Explain how organs and organ systems are formed.

(N/A) $\Rightarrow$ Basic tissues organize to form organs,which in turn associate to form organ systems in multicellular organisms. Such an organization is essential for more efficient and better-coordinated activities of millions of cells constituting an organism.
$\Rightarrow$ Each organ in our body is made of one or more types of tissues.
$\Rightarrow$ For example,our heart consists of all four types of tissues (epithelial,connective,muscular,and neural). We notice after careful study that the complexity in organs and organ systems displays certain discernible trends.
$\Rightarrow$ The morphology and anatomy of organisms at different evolutionary levels explain their organization and functioning.
$\Rightarrow$ Morphology refers to the study of form or externally visible features.
$\Rightarrow$ In the case of animals,this refers to the external appearance of organs or parts of the body.
$\Rightarrow$ The word anatomy is conventionally used for the study of the morphology of internal organs in animals.
$\Rightarrow$ Examples include the morphology and anatomy of the earthworm,cockroach,and frog,representing invertebrates and vertebrates.