<span>Every living organism begins life as a single cell. Unicellular organisms may stay as one cell but they grow too. Multicellular organisms add more and more cells to form more tissues and organs as they grow. </span>
        
             
        
        
        
An alteration to chromosome structure which only involves one chromosome is called MONOSOMY.
Alterations in chromosomes structures usually leads to mutation. Monosomy refers to the condition of heaving a diploid chromosome complement in which one chromosome lacks its homologous partner.
        
             
        
        
        
Answer:
Smooth muscle is found in the walls of hollow organs like your intestines and stomach. They work automatically without you being aware of them. Smooth muscles are involved in many 'housekeeping' functions of the body. The muscular walls of your intestines contract to push food through your body.
Explanation:
 
        
             
        
        
        
1.Tyrannosaurus Rex Lived in the Mesozoic Era
2.The largest mass extinction happened in the Paleozoic Era
3.Life exploded for the first time in the Precambrian Era
4.The Chicxulub crater in the Cenozoic Era
 
        
                    
             
        
        
        
Answer:
<em>Geographic isolation</em>
Explanation:
Geographic isolation can be described as a term that describes the model of speciation in which a biological population becomes isolated from other members of the population and can no longer have gene flow with them.
The same scenario of gene isolation is occurring in the species of taods which live at the top of the mountains in southern Arizona. This population has become reproductively isolated fro all other species of toads within the mountain range.