Answer:
Explanation:Population genetics is the field of biology that studies allele frequencies in populations and how they change over time.
 
        
             
        
        
        
Answer: Each body segment of an earthworm contains four pairs of setae, which are used to move the worm. The setae of marine worms are found in bundles. Leeches do not have setae at all.
Sample Response
Explanation:
 
        
             
        
        
        
Answer:
 Deserts
Explanation:
Short for desertification 
 
        
             
        
        
        
Lead emission since early 1980s have DECREASE DUE TO LEAD FREE GASOLINE. 
Lead is a natural occurring element that is found in small quantity in rocks and soils. Lead emission is an important environmental health issue because a very small quantity of lead can cause adverse effects on the nervous system of unborn babies and young children. Because of this, the government took all necessary measures to ensure that its emission was drastically reduced.
        
             
        
        
        
The color spectrum from a rainbow.
The Electromagnetic spectrum from waves.