????????? Evolution

1. ?????????Evolution • What information does the fossil record contain about life on earth? • How does geographic distribution of organisms relate to evolution? • How are similarities in structure and development among different species evidence for evolution? • What molecular evidence for evolution exists?

2. Reproductive Isolation One population becomes separated and stops breeding with the rest of the species • Behavior: • Changes in courtship or other reproductive strategies • Geographic • Geographic barrier splits population (i.e.: river, mountain, body of water, etc.) • Populations are separated and cannot interbreed • Temporal/ Timing • Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

3. Changes in the Gene Pool • Gene Pools Diverge (become different): • The isolated populations become genetically different. • The new environments or behaviors favor different genetic traits (natural selection) • Genetic Barriers to Reproduction Arise • The two populations can no longer interbreed • Due to genetic differences in habitat preference, mating behavior, or physical compatibility They are now two separate species! • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

4. The Fossil Record • Fossils = preserved remains or markings left by organisms that lived in the past • Found in sedimentary rock • Fossil Record = chronological collection of life’s remains in the rock layers • Contain extinct species • Evidence of changes in life on Earth… • Fossilized bones of whale like creatures with legs

5. Deeper layers contain older, more primitive fossils

6. Geographic Distribution • Evolution of animals depends on their environment and where they live • In isolated habitats (like islands), will evolve differently • EX. Marsupials in Australia Lemurs in Madagascar

7. Similarities in Structures • Homologous Structures = similar structures in species sharing a common anscestor • Forelimbs in all mammals- share same bones • Functions might differ, but structure is the same • Descent with modification

8. Similarities in Structures • Vestigial Structures = parts of structures that used to have a function in ancestors, but no longer function in descendants • Hip bones in whales • Natural selections typically favors individuals with genes for smaller vestigial structures • No vestigial structures if species arose separately

9. Fossil evidence suggests whales evolved from ancestors with hind legs

10. Similarities in Embryonic Development • Early developing embryos look similar in all vertebrates • Pouches on sides of throat • Looks like a tadpole • Indicates common ancestor • HOMOLOGOUS STRUCTURES

11. Molecular Biology • DNA/ Amino Acid Sequences of proteins • Record of heredity (passed from parent to offspring) • Can show relationships between 2 species • Similar genes/proteins – common ancestor • Use DNA to confirm fossil evidence and skeletal similarities • Ex. Human hemoglobin- humans and primates are closely related (1 different amino acid)

12. Few differences in amino acid chain between Human and Gorilla… more recent common ancestor

13. Hybrid - • The offspring of a mating between two different species • If a hybrid can’t have offspring, there are still two separate species!

14. Reproductive Barriers That Maintain Separate Species • Before mating occurs • Geographic barriers • Ecological/habitat differences • Temporal differences • Behavioral/courtship differences • Mechanical differences • Chemical differences • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

15. Reproductive Barriers That Maintain Separate Species • After mating occurs: • Hybrid dies before birth • Hybrid is weak and sickly • Hybrid is sterile (can’t reproduce) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

16. Famous Hybrids that are strong but STERILE!

17. Macro-Evolution • Large-scale, often over a very long time • Branching of one species into two species • All species share a common ancestor Example:Evolution of whales from four-legged land mammals • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

18. Vocabulary • Population • Group of individuals from the same species that live in the same area and interbreed • Gene Pool • All the genes and all of their alleles in a population • Evolution (on a population scale) • Any change in the proportions of alleles over time • (One allele becomes more common, another becomes less common) • Change in a population NOT change in an individual • Fitness • How well a particular organism can survive and reproduce to pass on its genes to the next generation • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms