No, all organisms are not similar.
1. Organisms on the earth exhibit great diversity.
2. Organisms are grouped as microbes, plants (autotrophs), animals (heterotrophs) and decomposers.
3. Different microbes and decomposers have various shapes and sizes.
4. Plants can be further classified on their shape, size, structure, mode of reproduction, etc. Plants also differ greatly based on the locations in which they are found, e.g. Snowy, desert, forest, aquatic, etc.
5. Even animals show a high degree of variation. They are classified as unicellular, multicellular, invertebrates, vertebrates, etc. Also, based on the environment in which they live, they are classified as terrestrial,aerial, aquatic and amphibians.