Evolution by Natural Selection

1. Evolution by Natural Selection Developed by Charles Darwin

2. Darwin’s voyage Galapagos Islands • He went to the __________ ________ • He observed several variations of ________ and other animals including tortoises and iguanas • He described the anatomical (structural) adaptations of the finches, tortoises, and iguanas as evidence of changes in species over time which we know as __________ • The mechanism by which species change, Darwin called ________ __________ finches evolution natural selection

3. Anatomical Adaptations We Observe

4. Anatomical Adaptations Large eyes of nocturnal animals Camouflage Mimicry Claws for digging The anatomical adaptations allow these animals to find food and shelter or protects them from predators

5. Chemical adaptations such as DNA that can change in a short period of time… Physiological adaptations

6. We observe changes of physiological adaptations in… Antibiotic resistant bacteria and new strains of the cold and flu viruses every year

7. Mechanisms for Speciation How do anatomical and physiological adaptation change?

8. Mechanisms for speciation • Mutations • Natural Selection • Reproductive isolation • Genetic drift • Immigration or emigration

9. Mechanisms for speciation • What are mutations? • How do mutations affect populations? • How can mutations cause the creation of new species? Changes in the DNA sequence of individuals Some mutations have no affect on the genotype and phenotype of an individual while others change a single amino acid or many amino acids affecting protein production and genotypes and phenotypes. When individuals of a population mate together these mutations are inherited and passed along from parent to offspring. Favorable mutations will be inherited and can cause changes in the gene pool of a population eventually creating a new species.

10. Mechanisms for speciation When organisms with favorable variations in an area survive and produce offspring with the favorable traits • What is natural selection? • How does natural selection affect populations? • How can natural selection cause the creation of new species? Natural selection can lead to a change in the number of times a particular trait is seen in the gene pool. Over time, the genes that are inherited and passed from generation to generation change and begin to separate a population.

11. Natural Selection’s affect on single gene traits and polygenic traits

12. Natural Selection acts on single gene traits by • Providing two distinct phenotypes in a population • Providing many phenotypes in a population • Favoring individuals in a population in three different ways Natural Selection acts on polygenic traits by

13. Natural Selection and Single gene traits 2 phenotypes

14. Natural Selection favoring average individuals in a population • Called Stabilizing selection • Reduces variation in a population Number of birds in population Small beak Large beak

15. Natural Selection favoring one extreme variation in a population • Called Directional selection • Can lead to the rapid evolution of a population Number of birds in population Small beak Large beak

16. Natural Selection favoring both extreme variations in a population • Called Disruptive selection • leads to the evolution of two new species Number of birds in population Small beak Large beak

17. Mechanisms for speciation The random changes in allelic frequency within small populations • What is genetic drift? • How does genetic drift affect populations? • How can genetic drift cause the creation of new species? When mutations in a small population change the genotypes in that population the number of times an allele is seen may be different than those within a large population. If the variations after mutations are more favorable than the ones before the mutations then those organisms will mate and pass along the new traits in increasing numbers.

18. Mechanisms for speciation When two populations no longer interbreed and produce fertile offspring • What is reproductive isolation? • How does reproductive isolation affect populations? • How can reproductive isolation cause the creation of new species? The population no longer breeds together, therefore creating a new gene pool. This may happen when members of a population no longer recognize mating behaviors, are separated by a physical barrier, or mate at different times of the year than normal. When gene pools split and genes are no longer shared by a population over time a new species develops

19. Mechanisms for speciation The movement of individuals into a population • What is immigration? • What is emigration? • How does immigration or emigration affect populations? • How can immigration or emigration cause the creation of new species? The movement of individuals out of a population Migration changes the gene pool Migration will change the variations within a population in turn changing the species over a long period of time.

20. Evidence for Evolution Anatomical adaptations Physiological adaptations Fossil records Embryo development Biochemistry

21. Fossil Records Types of Fossils Trace fossil Cast Petrified fossil Imprints Amber preserved Mold Relative dating technique Radioactive dating

22. Evolutionary relationships are displayed through Have common evolutionary origin • Homologous structures • Analogous structures • Vestigial structures • Embryo development • Biochemistry Can be similar in arrangement, function or both Have NO common evolutionary origin but similar function Has no present day function, but probably useful in ancestors Early stage of growth and development are similar Similarities in DNA and RNA sequences

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