https://examstudyaid.com/igcse/edexcel/biology/summaries/1-the-nature-and-variety-of-living-organisms/1-1-characteristics-of-living-organisms/https://examstudyaid.com/igcse/edexcel/biology/summaries/1-the-nature-and-variety-of-living-organisms/1-2-variety-of-living-organisms/