Human blood type is determined by codominant alleles
Ventilation systems are needed in a <span>multicellular organism to actually obtain oxygen and give out carbon dioxide. Without this ventilation system, it would be very difficult for multicellular organisms to survive. It has been also observed that surface diffusion is not enough for a multicellular organism to breath.</span>
Covalent bonds share electrons and ionic bonds transfer them.
Analogous structures have different evolutionary ancestries but have the same function. some types of structures are the wings of birds, bats and insects. Homologous structures are the opposite, they have similar ancestries and common traits but not the same function.
