The youtube link to video “The Development of the Sea Urchin” is good to see . Just be aware there are some spelling /grammatical mistakes in the but at least you get to see what the stages look like in a living organism.
Here’s an article from CBC about a new find in the Burgess Shale fossil beds. How does this connect to to what we’re reading about animal diversity and evolution? What are some reasons why scientists decided to group it in phylum Arthropoda along with spiders and crabs?