1. Chapter 17 – Evolution of Populations
17.4 Molecular Evolution

2. Warm Up (solo)
What types of reproductive isolation may have been important in Galapagos finch species? Explain.
Explain how a finch that feeds only on insects might have evolved.

3. Developmental Genes & Body Plans
Key Question: How may HOX genes be involved in evolutionary change?

4. What are Hox genes?
Hox genes determine which parts of an embryo develop arms, legs, or wings.
Also control the size/shape of these structures
Hox genes are homologous—
They shape the bodies of almost all animals (common ancestry)

6. Hox Genes & Evolution
Small changes in HOX gene activity during embryological development can produce large changes in adult animals
Insects & Crustaceans are related to ancient common ancestors that had dozens of legs.
Insects have 3 pairs of leg? What happened to all the extra legs?
Mutation in a single Hox gene, Ubx, turned off the growth of some legs.
A change in ONE hox gene  major evolutionary difference!

8. Timing is Everything!
Each part of an embryo starts to grow at a certain time, grows for a specific time, and stops growing at a specific time.
Small changes in starting/stopping times can make a big difference in organisms!
Small timing changes can make the difference between long, thin fingers and short, stubby toes!