Succession.

As you should know, ecosystems are dynamic systems (they change), and the process by which they change over time is called succession. 

There are two types of succession: Primary succession and Secondary succession. Primary succession starts on new areas of land with NO organic material or soil (eg. bare rock/sand), for example, new land exposed when sea level drops, or a new surface formed by a volcanic eruption. Secondary succession is when the land has been destroyed or damaged, so succession must start again; the area has been cleared of all plants and must re-develop (eg. plants growing after a forest fire).

The succession occurs in stages called seral stages. The stages for primary succession are: 

1) PIONEER SPECIES COLONISE THE LAND. The abiotic conditions are harsh, there’s no soil to retain water, so these species are specialised to tolerate and survive in these conditions. 

2) PIONEER SPECIES CHANGE ABIOTIC CONDITIONS. As they die, the humus (dead organic material) is decomposed by microorganisms and create a thin, basic soil. 

3) NEW ORGANISMS CAN MOVE IN AND GROW. The soil means more water csn be retained and more nutrients are available for plants. As each organism arrives, dies and is decomposed, more soil is built up and larger plants can live there. Once enough and large enough plants live there, habitats emerge and animals can move in and survive. 

As more species move in and live there, the ecosystem becomes more complex and diversity increases. 
The final seral stage is called the complex community, this is when the ecosystem is at its largest and most complex and won’t change much more; it’s at a steady state. 

Secondary succession occurs the same way, except there is already soil present so succession starts at a later seral stage. 

11 months ago  1 note

Ecosystems.

An ecosystem is all the living and non-living things occurring together and the interelationships between them; the biotic and abiotic factors of an environment.

BIOTIC FACTORS = living things (predators, food, humans)

ABIOTIC FACTORS = non-living things (temperature, water availability, oxygen levels)

Ecosystems are dynamic systems - they’re always changing. The components of an ecosystem are:

  1. HABITAT - where an organism lives
  2. POPULATION - all the organisms of one species that live in the same space, at the same time, and can breed together.
  3. COMMUNITY - all the populations of different species who live in the same place, at the same time and can interact with each other. 

A niche is the role each species plays in an ecosystem and is almost impossible to define, it’s different for every species - it’s impossible for two different species to share the same niche. Things that define a species niche would include what it eats, how it eats, what it excretes etc. (great detail on everything an organism does that would somehow effect its ecosystem). 

The main way energy enters the ecosystem is photosynthesis when a plant converts light energy into a form that can be used by other organisms (although in sea ecosystems, bacteria use chemicals from deep sea vents as an energy source). Plants are hence called producers; they produce energy for the ecosystem. 

Energy is transferred through the living organisms of an ecosystem when one organism eats another. These organisms are the consumers; they consume other organisms. Depending on what trophic level (a trophic level is a stage of a food chain occupied by a particular group of organisms) of the food chain the organism is, it is either a primary, secondary, or tertiary consumer. 

So it goes:

PRODUCER —> PRIMARY CONSUMER —> SECONDARY CONS. —> TERTIARY CONS.

for example:

LETTUCE   —>            SLUG           —>       HEDGEHOG      —>          FOX

The arrows of a food chain show the transfer of energy from one trophic level to the next. A food chain show simple lines of this energy transfer, food webs show how lots of food chains in an ecosystem overlap. 

Energy ‘locked up’ in things that can’t be eaten (eg. bones, faeces) get recycled back into the ecosystem by decomposers which break down dead or undigested organic material. Examples of decomposers are fungi and bacteria. 

11 months ago 

Succession.

As you should know, ecosystems are dynamic systems (they change), and the process by which they change over time is called succession. 

There are two types of succession: Primary succession and Secondary succession. Primary succession starts on new areas of land with NO organic material or soil (eg. bare rock/sand), for example, new land exposed when sea level drops, or a new surface formed by a volcanic eruption. Secondary succession is when the land has been destroyed or damaged, so succession must start again; the area has been cleared of all plants and must re-develop (eg. plants growing after a forest fire).

The succession occurs in stages called seral stages. The stages for primary succession are: 

1) PIONEER SPECIES COLONISE THE LAND. The abiotic conditions are harsh, there’s no soil to retain water, so these species are specialised to tolerate and survive in these conditions. 

2) PIONEER SPECIES CHANGE ABIOTIC CONDITIONS. As they die, the humus (dead organic material) is decomposed by microorganisms and create a thin, basic soil. 

3) NEW ORGANISMS CAN MOVE IN AND GROW. The soil means more water csn be retained and more nutrients are available for plants. As each organism arrives, dies and is decomposed, more soil is built up and larger plants can live there. Once enough and large enough plants live there, habitats emerge and animals can move in and survive. 

As more species move in and live there, the ecosystem becomes more complex and diversity increases. 
The final seral stage is called the complex community, this is when the ecosystem is at its largest and most complex and won’t change much more; it’s at a steady state. 

Secondary succession occurs the same way, except there is already soil present so succession starts at a later seral stage. 

Ecosystems.

An ecosystem is all the living and non-living things occurring together and the interelationships between them; the biotic and abiotic factors of an environment.

BIOTIC FACTORS = living things (predators, food, humans)

ABIOTIC FACTORS = non-living things (temperature, water availability, oxygen levels)

Ecosystems are dynamic systems - they’re always changing. The components of an ecosystem are:

  1. HABITAT - where an organism lives
  2. POPULATION - all the organisms of one species that live in the same space, at the same time, and can breed together.
  3. COMMUNITY - all the populations of different species who live in the same place, at the same time and can interact with each other. 

A niche is the role each species plays in an ecosystem and is almost impossible to define, it’s different for every species - it’s impossible for two different species to share the same niche. Things that define a species niche would include what it eats, how it eats, what it excretes etc. (great detail on everything an organism does that would somehow effect its ecosystem). 

The main way energy enters the ecosystem is photosynthesis when a plant converts light energy into a form that can be used by other organisms (although in sea ecosystems, bacteria use chemicals from deep sea vents as an energy source). Plants are hence called producers; they produce energy for the ecosystem. 

Energy is transferred through the living organisms of an ecosystem when one organism eats another. These organisms are the consumers; they consume other organisms. Depending on what trophic level (a trophic level is a stage of a food chain occupied by a particular group of organisms) of the food chain the organism is, it is either a primary, secondary, or tertiary consumer. 

So it goes:

PRODUCER —> PRIMARY CONSUMER —> SECONDARY CONS. —> TERTIARY CONS.

for example:

LETTUCE   —>            SLUG           —>       HEDGEHOG      —>          FOX

The arrows of a food chain show the transfer of energy from one trophic level to the next. A food chain show simple lines of this energy transfer, food webs show how lots of food chains in an ecosystem overlap. 

Energy ‘locked up’ in things that can’t be eaten (eg. bones, faeces) get recycled back into the ecosystem by decomposers which break down dead or undigested organic material. Examples of decomposers are fungi and bacteria. 

Succession.
Ecosystems.

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