Because of underdeveloped lungs the frog has to breathe through moist skin. Therefore for exchange of gases the skin is thin and moist
        
             
        
        
        
→ Darwin believed that the need to adapt, in similar words, the changes occruing in the environment caused evolution. 
The main cause of evolution, according to Darwin, was natural selection. Natural selection is a process in which a group of organisms with certain characteristics survive and thrive, in comparison to other organisms with different characteristics. This idea basically means that having some characteristics makes you suited for an environment.
And how would that ↑ explain Evolution?
Well, evolution is the change in species that occurs during time. But for you to change, there must be a cause for that change, which is none other than the need to survive, reproduce, etc. 
→ As mentioned before, not all characteristics are enough to surive, and hopefully the image pasted below will help you.
Hope it helped,
BioTeacher101
 
        
             
        
        
        
Answer:
Taking shorter showers or turning off the faucet while brushing your teeth can reduce water waste in your home. Only use your dishwasher or washing machine when there is a full load, and switch to energy-saving appliances if possible.
Explanation:
 
        
             
        
        
        
Internal fertilization is the process when the syngamy (union of male and female gamete) occurs inside the female body after insemination using copulation. In contrast, External fertilization is the syngamy outside the female body, that is in the outer environment especially in water bodies.