Foothill High School Science Department Evolution of Populations The Process of Speciation

Foothill High School Science Department The Process of Speciation Speciation Speciation – The Formation of New Species Species Species – A Group of Organisms That Breed With One Another And Produce Fertile Offspring – Individuals In The Same Species Share A Common Gene Pool

Foothill High School Science Department Isolating Mechanisms Key Concept Key Concept : – As New Species Evolve, Populations Become More Reproductively Isolated From Each Other Populations Become More Reproductively Isolated From Each Other

Foothill High School Science Department Isolating Mechanisms Reproductive Isolation – When Members Of Two Populations Cannot Interbreed And Produce Fertile Offspring The Populations Have Separate Gene Pools The Populations Have Separate Gene Pools

Foothill High School Science Department Reproductive Isolation Can Occur Through Can Occur Through: 1.Behavioral Isolation 2.Geographic Isolation 3.Temporal Isolation

Foothill High School Science Department Behavioral Isolation Two or More Populations Are Capable of Interbreeding But Don’t Due To: Behavior Differences e.g. Behavior Differences e.g. – Different Courtship Rituals – Other Types of Behavior Courtship Songs Courtship Songs Courtship Behavior Courtship Behavior Sleep/Wake Cycles, etc. Sleep/Wake Cycles, etc.

Foothill High School Science Department Eastern Meadowlark Each Species Has Separate Mating Song Western Meadowlark Behavioral Isolation Populations May Share Overlapping Territories

Foothill High School Science Department Geographic Isolation Populations Are Separated By Geographic Barriers e.g. RiversMountains Bodies of Water Deserts

Foothill High School Science Department Geographic Isolation Grand Canyon Squirrels Grand Canyon Squirrels – Colorado River Formation Of The Grand Canyon Separated Populations Of Abert Squirrels About 10,000 Years Ago. – Separate species – The Kaibab Squirrel Developed

Foothill High School Science Department Kaibab Abert

Foothill High School Science Department Temporal Isolation Two Or More Species Reproduce At Separate Times – Three species of Orchids Each Release Pollen On Different Days – Frogs in same pond breed in different months

Foothill High School Science Department Testing Natural Selection In Nature Galapagos Finches Galapagos Finches – Darwin’s Radiation Theory Proven By Peter & Rosemary Grant of Princeton University – Required Variation Variation Beak Size Must Change Fitness Beak Size Must Change Fitness

Foothill High School Science Department Testing Natural Selection In Nature Grants Realized Darwin’s Hypothesis Relied On Two Testable Assumptions: 1.Inheritable Variation Must Be Present In Current Population 2.Variations Must Produce Enough Differences In Fitness That Natural Selection Will Occur

Foothill High School Science Department Variation On A Single Island The Grant’s Mapped: Populations Breeding Success Wing, Leg, Beak Length Beak Depth & Color Feather Colors Bird Mass They Verified Genetic Variation

Foothill High School Science Department Natural Selection The Grant's studied finches on Daphne Major, a small island (800 sq. yd) In 1977 island had only 2mm of rain instead of normal 130mm... The drought resulted in a loss of 84% of medium ground finch population. Most died of starvation!

Foothill High School Science Department

Rapid Evolution They Were Able To Document Several Incidences of Rapid Evolution On Daphne Major Over Several Decades

Foothill High School Science Department Speciation In Darwin’s Finches Key Concept Speciation In The Galapagos Finches Occurred By Founding Of A New Population, Geographic Isolation, Changes In The New Populations Gene Pool, Reproductive Isolation, And Ecological Competition

Foothill High School Science Department Speciation In Darwin’s Finches

Foothill High School Science Department Speciation In Darwin’s Finches

Foothill High School Science Department Speciation In Darwin’s Finches

Foothill High School Science Department Speciation In Darwin’s Finches A & B Don’t Mate

Foothill High School Science Department Speciation In Darwin’s Finches

Foothill High School Science Department Speciation In Darwin’s Finches