SuccessionEdexcel International A Level Biology: Flashcards

Exam questions on Succession

1. A volcanic eruption forms a new island of bare lava rock. Over many decades the rock is colonised, first by lichens, then by mosses, then by ferns and grasses, then by shrubs and finally by trees.
   Explain how the pioneer species change the abiotic environment so that other species are able to colonise.2 marks
2. In a coastal sand dune system the dunes become progressively older with distance inland. Near the sea the sand has an organic content of 0.2%, a pH of 8.5 and 3 species of plant. At a site 300 m inland the soil has an organic content of 12%, a pH of 6.0 and 24 species of plant, including shrubs and pine trees.
   Suggest why the number of plant species increases with distance inland.2 marks
3. A field that had been ploughed for crops was abandoned. Over about 100 years it changed from a field of annual weeds to grasses and herbs, then to shrubs such as bramble and hawthorn, then to birch trees, and finally to oak woodland. The oak woodland has now remained the same for many decades.
   Describe how the plant community changes as succession proceeds from the abandoned field to the oak woodland.3 marks