The History of the Earth

1. The History of the Earth • Earth has had living things for 3.8 billion years • Fossils provide evidence • Remains of organisms preserved in the earth. • Provide glimpse to the past • Types of fossils • Hard body parts • Bones • Skeletons

2. The History of the Earth • Minerals replacing remains of organisms • Trilobites • Radula (the toothed chitinous ribbon in the mouth of most mollusks, used for cutting and chewing food before it enters the esophagus.)

3. The History of the Earth • Rarely, the original remains • like the woolly mammoths • insects in amber Ice Age treasure ... the rare complete baby mammoth.Photo: Reuters

4. The History of the Earth • Finding age of fossils • Relative dating • Where they were found in the earth’s layers • Fossils get layered on top of each other. • Absolute age • Tells when it was formed • Study radioactive elements • Uranium • Lead (the more lead, the older it is) • Assembling the Fossil record • Combining absolute and relative dating estimate the age. • When done for fossils in a particular location can determine time periods organisms existed • Help develop an overview of the Earth’s history.

5. The History of the Earth • More complex organisms over time • Unicellular organism • Made of one single cell • Some responsible for oxygen that now makes up atmosphere • Multicellular organisms • Around 1.2 billion years ago • Began to live in Earth’s oceans • Most complex Multicellular organisms have cells that combine • Make up tissues • Organs • Systems

6. The History of the Earth • Earliest Multicellular organism were tiny seaweed • Earliest were similar to today’s jellyfish • Life on Land • 500 million years ago the first Multicellular organisms moved from water to land. • Needed structures to get water • First land organisms were simple plants and fungi • Plants got water through soil • They used roots • Fungi absorbed water through plants and soil

7. The History of the Earth • Insects were probably among the first living things to inhabit land • Plants provided food • and shelter • Animals such as amphibians, reptiles • Followed by birds and mammals • Earth’s history includes mass extinctions

8. The History of the Earth • About 10,000 years ago, the last woolly mammoth died • Species became extinct • The disappearance of organisms in a very short time is Mass Extinction. • Permian Extinction • About 250 million years ago • 90% of species living in the ocean became extinct • Many land animals disappeared

9. The History of the Earth • Cretaceous Extinction • Fossils from about 140 million years ago mostly dinosaurs • Lived all over the planet • Fossil records for dinosaurs end about 65 million years ago

10. The History of the Earth • Reasons for extinction. • Large meteorite from space collided with Earth • Collision and its after effects wiped out most of the existing species • The remains such as the Chicxulub crater off coast of Mexico

11. The History of the Earth • Species change over time • Scientists explore the concept of evolution • In BIOLOGY, evolution refers to the process though which species change over time • Change results from a change in the genetic material • Passed on from one generation to the next.

12. The History of the Earth • Early Ideas • Jean Baptiste de Lamarck • Early 1800’s • Proposed model of how life evolves • Convinced fossil record showed that species had changed over time • Organisms can acquire a trait and pass on to offspring • Giraffes stretched to eat • Passed on this trait to offspring with a longer neck • Although a highly respected scientist, never able to prove or support his idea

13. The History of the Earth • Charles Darwin • 50 years after Lamarck • Published his theory of evolution • Did so based on scientific discovery • Was aboard the HMS Beagle with British Navy • Sailed along coast of South America • Studied rocks and collected fossils • Compared new animals he was seeing to ones from his own country

14. The History of the Earth • Differences were obvious at Galapagos Islands • A chain of volcanic islands off South America • On those 18 islands plants and animals differed from those on mainland • Some from island to island • Observed several types of tortoises on the island • Short necks were in damp areas with plants close to ground • Longer necks in dry areas where cacti grew

15. The History of the Earth • He also observed the finches • Many had varying beak shapes and sizes • Short and heavy for pecking trees or seeds • Thin and small for capturing insects • Wondered if the birds had evolved from similar species

16. The History of the Earth • Natural selection explains how living things evolve • Darwin analyzed observations and specimens collected in 1836 • By 1844, hypothesized natural selection • Members of a species that are best suited to their environment survive. • They will reproduce at a higher rate then other members

17. The History of the Earth • Overproduction- • based on survival, how many will make it to reproducing age? • More offspring needed with only a few surviving • Variation • within a species, natural differences or variations in traits. • Differences result in genetic material or mutation

18. The History of the Earth • Adaptation • if the mutation is good, trait gets passed along • an Adaptation is any inherited trait that gives an organism an advantage in its environment. • Selection • Darwin felt that if organisms with a particular adaptation are more likely to survive long enough to reproduce • If this happens, the adaptation becomes more common.

19. The History of the Earth • New Species develop from earlier species • Darwin along with Alfred Wallace, led Darwin to write about this new idea. • On the Origin of Species was written in 1859. • These findings led to other ideas • Speciation • The evolution of new species from an existing species. • Can occur with both gradual and dramatic environmental changes • The Galapagos finches showed evidence to this.

20. The History of the Earth • Isolation • Darwin’s trip to the Galapagos Islands showed many new species had evolved after populations were separated from the mainland. • Darwin reasoned that isolation of populations by geography or other barriers could contribute to speciation