community sucession

Succession is a process of ecological change in which a series of natural community are established and then replaced over time. There are two kinds of succession, primary succession and secondary succession. Primary succession occurs in area where there is little or no soil and no living organism has become established. Secondary succession occur when a disturbance restarts succession at different point than that which primary succession. Laney's Edible Garden, for instance, is a secondary succession. It is located between the E building and the Oakland Estuary on the south end of campus. The growth of bacterial community in milk produces a succession of changes in milk. Dairy milk contains huge amount of nutrient such as carbohydrate (lactose), protein (casein) and lipid (butterfat) which will support the growth of microbes. Thus, dairy milk is heated- treat to kill disease causing pathogen through a process of pasteurization. Pasteurization kills most pathogen, increases the product's shelf life and preserve a natural taste of milk. After pasteurization, nonpathogenic bacteria such as Bacillus which is gram positive, rod shaped bacteria still present in milks and will metabolize protein into ammonia product and raise the milk's pH. Other bacteria such as lactobacillus and Streptococcus ferment lactose to lactic acid and acetic acid. Those acids sour the milk and convert the casein in milk to curd. The sour or putrid smell of milk is caused by Pseudomonas and Achromobacter. In small scale community such as in a container of milk, the community succession is examining through the presence of bacteria. In this exercise, we observe the physical change of milks at different conditions and identify the presence of microbes over time. Treatment 1 was used as control variable to compare the differences in treatments. Therefore, it was plotted on every graph. The pHs of milks drop gradually and are proportional to nutrient content, temperature and sealing on