Copyright Pearson Prentice Hall Warm Up 7 3/11 What is genetic equilibrium? What does the Hardy Weinberg principle state? Under what 5 conditions does Hardy Weinberg hold true for NO evolution to occur? Can there be evolution without natural selection? Copyright Pearson Prentice Hall

Hardy Weinberg Principle: states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change Genetic equilibrium- situation in which allele frequencies remain constant Must be random mating Population must be very large No movement into or out of the population No mutations No natural selection

16-3 The Process of Speciation Photo credit: ©MURRAY, PATTI/Animals Animals Enterprises Copyright Pearson Prentice Hall

16-3 The Process of Speciation Natural selection and chance events can change the relative frequencies of alleles in a population and lead to speciation. -Speciation is the formation of new species. -Species is a group of organisms that breed with one another and produce fertile offspring. Copyright Pearson Prentice Hall

True or False Individuals in different species can have the same gene pool.

Copyright Pearson Prentice Hall Isolating Mechanisms False What factors are involved in the formation of new species? The gene pools of two populations must become separated for them to become new species. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other. reproductive isolation- members of two populations cannot interbreed and produce fertile offspring Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Reproductive Isolation 1. Behavioral isolation 2. Geographic isolation 3. Temporal isolation Steps to Speciation Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 1. Behavioral Isolation  Behavioral isolation- two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior. Eastern Meadowlark And Western Meadowlark Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 2. Geographic Isolation  Geographic isolation- two populations are separated by geographic barriers (rivers or mountains). Kaibab Abert Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 3. Temporal Isolation   Temporal isolation- when 2 or more species reproduce at different times. Eastern spotted mates in Spring Western spotted mates in Fall Copyright Pearson Prentice Hall

What are the 3 types of reproductive isolation?

Speciation in Darwin's Finches STEPS OF SPECIATION founding of a new population geographic isolation changes in new population's gene pool reproductive isolation ecological competition Copyright Pearson Prentice Hall

Speciation in Darwin's Finches 1. Founders Arrive  A few finches—species A—travel from South America to one of the Galápagos Islands. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. Copyright Pearson Prentice Hall

Speciation in Darwin's Finches 2. Geographic Isolation Some birds from species A cross to a second island. Birds are separated by water. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. Copyright Pearson Prentice Hall

Speciation in Darwin's Finches 3. Changes in the Gene Pool Seed sizes on the second island favor birds with large beaks. The population on the second island evolves into population B, with larger beaks. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. Copyright Pearson Prentice Hall

Speciation in Darwin's Finches 4. Reproductive Isolation If population B birds cross back to the first island, they will not mate with birds from population A. Populations A and B are separate species. Copyright Pearson Prentice Hall

5. Ecological Competition As species A & B live together in same environment, they compete with each other for available seeds Species evolve in a way that increases the differences between them

6. Continued Evolution Process repeats itself 13 different finch species today

Copyright Pearson Prentice Hall 16-3 When two species do not reproduce because of differences in mating rituals, the situation is referred to as temporal isolation. geographic isolation. behavioral isolation. reproductive isolation. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 16-3 The most important factor involved in the evolution of the Kaibab and Abert squirrels of the American Southwest appears to be temporal isolation. geographic isolation. behavioral isolation. different food sources. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 16-3 All of the following played a role in speciation of Galápagos finches EXCEPT no changes in the gene pool. separation of populations. reproductive isolation. natural selection. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 16-3 List the steps of speciation. Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Studies showing natural selection in action involve descendants of the finches that Darwin observed in the Galápagos Islands. The finches Darwin saw were different, but he hypothesized that they had descended from a common ancestor. Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Detailed genetic studies have shown that these finches evolved from a species with a more-or-less general-purpose beak.  Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Detailed genetic studies have shown that these finches evolved from a species with a more-or-less general-purpose beak.  Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Peter and Rosemary Grant tested Darwin’s hypothesis, which relied on two testable assumptions: For beak size and shape to evolve, there must be enough heritable variation in those traits to provide raw material for natural selection. Differences in beak size and shape must produce differences in fitness, causing natural selection to occur. Copyright Pearson Prentice Hall

Testing Natural Selection in Nature When food was scarce, individuals with large beaks were more likely to survive. This graph shows the survival rate of one species of ground-feeding finches, the medium ground finch.  Copyright Pearson Prentice Hall