Signals in real world?especially natural signals? Do all the signals in real world ,that are of interest in engineering(for measurements or processing)are only continous/analog or there any other alternatives also?
For example birds make voice,animals make voices are examples of continous signals

Few natural discrete signals in my opinion 
Number of teeth and number of bones in human
Number of mountains in a range,height of a mountain/hill
Please kindly give me other examples from natural world 

Please kindly guide me if i am wrong in my understanding of continuous and discrete signals
Eventhough most engineering signals are continuous, not all are such. For example, statistics of many kinds provide discrete data such as daily stock market indicators, computer network stats, hourly number of customers in a queue, etc...  

Of course, audio signals are transmitted as acoustic pressure waves through air (typically) and pressure is a continuous modeled physical variable.