Autotrophs: The Producers That Build Ecosystems From Air and WaterAutotrophs synthesise their own carbon compounds from simple inorganic substances such as carbon dioxide and water.They rely on an external energy source to drive this synthesis, so they do not need to consume other organisms.DefinitionAutotrophAn autotroph is an organism that uses external energy sources to synthesize carbon compounds from simple inorganic substances.Carbon Fixation: Turning Inorganic Carbon Into Organic CompoundsCarbon fixation is the conversion of inorganic carbon such as carbon dioxide into organic compounds like glucose.Most autotrophs fix carbon through photosynthesis, which uses light energy and is covered in detail in C1.3.Two Types of AutotrophsNoteThe energy source used to fix carbon distinguishes photoautotrophs from chemoautotrophs, which is explored in C4.2.7.Producers: Why Autotrophs Sit at the Base of Every Food ChainPrimary producers: autotrophs form the base of food chains and supply the organic compounds that all heterotrophs depend on.Carbon entry point: they convert inorganic carbon into organic forms, making carbon available to the rest of the ecosystem.Oxygen supply: photoautotrophs release oxygen during photosynthesis, which sustains aerobic life.Active recallDefine an autotroph in terms of the substances it uses and what it makes.State the two simple inorganic substances autotrophs use as raw materials.Explain what carbon fixation means.Give three reasons autotrophs are essential to ecosystems.
