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What is a keystone species ?
A
A common species that has plenty of biomass, yet has a fairly low impact on the community's organization
B
A rare species that has minimal impact on the biomass and on other species in the community
C
A dominant species that constitutes a large proportion of the biomass and which affects many other species
D
A species which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community's organization and survival
Detailed Solution
A keystone species is one whose effect on the community is very large compared with its abundance or biomass.
Like the keystone at the top of an arch, removing it causes the whole structure of the community to change or collapse.
Example: the sea star Pisaster on rocky shores; when it was removed, mussels took over and the number of other invertebrate species fell sharply. Fig trees, which feed many animals when other fruit is scarce, are another example.
A species with a large share of biomass and a large effect is a dominant species, not a keystone species.
So a keystone species is a species that makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community's organisation and survival.
Like the keystone at the top of an arch, removing it causes the whole structure of the community to change or collapse.
Example: the sea star Pisaster on rocky shores; when it was removed, mussels took over and the number of other invertebrate species fell sharply. Fig trees, which feed many animals when other fruit is scarce, are another example.
A species with a large share of biomass and a large effect is a dominant species, not a keystone species.
So a keystone species is a species that makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community's organisation and survival.