Identify THREE major strategies used by sponges to reduce the impact or incidence of predation upon them. Briefly explain the basis of each of these strategies.

Question 1

Identify a physical characteristic used to reduce the impact or incidence of predation:

Answer 1

• Sponges have spicules and/or tough organic fibres
• These features are said to deter predators directly (e.g. because they make the sponge difficult to digest; spicules may also physically damage the predator) and/or due to their low nutritional value
• Spicules= skeletal elements of silica or CaCO3 – range of shapes and forms

Question 2

Explain how asexual reproduction is used to reduce predation:

Answer 2

• Sponges can use cell division to replace damaged/missing parts
• Hence sponges have potential to repair any damage done by a predator (minimise impact)

Question 3

Explain how chemical defence is used to reduce predation

Answer 3

• High incidence of biologically active compounds (toxic and/or microbial effects)
• Diverse spectrum of compounds, sometimes even within a single species
• Generally assumed that biologically active compounds deter predators and/or prevent fouling
• E.g. the compounds may be distasteful and/or toxic to the predator and therefore the predator will avoid the sponge
• Definitive evidence of the compounds requires direct knowledge of the chemical characteristics of compounds and their direct biological effects in situ