Answer:
1- Presence of phenotypic variation
2- some phenotypic variation due to genetic variation
3- the given trait has an impact on fitness  
Explanation:
The evolutionary theory by natural selection proposed by Darwin in his publication “On the origin of species” (1859) is based on a series of assumptions that enable to understand the amazing biodiversity on the Earth. First, individuals are not identical among them, i.e., there exists variation in the traits among the members of a given population, species, etc. Second, phenotypic variation leads to differential survival and reproduction of the organisms that are best fitted to the environment (i.e., competence among the members of the population). Finally, phenotypic traits are passed from generation to generation (i.e., phenotypic variation is inheritable), thereby favoring offspring from parents more adapted to the environment.
 
        
             
        
        
        
Answer:
how a freshwater ecosystem, such as a pond, can change into a terrestrial ecosystem.how a freshwater ecosystem, such as a pond, can change into a terrestrial ecosystem.how a freshwater ecosystem, such as a pond, can change into a terrestrial ecosystem.how a freshwater ecosystem, such as a pond, can change into a terrestrial ecosystem.
Explanation:
 
        
             
        
        
        
Chemical (mutagens)
usually either mimic the structure of nucleotides and are inserted in DNA or either cause
chemical changes  (such as alkylation) in nucleotides hence causing mismatching during replication.
Radiation, on the other hand, (due to its high energy) causes double-strand breaks in DNA causing an
increased likelihood of mutations during the repair of the DNA by cell
mechanisms. 
 
        
             
        
        
        
<span>Crop
is the part of the digestive system you would see in a cross-section anterior
to the gizzard in a worm. Crop is a thin wall organ that acts as a temporary food
storage chamber. The esophagus leads to the crop and the organ next to it is
the gizzard which serves as the food grinding chamber.</span>
        
             
        
        
        
Well what’s the statement