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Earth is endowed with living and nonliving things. The attributes of living things include growth, metabolism, Reproduction, Irritability and so on. Viruses are considered as Biological puzzle and exhibit both living and non living characteristic features. They are ultramicroscopic, obligate parasites and cause disease in plants and animals. They multiply by lytic and lysogenic cycle.
Five Kingdom classification was proposed by Whittaker, which include Monera, Protista, Fungi, Plantae and Animalia. Carl woese divided the living world into 3 domains- Bacteria, Archaeae and Eukarya. The domain Eukarya include Plantae, Animalia and Fungi. A new Kingdom called Chromista was erected to include Diatoms, Cryptomonads and Oomycetes. Bacteria are microscopic, prokaryotic organisms and possess peptidoglycan in their cell wall. Based on Gram Staining method they are classified into Gram positive and Gram negative type. They reproduce asexually by Binary fission. Sexual reproduction occurs through Conjugation, Transformation and Transduction. Archaebacteria are prokaryotic and are adapted to thrive in extreme environments.
Cyanobacteria are prokaryotic organisms and are also called Blue Green Algae. The members of this group are ensheathed by mucilage cover. They reproduce by vegetative and asexual methods.
Fungi are Eukaryotic, heterotrophic, unicellular or multicellular organisms. The cell wall is made up of chitin.
They reproduce asexually by producing sporangiospores, conidia, Thallospores, chlamydospores etc., The sexual reproduction is isogamous, ansiogamous and oogamous. In addition, gametic copulation, gametic fusion, spermatisation are also found. They are beneficial to mankind. Some are known to cause disease in plants and human beings.
Rhizopus is commonly called’ Bread mold fungi’. It belongs to the class Zygomycetes. Asexual reproduction occurs by the production of sporangiospores. During sexual reproduction gametangial copulation occurs and zygospore is formed. Agaricus belongs to the class Basidiomycetes.It is a saprophytic fungus. Three types of mycelium , primary, secondary and tertiary mycelium are produced. Sexual reproduction is present
Basidiocarps are produced after the sexual reproduction. It bears basidia on which four basidiospores are produced.
The symbiotic association between the roots of higher plants and fungal mycelium is called mycorrhizae. Lichen thallus includes both phycobiont and mycobiont. It is an example for symbiotic association.
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