a) Primary and Secondary Succession
Primary succession occurs in areas where no previous life existed, such as on bare rocks after a volcanic eruption or a glacier retreat. It begins with pioneer species like lichens and mosses that can survive harsh conditions and initiate soil formation. Over time, as soil builds up, grasses, shrubs, and eventually trees colonize the area, leading to a stable climax community. This process can take hundreds of years.
Secondary succession happens in areas where an ecosystem previously existed but was disturbed or destroyed by events such as forest fires, floods, or human activities like agriculture. Since soil is already present, succession occurs faster. For example, after a forest fire, grasses grow first, followed by shrubs and trees, eventually restoring the original ecosystem. Thus, the key difference lies in the presence or absence of pre-existing soil and life.
b) Direct and Indirect Use Value of Biodiversity
Direct use value of biodiversity refers to the tangible products that humans obtain directly from nature. These include food (fruits, vegetables, fish), medicine (herbal remedies, drugs from plants), fuelwood, and timber. These resources are essential for survival and economic activity. For instance, neem leaves are used in traditional medicine, and forests provide wood for construction.
Indirect use value relates to ecosystem services that support life but are not consumed directly. These include climate regulation, water purification, pollination, and soil fertility. For example, mangrove forests protect coastal areas from storms and act as nurseries for fish, benefiting fisheries indirectly. Both types of values are crucial for human well-being and must be conserved for sustainable development.