1. Modern Evolutionary Theory
What happened after darwin?

2. Problems with darwin’s theory
Why is there variation within a species?
How are traits passed from one generation to another?

3. Watson and crick’s model of dna structure
Central Dogma of Molecular Biology
DNA  RNA  protein
genes – portions of the DNA that code for a specific protein
proteins – amino acid sequences that are workhorses of living systems

4. Discovery of the genetic code
series of instructions that shows how proteins are made based on DNA/RNA

5. Sources of inheritable variation
Mutation
any change in DNA sequence
due to
mistakes in DNA replication
environmental factors

6. Sources of inheritable variation
2. Gene shuffling
independent chromosome movement during gamete formation (223~8.4 million gene combinations)
sexual reproduction causes variation within populations
members of a population interbreed and are acted on in similar ways by the environment; they evolve together

7. Evolution as genetic change
Natural selection on single-gene traits
Change in allele frequency
Evolution

8. Evolution as genetic change
Natural selection on polygenic traits
Change in distribution of phenotypes
Evolution

9. Evolution as genetic change
Natural selection is NOT always necessary for genetic change to occur
Genetic drift
when an allele becomes common in a population by chance
not all characteristics of an organism contribute to its fitness

10. Speciation Formation of a new species
Evolution
Reproductive isolation
Separation of gene pools
Different responses to natural selection and genetic drift
Speciation Formation of a new species
species  group of organisms that interbreed and produce fertile offspring
reproductive isolation
behavioral isolation
geographic isolation
temporal isolation

12. Experimental evolution
Darwin’s Hypothesis

13. Experimental evolution
Grant Experiment
Enough inheritable variation in beak size and shape
Identify and measure as many birds as possible on one island
Many of the characteristics appeared in bell-shaped distributions
There is great variation of inheritable traits among finches
Differences in beak size and shape  differences in fitness
Observe survival of different birds when resources are scarce
Birds with differently-sized beaks had different chances of surviving a drought
Big-beaked birds had higher chances of surviving during a drought

14. Speciation in darwin’s finches
Founders arrive
Separation of populations on different islands
Natural selection  changes in the gene pool
Reproductive isolation
Ecological competition
Continued evolution

15. Macroevolution Large-scale evolutionary changes that occur over long periods of time
MASS EXTINCTIONS
Disappearances of huge numbers of species
Asteroids, geological activity
Disappearance of dominant species allowed other species to take over
ADAPTIVE RADIATION
A single group of species evolved into different forms that live in different ways
Produces great diversity

17. Macroevolution Large-scale evolutionary changes that occur over long periods of time
CONVERGENT EVOLUTION
Unrelated organisms resemble one another
Due to similar environmental conditions
COEVOLUTION
When organisms that interact closely with one another evolve together

18. PUNCTUATED EQUILIBRIUM CHANGES IN DEVELOPMENTAL GENES
Macroevolution Large-scale evolutionary changes that occur over long periods of time
PUNCTUATED EQUILIBRIUM
Rapid evolution may occur after long stable periods
Usually occurs because of genetic drift or together with adaptive radiation
CHANGES IN DEVELOPMENTAL GENES
Similar hox genes are present in diverse organisms
These dictate the basic body plan of the organism
Major evolutionary changes may have occurred through these genes