The dependent variable would be anything that is not consistent. So outside factors such as how much sun and the environment that the plant is contained in.
Less developed countries have a higher rate of infant and maternal deaths than those of more developed country
There are so many examples for that in different areas, like biology experiment carried out in our lab recently.
Here's one link: https://www.creative-biogene.com/Robust-Tn5-Transposase-EMQZ1422-1271506-26.html
Answer: it is species!
Explanation: species is a GROUP of individual organisims that inter breed with others!