In general, yes, the dorsal blood vessel of a worm be seen from the worm's exterior because a worm's "skin" is very thin. Although of course there are exceptions.
Answer:
Biosphere
Explanation:
The biosphere is the part of the earth that supports life forms. It includes hydrosphere, atmosphere, and lithosphere. Various ecosystems, aquatic or terrestrial, are present in the biosphere. Biotic and abiotic components of a geographical region that interact with each other together make an ecosystem.
The biotic component of an ecosystem includes all the organisms present in it. Organisms may be unicellular or multicellular. All the organisms are made up of one or more cells. Cells are made up of various biomolecules that interact and enable cells to perform the life processes.
Molecules are defined as the smallest particles of a chemical compound or an element, and are made up of atoms. Cells are made up of semi permiable membranes that only allow selected materials to move in or out of the cell, therefore due to the big size of molecules compared to atoms the membrane doesn't allow their passage in the cell. Therefore the cell doesn't allow most molecules to diffuse passively to the cell. Secondly, molecules that can enter the cell requires specific carriers carriers that will enable entry of small molecules in the cell.
