Have your preschoolers color line drawings of leaves and vines and help them cut them out. Affix one half of sticky-backed hook and loop strips to the backs of the leaves and vines and the other half to some of the blocks in your block area. Encourage your students to build tall trees with the blocks and decorate them with the leaves and vines they've made. Once the forest is complete, challenge your students to attach pictures of rainforest animals onto the block trees at about the level where they reside in nature. For example, preschoolers can attach birds to the top of the block trees, monkeys in the middle or on the vines, snakes on the trunk and insects on the ground.
Add toy rainforest animals to the block area. Challenge your preschoolers to build homes for each of them. Encourage students to think about the resources available in the rainforest, such as what kind of housing is made possible by fallen leaves on the floor or by branches in the trees. Watch your preschoolers play and ask questions about how the animals get to places or where they find food. For example, if you see a preschooler put a tiger in a tree, ask her how it got there.
Use long strips of green yarn to help your preschoolers create vines in the block area. Show interested students how to stack blocks to create tall "trees" and let them tape the yarn to the tops of the stacks to create vines. Encourage your students to use the vines to connect the block trees by taping the dangling end to nearby "trees." Once the vines are in place, let your preschoolers play with the forest by adding toy animals. Challenge students to think about the different animals that use vines for food and as bridges.
Give each child three or four small pictures of rainforest animals. Challenge your preschoolers to use the blocks to build a rainforest. Once it is complete, encourage each child to hide one of her animal pictures within the block jungle and challenge a friend to find it. Encourage your students to repeat the game with the additional pictures as long as the game remains fun and you have time. Expand on the activity with interested preschoolers by talking about where the pictured animals live in the rainforest and how they would actually hide to hunt or escape predators.