The Geologic Coevolution of Plants and their Pollinators

Introduction

Angiosperms (or flowering plants) have evolved over time to form a very close connection with different types of pollinators (such as bees and other insects). Angiosperms pollinated by insects create less pollen then angiosperms that are pollinated by wind. This leads scientists to infer that a coevolution relationship may be taking place between flowers and insects. Coevolution is two different species evolving together (as one changes the other changes).

Teacher or Student Preparation work:

Select 4 to 5 different bottles and fill them with sugar water or juice to represent nectar. Then using creativity, construct a flower to sit on top each bottle. The flower should be unique in size, shape and structure. Construction paper, fabrics and artificial flowers are just some of the supplies that can be used to make these. The flower should be made so that some but not all straws should be able to retrieve the nectar. Straws should be different types and size (cutting a standard straw is a great way to change straw type).

Student Exercise

  1. Select 4 to 5 students and give them each a straw
  2. Students are to try to insert their straw in to the flower they choose.
  3. Each participant will report to the class if they can reach the nectar and then move on and explore with the other flowers. (student should not sip or drink the water)
  4. End the exercise with a class discussion about how flowers are a living organism that over time has created a relationship with insects. Ask questions about what patterns they saw; does every straw work with every flower; suppose your pollinator had a mutation that let it have a larger straw. Explain the concept that not all pollinator can pollinate all plants.

Student Questions:

  1. What is the difference between coevolution and mutualism
  2. Why must a pollinator hone in on one type of flower and NOT be random about the flower it chooses?
  3. Look at the attached pictures of a bee and flower anatomy and make prediction about where evolutional changes may have take place to promote their relationship.
  4. How might the flower change over time if its primary pollinator dies off?

References

coevolution and Pollination. J. Stein Carter. last modified on 29 Mar 2005. Copyright © 1999. .clc.uc.edu/courses/bio303/coevolution.htm

General Biology Program for Teachers: Mutalism and Co-evolution A study of Flowering Plants and their Pollinators with a focus on Form and Fuction. 2002.