BIOLOGY NEET NOTES

PART 10

KINGDOM FUNGI

These are multicellular eukaryotes except yeast(also called as sacrthromytes teravisae, baker's yeast and Ruar's yeast). Penicillin are obtained from fungus pennicilium. Always heterotrophic. The body is called mycelium which is made up of hyphae. Hyphae can be septate or aseptate. These are multinucleated.

MODE OF NUTRITION 

SAPROPHYTIC:- Grows and decaying matter. e.g bread mould(Rhizopus). Fungus release digesting enzymes and digest it in outside ovary. It then ingest already digested food. This is called as saprophytic nutrition or external digestion.

PARASITIC:- Grows inside living host body and harms them. e.g disease causing fungus. 

SYMBIOTIC:- Mutually beneficial relationship with the host. e.g lichen and micorrhiza.

Lichen:- Association of fungus with algae. Fungus is a dominant partner. Fungus absorb nutrition from soil very well due to large surface area of hyphae. It partners its partner to algae to perform photosynthesis. Glucose that is formed by fungus is also given to fungus 

Micorrhiza:- It is an association of fungus with root of the big tree. Fungus absorb water phosphate ions etc. and gives it to the tree. Tree will form glucose and gives it to the fungus. e.g pine tree always grow with micorrhiza. It cannot survive without fungi because nutrition required by tree can be made available only through micorrhiza.

GROUPS OF FUNGI

There are four types of fungi. They are:-

1]Phycomyctes:- Also called zygomycetes. It has more than 1000 species. It is unbranched and is aseptate. it is very innocent. It always says 'RAM RAM'. Now what doess this this RAM mean? It means rhizopus (bread mould), albugo, and mucor which are examples of zygomycetes. They are found in aquatic habitat and on decaying wood in moist and damp places. These are also found as obligate parasites on plants. It has coenocytic hyphae. These are the most primitive fungus. It prefers asexual reproduction but can perform sexual too. Fungal body is haploid(n). Spores (made up of nucleus and cytoplasm) are formed in sporangium by mitosis. There are two types of spores :-1] zoospore(motile) and 2] aplanospore(non-motile)

*NOTE: HAPLOID ORGANISMS CAN NEVER UNDERGO MEIOSIS*

ASEXUAL REPRODUCTION

Sporangium bursts open and spores are released. spores will germinate under favorable conditions and forms haploid fungal body.

SEXUAL REPRODUCTION

For sexual reproduction, 2 different hyphae from different mycelium has to be present. But gametes are formed by meiosis and since hyphae are haploid, they can't undergo meiosis. Therefore, nucleus of the hyphae acts as gamete. Hyphae gave out projection and brings nucleus over there. Cytoplasm gets fused i.e plasmogamy. But nucleus are not fused until now. In this sporangium, nucleus will be fused i.e karyogamy and form 2n structure. This stage is followed by meiosis. Zygospores are produced by meiosis which are haploid. These spores will give rise to new fungus.

2] Ascomycetes:- It is also called as sac fungi. Mostly multicellular. It is cocrofiller(grow in cowdung). It is rarely unicellular. This provides everything. 

FOOD->Morrels and truffles also aspergillus(these are delicacies in Europe)

DRINKS->Yeast(making of alcohol)

MEDICINE(for hangover)-> Penicillin

MIND(to calm down)-> Neurospora

BICEPS(workout because you had too much last time)-> Claviceps

ASEXUAL REPRODUCTION

Conidiophore is a special hypha for reproduction. Cells of conidiophore undergo repeated mitosis to form conidia which are asexual spores exogenously(outside). This conidia are blown by air and get attached to some surface and form mycelium.

SEXUAL REPRODUCTION

Conidia of some other sac fungi comes and sits on the top of some sac fungi. Then they perform plasmogamy and form dikaryon. Then they undergo karyogamy and fuse the nucleus. This nucleus is 2n nucleus. Later they undergo meiosis and form (n) nucleus. Then they form fruiting body which is covered by a layer called ascocarp(sac). Fruiting body ruptures and they form nuerospora. After they germinate the cycle of sexual reproduction in Ascomycetes continues. Neurospora is used in biochemical and genetic work.

3] BASIDIOMYCETES :- There commonly known forms are mushrooms, puff balls and bracket fungi. They are parasites and some of the forms are edible. Mycellium is branched and septate. No asexual reproduction takes place generally. Asexual vegetative reproduction takes place by fragmentation. Sex organs are absent but sexual reproduction takes place by fusion of two somatic cells of genotypes

SEXUAL REPRODUCTION

Two different basidiomytes form genotype somatic cells and then perform plasmogamy. This results in dikaryon whose branch grows continuously. Its single cell is called basidium(dikaryon). A single basidium has 2n nucleus. This nucleus perform meiosis and form (n) nucleus. This cell later form basidiospores(n) which are exogenous. When these spores get mature, they get detached. These later germinate and then the cycle of sexual reproduction in Basidiomycetes continues.

EUTEROMYCETES:- It is also called as imperfect fungi because of the absence of sexual reproduction. They show only asexual or vegetative phases of reproduction. If sexual reproduction stages some fungi are undiscovered so they are kept in this group. Later when other stages are discovered, then they are moved to ascomycetes or basidiomycetes. Some members are parasites and some are saprophytes. If the sexual stages of some fungus look very different to the asexual stage, then sexual stage and and asexual stage are kept in two different groups. Some members are also decomposers and therefore help in mineral cycling.