Main Idea: How does it benefit the ecosystem if it contains many species and habitats
A. Biodiversity(Definition) – is a measurement of the degree to which species vary within an ecosystem.
1. There is a strong connection between biodiversity and the stability of an ecosystem.
a. For example: A natural forest contains many
different species of trees. If disease or insects
attacks one population, nearby trees of another species are likely to survive.
b. The mix of species in the ecosystem also makes it difficult for the disease organisms to move quickly through this environment. Here biodiversity serves as a barrier to the spread of the disease.
c. In contrast, on a tree farm where all of the trees are planted and are of a single species, the entire population could be seriously damaged by a single disease or insect attack.
2. The interactions between organisms may allow an ecosystem to remain stable for hundreds or thousands of years.
3. In established, stable ecosystems, populations tend to increase and decrease in size in a predictable pattern. Over time, however, the size of the population remains relatively stable.
a. For example: when the prey population increases, a large food supply causes the size of the predator population to rise, because each predator will eat as many prey as it can, the prey population rapidly decreases.
b. With the decline in a prey population, some of the predators begin to starve. When only a few predators remain alive, the prey population reproduces and greater numbers of prey survive. The cycle begins anew.
4. The loss of biodiversity in an ecosystem upsets its stability.
a. Removing species from an environment often causes instability due to the loss of organisms that were filling critical ecological niches.
5. Many species may be lost when natural disasters or human activities cause large-scale destruction to habitats.
a. Clearing large areas of tropical rain foresthas disrupted many ecosystems; some may never recover.
1. Although some species may be able to return to a damaged ecosystem, others with critical roles may be totally lost.
2. The interdependencies between populations in the original ecosystem may have been so great that if biodiversity is lost, the ecosystem may never be restored to its original state.
b. Species can also be lost when humans do not consider the environment impact of their actions.
1. Offering bounties for the removal of mountain lions from some environments sounded like a good idea at one time, but it led to population explosions of deer herds.
2. Soon the deer overpopulated the area, and overgrazing reduced the food supply so much that deer starved. The over grazing also led to soil erosion that caused permanent environmental damage.
3. The negative effects begun by the removal of mountain lions were evident for many years.
c. When humans clear land for agricultural purposes, the loss of biodiversity may also lead to an unstable environment.
1. Disease and insect pests present major problems to farmers whose crops are genetically similar.
2. For these farmers, any disruption threatens to affect the entire crop.
3. Farmers are constantly in search of ways to control insect pests and diseases in their crops, because they have created an environment that is always in danger of serious disruption.
4. In natural ecosystems, the diversity of species provides no such concentration of one kind of making it far less likely that any single pest or disease will cause problems.
B. Biodiversity Benefits Humans
1. Biodiversity also represents one of the greatest resources known to humans.
2. It ensures the availability of a rich variety of genetic material, some of which may prove valuable to humans.
3. The genetic diversity found in rain forests has provided humans with medicines, insecticides, and other useful resources.
4. If we destroy ecosystems, we lose much of the biodiversity they hold.
5. As diversity is lost, potentially valuable resources are lost with it.
There will be a quiz on this entire packet on _____
There will be a TEST on this entire packet on_____
[.] Unit XV: Ecology Notes [Notes2000 #8]