Which statement best describes a keystone species

A keystone species plays a unique and crucial role in the functionality of an ecosystem. Without these species, the ecosystem will be different or can even cease to exist altogether.

Hence, the correct answer is option 4 - it has a strong influence on the ecosystem.

the potatoes have high sugar concentrations and although these potatoes were different we could seethe effects that their sugar concentrations had in different environments. for example, the potatoes in sample a, were placed in pure water. this created a hypertonic environment and caused the potatoes to draw in water from its surroundings. we saw the opposite happen with the potatoes in sample b when placed in the sodium chloride solution. the potatoes in this case were in a hypotonic solution and therefore lost water to their surroundings.

its probably to later but whats the question