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Biodiversity
Equilibrium
Succession
Biodiversity
Species at risk
Human Impact
Equilibrium
 When biotic and abiotic features remain
constant over time
 On a large scale, healthy natural ecosystems
are in a state of equilibrium

E.g. biomes maintain characteristics
 On a small scale, ecosystems are in a
constant state of change

E.g. forest fire, disease outbreak
Ecological Succession
 Process of establishing and replacing a
community following a disturbance
 Primary succession: occurs on soil or bare
rock where no life previously existed

E.g. following a volcanic eruption, sandy
shores of coastline
 Secondary succession: follows a disturbance
that disrupts but does not destroy the
community

E.g. regrowth after forest fire
http://zoology.muohio.edu/oris/ZOO121/notes/graphics/ch04/fig4_24.jpg
http://www.geographyalltheway.com/ib_geography/ib_ecosystems/imagesetc/ecological_succession.jpg
Pattern
 Coloniser:

Lichen, moss
 Pioneer Community:

Small, hardy plants (e.g. grass)
 Shrubs & small trees
 Climax community:


Forest (large trees)
reached equilibrium
Benefits of Succession
 Helps ecosystem maintain long-term
sustainability
Biodiversity
.
 the number and variety of species in an
ecosystem
 important for maintaining a stable population
 Species richness: measurement of species
numbers
Biodiversity
 Case: The Irish potato famine resulted in
great hunger because the potato was such an
important crop.
 Today, people in developed countries have a
lot of food choices so they are able to meet
their nutritional needs.
Analysis Question
Ecosystems with HIGH
biodiversity
Ecosystems with LOW
biodiversity
Analysis Question
Ecosystems with HIGH
biodiversity
Rain forests and oceans,
coral reef
both have warm
temperatures, regular,
precipitation, abundant food
supply
In general, ecosystems
closer to the equator are more
rich.
(little to no pollution or
disturbance)
Ecosystems with LOW
biodiversity
The Arctic tundra and the
desert
both have extreme
temperatures and short
growing seasons for plants at
the first trophic level
In general, ecosystems with
extreme physical conditions
are less rich
Ecotone
 Organisms often move from one ecosystem
to another.
 An ecotone is a transition area between two
ecosystems that includes members of the
community of both ecosystems.
 Ecotones often have a lot of biodiversity.
Monoculture
 A monoculture is an ecosystem in which there
is only one plant
 often created by humans in agriculture
 Example: a wheat field
Problems with Monocultures
 More susceptible to pest infestation than
natural ecosystems
 Invaders do not have to search for food and
can multiply uncontrollably.
 All it takes is one invader who is resistant to
pesticides and the whole monoculture
ecosystem can be destroyed by the invader.
Monoculture
Advantages of monocultures
Disadvantages of monocultures
Monoculture
Advantages of monocultures
- increased food production
- can adjust farming
conditions in the field to
maximize production
(irrigation, fertilization)
- easier to harvest if all the
plants are in one area
Disadvantages of monocultures
- decreased biodiversity and
damages the environment
- pests can multiply in the
absence of their natural
predators
Extinction
 A natural process
 Usually caused by catastrophic event (e.g.
asteroid, volcano)
 Human activity has increased rate of
extinction
Species at Risk
 When a population's size declines below a
critical level, the species will not longer be
able to fill it ecological niche
 COSEWIC: Committee on the Status of
Endangered Wildlife in Canada

Responsible for categorizing species into atrisk categories
 RENEW: Recovery of Nationally Endangered
Wildlife

Responsible for preparing action plans to
ensure recovery of endangered or threatened
species
Species at Risk classifications
Classification Definition
Extinct
Species no longer exists
Extirpated
Endangered
Threatened
Special
concern
Example
Passenger
pigeon
Species no longer exists in the wild in Atlantic
a specific area but live elsewhere
walrus
Species in imminent danger of going Barn owl
extinct or becoming extirpated
Species likely to become endangered Humpback
if current trends and conditions
whale
continue
Species may become threatened or
Polar bear
endangered because of a
combination of factors
Artificial ecosystem
Natural ecosystem
Definition
An ecosystem planned or
maintained by humans.
Members of this ecosystem
are free to interact with
the physical and chemical
environment.
Examples
Parks, gardens, farms,
schoolyard
Lakes, rivers, deserts,
forests, meadows