Final answer:
Irruptive population changes can occur due to environmental changes or the invasion of new species. Examples include changes in the environment, such as fluctuations in rainfall and food sources, and the establishment of invasive species in new areas.
Step-by-step explanation:
Populations are dynamic entities that can undergo irruptive population changes. These changes can occur due to a sudden and significant change in the environment, like a volcanic eruption that splits a population that once occupied the same habitat. On the other hand, a stable and unchanging environment can allow a species to flourish.
Examples of irruptive population changes include fluctuations in the environment, such as variations in rainfall and food sources, which affect birth and death rates in populations. Small isolated populations are particularly vulnerable to catastrophic events like floods, fires, droughts, or hurricanes. For example, a wildfire may eliminate a small local population while some individuals in extensive habitats survive and become a source for repopulation.
Invasive species can also cause irruptive population changes. Invasive species can spread rapidly and establish populations in new areas. They may overcome limitations of small populations and low genetic diversity through selection in previous colonization episodes. Examples include the medfly, Ceratitis capitata, which originated in Africa and spread worldwide, and the glassy-winged sharpshooter in French Polynesia.