2. What are pioneer species? What is the role of pioneer species?
Pioneer species are the first species that colonize places where there were previously no other living organisms, such as algae that colonize bare rocks. In general, pioneer species are autotrophs or maintain harmonious ecological interaction with autotrophic organisms(such as autotrophic bacteria, herbaceous plants, lichens).
A pioneer community is formed of species able to survive in hostile environments. The presence of these species modifies the microenvironment, generating changes in the abiotic and biotic factors of the ecosystem in formation. Therefore, they pave the way for other species to establish themselves at the location through the creation of new potential ecological niches.
Primary and Secondary Ecological Succession
3. What is the difference between primary ecological succession and secondary ecological succession?
Primary ecological succession is the changing sequence of communities starting with the first biological occupation of a place where there were no living organisms previously. For example, the colonization and the following succession of communities on a bare rock is a case of primary ecological succession.
Secondary ecological succession is the changing sequence of communities starting with the substitution of a community by a new one in a given place. An example of this is the ecological succession of the invasion of plants and animals on an abandoned crop or land.
4. What is the climax stage of an ecological succession?
The climax stage is the stage of the ecological succession in which the community of an ecosystem becomes stable and does not undergo significant changes. In the climax community, practically all ecological niches are explored and greater biodiversity is possible. In this stage the biomass, the photosynthesis rate and cellular respiration reach their maximum levels and therefore net primary production (NPP = organic material made by the producers – organic material consumed in the cellular respiration of the producers) approaches zero. During the climax, the amount of oxygen released by photosynthesis is practically equal to the oxygen consumed by respiration. (This is one more reason why it is wrong to say that the Amazon Rainforest, an ecosystem at the climax stage, is “the lung” of the earth. Other reasons are: because lungs are not producers of oxygen; and because the algae and cyanobacteria of phytoplankton are the main producers of the molecular oxygen on the planet.)
The Dynamics of the Ecological Succession
5. How do biodiversity, the total number of living organisms and biomass vary during ecological succession?
Biodiversity, the number of living organisms and the biomass of an ecosystem tend to increase as the succession progresses and stabilize when the climax stage is reached.
During the initial stage of succession, the use of carbon dioxide and the fixation of carbon into the biomass are high, since the total number of living organism in the ecosystem is increasing. During the climax stage, the use of carbon dioxide by photosynthesis equals its production by cellular respiration and the fixation of carbon into the biomass approaches zero.
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Primary And Secondary Succession Essay
Ecosystems are environments where biotic (living) organisms and abiotic (non-living) components interact together to create a functional, complex network of nutrient and energy cycling. These balanced environments take time, sometimes many years, to develop. During the course of development, species are replaced by other species within the ecosystem, a process known as succession. Primary succession happens when species grow in locations where organisms have never previously existed. Secondary succession occurs after an ecosystem disturbance. The basic difference between primary and secondary succession is the presence of soil. When primary succession begins, soil is not present; in the case of secondary succession, soil is already in place. What occurs during primary and secondary succession? How can an ecosystem recover from a natural or man-made disaster? By examining the workings of an ecosystem and a case of primary and secondary succession, environmental scientists can find the answers to these questions.
What is an Ecosystem?
As stated above, an ecosystem is a place where biotic and abiotic components interact within their environment. Living parts of an ecosystem include animals and plants. These animals and plants perform roles of producers, consumers, or decomposers. According to Raven & Berg (2004), these three roles are indispensable within ecosystems. Producers provide food and oxygen, consumers create balance between producers and decomposers, and decomposers prevent accumulation of dead organisms and waste products (p. 72). Non-living components of ecosystems include soil, sun, and weather conditions. Working together, the biotic and abiotic components cycle nutrients within the ecosystem. This is vital action because without nutrients the ecosystem and its inhabitants would not survive. Where do ecosystems come from and how do they begin? The answer lies in the definition of primary succession.
The very beginning of an ecosystem happens when primary succession occurs. After devastation from volcanism, glaciations, or sand dunes, an environment is devoid of soil and living organisms do not exist. From this barren emptiness, primary succession begins with a pioneer community. Raven and Berg (2004) give an example of primary succession within Glacier Bay, Alaska (p. 87). In the case at Glacier Bay, rocks remain after a glacier's retreat and the pioneer community is lichens. The lichens form soil, where colonies of moss thrive. The soil condition slowly progresses to the point where grasses and ferns can grow. Eventually the soil increases enough for shrubs to grow. Thanks to primary succession, over time the emptiness of Glacier Bay becomes a forest community. Once living organisms unite with non-living components, much like what happened at Glacier Bay, a new ecosystem is born. As the example at...
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