Embedded Files
Lincoln Index- Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
Top down control Vs. Bottom up control
Top down control Vs. Bottom up control
In the top down approach, the population of the organisms at the bottom of the pyramid are controlled by the organisms at the top.
Imagine a simplified ecosystem where there are plants, deer and tigers. The plants are the producers, the deer are the herbivores and the tigers are the top carnivores. The presence of tigers keep the deer population in check. If there were no tigers in this ecosystem, then the deer population would flourish to no end. Because of that, the plants would all be eaten. This would lead to a situation where almost all the plants are eaten by the huge, unsustainable population of deer and there is no food left for the deer. And so, that population of deer would eventually starve to death and the ecosystem would collapse.
Tigers eat the deer and make sure that their population is not too high, so that the plants are not overeaten and the ecosystem will continue to function.
The bottom-up approach is driven by the presence or absence of the producers in the ecosystem. Changes in their population will affect the population of all the species in the food web, and thus, the ecosystem.
In the same simplified example, let us consider the reverse scenario. What if the population of plants in the ecosystem dwindled to extremely low numbers? Then, the deer would have less food to feed on. Consequently, their population numbers would fall to reflect the lack of food resources. When the population of deer decreases, the tigers will also automatically face a shortage of food. And their population would also fall. If plants disappeared altogether, then the ecosystem would collapse.
Report abuse