A scientist studying the blue-ringed octopus made the following observations.

• It inhabits shallow coral reefs where water temperatures are between 26 °C and 29 °C.
• It feeds on crabs, shrimp and fish.
• It uses a toxin to paralyse its prey and defend itself from predators.
  The toxin used by the blue-ringed octopus is produced by bacteria living in the nutrient-rich
  environment of the octopus’s salivary glands.
  Which of the following statements about the blue-ringed octopus is/are correct?
  1 Temperature is a biotic factor which restricts where the blue-ringed octopus can live.
  2 The relationship between the blue-ringed octopus and the bacteria is an example of mutualism.
  3 The blue-ringed octopus and the crabs, shrimp and fish that it eats make up a population of organisms.

Answer:

17) C

Temperature is an ABIOTIC factor, not a biotic factor that affects where the octopus can live. So 1 is wrong.
The relationship between bacteria and the octopus is in fact mutualism. Both benefit from each other. Bacteria survive in the octopus’ salivary glands and the octopus, in turn, uses the toxin produced by the bacteria to catch prey. So 2 is correct.
Populations are groups of organisms of the same species living in the same area at the same time. Therefore, crabs, shrimp and fish cannot make up a population. 3 is wrong.