In a tide pool, 15 species of invertebrates were reduced to 8 after one species was removed. The species removed was likely a(n) .

This question lacks options, options are:

A) pathogen.

B) keystone species.

C) herbivore.

D) resource partitioner.

E) mutualistic organism.  

The correct answer is B)

Explanation:

Keystone species are considered to be those whose activity generates an effect on other species in the community that considerably exceeds that expected according to their biomass or abundance, that is, the most connected species from a trophic point of view in an ecosystem are keystone species, given that its elimination has great effects on the stability and persistence of the network. Many times the absence of keystone species makes it difficult to conserve the community.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)