Energy and Ecosystems

HideShow resource information

Food Chains


Photosynthetic organisms that manufacture organic substances using light energy, water and carbon dioxide. Co2 + Water + Light energy = Glucose + Oxygen.


Obtain their energy by feeding on other organisms. Secondary and Tertiary predators are mainly predators.


Organisms that break down dead producers and consumers, releasing valuable minerals and elements in the form that can be absorbed by plants.

Food Chain: feeding relationship where the producers are eaten by primary consumers, which are eaten by secondary consumers, who are eaten by tertiary consumers..... Each stage in the chain is a trophic level. The arrows represent the direction of energy flow.

Food Web: many food chains linked together

1 of 7

Energy Transfer

  • some of the organism is not eaten
  • some parts cannot be digested and so are lost in faeces
  • some energy is lost in excretory materials, e.g urine
  • some energy is lost as heat from respiration. High in mammals and birds (high body temp)

net production = gross production - respiratiory losses

energy transfer = energy available after transfer/energy available before transfer x 100


2 of 7

Ecological Pyramids


(Biomass is the total mass of living material in a specific area at a given time. gm-2/3)

3 of 7

Agricultural Ecosystems

Agricultural ecosystems are made up of domesticated animals and plants that are used to produce food for mankind. Agriculture tried to ensure that as much of the available energy from the sun as possible is transferred to humans, who are often the 3rd or 4th trophic level. This increases the productivity of the human food chain.

Productivity is the rate at which something is produced.

Net Productivity = Gross Productivity - Respiratory Losses

In natural ecosystems, productivity is relatively low. The additional energy input to agricultural ecosystems is used to increase the productivity of a crop by reducing the effect of limiting factors on its growth.

This means that the crop has little competition for light, CO2, water and the minerals needed for photosynthesis. Fertilisers are added to provide essential ions and pesticides are used to destroy pests and prevent disease. Altogether, this ensures that productivity is much higher in an agricultural ecosystem.

4 of 7

Control of Pests

Pesticides are poisonous chemicals that kill pests

Herbicides kill plants, fungicides kill fungi, insecticides kill insects

An effective pest should be:

  • specific
  • biodegradeable
  • cost effective
  • not accumulate

Biological control can also be used. This is using living organisms to destroy pests. For example, parasatic wasps that destroy fly by planting eggs inside them.

Intergrated pest-control systems aim to integrate all forms of pest control rather than relying on just one type.

5 of 7

Intensive Rearing

Intensive rearing of livestock is designed to produce the maximum yield of meat, eggs and milk at the lowest possible cost. It attempts to minimise the energy losses from domestic animals so that more of the food energy they eat is converted into body mass.

This is achieved by keeping animals in confined spaces so:

  • movement is restricted so less energy is used in muscle contraction
  • the environment can be kept warm to reduce heat loss
  • feeding can be controlled so animals recieve the optimum amount and type of food for maximum growth
  • predators are excluded so there is no loss to other organisms in the food web

There is also:

  • selective breeding of animals to produce varieties that are more efficient at converting food energy into body mass
  • using hormones to increase growth rates
6 of 7

Features of Intensive Rearing

  • efficient energy conversion
  • low cost
  • lower quality of food
  • little space required
  • plants or animals are more vulnerable to diseases (monoculture) due to close proximity
  • however it is also easier to prevent infections being introduced
  • can result in antibiotic resistance (transferred to humans)
  • poor animal welfare
  • increase pollution due to large amounts of waste in small areas
  • reduced genetic diversity
  • uses fossil fuels
7 of 7


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Ecology, ecosystems and environmental biology resources »