<span>Changing one amino acid in the protein hemoglobin causes sickle-cell anemia.</span>
        
                    
             
        
        
        
The male fruit fly has an XY profile of the sex chromosomes, and the female has an XX profile of the sex chromosomes.
If a male is white-eyed, then it must have a white recessive allele on his only X chromosome and the red eyed female can be homozygous (having two dominant red eye alleles) or heterozygous (having both a dominant and a recessive allele).
If the female is homozygous then all of the offspring will be red-eyed, and if she's heterozygous then half of the offspring will be white eyed. (see the table provided below)
 
        
        
        
Answer:
When one thing dies, or is taken away from the food web, then this could happen:
Let's say plants are taken away. Then, herbivores have nothing to eat, sot hey die. Then, carnivores have nothing to eat, and the same thing happens, etc. 
Plants are the base of survival for every organism in nearly every ecosystem. 
 
        
             
        
        
        
It indicates what elements is composed by and how many atoms of one element are linked to the other.
For example, this is the formula for table salt is:
NaCl
The formula indicates that table salt (sodium chloride) is composed by sodium (Na) and chlorine (Cl) on a 1:1 ratio.
Hope it helped,
BioTeacher101