1. Chapter 17

2.  Fossils are the preserved remains of ancient organisms.  By observing fossils and making comparisons, scientists can determine relationships between ancient organisms  What is the structure of the organism?  What did it eat?  What ate it?  What was the organisms environment like?  By comparing fossils to one another, scientists ordered organisms according to when they lived (The Fossil Record)

3.  The fossil record reveals amazing facts!  Fossils occur in a particular order  Certain fossils appear in older rocks but not newer ones  This shows that life has changed over time  Out of all the species that have ever lived, 99% of them are extinct!

4.  Formation depends of a precise combination of conditions  Fossils are very rare, therefore the fossil record is incomplete  Most form in sedimentary rock  Erosion on the land forms silt  Travels through streams to lakes or seas  Might bury and preserve dead organisms  Sometimes soft tissue might be imprinted  Other times bones or solid tissues are saturated or mineralized into rocks  Occasionally organisms are buried quickly in clay or volcanic ash and become perfectly preserved

5.  Relative Dating – the age of the fossil is determined by comparing its placement with that of fossils in other layers of rock  Estimation, not exact  Fossils in lower layers of rock are older than those in upper layers of rock  Index fossils are found in rock layers of known age  These are used as the basis for comparison to unknown discovered fossils  Radioactive Dating (Numerical Dating)– determines the actual age of the fossil  All once-living and living tissues contain radioactive elements (Ex: C 14 )  Radioactive element decay over time  The half-life is the amount of time it takes for the element to become half decayed  The quantity of radioactive C 14 in comparison to regular non-active C 12 present in a fossil can determine the age of the fossil  Different elements have different half-lives and can be used to date differently aged fossils

6.  A scale used to represent evolutionary time  Created by studying rock layers and index fossils  Major, distinct changes in animals and plants occurred at various rock layers  These changes marked the beginning and ends of geological time segments  Radioactive dating revealed that each segment of time varied in length  These time periods were later divided into “eras” and further subdivided into “periods”  Paleo means “early”  Meso means “middle”  Ceno means “late” or “recent”

7.  Earth is estimated to be about 4.6 billion years old  Floating debris in outer space possible collided into collective mass made of different elements  This mass collided with one or more objects (probably the size of Mars) which melted the Earth into a ball

8.  As the ball cooled, matter settled based on density (about 4 billion years ago)  The Earth has an Iron core (very dense heavy metal)  Lighter, less dense melted metals make up the Mantel  The crust (surface) is made of the least dense solid material  The Atmosphere is made of all the gases (least dense of all the elements)  Originally the atmosphere probably had Hydrogen cyanide, CO, CO 2, N, Hydrogen sulfide and water….all toxic to life except for water!  3.8 billion years ago, the Earth may have cooled enough for water to form on the surface  Primitive toxic oceans formed  The earliest rocks we know of have been dated to this period

9.  Scientists Stanley Miller and Harold Urey showed that primitive atmospheric gases can spontaneously form building blocks of macromolecules with intense electric stimulation such as would have occurred during the violent thunderstorms of early Earth  They have made amino acids and the nucleotides Uracil and cytosine

10.  Up until 1 Billion years ago, the earth consisted of a primordial soup  As oxygen levels in the atmosphere were elevated, more single-cell living organisms appeared.  1 Billion years ago, prokaryotic cells began reproducing sexually. They also began to join together, creating the first eukaryotic cell. (Endosymbiotic theory)  This led to an increase in variation and the birth of multicellular organisms

11.  Out of all the species that ever lived, only 1% still exist  Extinction of species was caused by many factors, such as:  Competition for resources  Environmental changes  Gradual extinction via natural selection  Mass extinction  Humans are a leading cause of extinction too!  100 acres of rainforest are destroyed every day leading to the destruction of the most biodiverse habitats in the world  Without their habitat, many species are going extinct The Dodo bird, once common to the Indian Ocean island, now extinct since the mid- 1700’s due to humans

12.  Happens occasionally and wipes out entire ecosystems  Volcanoes, Sea Level changes, and continental drift have all lead to mass extinction  Scientists have reason to believe that an asteroid lead to the extinction of the dinosaurs

13.  Fossils and living organisms show that single species have evolved into diverse forms that live in different ways  More than a dozen finch species evolved from one species on the Galapagos  Dinosaurs and mammals showed up about the same time  Dinosaurs ruled the Earth while mammals were scarce and small  Mass extinction of the dinosaurs allowed mammals to diversify and evolved, becoming the predominant class of animals

15.  Unrelated organisms that look remarkably similar to one another  Occurs when groups of organisms undergo adaptive radiation in different places or times but in ecologically similar environments  The similarities in environmental demands leads to similarities in physical structure  Ex: Sharks, penguins and dolphins

16. BLUE MORPHO BUTTERFLY OF SOUTH AND CENTRAL AMERICA ULYSSES BUTTERFLY OF AUSTRALIA

17.  Some organisms are closely connected to one another  Ex: certain flowers can only reproduce if a specific pollinator carries their pollen to another flower  An evolutionary change in one of the organisms may lead to an evolutionary change in the other as well  The process by which two species evolve in response to changes in each other over time is coevolution

18.  Gradualism: Evolution happens gradually and continually over a long period of time  Punctuated Equilibrium: Evolution happens in short bursts interrupted by long periods of zero change