weight: measure of heaviness, number of kilos

in proportion to: in relationship with

species (in biology): a basic category of classification

manufactured: made

exposure to sunlight: being outside in daylight

phenomena: facts, occurences

melting point: temperature at which solid changes to liquid

crystalline: having a crystal structure

fertilizer: chemical compound used for feeding plants

detergent: chemical compound used for cleaning

semi-conductor: chemical substance used in computers

liver: internal organ

immune system: a group of internal organs and cells that fight disease