Question+3

Barnacles are filter feeders that populate the coastlines of countries around the world. Fertilisation is external, and microscopic larvae develop. The larvae live for a time as plankton in the surface layer of the sea before settling and cementing onto rocks, where they metamorphose into the sessile adults. The adults of two species of barnacle, // Chthamalus stellatus // and // Balanus balanoides //, are found on rocks in the inter-tidal zone of exposed shores in Scotland. // Chthamalus //, the smaller of the two barnacle species, is found in the upper tidal zone, whilst the larger // Balanus // extends to the low-tide mark. If // Balanus // is absent, // Chthamalus //can grow throughout the inter-tidal zone. Predators of the adult barnacles are found throughout and below the inter-tidal zone. Predatory starfish are predominantly found below the low-tide mark, whilst predatory whelks and fish may feed in the inter-tidal zone. Algae are dominant below the low-tide mark.

** Question ** Discuss how different ** biotic and abiotic factors ** act to ** determine the fundamental and realised niches ** of these two species, // Chthamalus stellatus // and // Balanus balanoides. //