Food Chains & Food Webs 

Chemical energy is necessary for survival. Autotrophs are able to make their own chemical energy through the process of photosynthesis. This chemical energy can be passed up to the food chain to support the consumers in an ecosystem. Without producers, there could be no consumers! Therefore, energy always flows from producers to consumers. Energy is first transferred from producers to herbivores (plant eaters), and then from herbivores to carnivores (meat eaters). Once energy is passed forward, it can never flow back.
If biodiversity is lost in an ecosystem, this means less available food for all others. As connections are lost in food webs, ecosystems become less stable.