Succession

Question 1

What are the two types of succession and what are they caused by?

Answer 1

• change of ecosystem, succession occurs as a result of changes to the environment (abiotic factors), causing the plant and animal species present to changwe
• primary succession
  
  • this occurs on an area of land that has been newly formed or exposed such as bare rock
  • there is no soil or organic material present to begin with
  • slow
• secondary succession
  
  • occurs on area of lands where soil is present,m but containes no plant or animal species
  • e.g. bare earth after forest fire
  • relatively fast

Question 2

When does prumary succession occur?

Answer 2

• volcanoes erupt
  
  • deposits lava
  • lava cools and solidifies igneous rock is created
• sand is blown by wind or deposited by sea to create new ssand dunes
• silt and mud are deposited at river estuaries
• glaciers retreat depositing rubble and exposing rock

Question 3

What are seral stages?

Answer 3

• stages at which succession takes palce

Question 4

What are the main seral stages and what changes as they progress

Answer 4

• (barren land)
• pioneer community
  
  • colonisers
  • e.g. lichen
• secondary colonisers
  
  • e.g. mosses
• tertiary colonisers
  
  • e.g. grasses
• scrubland
  
  • e.g. shrubs and small trees
• climax community
  
  • dominant species
• slow process
• conditions becomes
  
  • lesshostile
  • more stable m
  • more diverse

Question 5

How is the pioneer species introduced?

Answer 5

• spores or seeds carried by the wind from nearby land masses or droppings of birds or animals passing through

Question 6

What are the adaptations of the pioneers species that enable them to colonise this bare environment?

Answer 6

• ability to produce large quantities of seeds or spores, which are blown by the wind and deposited on the ‘new land’
• seeds that germinate rapidly
• produce own energy
  
  • photosyntehsis
  • light rainfall and air only abiotic factors
• tolerance to extremem environments
• fix nitrogen from atmosphere, adding to mineral content of soil

Question 7

How is soil formed? How is the soil made habitable?

Answer 7

• weathering of bare rock produces particles that form the basis of a soil
• cannot support species
• when organisms of the pioneers species die and decompose, small organic products are released into the soil
  
  • the organic componenet of soil is known as humus
• the soil becomes able to support further colonisers as it contains mineral including nitrates and ability to retain water

Question 8

How are other colonisers introduced?

Answer 8

• also as seeds or spores
• colonisers or pioneers species act as a food source for consumers, so animal species will colonise the area

Question 9

How does mass of organic matter increase?

Answer 9

• rock continues to be eroded
• decomposing results in nutrient-rich soil which rtains more water
  
  • abiotic conditions more favourable for organisms increasing in size

Question 10

What is the intermediate community?

Answer 10

• the period of succession
• multiple seral stages evolve during this period until climax conditions are attained

Question 11

How are dominant species formed?

Answer 11

• at each seral stage different plant and animal species are better adapted to the current conditions
• these organisms ocutcompete many of the species that were previously present and becomes the dominant species
• these are the most abundant species by mass present in the ecosystem

Question 12

What is the climax community?

Answer 12

• final stage
• community in stable state
  
  • ltttle change
• there are normally a few dominant plant and animal species
  
  • climax often not the most diverse
  • out-competing other species resulting in elimination

Question 13

What are the differences in animal succesion?

Answer 13

• primary consumers
  
  • insects and worms
  • consume and shelter in mosses and lichens
• move in from neighboiring areas so slower
• secondary consumers arrive once suitanle food source established and suitable habitats
• when biotic conditions are favourable

Question 14

What is deflected succession?

Answer 14

• human activites can halt natural flow of successions
  
  • prevent reaching climax community
  • when stopped the final stage is known it is known as a plagioclimax

Question 15

What are some examples of how agriculture results in deflected succession?

Answer 15

• grazing and trampling of vegetation by domesticated animals, results in large areas remaining as grassland
• removing existing vegetation to plant crops
  
  • becomes final community
• burning to clear forest
  
  • increase in biodiversity as it provides space and nutrient-rich ash for other species to grow

Question 16

How is deflected succession used in conservation?

Answer 16

• can be used to ensure survival of a certain specuies that would be outcompete