Download 16.4 – Molecular Evolution

16.4 – Molecular Evolution
Chapter 17 – Evolution of
Populations
17.4 Molecular Evolution
16.4 – Molecular Evolution
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.
16.4 – Molecular Evolution
Developmental Genes & Body Plans
Key Question: How may HOX genes be involved in
evolutionary change?
16.4 – Molecular Evolution
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)
16.4 – Molecular Evolution
16.4 – Molecular Evolution
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!
16.4 – Molecular Evolution
16.4 – Molecular Evolution
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!