Download Topic 6 Succession and Change in Ecosystems

Topic 6
Succession and Change in Ecosystems
Succession
 Changes are constantly occurring in an ecosystem
 Some changes can be fast (IE: landslide or forest fire completely destroying
an ecosystem) and some changes can be slow (IE: seeds being carried by the
wind to a vacant lot introducing a new plant population)
 This gradual process by which some species replace other species in an
ecosystem is called succession
Two types of succession:
1. Primary Succession
 The gradual growth of organisms in an area that was previously bare
(IE: Lichen growing on the bare surface of a rock)
 As they establish and grow, often times they change the conditions of
the area
 These new conditions usually let other plants and animals grow and
survive
 This can take hundreds or even thousands of years
2. Secondary Succession
 The gradual growth of organisms in an area that previously had a
number of organisms is known as secondary succession
 Example: growth in an area after a forest fire
Changes caused by human activity
 Humans usually have a number of affects on the environments around them
 Technologies, such as forestry and agriculture, can drastically alter the
environment around us
 Spreading urban areas is another good example (Think housing
developments, new road construction etc.)
 Sometimes these changes to the environment result in unexpected changes
to the ecosystem
Pest Control
 One downside to pest control and pesticides is that they may effect more
than just the targeted insect
 This can happen because many pesticides kill more than just the pest
 Another downside is they can also harm the beneficial insects that prey on
pests. This can actually cause pest populations to increase.
Biological Control
 Another way to control pests naturally is to use their natural enemies.
 This method is known as biological control.
 This can sometimes eliminate the need for pesticides.
 Biological controls are not without their downsides however, there is always
a risk when introducing a new species into an environment.
Introduces Species
 Today, introducing a new species into an environment is only done after
doing extensive research.
 However, new species are still sometimes introduced into an ecosystem
accidentally
 These are called introduced species
 Introduced species can become a problem when they thrive and become
more successful than the naturally occurring species in the area
 They can go on to completely take over an ecosystem
Species in danger
 Many different species in Alberta and across Canada are in danger of
extinction
 If an organism becomes extinct, it no longer exists anywhere else in the
world
 Habitat loss is the major reason so many species are threatened with
extinction
 Another cause of extinction are introduced species