Chapter 31 - Fungi

Fungi, like mammals, are heterotrophs: they cannot produce their own food, as plants and algae do. Fungi, on the other hand, do not absorb (consume) their food as mammals do. A fungus, on the other hand, takes nutrients from its surroundings.

Many fungi do this by secreting hydrolytic enzymes into their environment. These enzymes degrade complicated chemicals into smaller organic components that fungus can ingest and utilize.

Other fungi utilize enzymes to pierce cell walls, allowing them to take nutrients from the cells. The numerous enzymes present in distinct fungus species may digest substances from a broad variety of sources, both live and dead.

This variety of food sources reflects the many roles of fungus in ecological communities: Various species exist as decomposers, parasites, or mutualists.

• Decomposers are fungi that break down and take nutrients from nonliving organic material such as fallen logs, animal corpses, and wastes from living species. Parasitic fungus consumes resources from live hosts' cells. Pathogenic parasitic fungus includes several species that cause plant illnesses and others that cause animal diseases.

Mutualistic fungi receive nutrients from their hosts as well, but they return with activities that benefit the host.

The image attached depicts two forms of hyphae.

Cross-walls, or septa (plural, septum), separate the hyphae into cells (as shown in the image attached). Septa have pores that are big enough to allow ribosomes, mitochondria, and even nuclei to move from cell to cell. Some fungi do not have septa (as shown in the image attached).

These organisms, known as coenocytic fungus, are made up of a continuous cytoplasmic mass with hundreds or thousands of nuclei. The coenocytic state is caused by the recurrent division of nuclei without cytokinesis, as we'll see later.

Mycelium (plural, mycelia) is an interconnected mass of fungal hyphae that infiltrates the substance on which the fungus feeds (as shown in the image attached). A mycelium's structure maximizes its surface-to-volume ratio.

Although many fungi may reproduce both sexually and asexually, over 20,000 species are known to reproduce exclusively asexually. Asexual reproduction methods, like sexual reproduction, vary greatly among mushrooms.

Many fungi reproduce asexually by developing as the filamentous fungus that generates (haploid) spores via mitosis; such species are referred to informally as molds if they form visible mycelia. You may have seen mold in your kitchen, creating fuzzy carpets on bread or fruit, depending on your housekeeping practices.

Nucleariids, a type of single-celled protists, are the closest living cousins of fungi, according to molecular data. The paraphyletic nature of this group is indicated by the three parallel lines going to the chytrids. Phylogenetic studies indicate that fungus descended from a flagellated progenitor.

While the bulk of fungus lack flagella, some of the earliest-diverging fungal lineages (the chytrids) have. Furthermore, most protists that share a common ancestor with mammals and fungi have flagella. According to DNA sequence data, these three categories of eukaryotes—fungi, animals, and their protistan relatives—form a monophyletic group or clade.

Fungi are heterotrophic organisms that feed by absorption.

All fungus (including decomposers and symbionts) are heterotrophs, meaning they obtain nutrients by absorption. Many fungus produce enzymes that aid in the breakdown of complicated compounds.

The majority of fungus develop as thin, multicellular filaments called hyphae; just a few species grow as single-celled yeasts. Fungi in their multicellular state are made up of mycelia, which are networks of branching hyphae suited for absorption. Mycorrhizal fungi have unique hyphae that allow them to collaborate with plants in a mutually beneficial interaction.

Karyogamy produces diploid cells that undergo meiosis and produce genetically heterogeneous haploid spores.

As filamentous fungus or yeasts, many fungi may reproduce asexually. An aquatic, single-celled, flagellated protist was the progenitor of fungus.

Fungi and mammals split over a billion years ago from a shared unicellular ancestor with a flagellum, according to molecular data. The earliest fossils that are commonly regarded as fungus, on the other hand, are 460 million years old.

Some primitive lineages belong to the chytrids, a genus of fungus having flagellated spores.

Fungi were among the earliest land colonists, according to fossil evidence.