CHAPTER 5HOW 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 Successionoccurs 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 YELLOWSTONESince 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

Lichens Mosses

Small Plants

Pioneer Community – the first community of living things to inhabit an area

LICHENWhat 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

Succession CULMINATES when…a final, stable community is established – the final community is called a CLIMAX COMMUNITY

climax communityin

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?