Unit 4 Lesson 13: Modest Disturbances in Ecosystems Flashcards
ecosystem
all the organisms in a given area along with the nonliving things with which they interact
biodiversity
or biological diversity – the variation among organisms in an ecosystem
homeostasis
the process of an organism maintaining stable internal conditions despite changes to the ecosystem
Whatever the disturbance, there is always an impact on the
ecosystem
A tropical storm came ashore and severely damaged the trees and the underlying sand and soil. What kind of impact would this have on the ecosystem?
The damage will have an impact on both biotic and abiotic factors. Organisms that used these trees as their homes will be displaced, or at least severely disrupted. Their food supplies could be reduced, the amount of space they have to live would be smaller, and a number of possible mates could be gone. The tree roots have been disturbed, and are no longer as effective at anchoring their topsoil. This could cause an increase in erosion, which will reduce the soil nutrients available to the plants in the ecosystem.
Moderate disturbances like this one do not completely wipe out the ecosystem, but rather affect each part of it in some way, sometimes to the point where organisms can no longer live there.
Disturbances come in varying degrees of severity. Some are light, meaning they do not have much of an impact on the community. What is an example of a light disturbance
A light disturbance could be something like a single tree falling over, or a quick freeze of a pond during the fall.
Other disturbances are moderate. This type usually has some form of impact on the ecosystem. What are some examples
Storms, disease, and fires can all impact biodiversity.
What happens to homeostasis during a disturbance
As happens with any disturbance, the homeostasis, or equilibrium, of the ecosystem will become unbalanced. The damage will have an impact on both biotic and abiotic factors.
What happens to biodviery during a moderate disturbance
Moderate disturbances to an ecosystem can have varying degrees of effect on biodiversity. Biodiversity is not necessarily decreased, but individual population sizes may change. Things like scheduled hunting seasons, seasonal flooding, or drought may have a great impact initially, but over time, might not damage the ecosystem very much.
In fact, some scientists believe that these types of disturbances may actually serve to maximize ecosystem diversity. This is called the
intermediate disturbance hypothesis.
intermediate disturbance hypothesis.
the hypothesis that moderate levels of disturbance will promote a larger diversity of species over a low or high level of disturbance
In areas that experience only light, low-level disturbances, species may tend to overspecialize. Elaborate
If a river’s level is always stable, then the most competitive species will be those who are best adapted to the river’s level. In this low-stress environment, competition between species, not adaptation to change, will determine the makeup of the ecosystem. That means that the dominant species will out-compete all others for food and resources. As less competitive populations decrease, there will be a loss of biodiversity.
In areas that experience high-level disturbances, on the other hand, species are at risk of total extinction. Elaboraet
Consider a high-level disturbance like a meteor strike. No species can adapt to survive a direct hit from a meteor, and only highly mobile individuals can possibly escape it. High-stress environments can be lethal to entire ecosystems.
Areas that experience regular, moderate disturbances offer conditions that encourage the greatest species diversity. Picture a low-lying area that seasonally floods when the mountain snows melt and flow downstream. The banks of the rivers overflow their boundaries, flooding the surrounding areas. What impact would this have
The banks of the rivers overflow their boundaries, flooding the surrounding areas. At this time, the organisms living in those flooded areas may be displaced. Some species will have to move to higher ground to search for resources. They may experience a reduction in population. In their absence, species which can live in the wetter conditions will be able to find food more easily, and from different sources. These species may find their populations increasing.
If the flood lasted forever, those species that remained by the river would become dominant. Seasonal flooding usually only lasts for a short time, though, so the ecosystem will return to normal after a while. Once the floodwaters recede, those displaced individuals can return to their normal hunting and breeding grounds to resume their activities. The more adaptable species will compete for food again. Population levels will normalize. Biodiversity will be preserved.
Why is the gypsy moth caterpillar not considered an invasie species but a modest distrubance
Gypsy moth caterpiller domlish tress leaves but gypsy moth populations are not consistently high year after year. Like all insects, in each life stage the moths can die due to weather events, disease, and predation which will impacts their numbers the following year. When the moth population is high predators will flock to them. Researchers have determined that heavier outbreaks occur every seven to ten years.
The amount of damage done during an outbreak depends on the moth population. Generally, damage from a gypsy moth outbreak is quite localized. Outbreaks only occur seasonally, which also limits the scope of the damage. With these limitations, the ecosystem is able to return to equilibrium even after a heavier moth outbreak. For these reasons, gypsy moth outbreaks can be considered modest disturbances in the ecosystem.
During the dry season, a campfire burns out of control in a small stand of trees. The fire is contained, but not before 20 oak trees are completely destroyed. What is the likely effect on ecosystem biodiversity?
In a moderate disturbance like a forest fire, biodiversity is likely to remain at a high level.
How does a modest ecosystem disturbance compare with one that is more severe? What would be an example of each?
A modest ecosystem disturbance is one that does not affect the biodiversity of the area over the long term. It may change it slightly at first, but then the populations are able to return to normal once the disturbance subsides. A seasonal flood is an example. A severe disturbance impacts biodiversity on a much larger scale, such as when a forest fire completely destroys a forest. Here, the ecosystem is less likely to recover less quickly due to the devastation.
Why is a gypsy moth infestation considered only a modest disturbance to an ecosystem?
The main reason a gypsy moth infestation is considered a modest disturbance is because its overall impact on the biodiversity of the ecosystem is usually minimal, seasonal, and cyclical.
What regulations are placed on hunting to try to maintain biodiversity of the ecosystem?
The number of deer taken, what time of year the deer are taken, and the hunting method used are regulated to maintain biodiversity.
Is hunting good for maintaining biodiversity in a forest? Explain.
