Michelle,
thank you for sharing the video link, what a lovely, informative video it is to act as a clear prompt for the children.
The questions that you ask and the children can then wonder allows them to share what they understand as they pose their own starter questions.
Blubber glove can be a very clear way to show the effect of insulation.
Some of the concepts will also be covered by older classes, particularly in relation to adaptation for environmental conditions, but this is such a clear theme that is very suitable for younger children.