Download Change and the Environment Completed Notes

TEACHER COPY – PLEASE RETURN TO TEACHER
Change and the Environment
S8.B.3.2
Ecological Relationships
• Competition – Occurs when organisms sharing an ecosystem compete with
each other for resources such as food, water, sunlight and living spaces
Relationships
• Predator-Prey
– Predators – organisms that kill and eat other organisms
– Prey – Organisms that are killed and eaten
• This relationship is important in maintaining balance in an ecosystem for:
– Food
– Mates
– Habitat
Types of Relationships
• Symbiosis – A relationship between two organisms in which at least one
benefits
• Three types of symbiosis
– Mutualism
– Commensalism
– Parasitism
• Mutualism
• A symbiotic relationship in which both species benefit for the interaction
– Examples:
• Lichen – Algae and fungus live together
– The algae provides food and the fungus provides a place to live
and protection
•
•
Commensalism
A relationship where one organism benefits and the other neither benefits or
is harmed
– Example:
• Orchids living on the branches of high trees
– The orchid is able to get more sunlight, the tree is unaffected
•
•
•
•
Parasitism
A relationship where one organism benefits and the other is harmed
Parasite – an organism that lives on or in another organism (usually for food)
Host – The organism affected by the parasite
– Example:
• Tick on a dog
Carrying Capacity
• Carrying capacity – the number of individuals an ecosystem can continue to
support
• A ecosystem will grow until the carrying capacity is reached
• Growth stops when limiting factors are reached
– Food, water, climate, shelter, space, disease and predators
Succession
•
•
Ecological Succession is a process in which the communities of an
ecosystem change over time.
There are two types of succession: primary and secondary. Both types of
succession follow a similar pattern.
Let’s focus on primary succession.
A. Primary succession occurs in places where an ecosystem has never
existed before. This could be a newly formed volcanic island or land
exposed from a receding glacier.
B. As the exposed rock is weathered, the first species appear. These species are
called pioneer species. They are small, grow quickly, and need minimal
resources to survive. Often are mosses and lichens.
C. The pioneer species breakdown the rock to form soil. This allows other species
to grow among the mosses and lichens. Eventually the other species out
compete with the pioneer species and change the community.
D. At each stage, competition among the species causes a change in the dominant
community. In the later stages, larger, slower growing species displace the
smaller, faster growing species.
•
As the ecosystem ages, the community becomes more diverse. The process
of succession will continue until the ecosystem reaches a climax
community.
–
•
•
A climax community is the last stage of succession. If left
undisturbed, the ecosystem will stay at the climax community.
–
The Oak-Hickory forests of PA is a climax community.
Disturbances in the ecosystem, such as fire, flood or human activity, can
slow the process of succession down.
If the disturbance is catastrophic, like a tornado or volcanic eruptions, the
process may have to start over from the beginning.
Which leads us to….
•
Secondary succession is the process that begins in an ecosystem that has
been disturbed or destroyed.
–
Typically occurs on abandoned farmlands, burned or cut forests, etc…
I. Secondary succession has similar stages compared with primary succession.
Remember that secondary is regenerating an existing ecosystem. Primary is
forming a new ecosystem where none existed before.