Chemical energy: When animals eat plant, they get the chemical energy in the plants stored as sugar.Mechanical energy: Carbon dioxide rising through the air gains mechanical energy (as well as gravitational potential energy).Thermal energy: The heating of fossil fuels releases the energy stored inside.Electrical energy: Burning fossil fuels creates electrical energy for us to use.
Answer: According to Darwin theory of evolution the struggle for existence is considered as major part for competition among living things.
Explanation:
Coexisting species that belong to the same genera compete for same kind of resources for their survival. Some phenotypic variations gives an survival advantage over others. The superior ones dominate the inferior ones and compete for resources. The one who receives the resources like mates, food, shelter, and others the chances of survival also increases considerably.
Aerobic respiration uses oxygen to produce ATP. Anaerobic respiration uses inorganic molecules to produce ATP. I hope that answered your question, my friend. :)