Unicellular organisms can be found everywhere. The oldest forms of life existed 3.8 billion years ago, if not longer. They pursue a variety of strategies for survival: photosynthesis (cyanobacteria), chemotrophy (many archaea), and heterotrophy (amoeba). Some unicellular organisms have flagella, little tails they use for locomotion, or lobopods, extensions of the cellular skeleton (cytoskeleton), which appear as bloblike arms. The flagella of our unicellular ancestors occurs all the way up into the animals, where it makes an appearance as flagellated sperm.