You find one celled organisms in both plants and animals. They fill what we called a niche or space in the environment and they do well there.
A one-celled organism is the smallest organism that can carry out all functions of life. Two examples would be a paramecium (Protista kingdom), and Cyanobacteria (Eubacteria kingdom).
Archaea
animal kingdom
Single celled organisms are found in the Kingdom Protista.
Protist
I think you would classify it as a prokaryote
Linnaeus' original hierarchy of organism classification included only two kingdoms. Later, this would be expanded to three by Ernst Haeckel, as some single-celled organisms couldn't be classified as animal or plant. Later still, Edouard Chatton's idea for dividing between single-celled organisms with and without a distinct nucleus was popularized, leading to four kingdoms. Finally, Robert Whittaker addressed the ambiguous classification of fungi between plantae and Protista by making them their own, fifth kingdom.
There are currently millions of species of single-celled organisms, and million of others that were once here and are now extinct. Which of these would BEST describe the first, most primitive organism to arise on Earth from which all other life evolved?
There are currently millions of species of single-celled organisms, and million of others that were once here and are now extinct. Which of these would BEST describe the first, most primitive organism to arise on Earth from which all other life evolved?
This is a vague questions because many aspects of evolution takes place in single-celled organism. For a single celled organism to evolve into a multicellular organism this would require cell division. You might know the terms mitosis and meiosis which are processes of cell division. If you question is how they evolve to adapt to the enviornment, this would be natural selection. The strongest of the cell would survive while the weak dies. This would mean only the strongest would reproduce and live which from an outer point of view, the single-celled organism has evolved.
Organism that have one cell (single celled) are so small, you would need a microscope to see them. So, orchids are multicellular.
* Kingdom Animalia, Phylum prokaryotae. i disagree, its kingdon prokaryote