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A section of DNA in a chromosome, that codes for the production of a specific protein. Genes have different alleles that provide variation.

Passive transport Diffusion = occurs in gases or aqueous solutions whereby particles are free to move and spread from a higher concentration to a lower concentration. An example is air freshener being spr...

In most food chains, all of the energy which is used originally comes from the sun. Plants are "photoautotrophs", which means that they can use light energy from the sun to fuel their life proce...

Enzymes are biological catalysts that work by increasing the speed of a reaction, without being altered or used up in the reaction. Each enzyme has an active site specific to a particular substrate and th...

Receptors in the skin detect changes in the environment, so called stimuli. These could include a change in temperature or sensation, such as increased pressure, being touched somewhere or experiencing pa...