What is being taught lesson by lesson:

Key Terms for this topic (Tier 3 vocabulary)

Competition – resources – communities – habitat – interdependence – biotic factors – abiotic factors – adaptation – quadrat – transect – cycling of materials – recycling – carbon cycle – detritus – biodiversity – global warming – migration – deforestation – ecosystem.


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What everyone needs to know:

Build on the ideas of food chains and food webs, describe how each level is dependent on the previous one. Be able to describe how the population of one species affects those above and below in a food web. Describe how certain animals have adapted to their environment, remember obvious ones like penguins and camels but examiners are likely to select an obscure one, don’t panic, the principle is the same. Do not forget extremophiles.

Describe the influences in a habitat, biotic (living) and abiotic (not living ) factors. The community within an ecosystem depends on the resources such as ions in soil and photosynthesising organisms, this is interdependence. Animals compete for space, food and mates. Plants compete similarly but use seed dispersal as well. You need to be able to interpret data on populations and how they are affected.

Abiotic factors:

  • The amount of light,
  • Soil pH,
  • Availability of water,
  • Temperature,
  • Wind direction and speed,
  • CO2 levels (plants),
  • O2 levels in water (fish).

Biotic factors:

  • How much food is available,
  • Predators,
  • Pathogens,
  • A species driven to extinction as not enough to mate.

From both biotic and abiotic – you need to be able to interpret graphs and data.

Photosynthesising organisms are producers, they use the energy from the sun to make biomass. Producers are eaten by primary consumers, then secondary and tertiary. Animals that kill and eat others are predators, those eaten are prey. They have a very well balanced population relationship. You need to be able to interpret data on these relationships.

Maths skills – as well as graphs, make sure you can calculate the mean, median and mode. If you have an anomalous number, do not include it in the mean.

Required practical 7 – Measure the population size of a species in a habitat and use a variety of sampling techniques. Outside with the quadrats counting daisies and collecting bugs (humanely and releasing them straight after).

Water and carbon are essential to these systems so ensure that you understand the carbon cycle and the water cycle. Look at the crucial role played by detritivores in the carbon cycle where CO2 is released into the atmosphere and minerals are left in the soil to be absorbed by new producers.

Ecosystems are more stable if there is a high biodiversity, this is a large number of different species. We are reducing this in nature with our activities but it is essential that we stop.

It is vital for the environment that any waste that we produce is returned safely, chemicals removed from wastewater, nothing toxic in landfill waste and no gases released into the atmosphere. These examples of pollution kill plants, animals that eat those plants and some animals directly which reduces biodiversity.

As we spread out on the world, our land use increases which takes space previously occupied by ecosystems. When we take peat from peat bogs to make compost, we destroy habitats and their plants, animals and microorganisms. The peat decays in our gardens releasing even more CO2. Likewise, deforestation to make room for cattle, farming and even growing biofuels reduced biodiversity and the burning of trees increases atmospheric CO2 and reduces the amount of photosynthesis.

Global warming is the slow increase in the average surface temperature of this planet and it is not a myth, This is caused by a steady increase in the levels of CO2 and methane being released. Be aware of ways that we are trying to preserve biodiversity:

  • Breeding programmes to save endangered species (Chester Zoo).
  • Protecting rare habitats (preventing building on these sites).
  • Hedgerows where farmers only grow one crop.
  • Some governments reducing deforestation and CO2 emissions.
  • Increasing the amount recycled rather than using landfill.

Extra topics needed for the Higher papers:

In this topic, there is nothing extra for the higher papers, the questions will just be more challenging.