Question

If an egg rolls out of the nest, a mother graylag goose will retrieve it by nudging it with her beak and head. If researchers remove the egg or substitute a ball during this process, the goose continues to bob her beak and head while she moves back to the nest. Explain how and why this behavior occurs. How is the seasonal timing plant flowering similar in mechanism and function to the lunar-linked rhythm of fiddler crab courtship? (See pp. 839-841 of Concept 39.3.) Suppose you exposed various fish species to the alarm substance from minnows. Based on what you know about natural selection, suggest why some species might respond like minnows, some might increase activity, and some might show no change.

Answer 1

1. This behavior is called Fixed Action Pattern. It is an innate behavior sequence which can be a very short to medium length sequence of actions occurring instictively in response to external sensory sign-stimulus. The sight of a missing or displaced egg acts as a sign stimulus for the bird and it initiates the sequence of actions for retriving the missing egg. Once the response is initiated, the bird does not check it during the middle of the process until the completion. Thats why, it doesn't matter whether the egg is replaced by a golf ball or is removed, the bird continues the series of actions. Such behavioral patterns are in control of Neural network ( or innate releasing mechanism) triggered in response to a sign stimulus.

2. Behaviours like Migration and Reproduction in fiddler crabs reflect biological rhythms like yearly cycles of seasons in flowering plants. And are influenced by the periods of daylight and darkness in the environment. Seasonal flowering in plants occurs at arrival of particular season only. The same way the crab male's claw waving courtship happens at the timing of new and full moon. Crabs link their reproduction to the timings of greatest tidal movements.

3. Pheromones can act as alarm signals. When various fish species are exposed to the alarm substance from minnows, the substance that is released from the skin of minnow fish disperses in water and induces a frightening stimulus in other fishes. The surrounding fishes become more vigilant and gather in groups near the river bottoms to save themselves from the attack. Pheromones can affect different species of fishes at different levels.