• Distinguish between biotic and abiotic (physical) components of an ecosystem.

*Biotic: refers to the living components of an ecosystem. (the community)

*Abiotic: refers to the non-living factors of an ecosystem. (the environment)

Ecosystems are made up of living and non-living components. The living part of the environment consists of the organic part of the ecosystem; animals, plants, algae, fungi and bacteria. These are called biotic components. The non-living part of the environment is made up of physical components such as; air, light, water, temperature, soil, minerals and climatic atmosphere. These are called abiotic components. These two components work together to sustain the environment.

  • Define the term trophic level.

Trophic level refers to the feeding level within a food chain. It is the position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains.

  • Trophic level 1 – producer
  • Trophic level 2 – herbivore (primary consumers)
  • Trophic level 3 – carnivore (secondary consumers)
  • Trophic level 4 – carnivore (tertiary consumer)
    • Identify and explain trophic levels in food chains and food webs selected from the local environment.

    *Producer: The organism in the ecosystem that converts abiotic components into living matter, they help the ecosystem by producing new biological matter.

    *Consumer: These organisms cannot produce their own food, so they eat other organisms to get the energy and matter they need.

    * Decomposer: Feed on dead biomass which is created by the ecosystem.

    *Herbivore: Only feed on producers.

    *Carnivore: Feed on all organisms including producers and consumers.

    *Top carnivore: This organism can not be eaten by any other organism.

    Sun: Provides the abiotic matter to the grass

    Grass: Producer and autotroph, provide food for the deer.

    Deer: The primary consumer and herbivore of the grass.

    Wolf: The secondary consumer/Top consumer and carnivore, feeds on the deer and cannot be eaten by any other organism.

    Ecosystems contain many interconnected food chains that form food webs. Food chains always begin with the producers (usually photosynthetic organisms), followed by primary consumers (herbivores), secondary consumers (omnivores or carnivores) and then higher consumers (tertiary, top). Decomposers feed at every level of the food chain.

    Diagrams of food webs can be used to estimate the knock-on effects of changes to the ecosystem.

    Biomass and energy decrease at each trophic level so there is a limit in how much trophic levels can be supported in a ecosystem. Energy is lost as heat at each stage of the food chain, on only energy stored in biomass is passed on to the next trophic level. After 4 or 5 trophic levels there is not enough energy to support another stage.

    Local example: (Lake in Sweden)

    Producer: Freshwater shrimp

    Primary consumer: Bleak

    Secondary consumer: Perch

    Secondary consumer: Northen Pike

    Top consumer: Osprey

    • Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.

    Pyramids are graphical models showing the quantitative differences between the trophic levels of an ecosystem. There are three types:

    • Pyramids of numbers: This records the number of individuals in each trophic level.

    • Pyramid of biomass: This represents the biological mass of the standing stock at each trophic level at a particular point in time. Biomass should also be measured in units of energy, such as J m-2. They can show greater quantities at higher trophic levels because they represent the biomass present at a given time. Both pyramids of numbers and biomass represent storages.

    • Pyramid of productivity: This shows the flow of energy through each trophic level. Measured in units of flow gm-2 yr-1 or Jm-2 yr.

    In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore pyramids become narrower as one ascends.

    • Discuss how the pyramid structure affects the functioning of an ecosystem.

    This Youtube clip explains the interactions in food chains and the vulnerability of the top carnivores.

    • Define the term species, population, habitat, niche, community and ecosystem with reference to local examples.

    *Species: A group of of organisms that interbreed and produce fertile offspring. If two species breed together they create a hybrid, this cannot produce viable gametes and is sterile.

    *Population: A group of the same species living in the same area at the same time, and can interbreed.

    *Habitat: The environment in which a species normally lives.

    *Niche: Where and how a species lives. A species share of a habitat and the resources in it.

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

    *Ecosystem: A community of inter-independent organisms and the physical environment they inhabit.

    • Describe and explain population interactions using examples of named species.

    Ecosystems contain many interactions between the populations, the interactions are varied and can be divided into; competition, predation, mutualism and parasitism.

    *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.

    *Parasitism: A relationship between two species in which one species (the parasite) lives in or on another (the host), gaining all or much (in the case of the partial parasite) of its food from it.

    *Mutualism: A relationship between individuals of two or more species in which all benefit and non suffer.

    *Predation: This is when on animal or plant hunts and eats another animal.

    Here are 3 Youtube links about Interspecific interactions.

    • Explain the concept of an ecological footprint as a model for assessing the demands that human populations make on their environments.

    The ecological footprint of a population is the area of land, in the same vicinity as the population, that would be required to provide all the population’s resources and assimilate all its wastes. As a model, it is able to provide a quantitative estimate of human carrying capacity. It is, in fact, the inverse of carrying capacity. It refers to the area required to sustainability support given population rather than the population that a given area can sustainably support.

    Ecological footprints can be increased by:

    • greater reliance on fossil fuels
    • increased use of technology and energy (but technology can also reduce the footprint)
    • high levels of imported resources (which have high transport costs)
    • large per capita production of carbon waste (high energy use, fossil fuel use)
    • large per capita consumption of food
    • a meat-rich diet

    Ecological footprints can be reduced by:

    • reducing use of resources
    • recycling resources
    • reusing resources
    • improving efficiency of resource use
    • reducing amount of pollution produced
    • transporting waste to other countries to deal with
    • improving country to increase carrying capacity
    • importing resources from other countries
    • reducing population to reduce resource use
    • using technology to increase carrying capacity
    • using technology to intensify land

    There are many plans and innovations being set to reduce the ecological footprint in the future, this is funded by the MEDCs who have the biggest problems with their ecological footprints.

    • Calculate from appropriate data the ecological footprint of a given population, stating the approximations and assumptions involved.

    The ecological footprint calculation is very complex, however approximations can be obtained through the steps outlined in this figure:

    The total land requirement (ecological footprint) can then be calculated as the sum of these two per capita requirements, multiplied by the total population.

    This calculation clearly ignores the land or water required to provide any aquatic and atmospheric resources, assimilate wastes other than CO2, produce the energy and material subsidies imported to the arable land for increasing yields, replace loss of productive land through urbanzation, and so on.

    Factors used in a full ecological footprint calculation would include those in the following list:

    • bioproductive (currently used) land: land used for food and materials such as farmland, gardens, pasture and managed forest
    • bioproductive sea: sea area used for human consumption
    • energy land: an amount of land that is required to support renewable energy instead of non-renewable energy. The amount of energy land depends on the methods of energy generation ad is difficult to estimate for the planet
    • built land: land that is used for development such as roads and buildings
    • biodiversity land: land required to support all of the non-human species
    • non-productive land: land such as deserts is subtracted from the total land available

    There are factors ignored when calculating the ecological footprint which influence the amount of land a population needs to support itself:

    • the land or water required to provide and aquatic and atmospheric resources
    • land or water needed to assimilate wastes other than carbon dioxide
    • land used to produce materials imported into the country to subsidize arable land and increase yields
    • replacement of productive land lost through urbanization

    If everyone on Earth had the same lifestyle as the ones in the MEDCs, many Earths would be needed to support the global population.

    • Describe and explain the differences between the ecological footprints of two human populations, one from an LEDC and one from a MEDC.

    Data for food consumption are often given in grain equivalents, so that a population with a meat-rich diet would tend to consume a higher grain equivalent than a population that feeds directly on grain.

    The standards of living between MEDCs and LEDCs  change according to the resource consumption, energy usage and waste production, disparities should be expected between the ecological footprints of LEDCs and MEDCs. LEDCs have small ecological footprints as MEDCs have much greater rates of resource consumption. This is partly because MEDCs have higher incomes and the demands for energy resources is high. MEDCs consume a lot of resources as they are wasteful, they also have more waste and pollution. LEDCs are the opposite with lower consumption as people do not have too much to spend. The economy of the country forces them to recycle many resources, however they are developing and they’re ecological footprint is increasing. MEDCs use twice as much energy in their diet provided by animal products than LEDCs.

    • Discuss how national and international development policies and cultural influences can affect human population dynamics and growth.

    Many policy factors influence human population growth. Domestic and international development policies (which target the death rate through agricultural development, improved public health and sanitation, and better service growth by lowering mortality without significantly affecting fertility.

    Some analysts believe that birth rates will come down by themselves as economic welfare improves and that the population problem is therefore better solved through policies to stimulate economic growth.

    Education and birth control encourages family planning. Parents may be dependent on their children for support when they get older and this may create an incentive for more children.

    Urbanization  may also be a factor in reducing crude birth rates.

    Policies directed towards the education of women, enabling women to have greater personal and economic independence, may be the most effective method for reducing population pressure.

    • Describe and explain the relationship between population, resource consumption and technological development, and their influence on carrying capacity and material economic growth.

    Because technology plays such a large role in human life, many economists argue that human carrying capacity can be expanded continuously through technological innovation. For example, if we learn to use energy and material twice as efficiently, we can double the population or the use of energy without necessarily increasing the impact imposed on the environment. However, to compensate for foreseeable population growth and the economic growth that is deemed necessary, especially in developing countries, it is suggested that efficiency would have to be raised by a factor of 4 to 10 to remain within global carrying capacity.


    • Explain difficulties in applying the concept of carrying capacity to local human populations.

    If one were to examine the needs of a given species and the resources available, it could be possible to estimate the carrying capacity of that environment for the species. This is problematic when it comes to the human population for many reasons like:

    • Resources used by humans are much more than any other species and when this source becomes limited humans begin to substitute one resource for another. The use of resources change from person to person, lifestyle to lifestyle, time to time and population to population.
    • Developments in technology increase the changes of the resource consumption.
    • The human population also import resources very often which come from outside their environment, which makes the grow beyond the boundaries set by their local resources and lets their carrying capacity increase. This however does not affect the global carrying capacity.

    These variables make it almost impossible to make reliable estimates of carrying capacities for the human populations.

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

    Here we can see 3 models of a population growing and approaching carrying capacity.

    *Optimum population: the number of people which when working with all the available resources, will make the highest per capita economic return. it shows the point at which the population has the highest standard of living and quality of life.

    Standard of living is the result of the interaction between physical and human resources and can be expressed as:

    Standard of living: (natural resources X technology) / population

    *Over-population: this happens when there are too many people compared to the resources and technology available for the standard of living. They suffer from natural disasters such as droughts and famine, low incomes, poverty, poor living conditions and a lot of emigration.

    *Under-population: this happens when there are too many resources in one area that is too much for the people living there. Countries like this could export their surplus food, energy and mineral resources.

    • Explain how absolute reductions in energy and material use, reuse and recycling can affect human carrying capacity.

    Human carrying capacity is determined by the rate of energy and material consumption, the level of pollution and the extent of human interference in global life-support systems. While reuse and recycling reduce these impacts, they can also increase the human carrying capacity.

    *Recycle: when a household or industrial waste is reused and made into another product, like plastic, metals and paper.

    *Re-use: when a product is used more than once by returning it to the manufacturer or processor each time. This is very energy efficient and more efficient than recycling.

    *Reduce: this is when energy use is decrease for example turning off the lights when not needed or using the amount of water needed in a kettle.

    *Substitution: when using one resource over the other, the use of renewable source over a non-renewable source is a major benefit to the environment.


    • Describe the Earth’s water budget.

    There is only a small part of the Earth’s water that is fresh water, and of this over 80% is in the form of ice caps and glaciers, 0.6% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage. This means that most of the Earth’s water budget is not directly accessible by human populations. Fresh water is therefore an extremely limited resource. (precise numbers are not needed on exam)

    *Turnover time: The time it takes for water to completely replace itself in part of the system it is in, this charges from different parts of the systems.

    The degree to which water can be looked at as renewable or non-renewable depends on where it is found in the hydrological cycle. Renewable water resources are renewed yearly or even more frequently, however groundwater is non-renewable resource.

    • Describe and evaluate the sustainability of freshwater resource usage with reference to a case study.

    Irrigation, industrialization, and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle gives humans fresh water but we are taking up so much water from the underground aquifers that there is no time for it to replenish.

    The demand of water has increased in both MEDCs and LEDCs, as populations are increasing as well as agriculture changing and expanding industry. MEDCs need more water as they wash more often, water their gardens, and wash their cars. This means that the increasing use of water is making the demands higher. Water is not an infinite resource and has to be controlled more carefully, and new water resources need to be found.

    Water can be managed if individuals and communities make changes and this should be supported by the government. Water should not be over used or wasted so that it is insured it can be enough for everyone.

    This can be reached by:

    • making new buildings water efficient (rainwater for sanitation and showers)
    • fitting new homes with more water-efficient appliances (dishwashers and toilets)
    • expand metering to encourage households to use water more efficiently
    • in some rural areas drought resistant crops should be planted to reduce the need for irrigation
    • organic fertilizers cause less pollution and bio-control measures can be used to reduce crop pests

    Environmental philosophies:

    Environmental philisophies: plan to manage resources sustainability without diminishing them to a degree where they become non-replenishable. Techno-centrists would argue that solutions can be found to sustain both human population and overcome unsustainable use of water resources.

    As populations grow, greater demands are made on water resources. Water resources are now becoming a limiting factor in many societies, and the availability of water for drinking, industry and agriculture need to be considered. Many societies now are dependent on groundwater which is non-renewable. As societies develop, water needs to be increased. The increased demand for water can lead to inequity of use and political consequences. When water supplies fail, populations will be forced to take dramatic steps, such as mass migration. Water shortages may also lead to civil unrest and wars.


    Water shortages in the Middle East:

    Water shortages in the Middle Eastern countries are very common and as time passes their water supply is decreasing. Even though the region only inhabits 5% of the world’s population, it only has 0.5% of the worlds fresh water. It is predicted that the water supply will decrease from 3430 cubic meters per year to a 667 cubic meters by 2025. This is causing countries such as Israel who is suffering from a major drought to stop pumping from their major pumps of fresh water. Many factors have lead to the demand of more water and the droughts have made this worse. Despite the shortages Israel is still sharing their supply with neighbouring country Jordan. Israel is building at the moment plants that supply a third of the countries water supply and a few more plants are also going to be completed in 2013 which could double this amount. Future water shortages could lead to conflicts between the neighbouring countries.

    We got these handouts in class today, Psychology – Paper 3 HL 2009 and Psychology- Case Methods Handout. Hope it helps 🙂

    My psychology teacher recommended this link for help with extra worksheets you can print and work on your own with. The more help the better right 🙂 Good luck with the revising !


    Qualitative research
    Takes place in the real world

    • How people give meaning to their own experience

    Words and analysis

    1. Interviews
    2. The researchers need to be flexible and sensitive to the needs of the patient
    When dealing with qualitive research – it is imperative to be able to tolerate a degree of uncertainty
    “reasearchers can only come to understand the social world through participants’ interpretations” – Interpretative approach

    Reality is diverse and multifaceted. The goal is to get a picture of this reality. To measure means to reduce it – and therefore lose meaning.


    1. Provides rich data
    2. Particularly sueful for investigating complex and sensitive issues
    3. Explain penomena – that is, go beyond mere observation to understand what lies behind them (eg. why do people become homeless?)
    4. Generate new ideas and theories to explain and overcome problems.
    5. People are studied in their own environment, which increses credability

    1. Can be very time consuming and  generate a huge amount of data.
    2. Data analysis can be difficult because of the amount of data and no clear strategy for analysis
    3. Interpretation of data may be subjective (but reflexivity can help to minimize this)
    Generalization is not always the aim

    Quantitative research 

    Numbers and statistics
    Have been used partly in order to maintain the appearence of psychology as a scientific dicipline with valid knowledge claims.
    During the 20th century there was a shift away from seeing quantitative methods as the only valid way fo gaining data. 


    qualitative-vs-quantitative powerpoint