' In the absence of microorganisms the earth would become a heap of Dead plants and animals .' justify this statement.
Answers
yes without the decomposers the waste can't be decomposed and slowly the wastes accumulate and the earth would become a heap of wastes...
I think this question is interesting from the perspective of human exploration of other planets. I was just reading an article about the problem of preventing microbiological contamination of Mars by human explorers. We carry our microbes with us wherever we go. If we want to study microbial life on Mars, should there be any, we want to make sure it is from Mars, and that it is not wiped out by microbes from Earth.
A totally artificial environment could be established without microorganisms of any kind in it and that could support human life (think space station). Humans carry a microbiome that is intricately tied up with our health and nutrition, so there is a question about whether people could remain healthy with no microrganisms within and upon them. Germ-free mice are able to survive, so perhaps germ-free people could, too. They would probably need some nutritional supplements to make up for the lack of vitamins provided by the gut microbiome. Their immune systems might not work normally, and they might suffer more from autoimmune diseases.
Next we have to consider the food supply. Plants can be grown in culture medium lacking microorganisms, but can the culture medium be prepared from feedstocks that do not ultimately depend on microorganisms? For the purpose of space exploration, the ship could be supplied in advance with microbe-free materials needed for the entire journey, but would it be possible to set up a sustainable, completely contained artificial ecosystem with no microorganisms of any kind? Sounds like an interesting experiment.
As for the Earth, I agree with Nikolay. I don't think human life on Earth, as it is currently operating, could persist without microorganisms. They are responsible for producing most of the oxygen, permit decay of dead plants and animals, fix nitrogen in soil, and are the base of every food web