Energy and Ecosystems

EcologyHabitat : Place where an organism livesPopulation: Group of the same species of organisms

which live in the same place at the same timeCommunity: All of the different species living in a

habitat at the same timeEcosystem: A self contained system of organisms

interacting, which recieved energy as sunlight, and loses energy as heat. Nutrients are recycled within the ecosystem.

Niche: The place occupied by an organism in the food chain

Energy flow through ecosystems

Energy losses in food chains

Energy loss in ecosystemsNot all sunlight hits a photosynthesising

plantSome sunlight is reflected from leaf surfacesSome sunlight passes through the leaves and

is not converted to chemical energy.Some wavelengths of light cannot be used by

plants

Respiration – The building of ATP produces heat, which is lost to the surrounding environment

Food chains and food webs

Trophic levelsProducer : Photosynthesising organisms (plants)

produce all of the food for the ecosystem.1st order consumer: First animal consumer in the food

chain (herbivore)2nd order consumer Second animal in the food chain

(carnivore)3rd order consumer animals high in the trophic levels

often consume food from lower levels also (can be omnivores)

Detritis : Dead organismsDecomposer : Bacteria and fungi decay dead organismsDetrivores: Larger organisms which eat dead

organisms

ProductivityProductivity is the rate at which plants

convert sunlight to energy in an ecosystem.It is measured in kilojoules per m2 per yearGross productivity : Total energy convertedNet primary productivity: Remaining

chemical energy after plants have supplied their own needs for repiration.

Matter recycling : Nitrogen cycleNitrogen is essential for all living organisms

as a building block of proteins and nucleic acid

Most nitrogen is present in the atmosphere 78pc.

Nitrogen gas is unusable by most organisms, as the triple covalent bond in N2 molecules makes them too unreactive.

The most common useable form of nitrogen is in ammonia NH3 and nitrate NO3.

The conversion of nitrogen gas to useable nitrogen is called nitrogen fixation.

Nitrogen FixationNaturalLightning in atmosphere creates nitrogen oxide gasses

by reacting oxygen with Nitrogen. These gasses fall to the soil in rain. Tropical ecosystems obtain a very large amount of useable nitrogen this way.

Nirogen fixing bacteria ie Rhizobium use an enzyme called nitrogenase. This catalayses nitrogen to ammonia.

Rhizobium can live in soil and in the roots of legumous plants. Legumous plants have root nodules which the bacteria can live in, and get supplied with atp

Nitrogen Cycle

SyntheticHaber proccess : This is the synthetic

proccess used to make ammonia for fertilisers. It uses very large ammounts of electrical energy, and has made it possible for farmers to produce march larger crop yields.

use of nitrogenNitrate ions are obtained from the soil by

plants in their xylemAnimals obtain nitrogen by digesting plants,

or other animals. Digestion breaks proteins into amino acids ready to use by the animal

Denitrification bacteria can reverse nitrogen fixation in their metabolic proccesses. They are common in sewage treatment plants and compost heaps.