The energy for nearly every organism in almost every ecosystem ultimately comes from

The sun passes energy to the producers, then to the first level consumers eat them and get energy, and then second level consumers eat them, and then eventually it gets to the decomposers and scavengers, which put nutrients and energy back in the soil for the producers.

Three reasons of the deaths of native americans: new illnesses that their immune systems couldn't cope with. genocides so the settlers could have the good land.starvation from lack of rations and poor infertile land on resevations