7.1. Succession

Question 1

EXAM QUESTION

Marram grass is a pioneer species that grows on sand dunes. It has long roots and a
vertically growing stem that grows up through the sand.
Sand dunes are easily damaged by visitors and are blown by the wind. Planting marram grass is useful in helping sand dune ecosystems to recover from damage.

Use your knowledge of succession to explain how. (2)

Answer 1

1. Stabilises sand / stops sand
   shifting;
2. Forms/improves soil / makes
   conditions less hostile;

Question 2

EXAM QUESTION

Farmland previously used for growing crops was left for 30 years and developed into
woodland. During this period, ecologists recorded an increase in the diversity of
birds in the area.

Name the process that resulted in the development of woodland from farmland. (1)

Explain the increase in the diversity of birds as the woodland developed.(3)

Answer 2

Succession;

1. Greater variety/diversity of plants/insects / more
   plant/insect species;
2. More food sources / more varieties of food;
3. Greater variety/more habitats/niches;

Question 3

EXAM QUESTION

Use your knowledge of succession to explain the increase in biomass during the first 20 years. (3)

Answer 3

1. Pioneer species;
2. Change in abiotic conditions / less
   hostile / more habitats/niches;
3. Increase in number/amount/diversity
   of species/plants/animals;

Question 4

EXAM QUESTION

Algae are photosynthesising organisms. Some algae grow on rocky shores.
A scientist investigated succession involving different species of algae. He placed
concrete blocks on a rocky shore. At regular intervals over 2 years, he recorded the
percentage cover of algal species on the blocks.

Some scientists reviewing this investigation were concerned about the validity of the
results because of the use of concrete blocks.
Suggest one reason why these scientists were concerned about using concrete blocks
for the growth of algae. (1)

Use the results of this investigation to describe and explain the process of succession. (4)

Answer 4

Any described feature of concrete eg
texture / flat / composition chemicals
/ nutrients etc;

1. Pioneer species/Ulva
increases then decreases;
2. Principle of a species
changing the conditions / a
species makes the conditions
less hostile;
3. New/named species better
competitor /
previous/named/pioneer
species outcompeted;
4. G. coulteri/Gelidium
increases and other/named
species decreases;

Question 5

Define succession

Answer 5

The changes, over time, in the species that occupy a particular area.

Question 6

Define pioneer species

Answer 6

A species that can colonise bare rock or ground.

Question 7

Give 5 common features of pioneer species.

Answer 7

Many wind dispersed seeds/spores - reach isolated areas
Rapid seed germination - no dormant period required
Photosynthesising - for food
Nitrogen fixing - for nutrients
Xerophytes

Question 8

Succession process (5)

Answer 8

1. Pioneer species colonises
2. Makes abiotic conditions less hostile
3. New species outcompetes pioneer species because better competitor
4. New species increase in number, pioneer species decrease in number.
5. Climax community established
   = the organisms that make up the final stage of ecological succession
   - normally has one dominant plant species, one dominant animal species

Question 9

Alternative process

Occurs when?
Begins with? because?
More?
Different?

Answer 9

Land altered suddenly (e.g. forest fires, land clearance)
Organisms from subsequent successional stages - spores and seeds remain alive in soil
more rapid
different organisms in climax community

Question 10

5 features following succession?

Answer 10

Abiotic conditions less hostile/more habitats/more niches
Increased biodiversity
More complex food webs
Increased biomass
Increased stability

Question 11

Define climax community

Answer 11

The organisms that make up the final stage of ecological succession