Succession Part 4. Brainstorm How do Ecosystems Form?

SuccessionSuccession

Part 4Part 4

BrainstormBrainstorm

How do Ecosystems Form?How do Ecosystems Form?

SuccessionSuccession Ecosystems are constantly changing Ecosystems are constantly changing

in response to natural and human in response to natural and human activities or events.activities or events.



Sometimes, an ecosystem changes Sometimes, an ecosystem changes in response to an abrupt disturbance. in response to an abrupt disturbance.



Sometimes, an ecosystem changes Sometimes, an ecosystem changes in response to an abrupt disturbance. in response to an abrupt disturbance.

At other times, change occurs as a At other times, change occurs as a more gradual response to natural more gradual response to natural fluctuations in the environment.fluctuations in the environment.



Natural EventsNatural Events Human EventsHuman Events




- Fires- Fires

- Volcanic - Volcanic eruptionseruptions

- Retreated Glacier- Retreated Glacier

- Flood- Flood

- Storms- Storms

- Fallen tree- Fallen tree




- Fires- Fires

- Volcanic - Volcanic eruptionseruptions

- Retreated Glacier- Retreated Glacier

- Flood- Flood

- Storms- Storms

- Fallen tree- Fallen tree

- Logging- Logging

- Land Clearing for - Land Clearing for

ConstructionConstruction

- Live-stock - Live-stock Grazing Grazing

in Farmingin Farming

What is ecological What is ecological succession?succession?

The series of predictable changes The series of predictable changes that occurs in a community over that occurs in a community over time, due to natural or human time, due to natural or human disturbances is called disturbances is called ecological ecological successionsuccession. .

There are two types of succession:There are two types of succession:


1. Primary Succession 1. Primary Succession


1. Primary Succession 1. Primary Succession

2. Secondary Succession2. Secondary Succession

Primary SuccessionPrimary Succession

Succession that occurs on surfaces Succession that occurs on surfaces

where where no soilno soil exists. exists.


Succession that occurs on surfaces Succession that occurs on surfaces where no soil exists.where no soil exists.

Examples:Examples: Retreating GlaciersRetreating Glaciers Volcanic EruptionsVolcanic Eruptions

Primary SuccessionPrimary SuccessionThe first species to populate the area are The first species to populate the area are

called called pioneer speciespioneer species..


Pioneer speciesPioneer species physically break physically break up the rocks, up the rocks, extract minerals, extract minerals, and provide and provide organic matter organic matter that will that will decompose and decompose and become the soil become the soil for later species. for later species.

The first species to populate the area are The first species to populate the area are called called pioneer speciespioneer species..

Pioneer SpeciesPioneer Species

Pioneer species share some of the Pioneer species share some of the following characteristics, which allow following characteristics, which allow them to be the first to grow in an them to be the first to grow in an area.area.

– Reproduce quicklyReproduce quickly– Mechanisms for distant seed dispersal Mechanisms for distant seed dispersal

(birds, insects, wind (birds, insects, wind – Shade Intolerant Shade Intolerant – Need little or no soilNeed little or no soil– Survive in harsh environmentsSurvive in harsh environments– Need little waterNeed little water

Pioneer SpeciesPioneer Species

Example of pioneer species:Example of pioneer species:– LichenLichen

Two organisms (algae and fungus)Two organisms (algae and fungus)

Stages of Primary Stages of Primary SuccessionSuccession

1. Primary succession begins when 1. Primary succession begins when lichens populate bare rock. Because lichens populate bare rock. Because lichens are the first species to live lichens are the first species to live where no life has lived in the past, where no life has lived in the past, they are called pioneer species. As they are called pioneer species. As the lichens grow, they help break up the lichens grow, they help break up the rocks and when they die their the rocks and when they die their organic material helps to form soil in organic material helps to form soil in which plants can grow. which plants can grow.


2. Mosses may grow next 2. Mosses may grow next and then grasses and and then grasses and small weeds will root in small weeds will root in the soil trapping soil the soil trapping soil and organic matter that and organic matter that blows their way. In blows their way. In addition, the addition, the decomposition of decomposition of grasses and weeds will grasses and weeds will accelerate the soil accelerate the soil formation process.formation process.

Important NOTEImportant NOTE

As the vegetation begins As the vegetation begins to grow, animals begin to to grow, animals begin to arrive in the area. arrive in the area.

These animals also die, These animals also die, decompose, and add to decompose, and add to the soil being formed for the soil being formed for other plants to take root other plants to take root and more organisms and more organisms arrive as their habitats arrive as their habitats form. form.

Important NOTEImportant NOTE As the vegetation begins As the vegetation begins

to grow, animals begin to to grow, animals begin to arrive in the area. arrive in the area.

These animals also die, These animals also die, decompose, and add to decompose, and add to the soil being formed for the soil being formed for other plants to take root other plants to take root and more organisms and more organisms arrive as their habitats arrive as their habitats form. form.


3. Small shrubs and pine 3. Small shrubs and pine trees can now grow trees can now grow amongst the grasses amongst the grasses and weeds. and weeds.


4. The community then 4. The community then moves from a scrubby moves from a scrubby one to a pine dominated one to a pine dominated forest.forest.


5. Hardwood trees such 5. Hardwood trees such as Maple, Beech and as Maple, Beech and Oak grow in the Oak grow in the shade of the pines shade of the pines and eventually grow and eventually grow taller than the pines taller than the pines shading them and shading them and ultimately resulting in ultimately resulting in their death and their death and replacement by replacement by

the hardwood forest. the hardwood forest.

This is called the climax community. If This is called the climax community. If nothing changes, which in nature is highly nothing changes, which in nature is highly unlikely, this community will be stable.unlikely, this community will be stable.

PRIMARY PRIMARY

SUCCESSIONSUCCESSION

EXAMPLESEXAMPLES

Secondary SuccessionSecondary Succession

What happens if a community is disturbed at some stage of succession?


What happens if a community is disturbed at some stage of succession?

If a community is disturbed, without removing the soil, it will be set back to an earlier stage and succession will start over from there.


Secondary succession proceeds much quicker than primary succession, because there is soil present and often even seeds.



Results after a disturbance such as:– abandoning a plowed field– a wildfire or clear cutting a forest







Pioneer species: Grasses and weeds.


Primary or Secondary Primary or Secondary Succession?Succession?

Primary or Secondary Primary or Secondary Succession?Succession?

_____ As these plants live and die, the soil _____ As these plants live and die, the soil continues to develop to the point that grasses continues to develop to the point that grasses can successfully grow and grassland can successfully grow and grassland community forms. community forms.

_____ The shrub community may be replaced by _____ The shrub community may be replaced by a forest.a forest.

_____ Bare rock is first colonized by lichens* and _____ Bare rock is first colonized by lichens* and bacteria.bacteria.

_____ Over time, the soil level increases to point _____ Over time, the soil level increases to point that shrubs can grow in the grassland. The that shrubs can grow in the grassland. The grassland is replaced by a shrub community.grassland is replaced by a shrub community.

_____ The small amount of soil formed by the _____ The small amount of soil formed by the lichens* is colonized by mosses and ferns, lichens* is colonized by mosses and ferns, which do not have roots and require little soil. which do not have roots and require little soil.

____33__ As these plants live and die, the soil __ As these plants live and die, the soil continues to develop to the point that grasses continues to develop to the point that grasses can successfully grow and grassland can successfully grow and grassland community forms. community forms.

____55___ The shrub community may be replaced ___ The shrub community may be replaced by a forest.by a forest.

____11____ Bare rock is first colonized by lichens* Bare rock is first colonized by lichens* and bacteria.and bacteria.

____44__ Over time, the soil level increases to point __ Over time, the soil level increases to point that shrubs can grow in the grassland. The that shrubs can grow in the grassland. The grassland is replaced by a shrub community.grassland is replaced by a shrub community.

____22___ The small amount of soil formed by the ___ The small amount of soil formed by the lichens* is colonized by mosses and ferns, lichens* is colonized by mosses and ferns, which do not have roots and require little soil. which do not have roots and require little soil.

Arrange the species below in Arrange the species below in order of their appearance in order of their appearance in succession from bare rock to succession from bare rock to

forest:forest:Softwoods (conifer)Softwoods (conifer)

LichenLichen

Moss Moss

FernsFerns

Hardwoods Hardwoods (oak)(oak)


forest:forest:LichenLichen

Softwoods (conifer) Softwoods (conifer)

Moss Moss

FernsFerns




Moss Moss


FernsFerns




Moss Moss

Ferns Ferns



Succession Part 4. Brainstorm How do Ecosystems Form?

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