Explanation:
In the megasporan- gium of each ovule, the megasporocyte divides by meiosis, producing four megaspores. One survives and forms a female gametophyte. Fertilization: In nucleus of developing endosperm-- Double fertilization occurs. One sperm fertilizes the egg, forming a zygote.
 
        
             
        
        
        
The brain and is divided into two parts called the left and right cerebral hemispheres. The two hemispheres are connected by the corpus callosum.
        
             
        
        
        
Explanation:
The DNA contains many regulatory sequences that are very important, even though they do not code for proteins. 
For example, the expression of every gene is regulated by a region called the Promoter. The promoter sequence, located close by the coding region of the gene, usually binds the RNA polymerase (the enzyme that transcribes genes into mRNA) as well as other proteins necessary for transcription, 
The promoter sequence, thus, does not itself code for proteins, but is essential for transcription and must be highly conserved so that the RNA polymerase can find it.
 
        
                    
             
        
        
        
The difference<span> between the </span>birth rate<span> and the death </span>rate<span> of a country or place is called the </span>natural increase<span>. </span>
        
             
        
        
        
Answer:
Electron transport chain
Explanation:
Cellular respiration is the process whereby glucose is broken down in the cell to yield energy in form of ATP. This process, which is important to the metabolic functioning of every organism, occurs in three major stages namely: glycolysis, kreb's cycle and electron transport chain (ETC). 
According to this question, a stage of respiration is described as follows: 
- Two pyruvate molecules undergo a chemical reaction, combining with coenzyme A to form two acetyl-CoA molecules. 
- Two carbon dioxide molecules and two NADH molecules are formed as a result of this process.
The process depicted above is KREB'S CYCLE of cellular respiration, hence, the stage of respiration that immediately follows the process is called ELECTRON TRANSPORT CHAIN (ETC).