When an ecologist compares the diversity of different communities by counting the number of species within each community, the measure of diversity being used is called

When an ecologist compares the diversity of different communities by counting the number of species within each community, the measure of diversity being used is called "Species richness".

Explanation:

The species diversity can be measured by:

Species richness is the number of species present in a sample, within a community, habitat or microhabitat, ecosystem, landscape, region or any well defined spatial unit.

It is the standard metric for measuring biodiversity because of its simplicity and for being easy of interpretation. It is the simplest and straightforward measure of biodiversity. It is just a count of species, with no need for abundance data. In some cases, this can be the cause of criticism, as it ignores information about the species-abundance distribution.  

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.

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emerald ash borer

the emerald ash borer is a green buprestid or jewel beetle native to north-eastern asia that feeds on ash species. females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years. hope this !