The History of Earth and Life

1. The History of Earth and Life

2. Fossils & Ancient Life • The study of ancient life using fossil records • Paleontologist-A scientist who studies fossils to infer what past life and life forms were like. • Fossil Record-Collection of fossils used as information about past life. • Provides evidence about the history of life on Earth. • Shows how different groups of organisms changed over time. • 99% of all species that have ever lived on earth have become extinct.

3. How Fossils Form • The Steps to fossil formation • Water carries small rock particles to the bottom of lakes and seas. • Dead organisms at the bottom of lakes and seas are buried by the layers of sediment which forms new rock. • The weight of the new rock compresses on the lower layers of the new rock and minerals replace all or part of the dead organisms body • The preserved remains may later become exposed due to a variety of factors. • Most fossils form in sedimentary rock.

4. Interpreting Fossil Evidence • Relative Dating: The age of a fossil is estimated by comparing the fossil to other fossils. • Index Fossils- Those fossils used for comparison purposes in relative dating. These fossils are distinctive fossils from specific time periods. • This type of fossil dating provides no information about absolute age of the fossil • Radioactive Dating: The age of the fossil is calculated based on the amount of remaining radioactive isotopes it contains. • Half-life- the length of time it takes for half of the radioactive atoms in a sample to decay. • Radioactive dating uses half-lives to determine the age of the fossil.

5. Geologic Time Scale • Scale used to represent evolutionary time. • Major changes on fossil records of plants and animals are used to mark where one segment ends and another begins. • The basic divisions of the scale are • Eras & Periods

6. Formation of Earth • Earth was created approximately 4.6 billion years ago. • Clouds and dust condensed into a sphere. • Gravity pulled this cosmic debris (matter) together to form a planet. • Collisions with other objects ( some as large as planets) produced enough heat to melt the globe. • After the earth melted its elements rearranged themselves according to density.

7. Formation of Earth Cont… • 4 Billion years ago Earth cooled. • Volcanic eruptions and meteor showers brought the materials to earth to create solid rock. • 3.8 Billion years ago the Earth’s surface cooled off enough for water to remain in liquid form. • Oceans form. • Earths original atmosphere lacked oxygen to support life.

8. The First Organic Molecules • Stanley Miller and Harold Urey conducted laboratory simulations of early earth to explain how early organic molecules emerged from simpler compounds. • Energy from an lightning strike may have provided the electrical spark needed to combine atoms of the atmosphere and form molecules necessary for life on Earth to exist. • Earth can now produce organic molecules like carbohydrates, proteins, lipids and amino acids.

9. The Puzzle of Life’s Origin • Formation of Microspheres • Under certain conditions large macromolecules can form tiny bubbles called proteinoid microspheres, which can exhibit the properties of cells. • Some scientists believe these microspheres took on more and more of the cells characteristics and eventually became what we know of as cells. • Evolution of RNA and DNA • Neither DNA or RNA can exist without each other. • So which can first?????? • Scientists think RNA existed first and gave way to DNA • However, many questions still exist about the evolution of DNA and RNA.

10. Free Oxygen • Microfossils- fossils of microscope organisms found in rock 3.5 million years ago. • These organisms were single celled prokaryotic organisms known as anaerobes(organisms that lived without oxygen). • Anaerobes today exist in airless environments. • Photosynthetic bacteria evolved and began to put oxygen into the atmosphere. • Gives way to aerobes (organisms that need oxygen). • Many anaerobes died because oxygen was toxic to them. • Ozone layer now forms.

11. Origin of Eukaryotic Cells • Prokaryotic cells (those cells that don’t have a nucleus) gave way to Eukaryotic cells (those cells that do have a nucleus). • Endosymbiotic Theory- Eukaryotic cells formed from a symbiosis among several different prokaryotic organisms. • Sometime after eukaryotic cells emerged they began to reproduce sexually which allowed evolution to speed up.

12. Evolution of Multi-cellular Life • Eras: • Cenozoic • Mesozoic • Paleozoic • Precambrian • Periods: • Quaternary • Tertiary • Cretaceous • Jurassic • Triassic • Permian • Carboniferous • Devonian • Silurian • Ordovician • Cambrian • Vendian

13. Patterns of Evolution • Macroevolution: The large scale evolutionary patterns and processes that occur over long periods of time. • Extinction: The elimination of the existence of a species. • Natural selection has caused 99% of all species to go extinct. • Mass extinction- the extinction of an entire ecosystem. • Serious large event that causes the mass extinction. • Dinosaurs wiped out this way. • Clears the way for the evolution of modern species like mammal and birds.

14. Patterns of Evolution Cont…. • Adaptive Radiation: Process by which a single species or group of species evolves into several different forms that live in different ways. • Leads to rapid growth in diversity • Convergent Evolution: Process by which unrelated organisms independently evolve similarities when adapting to similar environments.

15. Patterns of Evolution Cont…. • Co-evolution: The process by which two species evolve in response to change in each other over time. • EX: Plants and the insects that pollinate them. • Punctuated Equilibrium: Describes pattern of long stable periods interrupted by brief periods of more rapid change. • Gradualism: Slow, steady, gradual change.

16. Developmental Genes and Body Plans • Small changes in the activity of control genes that can many other genes and cause larger changes in adult animals. • Changes caused by changes in activation genes. • EX: Many pairs of wings on ancient insects but only a single pair of wings on modern insects.