No, not all biological organisms on Earth depend on trace elements with an atomic number greater than iron (26). While iron is an essential trace element for many organisms, there are other elements with lower atomic numbers that are also essential for life.
For example, carbon, hydrogen, nitrogen, and oxygen are four of the most abundant elements in living organisms and are crucial for their biological processes. These elements, along with others like phosphorus and sulfur, are considered macronutrients because they are required in relatively large quantities.
Trace elements, on the other hand, are required in much smaller amounts, but they still play important roles in various biological processes. Some examples of trace elements include zinc, copper, manganese, molybdenum, and selenium. These elements are involved in enzyme function, electron transfer reactions, and the formation of structural components.
While many trace elements with atomic numbers greater than iron are important for certain organisms, it is not accurate to say that all organisms depend on them. Different organisms have different requirements for trace elements, and some organisms may have adapted to thrive in environments with limited availability of certain elements.