3.3: The Importance of Biodiversity
pg. 83
Key Concepts:
3. Biodiversity describes the variety and abundance of life in an ecosystem.
4. Many human activities impact and threaten the sustainability of natural ecosystems.
Biodiversity: the variety of life in a particular ecosystem; also known as biological
diversity.
Species Richness: the number of species in an area.
- There are approximately 1.5 million species that have been identified by scientists.
- It is estimated that there are between 5 – 50 million species on our planet.
- In Canada has identified 71 000 species.
- The estimate of species to be found in Canada is 140 000 to 200 000 species.
- The variety of organisms found in a given area is called biodiversity.
- The actual species measured in a given area is called species richness.
- Species richness is highest closer to the equator and decreases as you move towards the
poles.
Biodiversity under Attack
Extinct: refers to a species that has died out and no longer occurs on Earth.
- Many species are going extinct before some have been identified.
- Humans have destroyed their habitats, through deforestation, urban and agricultural
development, pollution, and climate change.
- Extinction is a natural process. As species become extinct, new species evolve.
- As humans colonize areas, the negative impact causes specie to become extinct.
- Within 440 years, over 700 species have become extinct. The rate is increasing.
Figure 4: Timeline of recent species extinctions in Canada.
Species at Risk
Extirpated: a species that no longer exists in a specific area.
Endangered: a species facing imminent extirpation or extinction.
Threatened: a species that is likely to become endangered if factors reducing its survival
are not changed.
Special Concern: a species that may become threatened or endangered because of a
combination of factors.
- As species population size decreases and move below a critical level, the specie will no
longer be able to fulfill their ecological niche.
- The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) is
responsible to monitor the decline of species in Canada.
- there are four categories in which at risk species are classified; Extirpated, Endangered,
Threatened, and Special Concern.
Table 1: Examples of Canadian Extinct Species and Species at Risk.
Classification
Number of Canadian
Species (2008)
Extinct
13
Extirpated
23
Endangered
238
Threatened
146
Special Concern
157
Examples
Great Auk, Passenger
Pigeon, Sea Mink.
Paddlefish (from all of
Canada), Atlantic Walrus
(from the Northwest
Atlantic)
Barn Owl (in some
regions), Swift Fox,
Northern Cricket Frog.
Humpback Whale, Wood
Bison, Kentucky Coffee
Tree.
Polar Bear, Red-headed
Woodpecker, Atlantic Cod.
- When species are identified to be at risk, another agency develops an action plan,
Recovery of Nationally Endangered Wildlife, (RENEW).
- Humans must reverse their negative impact, to protect Earth’s biodiversity.
Evidence of Learning: Students can …
- recognize that most species have not yet been identified or studied.
- understand that extinction is a natural process.
- explain how human activities cause a growing number of extinctions.
- distinguish among Canada’s categories of at-risk species.
Check Your Learning
Questions 1 – 8, page 86
Summary:
- Most species have not been identified or studied.
- Biodiversity tends to be higher near the equator.
- Human activities threaten biodiversity.
- Extinction is a natural process, but human activities have greatly increased the rate of
extinction.
- The Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
categorizes at-risk species as extirpated, endangered, threatened, or of special concern,
- The Recovery of Nationally Endangered Wildlife (RENEW) agency prepares action
plans for endangered or threatened species.