SUCCESSIONNatural Change Over Time

Organization in Ecology

Ecosystem

Community

Population

Organism

Ecology also studies how ecosystems

change over time and how communities

recover from a disturbance.

This is called SUCCESSION.

What Is Succession?

The orderly, natural progression of stages that communities of an ecosystem go through

Two kinds of SUCCESSION.

There are two kinds of succession, depending on how the ecosystem starts out or how an ecosystem is disturbed

PRIMARY SUCCESSION

The colonization of barren land by communities of organisms

Primary Succession happens when a disturbance destroys the entire community so that there is not even any soil left behind

For example a glacier could melt away to expose bare rock.

Another way to think of primary succession is that it occurs when life enters an area for the first time.

In this case the land is completely devoid of soil and vegetation

PRIMARY SUCCESSION

SECONDARY SECESSION

Sequence of changes that takes place after an existing community is severely disrupted in some way

However, the disturbance was not big enough to remove the soil.

Secondary succession might occur after land is cleared for farming, or after a forest fire.

In secondary succession, the dominant plants in the community are removed, allowing new plants to colonize.

SECONDARY SECESSION

PIONEER SPECIES

The first species that move into a barren or disturbed area

Pioneer Species are tough and can live in conditions that other organisms cannot

Many PIONEER SPECIES create soil. For example, lichen attaches to rocks and breaks them down into soil. Mosses and grasses can also be pioneer species.

Pioneer Species often colonize a new area by seeds being blown by the wind.

Please answer the following questions on your own:

Why are mosses and lichens pioneer species, but pine trees and deer are not?

PIONEER SPECIES

CLIMAX COMMUNITY

A stable, mature community that undergoes little or no change in species

A CLIMAX COMMUNITY is what the community would be like if no disturbances ever occurred.

Some ecosystems contain a climax community for hundreds or thousands of years. In other ecosystems, as soon as a climax community is reached a disturbance becomes much more likely. For example, some climax communities use

up the nutrients in the soil or increase the likelihood of a fire

Another way to think of a climax community is an ecosystem that has a steady amount of TOTAL BIOMASS.

CLIMAX COMMUNITY

#1.6 Aim:How do ecosystems change over time?

AgendaQOD (10)

Lesson: succession (15)

Activity: courtyard scavenger hunt (15)

SummaryShare (5)

HW #5

Pioneer species – the first species to populate an area. These species start making the soil

Climax community – a mature, stable community - what the community would be like if no disturbances ever occurred.

Lichens and mosses are an important pioneer species

Typical forest succession Lichens and mosses

Flowers and weeds

Non-woody plants and grasses

Woody shrubs, grasses, tree saplings

Young forest

Mature treesAs the ecosystem changes, the animals change to accommodate the available food and shelter.

Forests

What does this graph tell us about succession?

Primary or Secondary?

Volcanic Eruption Clear Cutting

Primary or Secondary?

Tornados Mudslide

Exit Ticket

1) What is the difference between PRIMARY and SECONDARY succession?

2) How do PIONEER SPECIES help speed up the process of ecological succession?