How can researchers understand if a human activity, such as pollution, negatively affects the abundance of a native species in a short amount of time? Measure the density of the native species in a single location for many years. If pollution negatively affects the native species, there will be a negative correlation between the density of the native species and pollution. Measure the density of the native species in many different locations. Measure the density of the native species and a range of intensity of pollution in many different places. If pollution negatively affects the native species, there will be a negative correlation between the density of the native species and pollution. Measure the abundance of the native species in different places that might have been affected by different pollutants.

Measure the density of the native species in many different locations.

Explanation:

Native species is the one which is inhabitant of an area or location for a prolonged period of time. To determine the impact of population on the native species researchers must check upon the overall density of the population of species at distinct locations as many native species can migrate to different locations in search of food, water, shelter, and mates. At the site being migrated the native species may experience less pollution as compared to native site and if their mortality rate is less than the native place then this means that the native site is not suitable for the survival of the species because of pollution.

a compound light microscope is used to magnify objects in steps.  

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all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

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