| Date | November 2016 | Marks available | 3 | Reference code | 16N.3.SL.TZ0.11 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Describe | Question number | 11 | Adapted from | N/A |
Question
Chthamalus and Balanus are two species of barnacles that live attached to rocks between the low and high tide level of the sea. The distribution of each species is influenced by the presence of their own species and different species.
Distinguish between a fundamental niche and realized niche.
Suggest reasons that Chthamalus cannot live higher up the shore.
Describe how the distribution of Chthamalus and Balanus is affected when both are present.
Markscheme
realized is actual niche, fundamental is potential niche
a. must spend some of their time under water / prevent dehydration
b. need water for food/nutrients
c. need water for reproduction
d. more accessible to their predators
e. there are no rocks for them to live on
OR
there is no suitable habitat for them
a. Chthamalus and Balanus / both have a reduced distribution
b. they are in competition for part of the habitat on the rock
c. Balanus occupies some of the habitat of the fundamental niche of Chthalamus
OR
where the fundamental niche overlaps Balanus prevails/survives
d. the distribution of Balanus is unchanged in areas colonized by Chthalamus
e. Balanus is in competition with other species closer to low water
