Describe Kingdom - Fungi.

Explanation

The Kingdom-Fungi or Mycota constitute a unique kingdom of heterotrophic organisms.
They show a great diversity in morphology and habitat.
Mycology is the branch of science that deals with the study of various fungi.
A scientist having specialisation in the study of fungi is called mycologist.
Examples of fungi :
(1) When your bread develops a mould or your orange rots it is because of fungi.
(2) The common mushroom you eat and toadstools are also fungi.
(3) White spots seen on mustard leaves are due to a parasitic fungus.
(4) Some unicellular fungi, e.g. yeast are used to make bread and beer.
(5) Other fungi cause diseases in plant and animals, wheat rust. causing puccinia is an important example.
(6) Some are the source of antibiotics e.g. Penicillium.
Habitat : Fungi are cosmopolitan and occur in air, water, soil and on animals and plants.
They prefer to grow in warm and humid places.
Body organisation : With the exception of yeasts which are unicellular, fungi are filamentous.
Their bodies consists of long, slender thread - like structure.
Fungal hyphae are thin tubular transparent threads or filaments filled with protoplasm are covered by wall.
The network of hyphae is known as mycelium.
Some hyphae are continuous tubes filled with multinucleated cytoplasm - these are coenocytic hyphae.
Other have septate or cross wall in their hyphae.
The hyphae are of following types found in fungi :
(i) Aseptate hyphae : In aseptate hyphae cross walls or septa are not formed at the time of nuclear division.
Such hyphae are multinucleate.
It is called coenocytic, if mycelium contain aseptate and multinucleate hyphae.
(ii) Septate hyphae : In this type, cross walls or septa form after the nuclear division.
The cells may have one, two or many nuclei.
These have septal pores or cross walls in their hyphae, which allow movement of substances between adjacent cells.
Fungal tissue : In fungi, fungal tissue is formed by interweaving of fungal hyphae called as plectenchyma.
Fungal cells : Fungi are eukaryotic cell
A cell wall is present on the outside, made of chitin and polysaccharide.
They posses all the eukaryotic cell organelles except plastids.
Nutrition : Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes.
Those that depend on living plants and animals are called parasites.
They can also live as symbionts in association with algae as lichens and with roots of higher plants as mycorrhiza.
Reproduction : Reproduction in fungi can take place by vegetative means - fragmentation, fission and budding.
Asexual reproduction is by spores called conidia or sporangiospores or zoospores and sexual reproduction is by oospores and basidiospores. The various spores are produced in distinct structures called fruiting bodies.
The sexual cycle involves the following three steps:
(i) Fusion of protoplasms between two motile or non-motile gametes called plasmogamy.
(ii) Fusion of two nuclei called Karyogamy.
(iii) Meiosis in zygote resulting in haploid spores.
When a fungus reproduces sexually, two haploid hyphae of compatible mating types come together and fuse.
In some fungi the fusion of two haploid cells immediately result in diploid cells (2n).
In other fungi (ascomycetes and basidiomycetes) an intervening dikaryotic stage (`n + n`, i.e. two nuclei per cell) occurs, such a condition is called dikaryon and the phase is called dikaryophase of fungus.
Later, the parental nuclei fuse and the cells become diploid.
The fungi form fruiting bodies in which reduction division occurs, leading to formation of haploid spores.