1. The History of Life What scientific evidence supports the theory of evolution? How is this evidence incomplete?

2. Fossils We can study the history of life using preserved remains of ancient life in fossils. –Remains of hard parts (bones, teeth, shells) –Refrigeration (preserved in ice) –Imprints (impressions) –Molds (rock forms around dead organism) –Casts (molds filled with minerals) –Insects preserved in sap or amber –Petrification (skeletons or cellulose covered in water and filled with dissolved minerals) –Coal (fossilized remains of plants) –Tar pits (animal remains)

3. The Fossil Record Paleontologists = scientists that study fossils (structure, food chain, & habitat) Fossil Record = all this information about past life and provides evidence about the history of life on Earth and how different groups of organisms have changed over time. Fossils occur in a particular order –More than 99% of species that ever lived on Earth have become extinct (the species died out)

4. Making Fossils For a fossil to form, either the remains (parts or whole) of the organism or some traces of its presence must be preserved. The formation of fossils depends on precise conditions, so it provides incomplete information about the history of life due to the varying quality and small numbers of fossils. Fossils often form in sedimentary rock from layers of rock particles building up on dead organisms and compress into rock over time Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied.

5. Rock review Igneous = formed from cooling and solidification of lava deep in Earth’s crust Sedimentary = formed from sediment from preexisting rock and subject to high pressure becoming solid rock Metamorphic = when igneous or sedimentary rock is subject to high pressure and temperature, rock changes and destroys any fossils already present

6. Interpreting Fossils One of the most important pieces of information is the age of the fossil. Paleontologists determine the age of fossils using: –Relative dating = age of a fossil is determined by comparing its placement (age) with that of fossils in other layers of rock (oldest layer on the bottom, more recent layers closer to Earth’s surface), however, this provides no information about its absolute age in years Index fossils = a species that must be easily recognized and must have existed for a short period but in a wide geographic range (in a few layers, but in many geographic locations) used to compare the relative ages of fossils

7. Interpreting Fossils –Radioactive dating = determine absolute age (in years) by measuring the decay of radioactive elements in rocks (half-life) Half life = length of time required for half of the radioactive atoms to decay (constant) Different radioactive elements have different half- lives (ex. Carbon-14 has a half-life of about 5730 years; the less carbon-14, the older the fossil) Licorice half-life lab

8. Geologic Time Scale By studying rock layers and index fossils worldwide, scientists placed Earth’s rocks in order according to relative age and found major changes in the fossils at specific layers. Each major change marks the end of one time and beginning of the next. Then, using radioactive dating, specific ages were assigned to each time period creating the geologic time scale. The divisions represent evolution. –Precambrian Time = 88% of Earth’s history from 650 to 544 million years ago –Eras = larger amounts of time (multiple time periods) –Periods = smaller amounts of time within eras (tens to less than two million years)

9. EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – 245 363–290 410–363 440–410 505–440 544–505 1.8–present 65–1.8 145–65 208–145 245–208 Quarternary Tertiary Cretaceous Jurassic Triassic Vendian650–544 Section 17-1 Figure 17-5 Geologic Time Scale Go to Section: Many names of periods were created based on where geologists first found the rocks, for example, Jurassic came from Jura Mountains in France

10. Earth’s Beginning 4.8 billion years ago – Earth and solar system formed –Pieces of cosmic debris were attracted to each other, melted together after a collision, rearranging elements (dense radioactive elements generate heat in the core, less dense elements floated to the surface and cooled forming a crust and least dense elements formed the atmosphere) 4 billion years ago – Earth’s surface cooled to form rocks, but Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water –This would have killed you! 3.8 billion years ago – Earth’s surface cooled enough for water to remain a liquid, forming earliest sedimentary rocks and they contain the first evidence of life on Earth.

11. First Organic Molecules Remember: Organic molecules contain carbon and are the basis for life Electricity stimulated inorganic molecules to become simple organic molecules (simple sugars, amino acids, and nucleotides) and they began to cluster together to form larger organic molecules (carbohydrates, proteins, and nucleic acids)

12. First Forms of Life Microspheres existed, which were not living organisms, but had characteristic similar to living cells (energy use, growth, and reproduction). RNA may have existed and led to the formation of DNA Microfossils of single-celled prokaryotic organisms were found more than 3.5 billion years ago… first photosynthetic bacteria created oxygen, spurring the ocean (marine life) and atmosphere to change and other life forms evolved to survive, such as respiration using oxygen. At end of Paleozoic Era, 95% of complex life became extinct, but fish and reptiles survived. Natural selection could have allowed these things to evolve since they were able to survive and reproduce.

13. First Eukaryotic cells Prokaryotic organisms entered ancestral eukaryotic cells, living together in a symbiotic or interdependent relationship. Endosymbiotic theory = eukaryotic cells formed from symbiosis of prokaryotic organisms

14. Sexual Reproduction Cells began to reproduce sexually allowing evolution to occur much faster by shuffling genes and mutations increasing variation and increasing evolution due to natural selection

15. Multicellular Life Due to major changes in Earth’s climate and geography, multicellular organisms developed from single-celled organisms, increasing diversity and complexity of life.

16. Macroevolution Patterns Macroevolution = large scale evolutionary changes –Mass Extinction –Adaptive Radiation –Convergent Evolution –Coevolution –Punctuated Equilibrium –Changes in developmental genes

17. Mass Extinction Extinction occurs all the time: more than 99% of all species that ever lived on Earth are now extinct! Mass extinction = huge numbers of species disappear Mass extinctions extinguish species and also wipe out whole ecological systems It is difficult to determine the causes of mass extinctions, possibly volcanoes, continental shifts, changing sea level, asteroids? Mass extinctions often result in bursts of evolution producing many new species

18. Adaptive Radiation A single species or a small group of species evolved into several different forms that live in different ways –For example, Darwin’s finches –When dinosaurs became extinct, it made way for adaptive radiation of mammals

19. Convergent Evolution Groups of different (unrelated) organisms can undergo adaptive radiation in different places or at different times but in similar environments and natural selection may mold different body structures to look very similar So, unrelated organisms come to resemble one another –Analogous structures = structures which look and function similarly, but do not share a common evolutionary history

20. Coevolution Organisms that are closely connected to one another by ecological interactions can evolve together in response to each other’s changes over time –For example, flowers and pollinators

21. Punctuated Equilibrium Evolution can occur at different rates for different organisms at different times during Earth’s history: –Gradualism = biological changes occur slow and steady or gradually over time –Equilibrium = little or no change over time –Punctuated equilibrium = new species produced by period of rapid change after long periods of equilibrium Can be due to isolation, genetic variation, mass extinctions, etc

22. Development of Genes and Body Plans Hox genes are “master control genes” that control the growth of embryo – what will be on top, middle, and bottom Homologous hox genes establish body plans in many different organisms, for example, insects and humans even though they have not shared a common ancestor in 700 million years

23. Do Now What is the difference between gradualism and punctuated equilibrium? Which is demonstrat ed by a family tree?

24. Phylogenic Tree A diagram that indicated probable pathway of evolution. Branches were species separate and form new species. The more branches shared, the closer the relationship.

25. Modern Evolutionary Theory Theory of Mutation - Hugo DeVries (1901) Mutations can be favorable or unfavorable, but if favorable, the organism will survive and reproduce, increasing that mutation characteristic in the population, for example: –Peppered Moths: Before Industrial Revolution, white moths flourished; after Industrial Revolution and pollution, gray/black moths flourished… why? –Insects Resistant to Insecticide: Some mosquitoes have a natural immunity to DDT, because they will survive and pass immunity mutation on until entire population is immune and DDT is useless.

26. Peppered Moths