Some lichen symbionts can survive independently on bare rocks in the absence of any external source of organic matter due to the ability of the phototrophic partner to fix CO2 from the air, and .

Some lichen symbionts can survive independently on bare rocks in the absence of any external source of organic matter due to the ability of the phototrophic partner to fix CO2 from the air, and nitrogen fixation by the cyanobacterial partner.

Explanation:

Lichen are organisms formed from the symbiotic association of a fungus with an organism capable of photosynthesis, be it an algae, a cyanobacterium, or both.

The fungus depends entirely on the photosynthetic organism in its metabolism of carbohydrates, receiving sugars or saccharine alcohols from it. For its part, the algae depends, for its metabolism, on the water and the mineral substances that the fungus provides it, at the same time that it is also protected by it from too high light intensities.

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in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: