Complex organisms like humans show organ system levels of organization in the body. Groups of Cells similar in structure, function and origin form a tissue.Complete answer:
To answer this question, we should know about how the organ system is formed in an organism. Basic unit in any organism is the cell, these cells are attached together to form tissue. Similar Tissues come together to form an organ performing a common function. Organ system is a higher level of organization that consists of functionally related organs. A number of organ systems are present in the body which performs their function and helps the organism to survive as a unit.
Now, complex organisms show different levels of organization. They have different organs to carry out different functions. Like lungs for respiration, heart for blood purification, digestive system to feed, and excretory system with organs like kidneys and liver that help is the whole process. The tissues found in the complex organisms are very well arranged so that it carries out all the function. We have a proper skeleton system that gives us strength and support to our body.
Hence, finally we can say cells make up tissues, tissues make up organs, and organs make up organ systems.Note:
Similarly, in Plants also complexity can be seen. But in the single celled organisms the cell organelles are not well designed they do not have the nucleus and even do not have tissue like that of the complex organisms like humans. Hence, they do not have organs for the organ system.