I think it's the simple columnar epithelium.
Each of these animals have adapted in very similar ways to similar habitats. This us similar to a homologous structure, but that is a term used for the presence of similar bones.
Reproduction is the production of offspring by a sexual or asexual process to make a copy of something or someone. Hope it helps!
Endoplasmic Reticulum. -- Transport System.
Golgi Apparatus -- Delivery System.
Lysosomes - Intracellular Digestion Centers.
Ribosomes - Sites of Protein Synthesis.
ENERGY RELATED ORGANELLES.
Cytoskeleton - Support System.
Related to Movement.
