Download Chapter Three Notes

Science 7
Unit 1: Interactions within Ecosystems
Chapter 3: Natural events and human activities cause changes
in ecosystems
Section 3.1
Natural Disturbances & Succession
Succession (p.68)
 The process in which a community changes
over time.
 Change may be slow and difficult to notice
over short periods of time.
 Changes may be rapid and destructive.
 Changes can be the result of a natural
occurrence or human activities.
Primary Succession (p.70)
 The sequence of changes that starts with
bare rock and eventually develops into a
complex community of plants and animals.
 Pioneer species are the first species to
inhabit an ecosystem undergoing succession.
1
 They can thrive in an area with little or no soil
and few nutrients. Examples: bacteria, mosses,
and lichens.
 Occurs on bare rocks, sand dunes, surface
mining areas and cooled volcanic lava.
 If an area is not disturbed it will form a
climax community.
 A climax community is the final community in
the process of succession that remains
unchanged for many years.
2
Secondary Succession (p. 71)
 The sequences of changes that are involved in
the re-growth of a community after it has been
disturbed.
 Occurs on abandoned farm land, burned
forests, and polluted areas.
 The development of a climax community can
occur more quickly through secondary
succession than primary succession.
 The reason for this is that the disturbed area
is usually surrounded by undamaged
communities.
3
Succession can have environmental changes in:
1. Soil composition
2. Plant types
3. Animal types
4. Amount of light
Pioneer Species- Species that are the first to
appear in an area undergoing succession, and can
establish themselves with little or no soil and few
nutrients. (Ex. Lichens)
Climax Community- A diverse group of species that
form a stable ecosystem which can remain
relatively unchanged for centuries if there is no
disturbance. The final community in the process of
succession. (Ex. Balsam Fir)
4
Section 3.2
The Impact of People on Ecosystems
Know Key Vocabulary for this section:
Acid Rain
Endangered
Introduced
Species
Extinct
Monoculture
Native Species
Natural
Resources
Pollutants
Sustainable
Unsustainable
Renewable
Resources
Humans have a major impact on ecosystems
because of our powerful technologies and large
population.
The 4 main impacts humans have on the
environment include (pg. 77-82):
1.
2.
3.
4.
Habitat Loss
Introduced Species
Overharvesting
Pollution
5
1. Habitat Loss
 Removing vegetation and soil removes shelter
and food for animals.
 Changes on land alter drainage of water which
affects rivers and lakes.
2. Introduced Species
 Species that have spread beyond their natural
range into new locations as a result of human
activities.
 Also called alien, exotic, or non-native species.
3. Overharvesting
 The demand for natural resources has
increased due to the increase in the human
population.
 Our technologies have enabled us to remove
the resources we need.
4. Pollution
 Substances that cause harm to the air, soil,
water, or living things are called pollutants.
 Can have direct and indirect impacts on the
environment.
6