Answer:
used by scientists in classification
Explanation:
Classification is the orderly arrangement of organisms into groups based on their similarities biologically, morphologically and phylogenetically. Those with similar characteristics are put under the same group or taxon.
Answer:
you meant what are the main sources
they are: fossil
clean energy
energy storage
hydrogen& fuel
electric power
The ecological footprint is defined as the biologically productive area needed to provide all the resources that a human population needs to survive. It is a measure that calculates the human demand on nature and can be used as an indicator of the human impact and dependency on Earth's ecosystem. The ecologists use the ecological footprint concept to estimate the earth's carrying capacity for humans.