Eutrophication of lakes. Some lakes also demonstrate the reverse process (meiotrophication), becoming less nutrient rich with time. The main difference between natural and anthropogenic eutrophication is that the natural process is very slow, occurring on geological time scales. Eutrophication is a common phenomenon in coastal waters. In contrast to freshwater systems, nitrogen is more commonly the key limiting nutrient of marine waters; thus, nitrogen levels have greater importance to understanding eutrophication problems in salt water. Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters a confined channel. Upwelling in coastal systems also promotes increased productivity by
Artificial reproduction Artificial reproduction Artificial reproduction/propagation is the creation of new life by other than the natural means available to an organism. Examples include artificial insemination, in vitro fertilization, cloning and embryonic splitting, or cleavage. Cutting plants' stems and placing them in compost is also a form of artificial reproduction. We can grow many plants from one plant by using the man-made methods. The process of growing many plants from one plant by man-made methods is called artificial propagation of plants. A number of methods of artificial propagation of plants are used in agriculture (for raising crops), and horticulture (cultivation of vegetables,