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Some prokaryotes are pathogenic, causing disease and even death in plants and animals. [5] Marine prokaryotes are responsible for significant levels of the photosynthesis that occurs in the ocean, as well as significant cycling of carbon and other nutrients. [6] Prokaryotes live throughout the biosphere.
Eubacteria are important photosynthetizers in both oceanic and terrestrial ecosystems, and while some archaea are phototrophic, none are known to utilise oxygen-evolving photosynthesis. [6] A number of eukaryotes are significant contributors to primary production in the ocean, including green algae , brown algae and red algae , and a diverse ...
Heliobacteria are a unique subset of prokaryotic bacteria that process light for energy. Distinguishable from other phototrophic bacteria, they utilize a unique photosynthetic pigment, bacteriochlorophyll g and are the only known Gram-positive phototroph. [ 2 ]
They can occur as planktonic cells or form phototrophic biofilms. They are found inside stones and shells (in endolithic ecosystems). [90] A few are endosymbionts in lichens, plants, various protists, or sponges and provide energy for the host. Some live in the fur of sloths, providing a form of camouflage. [91]
Many protist species can switch between asexual reproduction and sexual reproduction involving meiosis and fertilization. [6] In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organised. Plants, animals and fungi are usually multi-celled and are typically macroscopic. Most protists are single-celled and microscopic.
Prokaryotes evolved before eukaryotes, and lack nuclei, mitochondria, and most of the other distinct organelles that characterize the eukaryotic cell. Some unicellular prokaryotes, such as cyanobacteria, form colonies held together by biofilms, and large colonies can create multilayered microbial mats.
Photoautotrophs are organisms that can utilize light energy from sunlight and elements (such as carbon) from inorganic compounds to produce organic materials needed to sustain their own metabolism (i.e. autotrophy). Such biological activities are known as photosynthesis, and examples of such organisms include plants, algae and cyanobacteria.
Prochlorococcus is a genus of very small (0.6 μm) marine cyanobacteria with an unusual pigmentation (chlorophyll a2 and b2).These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth.