Before the introduction of the yellow crazy ant to Christmas Island, land crabs ate many plant seedlings in the forest, maintaining a relatively clear forest floor. As the crab population has declined, plant seedlings have flourished. The forest floor is now covered with plants. Choose the statement that best describes what is occurring on the forest floor.

A. Primary succession is occurring because the ant is a new species changing the ecosystem.

B. Secondary succession is occurring because the organisms on the forest floor are changing.

C. Climax vegetation is occurring because the seedlings finally have the chance to grow.

D. Primary succession is occurring because more plant life is healthier for the ecosystem.

B. Secondary Succession

Explanation:

Secondary succession is when an ecosystem that has been occupied by one organism is displaced or disturbed and is then replaced by another organism.

For many decades the Christmas Island red crab (Gecarcoidea natalis) were a feature of the island. The were also indispensable for soil health as they were known to dig burrows, eat leaf letter and other organic matter in the soil. They also excrete nutrients in their faeces which along with burrow digging and nutrient recycling enriched the soil.

On the recent boom of the yellow crazy ants, the crabs are no longer able to flourish in population since these ants are aggressive and will attack the crabs at the most vulnerable areas in the eyes mouth etc.

This reduces the mating population and by extension the new crabs that would be born. Fewer crabs means fewer incidences of nutrient recycling and where the soil is not being constantly cultivated the vegetation on the forest floor will flourish since the crabs are not able to eat them.

B. Secondary succession is occurring because the organisms on the forest floor are changing.

Explanation:

Secondary succession is a process of change that occurs in a community that has been colonized or occupied by organisms before. This change occurs when the previously occupied habitat becomes disrupted or disturbed by an event, causing a change in the population of organisms in the habitat as new organisms re-colonized the habitat.