How is Data Science related to Machine learning?
Data science is much broader concept than machine learning.
It starts from simple data visualization and descriptive statistics to get insights, manipulations like cleansing to prepare data. Before you can use some ML algorithms. 

Basically such huge stacks as bigdata, visualization and data preprocessing are out of machine learning scope. And they are all integral parts of "Data Science".



Large resolution image:
https://whatsthebigdata.files.wordpress.com/2013/07/datascientistmap.png