Prepare before the class:
Build lego animal for each student pair. See photo for an example, but any simple creature will work. Make a collection of separate lego pieces to hand to students to replace parts of their lego animal - the pieces do not need to be identical for each student pair (as different DNA mutations make different physical changes in an animal.)
Cut out Pangea pieces from https://www.amnh.org/content/download/49383/751589/file/dinos_plate_tec…
Introduce the activity:
Ask students to sit in a large circle, next to a student that they will partner with for this activity.
Assemble the Pangea puzzle and place identical lego animals on different parts of the landmass.
Show students the animals on the landmass, called Pangea, in a population (group).
Tell them that over millions of years, the landmass separated into different continents - demonstrate the land masses separating into our familiar continents. The animals move with their landmass. Tell students that once the animals are separated they start to evolve separately from each other. This activity models how that happens.
(Note that, in reality, it is large populations of animals that are separated and evolve as a group, not single animals. But to convey how random small changes lead to different evolutionary paths, this simplification with single animals is suitable for Elementary students.)
Students model evolutionary change:
Tell students that with their partner, they will be an island with their own lego animal - hand out the lego animals to each student pair.
If students are sitting in a large circle next to their partner, it makes it easier for later steps.
Over time these lego animals have changes to their DNA (called mutations) which might make them look a little different.
Tell students that for the first mutation, one of the students in the pair should take off a piece from their animal. Hand a new lego piece to their partner, who should add it in any place on the lego animal that they like.
(By asking one student to remove a piece and another to replace it with another piece, we are trying to remove as much of the "design" and "thinking ahead" of new animals as possible - evolution does not plan or think ahead - it is a randomized, blind process.)
Then students can switch roles with the next lego piece you give them: one of them removes a piece of lego from the animal and their partner adds on the new piece of lego where they like.
After a couple of mutation events, ask students to place their animal towards the centre of the circle, so that everyone can see all animals. Comment that even after only a couple of mutations, the animals living on different islands are already starting to look different from each other.
Then continue with mutation events, each time giving all the student pairs similar, but not necessarily identical lego pieces. Some of the mutations can effect both sides of the body, so students can be asked to remove two legs and give them two new identical lego pieces to replace them (maybe as wings or other appendages).
If appropriate for the age, stress that in reality not every DNA mutation results in a physical change to an animal's body. We are speeding up evolution with every mutation causing a physical change.
In addition, if appropriate for the age, tell the students that, in reality, the only changes that are retained are the ones that allow the animal to survive better in their environment. If there is no survival advantage the mutation might not stay. (There are other mechanism that also account for mutation persistance, such as genetic drift, but these are beyond Elementary level evolution.)
Optional addition to a round of mutations:
Tell each student pair an environmental event that happens on their island e.g. flooding, or a cold period. They should make adaptations on their animal that will help it survive this environmental shift.
Once the mutations (lego replacement pieces) have all been used, stop the activity, and ask student pairs to each show and explain to the class the adaptations that their animal now has and how they help it survive in their environment.
Add real life examples to the conversation as and if these adaptations are showcased:
The evolution of wings from legs occurred with the evolution of birds, about 150 million years ago (Mya), with Archaeopteryx as the intermediate fossil. Wings also evolved in Pterosaurs (flying dinosaurs) 225 Mya, in bats (60 Mya) and in insects (400 Mya) - so flight evolved four independent times through evolution.
The evolution of legs into fins and also tails into a flippers happened when whales evolved from land animals, about 50 million years ago. (Hippos are the closest living land animal relatives of whales.)
(Another major evolutionary event which will likely not be demonstrated with the lego animals, is when life moved onto land: tetrapods (animals that walk on land) evolved from fish, with fins evolving into legs, about 390 million years ago. The discovery of the Tiktaalik in Nunavut was some excellent science that looked for and found the missing link fossil.)
Wrap up and summarize:
In the same way that your lego creatures evolved different features on each of your islands, living things have evolved along separate evolutionary paths from a common relative when they are separated on different islands or continents. On the separated islands, the different populations respond to different evolutionary pressures (e.g. different climate) which result in the evolution of features that allow survival in each environment.
The longer a population has been separated, the more different it will look from its relatives on another land mass. We find these changes in both fossils and living things that are alive today.
By studying where different animals are found on Earth and the fossils found in each landmass, scientists construct an evolutionary tree of all living things.