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The blue mussel, Mytilus edulis, lives along the northeastern coastline of the USA - VCE - SSCE Biology - Question 4 - 2010 - Paper 1
Question 4
The blue mussel, Mytilus edulis, lives along the northeastern coastline of the USA. A species of Asian shore crab, Hemigrapsus sanguineus, was accidentally introduce... show full transcript
Worked Solution & Example Answer:The blue mussel, Mytilus edulis, lives along the northeastern coastline of the USA - VCE - SSCE Biology - Question 4 - 2010 - Paper 1
Step 1
Explain the process of natural selection that has occurred in the population of southern blue mussels over the last 15 years that has resulted in thicker shells.
Answer
Natural selection is a process where organisms better adapted to their environment tend to survive and produce more offspring. In the case of southern blue mussels, the introduction of the Asian shore crab created a new selection pressure. The crabs preferentially prey on mussels with thinner shells, as these are easier to crush.
Over time, southern blue mussels with thicker shells had a survival advantage because they were less susceptible to being eaten by the crabs. Consequently, these thicker-shelled mussels survived longer, reproduced, and passed on their genes, leading to an overall increase in shell thickness in the population.
As a result, the population that remains today is predominantly made up of mussels with thicker shells, a direct outcome of natural selection in response to predation by the Asian shore crab.
Step 2
What would you expect to happen to the shell thickness of the northern blue mussels over time? Explain your reasoning.
Answer
If the Asian shore crab cannot migrate into the northern blue mussel area, the shell thickness of northern blue mussels is expected to remain relatively unchanged over time. Without the predation pressure from the crabs, there is no significant selective advantage for thicker shells.
Additionally, if environmental conditions remain stable and no other significant pressures are introduced, the northern blue mussels will likely continue to exhibit the shell thickness present in their current population. Thus, their shells may remain thinner than those of the southern blue mussels due to the absence of the selective pressure exerted by the crabs.