Feathers are modified as scales. According to the history, birds which have feathers are the descendants of the dinosaurs which have scales.
That's why feathers are categorized as scales in the present record according to studies. <span />
        
             
        
        
        
Answer:
The correct answer is D) assimilation of external DNA into a cell
Explanation:
A bacteria is called transformed when it consist a genetic material that is not it's own but taken from outside the cell. So transformation of bacterial cell defines the uptake of foreign DNA by bacterial cell from its surrounding.
This transformation in bacteria is necessary because it provides bacteria some new and extra genes that help it to survive in the adverse and changing environment.  
Transformation can result in getting the antibiotic-resistant gene to the bacteria which protect the bacteria from antibiotics during infection when antibiotic is used against it.
So the right answer is D) assimilation of external DNA into a cell. 
 
        
             
        
        
        
Answer:alveoli; lactiferous ducts
Explanation:
 
        
             
        
        
        
Energy from the sun heat and chemicals
        
             
        
        
        
The value of n, the Hill coefficient, for hemoglobin is about 2 to 3 times as great as the value for myoglobin.
Hill Equation
The two closely related equations that help to explain the binding of macromolecules to ligands are called the Hill equation. It helps to quantify the interaction between various ligand binding sites. 
Hill coefficient
It is used to describe the cooperativity of ligand binding. It can be positive and negative depending on the value of the Hill coefficient. If the value of the Hill coefficient is more than one then it exhibits positively cooperative binding and if it is less than one then it exhibits negatively cooperative binding. Then there is the noncooperative binding where the Hill coefficient value is one. As for the hemoglobin and myoglobin, the values are, 
- Hill coefficient of hemoglobin is 2.7 - 3.
- Hill coefficient of myoglobin is 1.0.
Thus hemoglobin is positively cooperative and myoglobin exhibits noncooperative binding. 
Learn more about hemoglobin:
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