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keystone species

species that have low biomass, but large impact on community and it's biodiversity (can be a predator)


keystone species and competitive excluesion

keystone species may keep a predator below the carrying capacity to reduce the risk of competitive exclusion


Bob Paine

took piaster starfish (top predator) out of tidepools
-decreased tidepool biodiversity
-allowed bivalves and barnacles to dominate
-15 species to 8 (or 5)


Malaysian Strangler fig

keystone species
-provides resting location for a ton of species even though it's parasitic to the tree
-provides year round resources that support monkeys and 50 kinds of birds


communities with higher biodiversity:

-more productive and produce more biomass
-more stable in their productivity
-handle environmental stress better
-more resistant to invassive species


Dominant species

-most abundant with highest biomass (not necessarily keystone)
-some ppl think they're the best competitors; others think they're the best at avoiding prey
-often times invassive species become dominant


Chestnut blight introduction

killed a lot of the American chestnuts
-had small impact on some species, but big impact on others


sea otters

-eat sea urchins
-w/o otters, urchins eat kelp forests
-no more habitat for a bunch of marine life
-even affected bald eagle


ecosystem engineers

-cause physical changes in environment that affect community structure
-e.g. beavers


herbivore affect on plant diversity

-can increase, decrease, or have no effect
-have to look at food preference and plant competition across ecosystem


Intertidal snails

-eat red (Chondrus crispus) and green ((Enteromorpha spp.) algae
-when snails are excluded, the green algae competitively displace the red one


wolves in yellowstone

-ate elk and changed elk behavior
-elk avoided valleys
-vegetation returned, banks stabilized, rivers were fixed
-more birds, beavers, ducks, and muskrates
-wolves ate cayotes = more rabits and hawks