Download Ch. 17 Speciation and Molecular Evolution

Chapter 17
Speciation and Molecular Evolution
Reproductive Isolation
• Species: a group of organisms that can mate
with each other an produce fertile offspring
• Speciation: the formation of a new species
• Reproductive Isolation – when members of a
population stop reproducing with each other
and this eventually leads to evolution into two
separate species
– Mechanisms for reproductive isolation:
behavioral, geographic, and temporal
Behavioral isolation
• Use of different courtship rituals or behaviors
that prevent related organisms from
reproducing
• Western meadowlark song: http://www.yo
• utube.com/watch?v=lvAUgFb1cLY
• Eastern meadowlark song:
• https://www.birdjam.com/birdsong.php?id=4
3
Geographic isolation and temporal
isolation
• Geographic isolation: Separation of
populations by rivers, mountains, or water
• Temporal isolation: timing of reproduction
isn’t in sync
– Ex. Timing of flowering plants
Hypothesizing about Speciation in
Darwin’s Finches
• Founding of a new population (founder effect) –
original species on island reproduced, change in allele
frequency compared to population in S. America
• Geographic isolation – movement to different islands
caused isolation and speciation
• Changes in the gene pool – adaptation to local
environments on each island
• Behavioral isolation – movement back to original island
– no reproduction between these species
• Ecological competition – more evolution due to natural
selection
Molecular Evolution
• Molecular clock: rates of DNA mutations used
for estimating the time that two species have
been evolving independently
• Analyzing Data: Fishes in Two Lakes page 500