Archive for March, 2011

  • 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.

  • Outline the range of energy resources available to society.

Energy can be generate by both non-renewable and renewable resources:

  • Renewable resources like solar, hydroelectric, geothermal, biomass, and tidal schemes are all sustainable as there is no depletion of natural capital. These energy resources can be large-scale for a whole country or small-scale for houses or communities for example.
  • Non-renewable resources however cannot be replenished at the same rate it is used which leads to depletion of the stock, examples of these are fossil fuels like coal, gas and oil. Nuclear power can be considered as a non-renewable source as the source of fission is uranium, which is non-renewable.

Energy consumption is much greater in the MEDCs as the LEDCs do not have the technology to have such energy resources used. MEDCs use a lot of energy from fossil fuels as it was not that it caused pollution and global warming when first adapted as a primary source of energy generation. The main reason for non-renewable energy consumption being used is that it is the cheaper and easier choice. Renewable sources of energy are a bit slow when being adopted globally, compared to non-renewable sources it is expensive and still be newly used which makes them vulnerable to failures. Non-renewable resources are generally cheaper and can be burned directly. The technology at the moment is ready for this type of energy and no set-up costs are required. The cost of the non-renewable energy is likely to increase as the stocks will be depleted, especially the resources that are easily to mine, leaving the resources harder to mine. Which will cost a lot to reach. This will make fossil fuels more expensive and then renewable energy sources will be more popular and used more.

  • Evaluate the advantages and disadvantages of two contrasting energy sources.


Fossil fuels:


  • cheap
  • plentiful
  • technology exists
  • oil can be transported over long distances by pipeline


  • contributes to climate change (builds up carbon dioxide in atmosphere)
  • unsustainable (liquidation of stock over time)
  • will become difficult to extract ( becomes dangerous as they go further into the sea or deeper into the ground)
  • oil spillages and pipelines burst damage ecosystems ( expensive to clear up)
  • mines clear up habitat from surface
  • coal not easily transported over long distance

Nuclear Energy:


  • does not emit carbon dioxide
  • technology is available
  • vast amounts of electrical energy produced by a single power plant
  • very efficient ( 1kg uranium contains 20000 times more energy than 1kg of coal


  • nuclear waste is VERY dangerous, remains for thousands of years with no solution found yet
  • the more power plants, the higher risks of having a disastrous failure somewhere in the world
  • uranium is the energy source which is scarce and a non-renewable source with a estimated time of 30-60years left before depletion (depending on demand)
  • time to plan/build a nuclear plant is 20-30 years



  • no pollutants released
  • will not  run out (renewable hello)
  • small ecological footprint


  • expensive to set-up
  • need to set them up
  • might spoil environment for people living nearby

Hydroelectric power:


  • blocked lake can be used for leisure, irrigation and electricity generation
  • once built they are cheap to run


  • vast areas may be flooded, which causes loss of homes, farmlands and displacement of people
  • expensive
  • erosion rates increase
  • might silt up area and become unusable

Tidal Power:


  • expensive
  • might be harmful to wildlife
  • needs good tidal range

Solar energy:


  • solar energy with insulation is cheaper than fossil fuel energy when heating homes


  • expensive
  • useless in winter in northern countries

Wind Power:


  • no wind = no energy
  • placement is critical, needs constant wind



  • produces emissions
  • requires large areas of land to plant biofuel crop
  • pushes up food prices
  • locals do not get enough food
  • may destroy surrounding ecosystems to grow on



  • available
  • does not deplete natural gas
  • useful way of getting rid of waste


  • global warming gases released into atmosphere

Geothermal energy:


  • no pollution


  • needs to be buried deep into the ground for greater heat capture
  • Discuss the factors that affect the choice of energy sources  adopted by different societies.

MEDCs have higher energy demands than LEDCs, as they depend on energy for many things such as transport, heating, air-conditioning, cooking and all other aspects of their lives.

The choice of what energy source should be used is different to countries. Some have large oil, coal and gas reserves and that makes fossil fuels an obvious choice for an energy source. However generation of energy also depends on its availability, economy, cultural, environmental and technological factors. When an energy resource is available and close, it is more easier and efficient to use.

Culture fears based on the fear of nuclear accidents and waste, have made it quite unpopular to choose. Cultural and tradition means that non-renewable resources are favoured, and the places with renewable energy resources are limited. Renewable energy sources are not being used so much globally which means that it is still not ready to meet current demands. Renewable sources can be used more if the production prices of the non-renewable sources are increased. This may better the environment as higher costs of the fossil furls means that peoples view will change. Peoples interest in renewable resources has led to an increased demand for renewable and non-pollution sources. This leads to a greater investment and research into more alternatives or improvements.

  • Explain the concept of resources in terms of natural income.

Ecologically minded economists describe resources as ”natural capital”. If properly managed, renewable and replenishable resources are forms of wealth that can produce ”natural income” indefinitely in the form of valuable goods and services.

This income may consist of marketable commodities such as timber and grain (goods) or may be in the form of ecological services such as the flood and erosion protection provided by forests (services). Similarly, non-renewable resources can be considered in parallel to those forms of economic capital that cannot generate wealth without liquidation of the estate.

*Natural capital + natural income: raw materials from the environment (natural capital), are harvested and used by producers to generate products and services (natural income) that are then used by consumers.

  • Define the terms renewable, replenishable and non-renewable natural capital.

*Renewable resource: is a natural resource that the environment continues to supply or replace as it is used, and whose emissions and wastes are recycled in a sustainable way. They can be used over and over again. Renewable natural capital, such as living species and ecosystems, are self-producing and self-maintaining and uses solar energy ad photosynthesis. This natural capital can yield marketable goods such as essential services when left in place, for example, climate regulation.

*Replenishable resource: non-living resources which are continuously restored by natural processes, (ex. rivers, ozone layer) as as they are used up. They provide sustainable natural income as the natural capital is not diminished. They depend on abiotic processes for their replenishment. (in contrast to renewable resources which depend on biotic processes)

*Non-renewable resource: natural resources which cannot be replenished within a time scale of the same order as that of which they are take from the environment (cannot be replenished at the same they are used). Any use of these resources results in depletion of the stock. These include: fossil fuels, and minerals.

Renewable: solar energy, biomass energy, wind energy, hydro-power energy and geothermal energy.

Non-renewable: fossil fuel oils, coal, nuclear and natural gas.

  • Explain the dynamic nature of the concept of a resource.

Cultural, economic, technological and other factors influence the status of a resource over time and space. For example, uranium, due to the recently become a valuable resource. What this all means is that resources are dynamic, its status may change, it might become valuable.

  • Explain the concept of sustainability in terms of natural capital  and natural income.

* Sustainability: means living, within the means of nature, on the ”interest” or sustainable income generated by nature capital. So using the global resources at the rate that allows natural regeneration and minimizes damage to the environment.

This can be encouraged by:

– ecological land-use to maintain habitat quality and connectivity for all species.

– sustainable material cycles, (ex carbon, nitrogen, and water cycles).

– social systems that contribute to a culture of  sufficiency that eases the consumption pressures on natural capital.

  • Discuss the concept of sustainable development.

* Sustainable development: development that meets current needs without compromising the ability of future generations to meet their own needs. Focuses on the quality if environmental, economic, and social and cultural development. The concept encompasses ideas and values that inspire individuals and organizations to become better stewards of the environment and promote positive economic growth and social objectives.

  • Calculate and explain sustainable yield from given data.

sustainable yield may be calculated as the rate of increase in natural capital, that is, that which can be exploited without depleting the original stock or its potential for replenishment. For example; the annual sustainable yield for a given crop may be estimated simply as the annual gain in biomass or energy through the growth and recruitment.

”development which meets the needs of the present without compromising the ability if the future generations to meet their own needs.”

SY= (annual growth and recruitment) – ( annual death and emigration)

  • Describe the nature and explain the implications of exponential growth in human populations.

* Exponential growth: refers to a growth rate which is increasingly rapid or an accelerating rate of growth. ( Basically means that the rate of  human population is increasing quickly )

The world’s population is increasing very fast, this is due to many factors such as education, health, poverty, place of residence, and social class. Population growth is more common in Less economically developed countries ( LEDCs ) as they are less educated, and believe they need more children to help them make a living and take care of them in the future. Around 95% of population growth is happening in the LEDCs which means education is needed especially between the women in the LEDCs so that the birth rates decrease and there standard of living improves. Governments have even tried to help improve this by improving health care as well as education. Some countries have tried to control birth control however this is not so successful (excluding China).

What is also a pro when it comes to MEDCs is that they believe that they cannot raise children with a low income which means that they only have children if it does not affect their standard of living. This shows us one more time that reducing birth rates in LEDCs can only be done by improving the standard of living in those countries.

  • Calculate and explain, from given data, the values of crude birth rate, crude death rate, fertility, doubling time and natural increase rate.

Calculating important rates:

  • Birth rates:

CBR- Crude birth rate is the number of live births per 1000 people in a population. Total number of births/total population X 1000 = CBR. However the CBR does not calculate the age and sex structure of the population.

  • Fertility:

TFR- Total fertility rate is the average number of births per woman of child-bearing age.

GFR- General fertility rate is the number of births per thousand woman aged between 15-49 years old.

ASBR- Age-specific birth rate is the number of births per 1000 women of any specific year group.

  • Doubling times:

This is the time it takes for a population to double in size. Doubling time=70/percentage growth rate.

  • Death rates:

CDR- Crude death rate is the number of deaths per thousand people in population. However it is a poor indicator as populations with many old people (MEDCs) have higher CDRs than countries with more younger populations. Ex: Denmark 11% and Mexico 5%. CDR= number of deaths/total population X 1000.

ASMR- Age-specific mortality rates is the number of deaths per 1000 women of any age group. ASMR= number of deaths/1000 women of any specific age group.

IMR- Infant mortality rates is the number of deaths  of children under 1 years old per 1000 live births.

  • Natural Increase:

NIR- Natural increase rate is the CDR from the CBR. CBR-CDR=NIR. This excludes migration.

A NIR of 1% will make a double of a population in 70 years. The doubling time is 70 divided by the NIR.

  • Analyse age/sex pyramids and diagrams showing demographic transition models.

*Population pyramids: is a structure which shows any measurable characteristic of the population; like sex, age, language, religion and occupation.

Population pyramids tell us a great deal of information about the age and sex structure of a population:

  • a wide base indicates a high birth rate
  • narrowing  base suggests falling birth rate
  • straight or near vertical sides reveal a low death rate
  • concave slopes characterize high death rates
  • bulges in the slope indicate immigration or in-migration
  • deficits in the slope indicate emigration or out-migration or age-specific or sex-specific deaths (epidemics, war)

High birth and death rates:

People want children: ( High Birth rates)

for labour

– to look after them in old age

– to continue the family name

– prestige

– to replace children who have died

People die from: (High Death rates)

– lack of clean water

– lack of food

– poor hygiene and sanitation

– overcrowding

– contagious disease

– poverty

Low Birth and Death rates:

Birth rates decline because:

– children are very costly

the government looks after people through pensions and health services

– more women want their own carreer

– there is a more widespread use of family planning

– as the infant mortality rate decreases there is no need of child replacement

Death rates decline because:

clean water

– reliable food supply

– good hygiene and sanitation

– lower population densities

– better vacations and healthcare

– rising standards of living

DTM- Demographic transition model shows us that countries progress through recognized stages in the transition from LEDC to MEDC. It suggests that death rates fall before birth rates and that the total population expands. For more info.

  • Discuss the use of models in predicting the growth of human populations.

Many factors affect population growth for example: national or regional change in population count in-migration and out-migration whereas a global population change does not even count migration at all.

Factors influencing birth rates include: population age-structure, women status, type of economy, wealth, religion, social pressure, educational status, availability of contraceptives, desire for children, and the need for governmental policies such as child benefits. It is very difficult to predict the populations birth rate changes in all of these factors.

Death rate is also affected by many factors. These include age-structure of the population, availability of clean water, sanitation, adequate housing, reliable food supply, prevalence of disease, provision of healthcare facilities, type of occupation, natural hazards, civil conflict/war, and chance factors. This is also difficult to predict changes for as there is too many factors.

Changing projections:

It has always been predicted that the world was not going to have enough food supply for everyone since the late 1700’s, however in the 1990’s there were warnings about having an increased population. It has been predicted that the population over 60 will increase and that the working population will have to work harder to keep the elderly alive, unless there is something done about it.

This has been discussed between Academics and Politicians and they keep coming to these 3 conclusions:

  1. Those who think this is all just a scare story which can be changed/fixed with some changes to the retirement ages and pension policies.
  2. Those who preach and doom, (poverty in old age, healthcare rationing, intergenerational warfare as young/old fight for scarce resources)
  3. Those in between 1+2 who try and come up with reasonable ideas to reduce the impact of global greying.

Biggest part of the solution lies in:

  • expanding the shrinking population of workers by increasing retirement age and persuading women to work.
  • increasing productivity of the labour force.
  • persuading people to save more for their retirement.

The Revision has began!

Posted: March 28, 2011 in IB

Today is the first day of the rest of my IB life! I have made an exam revision timetable so that I can organize my studying and make sure I go through all my subjects with the 35 days I have left! So I am starting with the last first so I make sure I have enough time for everything.

Qualitative deals with the real world, to give meaning to experiences, not in a lab. Aim is to describe and explain events and experiences. Wants to interpret. For example; Observations, Interviews and Case studies. Researchers need to be flexible and can not be involved with the participants and have an assistant instead. People should be studied in their own environments when it comes to Qualitative methods. To look for themes in the data is more common than confirming a hypothesis.

Qualitative is more about words where its easy to analyse but Quantitative is about numbers where it is easier to make statistics and summarize.

Quantitive methods: experiments for ex have been used to maintain psychology appearance as a scientific discipline with valid knowledge claims.

During 20th century they shifted from using only quantitative methods to gain data but also realizing that both methods are needed.

What decides whether a researcher should use qualitative or quantitative data?

– purpose of research

– Characteristics of participants

– researchers beliefs about the nature of knowledge and how it can be acquired.

Look in course companion and try to summarise it.

Rolfe: means that the distinction between qualitative and quantitative research is a textbook creation and that there is no unified qualitative paradigm. In fact, he claimed they are not separate.

The aim of qualitative data is not to generalize

Abiotic factor: A non-living, physical factor that may influence an organism or ecosystem; for example, temperature, sunlight, pH, salinity, precipation.

Biochemical oxygen demand(BOD): A measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity.

Biodegradable: Capable of being broken down by natural biological processes; for example, the activities of decomposer organisms.

Biodiversity: The amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity and genetic diversity.

Biomass: The mass of organic material in organisms or ecosystems, usually per unit area. Sometimes the term ”Dry Weight Biomass” is used where mass is measured after the removal of water. Water is not organic material and inorganic material is usually relatively insignificant in terms of mass.

Biome: A collection of ecosystems sharing similar climatic conditions; for example, tundra, tropical rainforest, desert.

Biosphere: That part of the Earth inhabited by organisms, that is, the narrow zone (a few kilometres in thickness) in which plants and animals exist. It extends from the upper part of the atmosphere (where birds, insects and windblown pollen may be found) down to the deepest part of the Earth’s crust to which living organisms venture.

Biotic factor: A living, bilogical factor that may influence an organism or ecosystem; for example, predation, parasitism, disease, competiton.

Carrying Capacity: The maximum number of a species or load that can be sustainably supported by a given environment.

Climax community: A community of organisms that is more or less stable, and that is in equillibrium with natural environmental condtions such as climate; the end point of ecological succession.

Community: A group of populations living and interacting with each other in a common habitat.

Competition: A common demand by two or more organisms upon a limited supply of a resource; for example, food, water, light, space, mates, nesting sites. It may be intraspecific or interspecific.

Correlation: A measure of the association between two variables. If two variables tend to move up or down together, they are said to be positively correlated. If they tend to move in opposite directions, they are said to be negatively correlated.

Crude birth rate: The number of births per thousand individuals in a population per year.

Crude death rate: The number of deaths per thousand individuals in a population per year.

Demographic transition: A general model describing the changing levels of fertility and mortality in a human population over time. It was developed with reference to the transition experienced as developed countries ( for example, those of North America, Europe, Australasia) passed through the processes of industrialization and urbanization.

Diversity:  A generic term for heterogenity. The scientific meaning of diversity becomes clear from the context in which it is used; it may refer to heterogeneity of species or habitat, or to gentetic heterogeneity.

Genetic Diversity: The range of genetic material present in a gene pool or population of a species.

Habitat Diversity: The range of different habitats or number of ecological niches per unit are in a ecosysm, community or biome. Conservation of habitat diversity usually leads to the conservation of species and genetic diversity.

Index Diversity: A numerical measure of species diversity that is derived from both the number of species (variety) and their proportional abundance.

Species Diversity: The variety of species per unit area. This includes both the number of species present and their relative abundance.

Doubling Time: The number of years it would take a population to double its size at its current growth rate. A natural increase rate of 1% will enable a human population to double in 70 years. Others doubling times can then be calculated proportionately, that is, the doubling time for any human population is equal to 70 divided by the natural increase rate.

Ecological footprint:  The area of land and water rewuired to support a defined human population at a given standard of living. The measure takes a account of the area required to provide all the resources needed by the population, and the assimilation of all wastes.

Ecosystem: A community of interpendent organisms and the physical environment they inhabit.

Entropy: A measure of the amount of disorder, chaos or randomness in a system; the greater the disorder, the higher the level of entropy.

Ecotones: where two habitats meet and there is a change near the boundary.