The growing plants carry a common microbiome on their surfaces. They could be contaminated by external sources. Animals too have a normal surface flora, as well as an intestinal one. They also release organisms through excretions and secretions. They can are also contaminated by outside sources. Animals and plants with parasitic diseases, of course, carry the pathogen responsible for the illness. The healthy tissues that are inside both animals and plants nevertheless are found to have a small number of living microorganisms or none at all.