fungi mushrooms mycology the fifth kingdom

Fungi - what are they?

Fungi are living organisms that are distantly related to plants, and more closely related to animals, but rather different from either of those groups.

Fungi can be recognized by the following five characteristics:

(1) The cells of fungi contain nuclei with chromosomes (like plants and animals, but unlike bacteria).
(2) Fungi cannot photosynthesize (they are heterotrophic, like animals)
(3) Fungi absorb their food (they are osmotrophic)
(4) They mostly develop very diffuse bodies made up of a spreading network of very narrow, tubular, branching filaments called hyphae. These filaments exude enzymes, and absorb food, at their growing tips. Although these filaments are very narrow, they are collectively very long, and can explore and exploit food substrates very efficiently.
(5) They usually reproduce by means of spores, which develop on, and are released by, a range of unique structures (such as mushrooms, cup fungi, and many other kinds of microscopically small fruiting bodies).

Organisms which have all five of the features just described can be found in two of the seven living Kingdoms - they make up the entire Kingdom Eumycota or true fungi, whose cell walls (the walls of the hyphae) are made largely of chitin (like the exoskeletons of insects); and part of the Kingdom Chromista, whose cell walls are made of cellulose (like plants), and which also include the brown algae - wracks and kelps (all these Chromista, though they may look very different, have similar swimming cells with two flagella at one stage in their lives). To read a fuller account of the living kingdoms, click here.

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