Explanation:

Impact of species extinction:

• Loss in crop pollination: According to the Center for Biological Diversity, when species go extinct, the impact can be tangible such as in the form of a loss in crop pollination and water purification. 
• Impacting food chain: Further, if a species has a specific function in an ecosystem, the loss can lead to consequences for other species by impacting the food chain.
• For instance, when the wolves in Yellowstone Park in California, US, were hunted to near extinction by the 1930s, the deer and elk they preyed upon thrived, as a result of which their grazing decimated the streamside willows and aspens, which provided habitat for songbirds.
• Contribution to ecosystem functions may be lost: When the number of individuals in a population or species drops too low, its contributions to ecosystem functions and services become unimportant, its genetic variability and resilience is reduced, and its contribution to human welfare may be lost. Hence all statements are correct.