Do Now

• On Whiteboard:– Fast swimming fish survive 50% of the time• Because they can get away from predators

– Slow swimming fish survive 25% of the time• Because they are more likely to get caught by predators

– Assuming each parent always has 4 offspring, if we started with 2 fast swimming fish and 4 slow swimming fish, what percentage of fish would be fast swimmers in generation 4?

• How did Buster “evolve” from the Gray Wolf?

Selective Breeding

• Selective breeding means that humans choose which animals survive to reproduce rather than nature– In other words, selective breeding depends on human

interest, not necessarily traits that help survival• Over many generations, humans selected the

wolves with the most desirable traits to reproduce and eventually these desirable variations of wolves evolved to modern dogs

Evolution by Selective Breeding

• EXAMPLE (not exactly how it happened) of how Buster’s spots may have developed

• Wolves with brown spots were selected to reproduce 50% of the time– Because breeders (humans selecting which dogs will

mate/reproduce) liked brown spots• Wolves without brown spots (normal gray wolf color) were

selected to reproduce only 25% of the time– Because only a few breeders like that color better

• Assuming each parent always has 8 puppies, if we started with 2 brown spotted and 4 gray wolves, what percentage of wolves would have brown spots in generation 4?

Evolution by Selective Breeding

• EXAMPLE (not exactly how it happened) of how Buster’s ears may have developed

• Wolves with floppy ears were selected to reproduce 50% of the time– Because breeders (humans selecting which dogs will

mate/reproduce) liked floppy ears more than pointy ears• Wolves with pointy ears(normal gray wolf ears) were selected

to reproduce only 25% of the time– Because only a few breeders like those ears better

• Assuming each parent always has 8 puppies, if we started with 2 floppy ear and 4 pointy ear wolves, what percentage of wolves would have floppy ears in generation 4?

Evolution by Selective Breeding

• EXAMPLE (not exactly how it happened) of how Buster’s short nose may have developed

• Wolves with short noses were selected to reproduce 50% of the time– Because breeders (humans selecting which dogs will

mate/reproduce) liked shorter noses• Wolves with long noses (normal gray wolf noses) were

selected to reproduce only 25% of the time– Because only a few breeders like those noses better

• Assuming each parent always has 4 puppies, if we started with 2 short nosed and 4 long nose wolves, what percentage of wolves would have short noses in generation 4?

Evolution by Selective Breeding

• EXAMPLE (not exactly how it happened) of how Buster’s loud bark may have developed

• Wolves with the ability to bark (instead of howl) were selected to reproduce 50% of the time– Because breeders (humans selecting which dogs will

mate/reproduce) liked barking more than howling• Wolves that howled (normal gray wolf noise) were selected

to reproduce only 25% of the time– Because only a few breeders like howling– Assuming each parent always has 4 puppies, if we started with 2

barking and 4 howling wolves, what percentage of wolves would bark in generation 4?