Link to help with researching average weight of different animals:
http://thewebsiteofeverything.com/animals/mammals/adult-weight.html
Links to help with researching different life cycles:
http://www.bbc.co.uk/education/topics/zgssgk7
https://www.stem.org.uk/elibrary/list/12775/year-5-living-things-and-their-habitats (Scroll down to find links)