because they are better and they grow faster
ruel p. campanilla
Yeasts are unicellular organisms. Some species with yeast forms may become multicellular through the formation of strings with connected budding.
The kingdom with the least amount of species is the kingdom Monera, which consists of unicellular prokaryotic organisms such as bacteria and archaea.
Isolation from the mainland.
No,there are both unicellular and multicellular species
A unicellular organism is a single celled organism. For example, yeast, E. coli, and most forms of algae.
it can be considered a multicellular organism
They evolved over time from older species.
No, that isn't a statement made about evolution. The theory of evolution concerns how organisms have changed over periods of time. Everything has to have come from something! However, all living organisms alive today have evolved from predecessors, or have not really evolved much at all, e.g. Gingko bilboa and several species of sea animals.
More complex species have evolved and the range of organisms have increased
Everything beyond single cell organisms have evolved (and some of those have too!).
Cells are the base unit of living organisms. At the beginning of life, the first organisms must have been single cells like today's bacteria. All organisms have evolved from that simplest prokaryotic cell, and from unicellular, multicellular organisms evolved. Also, all of biochemistry changes with Natural Selection, as does genetics. The biochemistry of the cell and cell differentiation has evolved. Photosynthetic cells, immune cells, nervous cells.... All have evolved with the higher organisms and have given them their identities of having neurological systems, immune systems or the ability to photosynthesise. Since life's basic unit is the cell, the basic unit of evolution (of the phenotype) is indeed largely the cell too. From zygote develops organism within the constraints of that species' evolution, cell by cell by cell by differentiated cell.