Question

A sunflower and an amoeba are both living organisms. How is the structure of a sunflower different from the structure of and amoeba

Answer 1

A sunflower is a plant and Amoeba is a protist. Structurally Amoeba is a unicellular, microscopic  organism and its cell does not have cell wall, whereas sunflower plant is a multicellular organism and its cell  have cell wall. Since Amoeba is made of only one cell, all the life processes such as nutrition, excretion and reproduction carried out by one cell. In sunflower plant is made of many cells.  All the cells are arranged in tissues, organs and organ systems. specific organ system performs specific life process, for example digestion system performs the function of digestion. Thus, Amoeba is a simple organism and sunflower is a complex organism.  

Answer 2

there are several differences, here are some:
kingdoms: sunflower = plant; amoeba = ProtistaCell
membranes: sunflower = cell wall; amoeba = semipermeable membrane only
organelles: sunflower = cholorplasts; amoeba = pseudopod 
Cell organization: sunflower = differentiated multicellular: amoeba = single cell 
Habitat: sunflower = confined to land areas; amoeba = confined to water
hope this helps