Statement I:  When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.

Statement II:  In the case of a coevolved plant-pollinator mutualism extinction of one invariably leads to the extinction of the other. explain

Both statements I and II are correct .

Statement I: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.

This statement is true and refers to the concept of coextinction. Coextinction occurs when a species, known as the host species, becomes extinct, leading to the extinction of other species that are closely associated with it and depend on it for survival. These associated species are often specialized and have evolved unique adaptations to live in close association with the host species.

For example, some plant species rely on specific pollinators for reproduction. If the pollinator species becomes extinct, the plants will not be able to reproduce, and this can lead to the extinction of those plant species as well. Similarly, some species of animals depend on a particular food source or habitat provided by another species. If the host species goes extinct, these dependent species may also face extinction.

Statement II: In the case of a coevolved plant-pollinator mutualism, extinction of one invariably leads to the extinction of the other.

This statement is also true and relates to a specific type of coextinction known as coevolution. Coevolution occurs when two or more species interact closely with each other and influence each other's evolution over time. A classic example of coevolution is the relationship between flowering plants and their pollinators.

Many flowering plants have evolved to rely on specific pollinators, such as bees, butterflies, birds, or bats, for their reproduction. In turn, these pollinators have evolved traits and behaviors that allow them to efficiently gather nectar and pollen from the flowers. This mutualistic relationship benefits both the plant and the pollinator.

If one of the coevolved species, either the plant or the pollinator, becomes extinct, the other species is likely to face serious challenges in its survival and reproduction. For example, if a specialized pollinator goes extinct, the plants that relied on it for pollination may have difficulty reproducing, leading to a decline in their populations and potential extinction.

In summary, both statements highlight the interconnectedness of species in ecosystems and how the extinction of one species can have cascading effects, leading to the extinction of other species that depend on it or are closely associated with it. This underscores the importance of biodiversity conservation and the need to protect all species to maintain the health and stability of ecosystems.