Ecology - Chapter 3 (Jared)
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Definition: The number and variety of different organisms found inside a specific region
Example: Say there were two ponds, one small pond and one big pond. The small pond only has about 100 different species within it. The larger pond has around 1000 different species. Because the larger pond has more different species in it compared to the small pond, the larger pond has a higher biodiversity.
- So far, scientists have identified 2 million different species, but there are estimates that the total number of species on Earth range from 5 million to 100 million
- Diverse ecosystems need to remain sustainable for biodiversity to remain high
- Protecting individual species is critical to biodiversity (see Protect for more details)
- There are many different ways scientists measure biodiversity, including canopy fogging, quadrat sampling, transect sampling, and netting
- Computer databases hold lots of information about biodiversity of specific areas
- Plants, insects, fungi, and small invertebrates are much more diverse than larger animals
- There are "hotspots" of biodiversity (see Biodiversity hotspot for more details)
Definition: To legally guard a species of special concern from harm
Example: In Kruger National Park in South Africa, elephants (see image below) had been hunted for the ivory in their tusks for years. In 1960, elephants in Kruger National Park were protected from hunting. As a result of this, the elephant population underwent exponential growth.
- Protecting individual species and the ecosystems they live in are very important to Earth's biodiversity
- Some Canadian biodiversity hotspots have extra protection from human development, to preserve biodiversity (see Biodiversity hotspot for more for more details)
Definition: A place with a very high density of different species
Example: Lake Malawi (see image below), in East Africa, is a biodiversity hotspot; although it is about the same size of Lake Erie, which has about 150 fish species, Lake Malawi is home to about 1000 fish species.
- Hotspots in Canada include Carolinian Canada and the Leitrim Wetlands
- Carolinian Canada only takes up 1% of Canada's landmass but has a higher number of species than any other ecosystem in Canada
- Some hotspots are given a special status, which protects the hotspot from human development, so as to preserve the biodiversity of the hotspot (see Protect for more details)
- Long Point Bay on Lake Erie has been named a World Biosphere Reserve, one of many in an international network
- Most of the biosphere's biodiversity hotspots are located in South America, South Africa, and South Asia
Definition: All the populations of different species that interact in an area or ecosystem
Example: The fish populations, the coral populations, and the sponge populations are all part of a coral reef's (see image below) community.
- Certain species can have a greater impact on a community
- Because species depend on interactions and relationships with other species (eg. symbiosis, competition, predation etc.) preserving the biodiversity of a community is essential to protecting each of the individual species
- Two types of species that greatly affect communities are dominant species and keystone species (see Dominant species and Keystone species)
Definition: Species that have the largest biomass of any member of the community it inhabits
Example: In the 1900s, American chestnut trees were a dominant species in North American forests, meaning they had the largest biomass in the entire community.
- In terrestrial ecosystems, dominant species are always primary producers
- The removal of a dominant species can greatly affect a community
Definition: A species that can greatly affect population numbers of an ecosystem
Example: Sea otters are keystone species, because without them, the health of their ecosystem would greatly decline. Sea otters eat sea urchins, which consume kelp, which act as a habitat for fish. Without sea otters, the sea urchin number would rise, causing kelp biomass to decrease, causing any fish populations that use kelp as a habitat to decrease also.
- Keystone species are much less common than dominant species but still extremely important to the health of an ecosystem
- Keystone species are generally not abundant
- Keystone species can be plants or animals
Definition: The breeding of endangered wildlife in settings controlled by humans to increase the species' population size
Example: The black-footed ferret nearly went extinct in the 70's, but a small American population survived. A few wildlife managers were able to capture this population and put them into a captive breeding program, to bring them back from the brink of extinction.
- There is a captive breeding program at Toronto Zoo
- Captive breeding is helpful for making a population stable again
Definition: A species that ends up creating a new ecosystem by making big changes to a landscape
Example: Beavers are ecosystem engineers; by creating dams in moving streams and creeks, they end up creating an entirely different ecosystem.
- Ecosystem engineers alter a landscape in a way that makes it suitable for additional species.
- The actions of an ecosystem engineer can start a succession of different ecosystems (see Succession for more details)
Definition: The string of changes in an ecosystem that occur over time, following a disturbance
Example: A beaver's actions (building a dam) begin a succession. The beaver's pond changes from forest, to flooded forest, to sunny pond, to an abandoned pond that becomes a beaver meadow.
- There are many different stages in ecological succession
- Each stage in ecological succession is ideal for different species
Definition: The alteration of an ecosystem that is so drastic that many species can no longer live within it; essentially the destruction of a habitat
Example: Forests contain many species. If a forest with many species inhabiting it were to be logged and cleared for human use, the habitat would essentially be destroyed (see Deforestation for more details)
- Habitat loss can cause Earth's biodiversity to decrease
- Habitat loss can be caused by natural disaster or human activity
- Volcanic eruptions, wildfires, droughts, and severe storms are all examples of natural events that cause habitat loss
- Deforestation, wetland draining, and river damming are all examples of human activities that cause habitat loss (see Deforestation for more details)
Definition: The clearing of forests for human use, without ever replanting them
Example: Canada has a very large boreal plains ecosystem with many boreal forests, and is home to more species of breeding birds than any other forest ecosystem in North America. From 1966 to 1994, the annual deforestation rates in this area (the rate that these forests are cut down) were three times higher the average rate of deforestation of worldwide.
- Large sections of forests are cut down for timber or cleared for farming
- Tropical forests cover about 7% of Earth's land, yet account for half of all species on Earth
- Deforestation can cause biodiversity to greatly decrease
Definition: A species that is introduced into a new part of the biosphere from another part of the biosphere
Example: In order to increase a ship's stability, ship collect seawater (which is filled with many organisms) and hold it in storage tanks. When they reach their destination, this water, and all the organisms in the water, is released (see image below). The species that are picked up by these ships and are dropped in a location are alien species.
- Alien species are also called introduced species, non-native species, and exotic species
- Alien species can be released on purpose, but mostly arrive by accident
- Most alien species are harmless or beneficial to their environments
- Alien species can also be invasive species (see Invasive species)
Definition: A species that can take over a native species' habitat or their bodies
Example: The zebra mussel (see image below) is an invasive species that were introduced to the Great Lakes from Asia. They have been able to out-compete native organisms, causing their populations to decrease. For example, the population of shrimp-like crustaceans that share the same food source as the zebra mussel have declined greatly since the arrival of the zebra mussel.
- In many cases, invasive species upset the equilibrium of an ecosystem
- Invasive species can reduce the biodiversity of an ecosystem
Definition: The excessive use or extraction of a resource, causing it's depletion
Example: The population of the passenger pigeon (see image below) was about 5 billion at some point in time. However, partly due to overhunting by early settlers, the passenger pigeon went extinct in the early 1900s.
- Overexploitation can lead to extremely low population numbers, and possibly the complete disappearance of a species
- Overexploitation is a major threat to biodiversity
Definition: The death of all the members of a species
Example: Many scientists believe that an asteroid hit Earth 65 million years ago, which caused huge changes to Earth’s climate and also caused all species of dinosaurs to go extinct. (see image below for artist rendition of asteroid hitting the Earth)
- Extinction has occurred before humans even existed
- Extinction occurs when the death rate of a species remains higher than the birth rate of that species for a long period of time
- There are two patterns of extinction: background extinction and mass extinction
- Background extinction occurs over long periods of time
- Mass extinction is sudden, and causes the extinction of many different species
Definition: The current accelerated rate of extinctions, which is hypothesized to be caused by actions from humans
Example: Humans make many heavy demands on ecosystems. As a result of this, more species are going to extinct. This increased rate of species' extinction is known as the biodiversity crisis.
- Some ecologists estimate that the current rate of extinction is 100 to 1000 times higher than a normal background rate
- In a study that judged the status of over 40 000 species, 39 percent of these species were found to be at risk of extinction
- Because of the extreme changes to ecosystems that humans cause, many organisms that live in these ecosystems are unable to survive, and go extinct
Definition: The renewal of degraded ecosystems through human intervention
Example: The Don Valley Brick Works were a business that used to operate at the edge of Toronto (see image below). Bricks were made there, and a quarry for mining rock was also there. In 1994, a restoration plan for the site was implemented, which involved filling in the old quarry and adding a series of ponds. These ponds have become a habitat for lots of wildlife.
- The more scientists learn about the effects of human activities on ecosystems, the more attention is given to decreasing human impact on ecosystems and restoring ecosystems that have been altered by humans
- One of the major goals of restoration ecology is stimulate natural processes of regeneration, and to reproduce a sustainable ecosystem
Definition: The regrowth of a forest
Example: In Eastern Canada in the early 1900s, red pine trees were planted in land that had previously been cleared for agricultural purposes. As these trees grew, they provided shade for native species of trees, such as sugar maple, American beech, hickory, and ash, which have returned to the forest after many years.
- The regrowth of a forest takes many years
- Reforestation can occur through natural processes or through the planting of seeds and/or trees by humans
Definition: The use of a species to control the population growth of an unwanted species
Example: European Gypsy Moths (see image below) are serious forest pests with the capability of removing all the leaves off a tree. To battle the Gypsy Moth, a European fly called a parasitoid was introduced, a species that kills European Gypsy Moths by laying eggs inside a Gypsy Moth caterpillar.
- Biocontrol is used by ecologists to control alien species
- Sometimes, the species used for biocontrol can attack native species as well
Definition: The use of organisms to clean contaminated areas naturally
Example: Some plants are grown at toxic sites, because they collect the poisons in their tissues, cleaning the soils. When these plants are harvested, the soil quality increases.
- Bacteria have been used to break down oil from oil spills
- Bioremediation is related to bioaugmentation (see Bioaugmentation)
Definition: The use of organisms to add nutrients to soil lacking in nutrients
Example: Clovers (see image below) have been planted to replenish nitrogen levels in soil.
Bioaugmentation is related to bioremediation (see Bioremediation)
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