Katie,
encouraging the children to compare and contrast is a great way to start an inquiry process. It can serve as the prompt and the wondering of the initial engagement.
To fully incorporate inquiry science learning the children should go to asking testable questions based on their understanding to deepen and confirm their mental models.
So, if the children have noticed that the polar bears are white and the front of penguins are white, (and they might think this is because ‘white colouring for camouflage’) they might carry out an simple research activity to find images of animals in the arctic regions and classify them by colour.
https://www.activewild.com/arctic-animals-list/
They could predict that there will be more white animals than non-white animals. Then, they check the list and see if they are right.