Explain how organ and organ system are formed ?

Explanation

The basic tissues organise to form organs which in turn associate to form organ systems in the multicellular organisms. Such an organisation is essential for more efficient and better coordinated activities of millions of cells constituting an organism. Each organ in our body is made of one or more type of tissues. For example, our heart consists of all the four types of tissues, (epithelial, connective, muscular and neural). We notice that after some careful study that the complexity in organ and organ systems displays certain discernable trend. The morphology and anatomy of three organisms at different evolutionary levels give explanation to show their organisation and functioning. Morphology refers to study of form or externally visible features. In case of animals this refers to the external appearance of the organs or parts of the body. The word anatomy conventionally is used for the study of morphology of internal organs in the animals. The morphology and anatomy of earthworm, cockroach and frog representing invertebrates and vertebrates.