Answer: Because it can change size based on the needs.
Explanation:
<u>The term niche defines an organism´s role in an ecosystem </u>and it also encompass what the organism eat or how it interacts with nonliving elements of the environent.
The realized niche could be regarded as flexible because it is able to change its size based on what it needs. For example, it could increases or decreases its size in competition between resources with other species since they are part of the same ecosystem.
 
        
             
        
        
        
Answer:
DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C). The order of these bases is what determines DNA's instructions, or genetic code.
Explanation:
 
        
             
        
        
        
The 3rd one I think not really sure
        
                    
             
        
        
        
A body of permeable rock which can contain or transmit groundwater.
        
             
        
        
        
Answer:
Index Fossils
Explanation:
Index fossils are used by scientists to help them figure out the dating of discovered fossils or the correlation. They are also very known to appear in a (very) certain/specific age range.
Hope this Helps!