Such direct observational evidence is limited, however, and clouds remain the biggest source of uncertainty--apart from human choices to control greenhouse gases—in predicting how much the climate will change
        
             
        
        
        
Answer:
b. hibernation to lower metabolism in the winter
Explanation:
Tundra, besides the one I live in apparently, are very, very dry because of the cold. This means that it may be helpful to hibernate for the part of the year where it is even too cold for plants and other animals.
 
        
             
        
        
        
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Answer:</u></h2>
<u>mechanism:</u>  the process of evoluton .
Evolution is the process by which veriety of  modern organisms have descended from ancient ancestors. Evolution is responsible for both the remarkable similarities of all  0rganisms and the amazing diversity of that organisms  but exactly how does it work? Fundamental of  the  process of evolution  is genetic variation upon which selective forces can act in order for evolution to occur.
Examines the mechanisms of evolution focusing on: 
•<u>Decent </u>: the  genetic differences that are heritable and passed on to the next generation successfully.  
• <u>mechanisms of change</u>:   Mutation, migration (gene flow), genetic drift, and natural selection are act as mechanism of change .  
• The random nature of genetic drift  and their effects .
• How variation, differential reproduction, and  heredity result in evolution natural selection
.
• How different species can affect each other's evolution through co-evolution.
 All of these mechanisms can cause changes in the frequencies of genes produce change in  in populations, and so all of them are mechanisms of evolutionary change. However, natural selection and genetic drift (genetic flow) cannot operate unless there is genetic variation among organisms.  
 
        
        
        
Answer:
Digestion, excretion and transportation of substances.
Explanation:
Chemical reactions such as breakdown of food, cleaning of blood and absorption of nutrients and digestion are the activities that our body done with the use of energy. Digestion of food needs energy for the breakdown of food with the help of several enzymes. Transportation of waste materials and other substances also needs energy. Our cells absorb nutrients with the help of energy molecules through active transport.