Abiotic factors (data)

Abiotic factors are non-living. They include light intensity, temperature and moisture levels. The abundance and distribution of living organisms in an ecosystem are affected by abiotic factors.

The effect of abiotic factors on organisms

A shingle beach has small stones instead of fine sand. Plant seeds can lodge between the small stones and start to grow, particularly at the top of the shore away from the waves. Two students set up a transect along a shingle beach. They started at top of the beach and worked towards the sea. Every five metres they placed a quadrat on the beach and measured the height of all the plants found in each quadrat. They found the mean of this data; their results are presented in a graph below.

Graph showing the heights of plants in relation to their distance from the shore
Question

What conclusions can you draw from this data about the mean plant height? Use numbers in your answer. [2 marks]

The average height of plants falls from 60 cm at the top of the shore to less than 10 cm after 25 metres [1 mark]. After this no plants were found [1 mark].

They also recorded the depth of the soil (an abiotic factor).

Distance from top of shore (m)Soil depth (cm)
016
513
1014
157
205
251
300
350
400
Question

What conclusions can you draw from this data? Use numbers in your answer. [2 marks]

The soil depth decreases from 16 cm at the top of the shore to 1 cm after 25 metres down it [1 mark]. Beyond this there was no soil [1 mark].

Question

What conclusion can you draw from the number of plants and the depth of soil? [1 mark]

As the depth of soil decreased so did the average height of plants.

Hint - It would be incorrect to state that the soil depth controlled the growth of plants unless you had further evidence.