How Organisms Cope With Biotic Environmental Factors Essay

How Organisms Cope With Biotic Environmental Factors - Essay Example Initially, organisms could survive without oxygen but with the evolution of the life forms, oxygen became inevitable for survival, which could be understood with the help of soft-bodied metazoans. This aids in the development of oxygen growth curve. On the other hand, ozone provides a shield that protects the biotic forms from harmful UV radiations of sunlight, without this shield life would have been impossible on the planet. Evolution of biotic forms from simple to the complex took place in a gradual manner. Single-celled life forms interact with each other, such interaction resulted in an evolutionary impact, as various species evolved due to such meaningful interactions, namely, symbiotic associations and other interactions, animal diversity prevailed. Evolution in life forms generated competition for food and shelter. Those who could survive the competition were considered as evolved and supreme. These organisms started adapting themselves to the environmental modifications and to the kind of food available, consequently, further diverse forms evolved. Eventually, some of the organisms migrated to land and demarcated themselves as land animals while others remained as sea animals. Over the eras, both these forms developed into numerous life forms from Prokaryotes to eukaryotes encompassing invertebrates protists, fungi, to vertebrates encompassing fish, amphibians, reptiles, birds, and mammals. Q. 3. Give a detailed account of the structure and differentiation of the fungi. Fungi are the eukaryotic life forms, they occur in filamentous form with the rigid cell wall of chitin (chain of N-acetylglucosamine), and yeast forms with a cell wall made up of mannose, but are devoid of chlorophyll. They are saprophytic, free-living organisms and derive their nutrition from dead, organic matter, by breaking down of complex chemical macromolecules, leading to the spoilage of food, leather, and other organic matter. They diverged from animal Kingdom 1.5 billion years a go. Fungi exist in three forms, which are: 1. Unicellular forms, e.g., yeast, Saccharomyces cerevisiae (budding yeast). They possess oval, ellipsoidal or rod-shaped morphology. The size is larger than the bacterial cells, they grow on agar as compact colonies. They display asexual mode of reproduction with the birth scar on daughter cell while a bud scar on the mother cell. Budding could be multipolar or bipolar. However, there are certain organisms which are capable of modifying their morphology and physiology so as to form discrete structures such as spores. Further, a swing between the filamentous and yeast forms could also be displayed in Histoplasma capsulatum, these forms are directed by growth conditions such as temperature, nutrient, and oxygen availability. Filamentous in the soil, asexual reproduction leads to conidia formation. Conidia disperse spores which may reach the lungs if inhaled leading to tissue damage and lesions. The yeast form does not produce conidia. 2. Mou lds which are filamentous and proliferate as elongated and branched hyphae called mycelium, which may be vegetative hyphae or aerial hyphae. The growth of the mycelium occur at the tip, they have well-developed vacuoles and vesicles which are involved in elongation.