來自 Hong Kong
That is what I found in book about cambrian explosion :
Actually, algae doesn't refer to any specific kingdom or phylum of organisms and only represent a form of life which adrfting on water and obtain food from photosynthesis.
So organisms from different kingoms can be refered the group 'algae', for example, cyanobacteria, spiragyra, seaweeds and other phytoplankton can be consider as 'algae'
But personally speaking, I don't consider cyanobacteria and plants as 'algae'. My definition for 'algae' is : unicellular ( the cell of each individual can be joined up together as a colonie ) autotrophic organism which adrift on sea and have true membrane bounded nucleus.