Mosses, liverworts, and fern
        
             
        
        
        
<span><span>a.   </span>Reproducing</span>
f. obtaining
energy
d.
maintaining structure
Why do these
three illustrate the great challenge for every species.
<span><span>
1.   </span>Reproduction, is as vital for an entire race to survive. It prolongs
their generation onwards and offspring to the next centuries to pass by.</span>
<span><span>
2.   </span>Obtaining energy. In both humans and animals, even plants is a
challenge because these creatures need to work in order to obtain these need
resource from food –preys.</span>
<span><span>
3.   </span><span>Maintaining structure. For the living organisms to still exist they
need to keep themselves intact. Combating diseases and having nutrition. This is
a by-product of having energy.  </span></span>
        
             
        
        
        
Answer:
Generally, a seismograph consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper, magnetic tape, or another recording medium.
 
        
             
        
        
        
The answer is graded potential<span>. Its made of various action potentials that depolarise the neuron incrementaly, in short interspersed intervals that do not give time for the neurons to return to resting potential. Therefore, the actions potentials, of varying sizes, grade up in  sum and when they cumulatively reach the threshold level, they invoke an impulse in the nerve</span>
 
        
        
        
Petiole, hopefully this helps you