A key stone is the central supporting stone at the top of an arch, it holds all the others in place. If a keystone is removed the arch collapses. A keystone species has the same role.
Keystone species maintain the balance in their ecosystem, keep it functioning and healthy. If a keystone species is removed or disappears then food webs, habitats, ecosystems and the plants and animals living there are all disrupted. Because they are so important, keystone species are often used as flagship or ambassador species. Some are predators, but not all. Typically they are not the most numerous species, but their impact is great.
Elephants are keystone species www.tusk.org/species/african-elephant
Vultures are keystone species www.tusk.org/species/vultures
Marine Turtles are keystone species www.tusk.org/species/marine-turtles
PACE Educators, get the kids around you, and grown ups as well, to think about the wildlife that lives in your area, reflect on which ones are keystone species? Discuss how the Covid-19 pandemic could affect keystone species and habitats in your country, and in other African countries. What do you think you could do to minimise any negative effects?
The PACE Living with Wildlife resources will give you some ideas.