Which is an example of geographic isolation? a) a species of chipmunk becomes extinct because of a lack of food. b) two groups of albatross live on separate islands but commonly cross from one island to the other. eliminate c) a group of snakes is unable to cross a river and is separated from a group of snakes on the opposite side. d) one group of frogs mates in spring and another mates in fall, effectively isolating the two groups from breeding with each other.

What kind of seafood would you expect to have the highest levels of mercury and why? kelp, because they use the sun to photosynthesize on the bottom trophic level. oysters, because they filter feed on plankton on a lower trophic level. small fish, because they eat plankton on a higher trophic level. sharks, because they feed on organisms on a higher trophic level.

What are 3 reasons that natural selection occurs

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?