2. Natural Selection Inferring What type of beak worked well for seeds? For insects? How are different- shaped beaks useful for eating different foods? Bird Beak Adaptations Use this activity to explore adaptations in birds. 1. Scatter a small amount of birdseed into a petri dish. Scatter 20 raisins on the plate to represent insects. 2. Obtain a variety of objects such as tweezers, hair clips, clothes pins, and hairpins. Pick one object to use as a “beak.” 3. See how many seeds you can pick up and drop into a cup in 10 seconds. 4. Now see how many “insects” you can pick up and drop into a cup in 10 seconds. 5. Use a different “beak” and repeat Steps 3 and 4.

3. Natural Selection Which species of finches appear to be adapted to a diet of seeds, and which to a diet of insects?

4. Natural Selection One year an island that usually receives 130 mm of rainfall experienced a drought with only 25 mm of rainfall. Many plants died. Very few small seeds were available so birds had to eat large seeds that were enclosed in tough, thorny seed pods. How, do you think this change in environment affected the finch population on the island? The next year, more finches on the island had larger and stronger beaks. The finches with smaller, weaker beaks did not survive long enough to reproduce. Is a larger and stronger beak an acquired trait or an inherited trait? Explain.

5. Natural Selection Dog breeders crop the ears of some breeds of dogs to make the ears stand up. Will the offspring of the dogs with cropped ears also have cropped ears? Can changes in an organism during its lifetime be passed on to its offspring? Explain. Only genes are passed from parents to their offspring. Because of this, only traits that are inherited, or controlled by genes, can appear in an organism or be acted upon by natural selection.

6. Natural Selection Type of Selection Type of Traits Selected Examples of Selected Traits How Traits are Selected Selective Breeding Natural Selection Traits that benefit humans Traits that benefit the organism Fine wool in sheep and many kernels in corn Ability to escape predators or resist drought Humans allow only organisms with the trait to reproduce Natural events

7. Natural Selection A B If you were a bird that feeds on moths, which moth in picture A would most likely be eaten first? Which moth in picture B would most likely be eaten first? Explain.

8. Natural Selection During the Industrial Revolution in the late 1700s, many factories were built in England. Soot from factories darkened the tree trunks. By 1850, almost all moths in the industrialized areas were black. The moths were not black because of soot on their wings. Explain why the population of light gray moths decreased and the black moth population increased. When people began to clean up the environment and control the soot, what do you think began to happen to the moth population? Explain how the population returned to consisting of both light-gray and black moths.

9. Natural Selection Time for a brainstorm! Brainstorm a way that geographic isolation could arise and lead to the formation of a new species. What natural events could cause a group to become isolated from the rest of the species? What human activities could cause a group to become isolated from the rest of the species? Why must a group become isolated to develop into a new species?

10. Natural Selection Kaibab Squirrel Abert’s Squirrel About 10,000 years ago, a group of squirrels became isolated from the rest of the species. Since then, the Kaibab squirrel has become different from Abert’s squirrel. What visible trait makes the two squirrels different? Kaibab has a black belly, Abert’s has a white belly.

11. Natural Selection What geographic feature separates the range of the Kaibab squirrel from that of Abert’s squirrel? The Grand Canyon How might new species form?