Download Disturbance and Succesion Worksheet - Ecosystem

LHS Academic Biology
Name:
Block:
ECOSYSTEM CHANGE = SUCCESSION and DISTURBANCES
(Major ecology concept #3.)
Ecosystems are constantly changing from and then returning to their natural
communities. The causes (called disturbances) can be either human changes or
natural events. Succession is an ecosystem’s slow and predictable (step by step)
return to its natural, native community of species – the Climax Community. (In
Pennsylvania, that is a Temperate Deciduous Forest – trees that shed their leaves.)
Examples of succession include a shallow lake changing into a forest, and a forest
(or field) covered by lava again growing back (in to a forest or field).
What is a disturbance?
What is succession?
Types of Disturbances
Human disturbances to an ecosystem include accidental fires, clearing a forest (or
plowing over a field) in order to grow crops or to build a highway or housing
development. Natural events include floods, earthquakes, lightning strikes and wild
fires, mudslides (filling in a pond or covering the ground), and volcanic eruptions.
What are examples of a Human Disturbance?
What are examples of a Natural Disturbance?
LHS Academic Biology
Name:
Block:
Types of Succession
Ecological succession is a gradual process of change and replacement of the types
of species in a community. There are two types of succession, Primary Succession
and Secondary Succession.
Secondary Succession
The more common type, it occurs on a surface where an ecosystem was disturbed
but still contains soil and life in the soil. After most forest fires, plants are killed
but their seeds remain in the soil and begin to grow very quickly.
The first species to colonize an area after a disturbance are called Pioneer Species.
(Plants are usually the pioneer species after secondary succession.) Pioneer species
make the ecosystem habitable (livable) for the next community in the process of
returning to the original species.
Succession ends when the original community of species, called the Climax
Community, is reestablished.
Primary Succession
Much slower than secondary succession, it occurs where there is no soil (such as
after a volcanic eruptions or the retreat of a glacier), or on any other surface that
has not previously supported life, such as bare rock. (It can take from several
hundred to a thousand years to produce fertile soil, naturally.)
After primary succession, the pioneer species that colonize bare rock or new soil
are usually lichens and bacteria (see first box, on left).
LHS Academic Biology
Name:
Block:
Succession Practice
What is Primary Succession?
What is Secondary Succession?
What is a Pioneer Species?
What is a Climax Community?
What type of succession – Primary or Secondary - is taking place in the pictures, below?
1) This is a former farm field that has been abandoned by the farmer.
Succession Type: _______________________________________________
2) This is a bare rock field from which a glacier receded.
Succession Type: _______________________________________________