Unit 4 Lesson 9: Disturbances in Ecosystems Flashcards
ecosystem
all the organisms in a given area along with the nonliving things with which they interact
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biodiversity
the variety of life in a community, and ecosystem, or the entire world
Healthy ecosystems are in homeostasis. What does that mean?
. That is, all the elements of the ecosystem relate to one another and are in balance, which tends to maintain the ecosystem’s stability.
Discribe how an ecosystem funcatiosn
Every part of an ecosystem interacts with every other part. In a healthy ecosystem, all the parts are in balance, but disruptions happen all the time. Those disruptions can be temporary or permanent. Some smaller disruptions can cause large, long-term changes, while some disturbances may look enormous, but only have a temporary impact.
homeostasis
Living things maintain a stable internal state evenwhen their evironemnt changes
Disruptions in a homeostatis ecosystem
This stability does not mean that the ecosystem is never disrupted, but that after most routine disruptions, the ecosystem can return to its original homeostasis. When an ecosystem becomes unstable though, homeostasis can be lost completely.
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population
all members of a species in a given area at a given time
community
all members of all species in a given area
Bwnfits of algae
Algae are beneficial to an ecosystem in many ways. They grow by converting energy from sunlight, water, and carbon dioxide. By converting those elements to organic matter, they provide a food source for innumerable other species.
Imagine a population of sharks living in a Pacific kelp forest. Giant kelp are the largest seaweeds in the world. They grow from the seafloor and can be up to 100 feet tall. In a kelp forest ecosystem, giant kelp tower up from the seabed, providing shelter and food to thousands of invertebrates, fish, and mammals. A healthy kelp forest is home to sharks, sea lions, sea urchins, and hundreds of species of fish and crustaceans.
Now, imagine that suddenly the sharks are removed from the ecosystem. This could happen through fishing/capture by humans, disease, or severe weather. The balance of the ecosystem will change. If the top predator is gone (or reduced), the prey species will increase in number.
A disturbance like this in an ecosystem can impact all members, both biotic and abiotic. Predator species that competed with the sharks, like sea lions, will not have to work as hard to find food. Without the sharks, more sea lions will survive to reproduce. Sea lions, with more fish to eat, will also spend less time foraging for more challenging foods, like sea urchins. That will cause the sea urchin population to increase. Sea urchins will eat anything they can find, but they particularly like giant kelp. A large number of hungry sea urchins can destroy all the kelp in a forest.
Giant kelp offer shelter to the smaller inhabitants of the kelp forest. If the kelp forest is removed, fish will have nowhere to live. In addition, giant kelp are the dominant algae species in their forests. They grow taller than any other species, capturing most of the available light. This keeps the populations of smaller algae low.
But when some algae are exposed to too much sunlight, they can experience a population overgrowth, an algae bloom, which is toxic to other species. Whats an algae bloom
During a bloom, a species of algae experiences exponential growth. That causes it to become densely concentrated in the water. A dense bloom of algae, dying and decaying, can deplete the water of oxygen. This kills oxygen dependent fish and other creatures, and can cause a ‘dead zone’ that covers miles of ocean. When giant kelp forests are removed, more sunlight penetrates to the sea floor, which sets up the conditions for just that kind of algae bloom. The entire kelp forest can become a place where nothing could survive.
In some areas, seasonal flooding happens on a regular basis, which impacts the organisms living there. Seasonal floods can be very dramatic, altering the entire landscape. Imagine a river ecosystem after a snowy winter. As snow melts, its water flows into the river, increasing the depth and width of the river. The riverbanks overflow, causing flooding in the surrounding areas.
The flooding creates a temporary wetland. Birds, frogs, lizards, and many other organisms use the additional water for feeding, mating, and growing. During these times, the biodiversity of the area increases because of the large influx of wildlife taking advantage of the new conditions.
As the river returns to normal, the waters recede and the wetlands disappear. The wildlife that has depended on the wetlands disappear. Disturbances like this can temporarily alter the ecosystem, but, overall, the area remains the same (or at least returns to its original condition once the disturbance has gone away). After the floods end, homeostasis is restored.
Like sharks leaving the kelp forest, though, some disturbances to an ecosystem have long-term consequences. More permanent disturbances to an ecosystem can include:
- Severe weather
- Introduction of a new species
- Increased predation
- Damming of a river
Water from the upstream source accumulates behind the dam, forming a lake and flooding the surrounding areas. Places that were once dry are now under water. What imapct could a dam have
This changes the dynamics of the ecosystem, forcing some organisms to move to other areas and drowning the original plant life. Biodiversity is also impacted due to this loss of species.
Here, the water levels are almost permanently increased. Over time, the once dry areas that are now flooded may become an entirely new ecosystem, supporting a completely different community of life. This community includes plants, insects, animals, and bacteria. A new homeostasis has been achieved.
Any environmental changes can alter the biodiversity of an ecosystem.
Some cause an impact for a short time. The disturbance does not last very long, nor cause much damage, so the amount of biodiversity is not permanently affected. Some disturbances cause more permanent effects, and can even give rise to a completely new ecosystem.
How could a disturbance, such as seasonal flooding, change the biodiversity of an ecosystem?
Seasonal flooding, like melting snow or rains, can change an ecosystem temporarily. This type of disturbance changes the environment so organisms can reproduce or feed, and then changes back to the way it was once the water has subsided.
What could occur that would reduce the biodiversity of an ecosystem at the community level?
Since a community is all of the living organisms in an ecosystem, a large change that impacted all of them would have to occur. This could include a severe storm or large oil spill.
Would a road be included as part of an ecosystem?
Yes. An ecosystem is all the living and nonliving things in an area.
