A keystone species is a central stone at the summit of an arch, locking the whole together.
a species on which other species in an ecosystem largely depend, such that if it were
removed the ecosystem would change drastically.
capable of causing extinctions of native plants and animals, reducing biodiversity
competing with native organisms for limited resources, and altering habitats.
Which one is it?

4.06 hc)a five-year review of threats to the southern resident orca population of the united states concluded that the top threats were prey availability, contaminants, and effects from recreational and whale watching vessels. further down the list are oil spills, disease, and effects from commercial vessels not targeting whales. how might this list be different if it were for transient whale populations, which have a larger average population size and live farther offshore in open waters? a)the transient population is more likely to be affected by contaminants. b)the transient population is less likely to be affected by whale watching vessels. c)the transient population is more likely to be affected by disease. d)the transient population is less likely to be affected by prey availability.

Round seeds and yellow seed color are dominant to wrinkled seeds and green seed color. which punnett square represents the correct way to set up the cross rryy  ´  rryy? 

What molecules will be best used to compare different species with the exact same sequence of amino acids? why would two species have the same protein even if the molecules in question is different? (hint: transcription to translation to protein).