit time remaining after allowing for respiratory losses. It is the energy left for the next trophic level to consume.
  • Define the terms and calculate the values of both gross primary productivity and net primary productivity from given data.
Gross primary productivity (GPP): is gained through photosynthesis in primary producers.
Net primary productivity (NPP): is the gain by prodicers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses. (Available for consumers in ecosystem)
Productivity calculation:
Primary productivity:

where R = energy used in respiration
  • Define the terms and calculate the values of both gross secondary productivity and net secondary productivity from given data.
Gross secondary productivity(GSP): is gained through absorption in consumers.
Net secondary productivity(NSP): The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses.
Secondary productivity:
GSP = food eaten – faecal loss
where R = respiratory loss
  • Construct simple keys and use published keys for the identification of organisms.

Keys called dichotomous keys are used to identify species, the key is written so that the identification is done in steps. At each step two options are given based on different possible characteristics of the organism you are looking at.  You go through all the steps until the name of the species is discovered. This is an example of a dichotomous key that divides 4 types of egg-laying species:

For the exams you need to have at least eight species in the key you construct. This can also be shown graphically:

  • Describe and evaluate methods for estimating abundance of organisms.
It is impossible for you to study every organism in an ecosystem, so limitations must be put on how many plants and animals you study. There are trapping methods which help obtain more samples, like:
  • pitfall traps
  • small mammal traps
  • light traps
  • tullgren funnels
You can either count them all or using percentage cover of an organism in a selected area or by using the Lincoln index and calculating the abundance.
Lincoln index:
This method allows you to estimate the total population size of an animal in your study area. This method includes collecting a sample from a population, then marking them like painting or attaching something to the animal, releasing them back into the wild, then resampling some time later and counting how many marked individuals you find in the second capture. IT is important to take into consideration that the marking methods are not harmful to the animal and clear so that they do not become easy targets for prey.
This method is also known as capture-release-mark-release-recapture techniques because of the processes involved. If all the marked animals are recaptured that is assumed to be the total population size of that species. whereas if half of the species is captured it is estimated to be twice as much as the first sample. The formula used to calculate population size:
N= total population size of animals in the study site
n1= number of animals captured of first day
n2= number of animals recaptured
m= number of marked animals recaptured on the second day
N= (n1 x n2) / m
Quadrats are used to measure the percentage cover of a certain species. Ecologists want to find out how many organisms are living in a specific area, however they cannot count them all so they make a sample count. Percentage cover is the area within the quadrat being used by one particular species.
Percentage cover is worked out for each species present. Dividing the quadrat into a 10×10 grid helps to estimate percentage cover.
Sample methods must allow for the collection of that is scientifically representative and appropriate, and allow the collection of data on all species present. Results can be used to compare ecosystems.
Percentage frequency is the percentage of the total quadrat number that the species was present in.
  • Describe and evaluate methods for estimating the biomass of trophic levels in a community.
*Biomass:  the mass of organic material in organisms or ecosystems, usually per unit area. Biomass is calculated to indicate the total energy within in a living being or trophic  level. The greater the mass of the living material the greater the amount of energy present. Biomass is taken as the mass of an organism minus water content, like dry weight biomass. Water is not included in biomass measurements because the amount varies from organisms to organism, it does not contain energy and is not organic.
To obtain the samples, the biological material is dried to constant weight. It is then weighed. The specimens are then heated in a  oven which is not hot enough to burn the tissue and left for a certain amount of time. Biomass is usually measured per unit area so that comparisons can be made between the trophic levels present.
  • Define the term biodiversity.
Diversity is often considered as a function of two components: the number of different species and the relative numbers of individuals of each species. This is different from species richness, which refers only to the number of species in a sample area.
  • Apply Simpson’s diversity index and outline its significance.
There are many ways of quantifying diversity, one of the ways is using the Simpson’s diversity index:
D= diversity index
N= total number of organisms of all species found
n= number of individuals of a particular species
E= sum of
D= (N(N-1)) / (En(n-1))
*It is not important to remember the whole formula, but good to know the meaning of the symbols.
D is a measure of species richness. A high value of D suggests a stable and ancient site, and a low value of D could suggests pollution, recent colonization or agricultural management. The index is normally used in studies of vegetation but can also be applied to comparisons of animal diversity.
  • List the significant abiotic (physical) factors of an ecosystem.

Ecosystems can be divided into 3 types:

  • Marine: the sea, salt marshes mangroves are all characterized by the salt content.
  • Freshwater: rivers, lakes and wetlands.
  • Terrestrial: land-based.

Each ecosystem has its on abiotic factors:


  • salinity
  • pH
  • temperature
  • dissolved oxygen
  • wave action


  • turbidity
  • flow velocity
  • pH
  • temperature
  • dissolved oxygen


  • temperature
  • light intensity
  • particle size
  • slope/aspect
  • soil moisture
  • drainage
  • mineral content
  • Describe  and evaluate methods  for measuring at least three abiotic (physical) factors within an ecosystem.

Abiotic factors that can be measured within an ecosystem include the following:


  • salinity: this can be measured  using electrical conductivity ( with a datalogger) or by the density of the water (water with high salt content is more denser than low-salt water).
  • pH: this can be measured using a pH meter, or datalogging pH probe. Indicator solution may also be used.
  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • dissolved oxygen: a meter with oxygen-sensitive electrodes connected that measures dissolved oxygen. One should be careful as doing things wrong may contaminate the air.
  • wave action: this is measured by using a dynomometer which measures the force in waves.


  • turbidity: can be measured using a Secchi disc, nephlometer or turbidimeter.
  • flow velocity: can be measured by timing how long it takes a floating object to travel a certain distance or by using a flow-meter.
  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • dissolved oxygen: a meter with oxygen-sensitive electrodes connected that measures dissolved oxygen. One should be careful as doing things wrong may contaminate the air.


  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • light intensity: is measured using a light-meter.
  • wind speed: a Beufort-scale is used to measure wind speed and precise measurements can be made with a digital anemometer.
  • particle size: this determines the drainage and water-holding capacity and is measured by using a series of sieves.
  • slope: this is measured using a clinometer and using a compass.
  • soil moisture: by weighing the samples then heating them it shows the amount of water that has evaporated and the moisture levels.
  • mineral content: the loss on the ignition test can determine mineral content. The samples are heated for several hours to let volatile substances to escape.
Abiotic data can be collected using instruments that avoid issues of objectivity as they directly measure quantitative data. Instruments allow us to record data that would otherwise be beyond the limit of our perception.
  • Outline how soil systems integrate aspects of living systems.

Soil forms the Earth’s atmosphere, lithosphere (rocks), biosphere (living matter) and hydrosphere (water). Soil is what forms the outermost layer of the Earth’s surface.

Soils are important to humans in many ways:

  • soil is the medium for plant growth, which most of foods for humans are grown in
  • soil stores freshwater, 0.005% of world’s freshwater
  • soil filters materials added to the soil, keeping quality water
  • recycling of nutrients takes place in the soil when dead organic matter is broken down
  • soil is the habitat for billions of micro-organisms, as well as other larger animals
  • soil provides raw material in the forms of peat, clay, sands, gravel and minerals

Soil has matter in all three states:

  • organic and inorganic matter form the solid state
  • soil water form the liquid state
  • soil atmosphere forms the gaseous state

* Soils are an important source for humans and take time to develop and therefore be counted as a non-renewable resource.

The Soil System

O – Organic Horizon:

  • l – undecomposed litter
  • f – party decomposed litter
  • h – well decomposed humus

A – Mixed mineral-organic Horizon:

  • h – humus
  • p – ploughed in field or garden
  • g – gleyed or waterlogged

E – Eluvial or leached Horizon:

  • a – strongly leached, and ash coloured
  • b – weakly bleached, light brown

B – Illuvial or deposited

  • Fe – iron deposited
  • t – clay deposited
  • h – humus deposited

C – Bedrock or parent material

  • r – rock
  • u – unconsolidated loose deposits

Transfers of materials (including deposition) results in reorganization of the soil. There are inputs of organic and parent material precipitation, infiltration and energy-outputs include leaching, uptake by plants and mass movement. Transformations include decomposition, weathering and nutrient cycling.

  • Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity.

Soil structure depends on:

  • Soil texture ( the amount of sand and clay )
  • dead organic matter
  • earthworm activity

For optimum struction, variety of pure sizes are required to allow root prevention, free drainage and water storage. Pore spaces over 0.1 mm allow roots growth, oxygen diffusion and water movement where as pore spaces below 0.5 mm help store water.


  • fertile in temperate locations
  • in tropical areas clay is permeable and easily penetrated by roots
  • nutrient deficient / easily  leached in tropics

The more clay present in soil the higher the force needed to pull a plough.

Different soil types have different levels of primary productivity:

  • sandy soil – low
  • clay soil – quite low
  • loam soil – high

Primary productivity of soil depends on:

  • mineral content
  • drainage
  • water-holding capacity
  • airspaces
  • biota
  • potential to hold organic materials

*Shrinking limit: state which the soil passes from having a moist to a dry appearance.

*Plastic limit: occurs when each ped is surrounded by a film of water sufficient to act as a lunricant.

*Liquid limit: occurs when there is sufficient water to reduce cohesion between the peds.

*Field capacity: maximum amount of water  that a particular soil can hold.

  • Outline the processes and consequences of soil degradation.

*Soil degradation: the decline in quantity and quality of soil. It is also erosion by wind and water, biological degradation (loss of humus and plant or animal life), physical degradation (loss of structure, changes in permeability), chemical degradation (acidification, declining fertility, changes in pH, salinity).

Causes of degradation:

  • Overgrazing: reduces the vegetation cover and allows the surface to be vulnerable to erosion. Dry regions are vulnerable to wind erosion.
  • Deforestation: removed of woodland cause roots in the soil to die and exposure to erosion if on slopes.
  • Cultivation: exposure of the bare soil before/after planting can cause large amounts of run-offs and create rills and gullies. Irrigation in hot areas can cause salinization.
  • Climate change: the higher the  temperature and changing precipitation patterns can lead to direct impacts on soil. Higher temperatures cause higher decomposition of organic matter. More precipitation and flooding cause more water erosion and droughts cause more wind erosion.

Many forms and causes of degradations:

  • Water erosion ( 60% of soil degradation)
  • Wind erosion
  • Acidification (toxification), when the chemical composition of the soil is changed.
  • Eutrophication (nutrient enrichment).
  • Desertification can be caused in extreme cases.
  • Climate can intensify the problem and effect of hydrology.

This shows that the soil degradation’s damage is world spread and has occurred on 15% of the world’s total area.

  • Outline soil conservation measures.

Strategies for combating soil degradation is not so common or widespread and to reduce this risk farmers are encouraged and informed about the processes and conservation methods. Farmers are in the need of beginning with extensive management practices like organic farming, afforestation, pasture extension, and benign (gracious) crop production. However to make this work there is a need of policies.

There are a few methods to reduce or prevent erosion, which can be mechanical or vegetation cover and soil husbandry.

Mechanical methods: are used to reduce water flow including bunding, terracing, and contour ploughing. The goal is to prevent and slow down the movement of rain water down the slopes.

Cropping and husbandry methods:

This method is used against water and wind damage.

It focuses on:

  • keeping the crops safe as long as possible
  • keeping the ground and place of the crop stable after harvesting
  • planting a grass crop

Grass crop keeps the action of the roots in binding the soil and also it decreases the action of wind and rain on the soil surface. with increased organic content it allows the soil to hold more water and reduce the mass, movement and erosion and stabilizing the soil structure.

To prevent damage to the soil structure, care should be taken to reduce the use of heavy machinery is necessary especially on wet soils and ploughing on soils that are sensitive to erosion.

Management of salt-affected soils:

The three main ways of managing salt-affected soils is by:

  • flushing the soil with water and leaching the salt away
  • putting chemicals to replace sodium ions on the clay and colloids with calcium ions for example by using gypsum a calcium sulphate
  • reduction in evaporation losses to reduce the upward movement of water in the soil

Summary of the conservations methods:

Both socio-economic and ecological factors have been ignored and integrated approach to soil conservation is needed, non-technological factors like population pressure, social structures, economy and ecological factors can determine the appropriate technical solutions. There are a variety of methods to use like  strip and ally cropping, rotation farming, contour planing, agroforestry, adjusted stocking levels mulching, use of cover crops, construction of mechanical barriers such as terraces, banks and ditches.