I love the Grade Six Ontario Science Curriclum. The first unit we are studying is Biodiversity. The kids are really loving this unit. It helps that I ordered 20 preserved specimens in jars from our Board's Resource Centre! There is nothing like a preserved snake or fetal pig in a jar to spike a child's interest in Science!
But I wanted the students to study some living creatures as well. So we got a couple of pets - Hermit Crabs! Hermit crabs make great pets because they are so inexpensive and easy to take care of. They will eat anything, (kids can even feed them bits of their lunches - but I haven't told my students that!)
They are actually social animals, so it is better to purchase more than one, (so they don't get lonely). They can get quite active, and the children really enjoy watching them.
The fun thing about hermit crabs is that they will "move into" a different shell when they grow or when the mood strikes them. The children can actually decorate shells, leave them in the tank, and wait to see if the crab will choose their shell.
I have a small portable case that I use on holidays when one student gets to take them home to "pet-sit". In June, one child is the lucky winner and gets to take them home to keep.
The only issue we have now is that we don't know what to name them! And it doesn't help that we can't tell which is male and which is female, but it sure is a more interesting arthropod than your old fasioned garden spider!