You notice that in forests with two species of woodpeckers, one is restricted to the tops of trees and the other is restricted to the lower trunks. however, in forests with only one woodpecker species, that species occurs on both the tops of trees and the lower trunks. what would you call the phenomenon occurring in the forests with two species?

The phenomenon is called: Ecological character displacement.

Explanation:

W L Brown and E O Wilson was the first who explained the theory of ecological character displacement. This theory explains that the two similar species using the same resources, likely to compete strongly for the same resources. The competition leads to competitive exclusion. The stronger ones may survive and weaker one will be eliminated. This is the one possibility. The other possibility is that in each population, those individuals whose phenotype allows them to use resources not used by members of the other species. The result may be that the populations diversify its external features (phenotype) and use of resources. This will reduce resource competition and will permit coexistence.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .