23.4 - Succession

Question 1

What is succession?

Answer 1

Occurs as a result of the changes to the environment causing the species present to change

Question 2

What are the two types of succession?

Answer 2

• Primary: occurs on newly formed/exposed land, there is no soil or organic material to begin with
• Secondary: occurs on areas where soil is present but contains no species e.g bare Earth after forest fires

Question 3

When would primary succession happen?

Answer 3

• Volcanies erupt
  
  • Sand dunes are made
  • Silt and mud are deposited at river estuaries
  • Glaciers retreat depositing rumbling/rock

Question 4

What are the stages of succession

Answer 4

Each stage is called a serial stage or sere
At each at age, key species can be identified that change the abiotic factors to make it suitable for other species to exist.
The main stages are
- Pioneer
- Intermediate
- Climax communities

Question 5

What is a Pioneer community?

Answer 5

• An inhospitable environment is colonised by a pioneer species.
• These species arrived as spores/seeds carried by the wind.
• They have adaptations that enable them to colonise the bare environment

Question 6

What are adaptations for a pioneer community

Answer 6

• Ability to produce large quantities of seeds/ Seeds that germinate rapidly
  
  • Photosynthesis, produce their own energy
  • Tolerance to extreme environments
  • Ability to fix nitrogen from atmosphere

Question 7

What is an intermediate community?

Answer 7

• Weathering of rock produces the basis of soil
• When organisms of the pioneer species die + decompose, organic material is released into the soil (humus)
• Soil supports the growth of a new species as it has minerals inc nitrates and water.
• These colonisers arrive as spores/seeds and pioneer species can be a food source so animals species can start to colonise.
• As conditions improve, tertiary colonisers will arrive
• These plants have a waxy cuticle and can survive without an abundance of water, most of their water needs to come from the soil
• At each stage, the rock erodes more, and more organic material enters the soil, which retains more water, causing more favourable abiotic conditions

Question 8

What is a climax community

Answer 8

• Final stage
• The community is in a stable state + doesn’t change much over time.
• There are a few dominant species.
• Biodiversity increases as succession takes place, but the climax community is not as biodiverse.
• Biodiversity peaks at mid-succession due to dominant species out-competing other species causing elimination.

Question 9

What is animal succession?

Answer 9

• Primary consumers are first to colonise an area + must move from neighbouring areas so succession is slower
• Secondary consumers arrive once a food source and habitat has been established.
• Eventually larger organisms will colonise the area when biotic conditions are favourable.

Question 10

What is deflected succession?

Answer 10

• When human activities can prevent succession from reaching a climax community
• Plagioclimax: final stage of succession when it is stopped artificially
• Agriculture is an example e,g grazing and trampling, burning the forest and removing existing vegetation