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cyanobacteria

serve as a food source for other organisms
are used for medicinal purposes
produce oxygen
perform nitrogen fixation
cause disease

serve as a food source for other organisms

are used for medicinal purposes

produce oxygen

perform nitrogen fixation

cause disease

Explanation:

Serve as a food source for other organisms: The cyanobacteria serves as a food for marine organisms like zooplanktons and fishes.

Are used for medicinal purposes: The cyanobacteria are used for the purpose of medicine these produced biologically active materials such as antiviral, antifungal, antibacterial and anticancer activities.

Produce oxygen: The cyanobacteria produces oxygen by the process of photosynthesis.

Perform nitrogen fixation: The Cyanobacteria produces nitrogen form that is absorbed by the plants. It converts the atmospheric nitrogen into the ammonia absorbed by the plants.

Cause disease: The cyanobacteria produces cytotoxin which is responsible for neurodegenerative diseases like Parkinson's disease, and  Alzheimer's disease.

a fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms, containing energy originating in ancient photosynthesis.[1] the age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.[2] fossil fuels contain high percentages of carbon and include petroleum, coal, and natural gas.[3] other commonly used derivatives include kerosene and propane. fossil fuels range from volatile materials with low carbon to hydrogen ratios like methane, to liquids like petroleum, to nonvolatile materials composed of almost pure carbon, like anthracite coal. methane can be found in hydrocarbon fields either alone, associated with oil, or in the form of methane clathrates.

the theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the earth's crust over millions of years was first introduced by andreas libavius "in his 1597 alchemia [alchymia]" and later by mikhail lomonosov "as early as 1757 and certainly by 1763".[4] the first use of the term "fossil fuel" was by the german chemist caspar neumann, in english translation in 1759.[5]

in 2017 the world's primary energy sources consisted of petroleum (34%), coal (28%), natural gas (23%), amounting to an 85% share for fossil fuels in primary energy consumption in the world.[6] non-fossil sources in 2006 included nuclear (8.5%), hydroelectric (6.3%), and others (geothermal, solar, tidal, wind, wood, waste) amounting to 0.9%.[7] world energy consumption was growing at about 2.3% per year. in 2015 about 18% of worldwide consumption was from renewable sources.[8]

x would be the most and the least would be y because there are more fruit   and seeds than flock z has insects