5.2 ecosystems rely on energy transfer

Ecosystems and energy transfers

Producers and productivity

  • The rate at which energy is converted into organic molecules is called the primary productivity of the ecosystem.

  • Producers/autotrophs are things that make their own food.

Living things are split like so: 



All living things have the following:

  1. Movement

  2. respiration

  3. sensitivity

  4. growth

  5. reproduction

  6. excretion

  7. nutrition


Photosynthesis is the process by which light from the sun is transformed into chemical energy in organic molecules. 

The complex organic molecules made during photosynthesis, such as glucose, are passed on through food webs. Animals are entirely dependant on plants for their existence. Plants are net producers of oxygen which is essential for aerobic respiration.


The process of photosynthesis occurs in two main stages

  1. the light dependant stage

  2. the light independent stage 


Photosynthesis occurs in the chloroplast, the light dependant occurs in the thylakoid membrane the light independent occurs in the stroma:


Light dependant reaction

  1. Light is absorbed by chlorophyll embedded in the thylakoid membranes. This raises two electrons in each chlorophyll to a higher energy level. (chlorophyll molecule is now excited)

  2. The electrons leave the excited chlorophyll molecules which are now positive and oxidised. The electrons pass along a series of electron carrier molecules, also embedded in the thylakoid membranes (electron transport chain). As the electrons pass from one carrier to the next they

Light independent reaction

  • This stage of photosynthesis occurs in the stroma, it uses the reduced NADP and ATP from the light dependant reaction and also CO2 . The CO2 is used to reduce the carbohydrate, the NADP acts as an electron carrier (hydrogen) to stop it reacting with oxygen.

  • The light independent


Sophie kendall


I left a space for a light dependent picture and the chloroplast needs to be labled- i find this useful for revision, hope it helps :)

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