Science

Kingdom Protista – Fungi like Protists & its Characteristics

Kingdom Protista – Fungi like Protists

· Fungi like Protists are saprophytic organisms (they feed on the dead and decaying matter). These are tiny organisms that have many nuclei.

· They were originally called fungi because they produce sporangia. These protists differ from fungi in that their cell walls have cellulose rather than chitin. Hence, placed in Kingdom Protista.

· Under suitable conditions, they form an aggregation called plasmodium which may grow and spread over several feet.

· These protists are heterotrophs. They have amoeboid body.

· The vegetative phase is without cell wall. During unfavourable conditions, they differentiates and forms fruiting bodies bearing spores at their tips. The spores possess true walls.

· They are extremely resistant and survive for many years, even under adverse conditions.

· They can cause disease in crops and animals.

Classification of Fungi like Protists

Fungus like protists can be classified as –

1.        Slime moulds

a.    Plasmodial Slime moulds

b.    Cellular Slime moulds

2.        Water moulds

Slime Moulds

· Occurs as brilliantly coloured irregular growth.

· Exhibits crawling movement over barks of trees, fallen twigs, leaves etc.

· Found in cool and moist habitat.

· They show Saprophytic Nutrition. Ingestion is by Endocytosis.

· Reproduction is by Spore Formation.

Plasmodial Slime moulds

·Acellular slime moulds commonly grow as slimy masses on damp places rich in dead and decaying organic matter.

·Exist as a plasmodium, a non-walled, multinucleated protoplasmic mass which has visible cytoplasmic streaming.

·The somatic phase is diploid and consists of amoeboid cell which undergoes mitosis without cytokinesis to form multinucleated protoplasm called plasmodium.

·The plasmodium slowly streams or glides over decaying organic matter putting out blunt finger-like pseudopodia showing amoeboid movement.

·Under unfavourable conditions the plasmodium contracts and gets surrounded by thick horny wall. It is called sclerotium.

·Each plasmodium reproduces asexually by the formation of several, small, sessile or stalked, brightly coloured fruiting body called Sporangia.

·The nuclei within the Sporangia divides by meiosis to form haploid spores which escapes out of plasmodium and develops into flagellated gametes.

·Zygotes are formed by fusion of flagellated gametes which gives rise to new plasmodium.

Cellular Slime moulds

·Found in fresh water and on rotting vegetation.

·The cellular slime moulds have multicellular plasmodia and haploid nuclei.

·They occurs in the form of, haploid uni-nucleated, naked (without cell wall) cell covered by plasma membrane.

·These cells are called myxamoebae. The myxamoebae move freely with the help of amoeboid movement and phagotrophic or holozoic nutrition.

·They grow and divide to form a large population of individuals.

·Under unfavourable condition a myxamoeba secrete a rigid cellulose wall to form the macrocysts. Macrocysts formation is a means of perennation.

Water Moulds

· Occurs as stationary filamentous growths mostly upon dead organisms in water and damp soil.

· Their Filaments are multinucleated coenocytic structures.

· They shows Saprozoic Nutrition.

· Some of Water moulds parasitize plants causing serious diseases. Eg. – Phytopthora causes late blight of Potato.

 

So, this was all about the Kingdom Protista – Fungi like Protists and their Characteristics. In the next post (Click here), we will discuss about the Animal like Protists in detail.

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