The extinction of this species changes an ecosystem forever.
a. threatened
b. keystone
c. genus
d. endangered

b. keystone.

Explanation:

A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.

Here are some examples of keystone species: Bison, prairie dog, and otter.

Hope it helps!

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

i think its white blood cells

i hope this