Bacterial pathogens most commonly use this class of metabolism. what are these pathogens?

Most pathogenic bacteria are chemoheterotrophs. This means:

•Chemo - they obtain energy by the oxidation of electron donors (get their energy from chemical reactions, unlike phototrophs which use solar energy.  

•Heterotrophs – they are unable to fix carbon to form their own organic compounds so they use organic (chemoorganoheterotrophs)  or inorganic (chemolithoheterotrophs) components as energy sources.

Evolution

Charles Darwin visited the Galapagos islands and found a lot of evidence supporting evolution

The finch species evolved to different habitats on the Galapagos, some had large beaks to crack open large nuts, some had longer, slenderer, and sharper beaks to get at insects (food) in small places like in dead trees