Darwin proposed his theory of evolution on the premise of natural selection. According to him, organisms which possess favourable characteristics which enable them to survive in their environment are more likely to survive and reproduce, passing on these favourable characteristics to their offsprings.
According to Mendel, the unit of inheritance passed on from parents to offspring are genes. Hence Darwin's factors are Mendel's genes.
If Darwin knew of Mendel's work. It might have influenced his presentation of the idea of passing on favourable characteristics from parents to offspring in the light of genetics.
This would have made Darwin's work to have more empirical backing hence making it more widely accepted.
Biogeochemical cycles represent the main system by which the energy of the Sun is transformed into energy of the chemical compounds by living beings and products of their activity. :)
Bacteria still offers its benefits. Like for example in the digestive system, they help break down food, like plant fibers. They also supply us with vitamins like biotin and Vitamin K.
