SuccessionAQA A-Level Biology: Flashcards

What these 14 flashcards ask

Define succession.
What is primary succession?
What is a pioneer species?
Give two examples of pioneer species.
How do pioneer species make the environment less hostile?
What is a seral stage?
How can a new species make conditions less suitable for earlier species?
What happens to biodiversity during the early stages of succession?
Why may species richness fall at the climax community?
What is a climax community?
Why is the climax community stable?
Why does soil depth increase during succession?
What does nitrogen fixation do for later colonisers?
What determines the type of climax community in an area?

Exam questions on Succession

A volcanic eruption created a new island of bare lava rock. Over several decades the island was colonised, first by lichens, then by mosses and grasses, followed by shrubs and finally by woodland.
Explain how the lichens make conditions on the bare rock more suitable for mosses.2 marks
On a coastal sand dune system, marram grass grows on the shifting dunes closest to the sea. Further inland, older and more stable dunes support other grasses, then shrubs such as gorse, and finally woodland. The depth of soil and the amount of humus increase with distance inland.
Suggest why there are more plant species on the older dunes inland than on the dunes near the sea.2 marks
After a glacier retreated, bare gravel was exposed. The first plants to establish were low-growing mat plants, followed by alder shrubs and then spruce trees. Alder roots have nodules containing nitrogen-fixing bacteria, and alder leaf litter makes the soil more acidic. Spruce grow taller than alder and eventually replace them.
Explain how the alder shrubs made the environment more suitable for spruce seedlings.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).