If an organism isn’t suited to survive in its environment, their genetic traits won’t likely be passed on to the next generation. This is natural selection at work. It’s survival of the fittest, and this book takes an in-depth look at why some organisms survive and thrive while others slowly die out. Elementary curricula and STEM concepts from the Next Generation Science Standards are covered in detail. Age-appropriate text and colorful images make this important life science topic easy for young readers to understand.