How Organisms Cope With Biotic Environmental Factors - Essay Example

Questions 1. Using examples from the major groups of life describe how organisms cope with biotic environmental factors. Biotic factors encompass diverse life forms such as prokaryotes involving bacteria; eukaryotes like protists, fungi, plants and animals. These diverse forms of life evolved from the abiotic or non-living components, with gradual change in the atmospheric conditions and enhanced concentration of the oxygen from ~ 5 X 10-9 to the current, 21% of all the atmospheric gases. This high percentage is attributed to the process of photosynthesis, which utilizes the CO2, solar energy water and chlorophyll, an essential component for the respiration of eukaryotes. Interaction of biotic and abiotic components together with biotic-biotic interaction is responsible for the proliferation of life. 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 rigid cell wall of chitin (chain of N-acetylglucosamine), and yeast forms with 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 ago. 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 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. Moulds which are filamentous and proliferate as elongated and branched hyphae called mycelium, which may be vegetative hyphae or aerial hyphae. Growth of the mycelium occur at the tip, they have well developed vacuoles and vesicles which are involved in elongation. They may develop septa or compartments with pores in the septa or remain aseptate with numerous nuclei, the coenocytic condition. The septal pores may become blocked due to Woronin body, a protein molecule surrounded by a lipid membrane. 3. Mushrooms (an edible fungi), bracket fungi and puffballs. Other roles: Fungal strains also live in associations such as lichens and Mycorrhizae, or they proliferate as human pathogens causing Athletes foot and histoplasmosis. They are imperative in biogeochemical cycles. Dormant structure called sclerotia, which enable the organism to survive in unfavourable conditions, germinate to form hyphae. Sclerotinia gladioli, an obligate pathogen germinate to form hyphae, sexual and asexual structures. Numerous translocating structures, aiding movement in water, are also present called mycelial strands. In certain cases more complex forms of mycelium is present called parallel hyphae, with branched nutrient absorption. The co-ordination is highly synchronized as all the hyphae grow at the same rate. Such incidents are reported in pathogenic and decomposing fungi of plant roots, allow proliferation from one plant to another over long distances. Q4. With reference to structure, physiology and life cycles, discuss the diversity of protists. The Kingdom Protista is considered to be one of the most diverse of all other Kingdoms, since a large variety of species belong to Protista, which encompass all the eukaryotic organisms which are not plants, animals or fungi. Members of the Kingdom may be microscopic unicellular organisms to colonial, multicellular organisms, e.g., kelps. However, phylogenetic studies reveal that most of the protists resemble plants and animals more as compared to other members of the Kingdom Protista. Protista include Planktons which are producers, these are widely found on the stagnant water surface as blooms, dinoflagellates, responsible for paralytic shellfish poisoning. On land, they display nutrient cycle, able to survive in extreme temperature conditions. Chlamydomonas nivalis is called the snow mould as it is able to survive cold conditions. Other protists also live as parasites such as Phytophthora infestans, which is responsible for potato blight and was responsible for Irish famine in 19th century. They proliferate in symbiotic association such as dinoflagellates and cnidarians, lichens, an association of chlorophytes and fungi and association of Chlorella and Paramecium. They play vital role in shells, sediment and land formations such as formation of silica (frustules of diatoms are silica), protein and polysaccharide. Frustule exists in two parts, of these one is larger due to asexual reproduction while the sexual reproduction restores their original size. Cells with time die and decay leaving the frustule resistant from decay. Shells are preserved as fossils, indicating the existence of diatoms about 200 million years ago. Motility in protists also vary, they move either by cilia (e.g. Paramecium), flagella (e.g. Euglena), gliding (e.g. Toxoplasma), amoeboid (e.g. Amoeba) by either beating or pulling their organs of locomotion through water. Protists display numerous kinds of nutrition uptake from phototrophy as in Euglena, Algae (displaying plant like behaviour), heterotrophy, where the organism display ingestive mode of nutrition like animals (e.g. Amoeba), some protists display absorptive mode of nutrition similar to fungus and mixotrophy is displayed when they displayed both heterotrophy as well as phototrophy such as Euglena. Some cells display pellicle, bands of proteins under cell membrane and eyespot a pigmented organelle, they also have contractile vacuole as well as osmoregulatory organelle to remove water from the cells. Other organisms such as Plasmodium, the causal organism of malaria, possesses alveolates, alveoli under the plasma membrane. They also possess apicomplexans at the apex of cell allowing them to penetrate the cells and tissues. The mode of reproduction of protists also varies from asexual mode to sexual mode of reproduction, sporozoites is introduced by Anopheles mosquito, in liver of humans they are converted to another form called merozoites which invade RBCs, where they release toxins and as a result an individual gets fever. Some merozoites develop into gametocytes and hence they develop into gametes, indicating that protists also display sexual reproduction. Protists interact with the non-biotic world to absorb nutrition and to perform the process of photosynthesis but they also interact with the biotic world as they cause various diseases, Trichomonas, possess parabasal bodies which supports the Golgi apparatus, anaerobic-hydrogenosomes to carryout fermentation, they live in symbiotic association in intestinal and urogenital tract of vertebrates and invertebrates. They also live as parasites such as Trichomonas vaginalis. Another biotic interaction is seen Trypanosoma, which exists in four forms amastigote (non-motile form), and other motile forms- promastigote, epimastigote and trypomastigote, flagellum arise from kinetoplast. Trypanosoma brucei exists as trypomastigote in human trypomastigote while it occurs as epimastigote in tsetse fly. Disease conditions occur with the bite of the fly. The protist multiplies by binary fission in blood and invades lymph nodes to display symptoms such as recurring fever, CNS attack, lethargy and tremors. The protists thus display abiotic interactions when perform photosynthesis, biotic interactions when they live as parasites or exists in symbiotic association. Q5. Describe a selected range of abiotic interactions likely to occur in a named habitat and using the concept of gametophytic reduction describe an evolutionary scenario where abiotic pressure had a major input. Terrestrialisation is land plant diversity and the progression of complexity from ancestral to modern together with the evolutionary consequences of autotrophic nutrition and the terrestrial environment. Numerous driving forces paved the way for the migration of plants on land and their adaptation to the land conditions. This was associated with numerous predicaments encompassing lack of water – support protection, commodity, reproduction, since water is an abiotic element, it plays a vital role in the proliferation and survival of the biotic world. With the evolution of plants, vascular tissues also formed just like the vertebrae of animals. These vascular tissues play vital role in the transportation of the water and food molecules throughout the plant height. Vascularization is lignified vascular system, promotes growth in phototrophic manner, i.e., towards the light, these tissues also aids in spore circulation, in bryophytes and pteridophytes as well as the vascular tissue helps in the conduction in gymnosperms and angiosperms which involve tall plants with large number of leaves (to have wider surface area for the absorption of sunlight) and support the plant. Since vascularisation could not fulfil the process of reproduction of higher plant forms, therefore a new form of reproduction evolved called the reproduction by gametes. This encompasses: Bryophytes: gametophyte (haploid) is dominant, Sporophyte grows upon it. Pteridophytes: Sporophyte (diploid) is dominant, gametophyte is independent. Gymnosperms: Sporophyte (diploid) is dominant, gametophyte grows on (in). Angiosperms: Sporophyte (diploid) is dominant, gametophyte grows on (in). The modification from haploid dominant to the sporophyte dominant condition is attributed to the lack of water and plant adopts every means to conserve energy and water to have the availability of water for a greater length of time and hence has shown such an evolutionary process. The plants also show conservation mechanism in the formation of spores from big to little spores, these micro and mega spores generated division of labour with large female, food laden spores and lots of small mobile male spores, ultimately giving pollen and eggs. The process of evolution also paved the way for the formation of diploid organisms from the haploid organisms. Diploid organisms have two sets of chromosomes which further enhance their potential for survival even under adverse climatic conditions. Such alterations are the moves towards the better adaptation to critical conditions. When life cycles are compared, ferns display almost equal duration of gametophyte and sporophyte stages, while the gametophyte stage is reduced with the evolution as observed in more evolved species of plant world, pine. On the other hand, the most evolved species of plants, the angiosperms display gamete stage only during the process of reproduction, indicating gametophytic reduction describes an evolutionary scenario where abiotic pressure had a major input. Read More