Organs only exist in animals are less complex than the tissues which make them perform functions that tissues cannot carry out on their own are made of only one type of tissue

perform functions that tissues cannot carry out on their own

Explanation:

In the hierarchy of living system organs come after tissues and before organ systems. Hence, organs are complex then tissues and perform functions that tissues wont be able to perform on their own.

A organ is made up of various types of tissues. They can be divided into two categories, main tissue and sporadic tissue. Main tissue or parenchyma is unique to that organ and defines the function of the organ. For example: Cortex and medulla together form the main functional tissue in kidney. Similarly, myocardium is the main tissue of the heart. Sporadic tissue has blood vessels, nerves and connective tissues.

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.