CHAPTER 5
HOW ECOSYSTEMS WORK
Chapter 5 - section 3
How Ecosystems Change
ECOSYSTEMS ARE CONSTANTLY CHANGING!!!
Ecological Succession - a regular pattern of
changes in a community that occur over time
* the process may take hundreds or thousands of years
ECOLOGICAL SUCCESSION occurs when
1. a new land area is exposed
or when
2. an existing land area is disturbed
Primary Succession
occurs on new land areas or where no soil exists
What are some examples of primary succession?
Secondary Succession
occurs when an existing community had been disturbed
What are some examples of secondary succession?
due to humans or natural causes ?
How are fires a necessary part of
secondary succession?
• Some trees only release seeds after
exposure to the intense heat of a fire
• Minor fires remove brush and dead
wood that accumulates
• Some animals depend on vegetation
that sprout s after a fire has cleared
the land
FIRES IN YELLOWSTONE
Since 1972 National Park Service policy on fires has been to …..
- allows fires caused by lightning to burn unless
they threaten lives, property or unique scenic areas
- put out all human-caused fires
Fires of 1988 – conditions were unusual
• little rain during the summer
• summer turned out to be driest on record
• the previous winters were dry
1988
1988
1988
2010 – 22 years later
2010 – 22 years later
Primary or Secondary Succession?
Primary or Secondary Succession?
Primary or Secondary Succession?
Primary or Secondary Succession?
Primary or Secondary Succession?
Primary or Secondary Succession?
Primary or Secondary Succession?
Pioneer Species –
the first species to inhabit an area
Pioneer Community – the
first community of living things
to inhabit an area
Lichens
Mosses
Small Plants
What is a lichen?
a mutualistic relationship
between a fungus and alga
Alga – produces food (by photosynthesis)
Fungi – absorbs nutrients from rocks and
makes the environment hospitable
for the alga
Why are lichens important?
the action of lichens begins to
break down rock which begins
the formation of soil so that
succession can occur
LICHEN
Succession CULMINATES when…
a final, stable community is established –
the final community is called a CLIMAX COMMUNITY
climax community
in
Baja, California
is a DESERT
SERAL COMMUNITY = a transitional
community or communities that occur
before a climax community is established
PIONEER COMMUNTIY to SERAL COMMUNITY(IES) to CLIMAX COMMUNITY
What would be the climax community
in the eastern US?
Deciduous Forest
What do you think old-field succession is?