Why do some trees have needles instead of broad, flat leaves?            
            
            
                                            
                                                    
                    they do not block sunlight
                    
                                        
                    37
                    
                    
                 
                
                    needles retain more water 
                    
                    
                    457
                    
                    
                 
                
                    because they can not shape leaves
                    
                                        
                    69
                    
                    
                 
                
                    in defense against pests
                    
                                        
                    384
                    
                    
                                             
               
                                                                                   
            Conifers, or cone-bearing trees, evolved to have needles that retain more water and seeds that could hang out until there was enough moisture to take root. It may not seem like it, but needles are leaves. They do the same job that broad leaves do—capture sunlight, “inhale” carbon dioxide, and “exhale” oxygen—providing the tree with food and air for us to breath. Instead of shedding every fall, though, needles can last three or four years!