To evaluate the relationships and identify those illustrating mutualism, we need to understand that mutualism is a type of symbiotic relationship where both species involved benefit.
Let's analyze each option:
A. Hermit crabs use the shells of dead snails for homes.
- This relationship does not involve mutual benefit, as the dead snail is not benefiting from the hermit crab using its shell. This is more of a commensal relationship or even an example of resource use (not symbiosis).
B. Egrets perch on the back of cows and eat the insects that have been disturbed as the cattle forage for food.
- This is a mutualistic relationship because the egrets benefit from getting food (insects), while the cows benefit from having the insects removed (which can be pests). Both parties gain from the interaction.
C. Fleas get food and a warm home by living on hosts such as dogs or cats and biting them to get nutrients from their blood.
- This is an example of parasitism, not mutualism. The fleas benefit at the expense of the host (dogs or cats), which experience negative effects.
D. The Egyptian Plover or “Crocodile Bird” will fly into the crocodile’s open mouth and feed on the decomposing meat stuck between their teeth.
- This relationship can be seen as mutualism because the bird benefits by getting food, and the crocodile benefits by having its teeth cleaned, contributing to better oral hygiene.
E. The pilot fish helps to rid the shark of parasites and clean away fragments of food caught between their teeth; it benefits from protection against other predators.
- This is a mutualistic relationship as well. The pilot fish benefits by getting food and protection, while the shark benefits from being rid of parasites and debris.
Based on this analysis, the relationships illustrating mutualism are:
B, D, and E.