Why do cells in multicellular organisms organized themselves into tissues organs and organ systems​

Their goal is to work together on a specific task to get it completed. They can only do this by working together

Explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.