23.4 Succession

Question 1

What is primary succession?

Answer 1

• Succession which occurs in 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

Question 2

What is secondary succession?

Answer 2

Succession which occurs on areas of land where soil has present but it contains no plant or animal species

Question 3

When does primary succession occur?

Answer 3

• volcanoes eruption - lava cools and solidifies, creating igneous rock
• sand is blown by the wind or deposited by the sea, forming new sand dunes
• silt and mud are deposited at river estuaries
• glaciers retreat, depositing rubble and exposing rock

Question 4

What is a stage of succession also known as

Answer 4

Seral stage

Question 5

What are the main serial stages?

Answer 5

• pioneer community
• intermediate community
• climax community

Question 6

What is pioneer community?

Answer 6

• the colonisation if an inhospitable, harsh environment, by a pioneer species

Question 7

How do pioneer species arrive at the environment?

Answer 7

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

Question 8

Examples of pioneer species

Answer 8

Lichen

Algae

Question 9

How are pioneer species adapted to colonise this bare environment?

Answer 9

• they can produce large quantities of seeds and spores which are blown by the wind and deposited on the new land
• seeds that germinate rapidly
• can photosynthesise
• tolerance against extreme conditions
• can fix nitrogen from the atmosphere

Question 10

What is intermediate community?

Answer 10

• particles of soil become present, because of the weathering of the bare rock
• when pioneer organisms die and decompose, small organic products are released into the soil (Aka humus)
• ## the souls is able to support the new species bc it contains minerals such as nitrates and had the ability to retain water

Question 11

How do secondary colonisers arrive at the environment?

Answer 11

• as spores it seeds

Question 12

Examples of secondary colonisers

Answer 12

Mosses

Some animals

Question 13

How are tertiary colonisers adapted to survive in the intermediate community?

Answer 13

• waxy cuticle to protect against water loss

Question 14

Examples of tertiary colonisers

Answer 14

Ferns

Question 15

Why are more and more species present during succession?

Answer 15

• The environmental conditions improves
• at each stage the rock continues to be eroded and the mass of organic matter increases
• when organisms decompose they contribute to a deeper, more nutrient-rich soil, which retains more water (making abiotic conditions more favourable)
• then shrubs and trees start to appear l

Question 16

Why does the biodiversity within the intermediate community change?

Answer 16

• there are multiple seral stages in the intermediate community
• at each seral stage different plant and animal species are better adapted to the current conditions in the ecosystem
• these organisms outcompete many of the species

Question 17

What is the climax community?

Answer 17

• the final seral stage
• community is more stable
• little change in community over time
• few dominant plant and animal species
• not the most diverse (biodiversity is greater at mid-succession
• more successful the dominant species = less biodiversity in an ecosystem

Question 18

How does animal succession take place?

Answer 18

Similar to plants

• primary consumers (e.g wines and insects) are the first to colonise and shelter in the misses and lichens present
• they move from neighbouring areas, so animal succession is usually much slower than plant succession
• secondary consumers arrive once a suitable food source has been established, and the existing plants will provide them with suitable habitats
• eventually lathered organisms e.g. mammals and reptiles colonise the area when the biotic conditions are favourable

Question 19

Wha is the plagioclimax?

Answer 19

The final stage when succession is stopped artificially

Question 20

What isbdeflected succession?

Answer 20

When succession is halted because of human activities

Question 21

Why does deflected succession occur?

Answer 21

• grazing and trampling of vegetation by domestic animals - results in large areas remaining as grassland
• removing existing vegetation to plant corps: the crops become the final community
• burning as a means of forest clearance: often leads to an increase in biodiversity as it provides space and nutrient-rich ash for other species to grow, such as shrubs

Question 22

How is deflected succession a conservation technique?

Answer 22

• to ensure the survival of certain species, it is important to preserve their habitat in its current form
• this may require ecological land management to prevent further succession from occurring

Question 23

Conservation case study : prevention of succession

national trust’s Studland Heath nature reserve Dorset, England

Answer 23

• is home to a number of reptiles, including the UKs rarest reptile, the smooth snake. This region is heathland. If succession were to occur, woodland would develop as the climax community
• this would lead to the replacement of the smooth snake by other species and risk the elimination of the smooth snake in the UK
• is the heathland is managed by the National Trust to ensure that the ecosystem is preserved
  Conservation techniques:
• physical removal of established bracken and saplings (e.g. birch and pine). gorse (a legume) adds to the nutrient value of the soil
  -heathlands are nutrient-poor areas of land, and so areas of gorse are also removed through physical means (returns heathland to former state)
• mimicking controlled grazing to limit the spread of bracken, gorse and free saplings. Livestock crush new growth (maintain the heathland in its current state)