Ecology Chapter 3
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- The number and variety of life forms, including species, found within a specific region as well as all the number and variety of ecosystems within and beyond that point.
- Scientists have identifies approximately 2 million species on Earth but the estimates for the total number of species on the planet range from 5 to 100 million species.
- For example: there might be 1000 species of organisms in a certain forest and this would be its biodiversity.
- To guard legally from harm a species that is listed as endangered, threatened, or of special concern.
- For example: governments can create conservation areas where an endangered species lives to stop hunting or habitat loss that would further decline the species population.
- A place where there is an exceptionally large number of species in a relatively small area.
- Hotspots in Canada include: Carolinian Canada, the Leitrim Wetlands, and the Georgian Bay Biosphere Reserve.
- It is a good idea to protect these hotspots to maintain the Biodiversity there.
- All the populations of the different species that interact in a specific area or ecosystem.
- Species interact with other species in many ways such as symbiosis, competition, predation, etcetera and all these interactions are part of the community.
- Species that are so abundant that they have the biggest biomass of any community member.
- In terrestrial ecosystems the dominant species are always primary producers because consumer biomass is always less than producer biomass.
- You can see how removing dominant species such as a species of plants could have a profound affect on the community because plants are always the base of the food chain, removing them can remove everything above them if that plant is the main food source of the higher organisms.
- A species that can greatly affect population numbers and the health of an ecosystem.
- Keystone species are generally not abundant but can still have a profound affect on their community of they are removed.
- An example would be the sea otter which helps keep the sea urchins population at a stable level for the rest of the community. If the sea otter populations decreases, then the sea urchin populations will increase and they will eat too much kelp and destroy the habitats of many species of fish.
- The breeding of rare or endangered wildlife in controlled settings to increase the population size. After they born and raised in captivity they are then released back into the wild.
- An example of captive breeding would be the breeding of the prairie dog by the Toronto Zoo to increase the health of prairie ecosystems.
- A species that causes such dramatic changes to landscapes that it creates a new ecosystem.
- An example of an ecosystem engineer would be the beaver. It creates a dam which turns a stream ecosystem into a pond ecosystem which suits their needs better because it creates a constant food supply of aquatic plants. Other organisms can benefit from this as well. The pond creates a safe place for young fish, migrating birds, and aquatic insects.
- The series of changes in an ecosystem that occurs over time, following a disturbance.
- The series of changes caused by beavers would be, change from a forested stream to a flooded forest, then to a sunny pond, and finally to a beaver meadow.
- The destruction of habitats, which usually results from human activities.
- Examples: Draining a wetland, deforestation, damming a river, etcetera, destroys the habitat of all the organisms that lived there.
The practice of clearing forests for logging or other human uses, and never replanting them.
A species that is accidentally or deliberately introduced into a new location. Alien species can arrive accidentally via shipments of food or other goods, or through the ballast water of foreign ships.
- A species that can take over the habitat of a native species.
- An example would be the zebra mussel which is native to Asia and was transported to the Great Lakes in the 1980s via ballast water, the zebra mussel can out compete native molluscs and crustaceans which has decreased the populations of these native species in the Great Lakes.
- The use or extraction of a resource until it is depleted.
- For example the passenger pigeon once had a population of about 5 billion but due partly to hunting the passenger pigeon went extinct in the early 1900s.
- The death of all the individuals of a species. This occurs when the death rate of a species remains higher than the birth rate of the species a long period of time.
- There is a normal background rate of extinction on the planet that would remain even if there was no humans simply because species can't adapt quick enough to their environment sometimes, but due to our huge exploitations of energy and resources the earth's biosphere is having a hard time supporting this and this results in more extinctions.
- The current accelerated rate of extinctions.
- Scientists estimate that the current extinction rate is 100 to a 1000 higher than the normal background extinction rate of the earth.
- The renewal of degraded or destroyed ecosystems through active human intervention.
- An example would be the restoration of the land surrounding the former Don Valley brick works. Bricks where made there in the past from rock mined from an on site quarry. The site was purchased in 1991 as conservation land. They filled in the quarry and created three ponds from diverted water from the Mud river that passed through the site. The ponds now filter water before in enters lake Ontario, provide habitats for organisms, and boardwalks for people to enjoy nature.
- The regrowth of a forest, either through natural processes or through the planting of seeds or trees in an area where a forest was cut down.
- In eastern Canada in the 1900s red pine trees where replanted in areas where the ground had previously been cleared for agriculture by European settlers, through natural succession over 80 years the forest eventually returned to a natural ecosystem with a variety of organisms.
- The use of a species to control the population growth or spread of an undesirable species.
- An example would by the use of a European fly called the parasitoid to control the population of an alien species; the gypsy moth. It does this by laying its eggs inside the gypsy moth caterpillars which eventually kills them. The introduction of this species did help control the population of the gypsy moth but it also had an unintended consequence of laying eggs in native moths as well an adversely affected the ecosystem in this way.
- The use of livings organisms to clean up contaminated areas naturally.
- Humans introduce certain plants to toxic sites because the plants absorb the toxins in their tissues. The plants are then harvested and this increases the soil quality of the toxic site.
- The use of organisms to add essential nutrients to depleted soils.
- For example, clover is often planted to replenish nitrogen levels in soils.
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