Changes Over Time Darwin’s Theory Evidence of Evolution The Fossil Record Table of Contents

Changes Over Time What is Evolution? -Evolution is the change in the hereditary features of a species over time. *A species is a group of similar organisms that can mate with each other and produce fertile offspring. Today, we have identified more than 1.7 million species. *How do species change over time?

Changes Over Time Lamarck’s Theory -Jean Baptiste de Lamarck (1809): *Proposed the “Theory of Acquired Characteristics” which states that species change over time by keeping traits that their parents developed during their lifetime. *This theory was rejected once we understood genetics.

Changes Over Time Darwin’s Theory -Charles Darwin (1859): *Proposed the “Theory of Natural Selection”. *This theory states that organisms with traits best suited to their environment are more likely to survive and therefore pass on these favorable traits.

Changes Over Time - Darwin’s Theory * Darwin was a naturalist on the HMS Beagle. *In Dec. 1831, he began a 5 year voyage to collect and study plants and animals from all over the world.

Changes Over Time *One stop on the voyage was The Galapagos Islands (a group of 19 small islands off the coast of Ecuador ).

Changes Over Time *Much of Darwin’s Theories were developed after studying the unique plants and animals of the Galapagos Islands.

Changes Over Time *Darwin spent over 20 years collecting his thoughts and writing a book. *He presented his book, “On the Origin of Species by Means of Natural Selection”, in 1859.

Changes Over Time - Darwin’s Theory Four Basic Points of Natural Selection -Overproduction—organisms produce more offspring than can possibly survive. -Variation—many differences are found among individuals of a species due to meiosis and genetic inheritance.

Changes Over Time - Darwin’s Theory -Competition—some variations allow members of a population to survive and reproduce better than others. -Selection—over time, offspring of individuals with helpful variations make up more and more of a population.

Changes Over Time Variations and Adaptations -A variation is any difference between individuals of the same species. -An adaptation is any trait that helps an organism survive and reproduce. *Examples: webbed feet on a duck: gills on a fish

Changes Over Time -If enough variations occur in a population over time, a new species could result. -The movement of individuals into or out of a population helps to bring about more variations.

Changes Over Time A sudden change in the climate or environment can bring about evolutionary change by suddenly favoring one variation over another. Example: Peppered moths of England. Eventually, a new species could form if the environmental change is drastic enough. What Brings About Change?

Changes Over Time - Evidence of Evolution Geographic isolation can also bring about evolutionary change. Example: Kaibab and Abert’s Squirrels. These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species.

Changes Over Time Evidence for Evolution -Similarities in Early Development *All vertebrate embryos resemble each other early in development. These similarities show an evolutionary relationship among all vertebrates.

Changes Over Time - Evidence of Evolution -Homologous Structures—similar structures that related species have inherited from a common ancestor. Example: the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg

Changes Over Time -Vestigial structures—body parts that are reduced in size and do not appear to have a function. Examples: human appendix, hip bones in whales and snakes. Scientists believe these once functioned in an ancestor.

Changes Over Time -DNA and Protein Similarities— organisms that are close relatives have similar DNA. Example: The DNA of humans and chimps differs by less than 1%. This supports the idea that primates all evolved from a common ancestor.

Changes Over Time -Development of chemical resistance— organisms that have genes that make them resistant to a particular chemical will be the only ones to survive in the presence of that chemical to pass on their traits. Examples: *Antibiotic resistant bacteria *Pesticide resistant insects

Changes Over Time -Fossil Evidence *A fossil is the preserved remains of an organism that lived in the past. *Fossils show that many organisms from the past are very different than organisms alive today. *Types of fossils:

Changes Over Time Fossils Click the Video button to watch a movie about fossils. - The Fossil Record

Changes Over Time Petrified Fossils Stone Casts or Molds Rock imprints Preserved remains in amber or ice

Changes Over Time - The Fossil Record How Do Fossils Form? Most fossils form when organisms that die become buried in sediments.

Changes Over Time Fossil Formation Activity Click the Active Art button to open a browser window and access Active Art about fossil formation. - The Fossil Record

Changes Over Time Two methods for dating fossils: Relative dating —fossils are dated according to the layer of rock in which they are found. This is just an estimate. Radioactive dating —fossils are dated by measuring the amount of radioactive material present. This is more accurate. Dating Fossils

Changes Over Time Radioactive Decay The half life of potassium-40, a radioactive element, is 1.3 billion years. This means that half of the potassium-40 in a sample will break down into argon-40 every 1.3 billion years. The graph shows the breakdown of a 1-gram sample of potassium-40 into argon-40 over billions of years. - The Fossil Record

Changes Over Time Radioactive Decay The red line represents the amount of potassium-40. The blue line represents the amount of argon-40. Reading Graphs: What does the red line represent? What does the blue line represent? - The Fossil Record

Changes Over Time Radioactive Decay Potassium-40–100%; argon- 40–0% Reading Graphs: At 2.6 billion years ago, how much of the sample consisted of potassium-40? How much of the sample consisted of argon-40? - The Fossil Record

Changes Over Time Radioactive Decay About 1.3 billion years Reading Graphs: At what point in time do the two graph lines cross? - The Fossil Record

Changes Over Time Radioactive Decay 50% of each; the half-life of potassium-40 is 1.3 billion years, which means that half will break down into argon-40 every 1.3 billion years. Interpreting Data: At the point where the graph lines cross, how much of the sample consisted of potassium-40? How much consisted of argon-40? Explain why this is the case. - The Fossil Record

Changes Over Time Fossil Record and Geologic Time Scale Geologic Time Scale —a calendar of Earth’s history. Using the fossil record (all the fossils scientists have collected) and fossil dating techniques, scientists have developed the Geologic Time Scale.

Changes Over Time Earth’s History as a Clock Fossils found in rock layers tell the history of life on Earth. The history of life can be compared to 12 hours on a clock. - The Fossil Record

Changes Over Time Precambrian Time and the Paleozoic Era - The Fossil Record

Changes Over Time Mesozoic and Cenozoic Eras - The Fossil Record

Changes Over Time Combining Evidence -DNA evidence is a newer source of evidence. -In most cases, evidence from DNA and protein structure has confirmed conclusions based on fossils, embryos, and body structure. -In some cases, scientists have had to change their hypothesis. -Scientists can use the combined evidence of species relationships to draw branching trees —diagrams that show how different groups of organisms are related.

Changes Over Time - Evidence of Evolution A Branching Tree This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related.

Changes Over Time How Fast Does Evolution Occur? Two Theories -Gradualism—very slow change from one species to another. *Involves intermediate species *Supported by some fossil records (like the horse) but not all.

Changes Over Time -Punctuated Equilibrium —more rapid evolution of a species brought about by the mutation of just a few genes. *Supported by some fossil records and bacteria experiments. -Today, scientists think both probably occurred.

Changes Over Time Extinction and Evolution -Extinction is the dying out of a species. *Occurs naturally because the environment is always changing. Through natural selection, species which are unable to adapt to a changing world are removed. *Earth’s history shows at least 4 mass extinctions followed by rapid explosion of new species.

Changes Over Time Human’s role in extinction of species -Human overpopulation and human activities are contributing to the rapid extinction of thousands of species. *This led to the passage of the Endangered Species Act of As a result, many captive breeding programs were established. They are expensive and for some species, they may be too late.

Changes Over Time Relating Cause and Effect In a graphic organizer, identify factors that cause natural selection. Natural Selection Overproduction: More offspring are produced than can survive. Causes Effect Variations: Members of the same species differ. Competition: Offspring compete for survival. Selection: Some variations make individuals better fit for survival. Environmental Change: Changes can affect an individual’s survival. Genes: Genes that help determine survival are passed from parent to offspring. - Darwin’s Theory

Changes Over Time Links on Charles Darwin Click the SciLinks button for links on Charles Darwin. - Darwin’s Theory

Changes Over Time End of Section: Darwin’s Theory

Changes Over Time Identifying Supporting Evidence Evidence consists of facts that can be confirmed by testing or observation. As you read, identify the evidence that supports the theory of evolution. Write the evidence in a graphic organizer like the one below. Evolution Fossils show that organisms that lived in the past were very different from organisms alive today. Patterns of early development show that some different organisms look similar during their early stages. Similar body structures in different species show that the organisms shared a common ancestor. Theory Evidence - Evidence of Evolution

Changes Over Time Links on Evolution Click the SciLinks button for links on evolution. - Evidence of Evolution

Changes Over Time End of Section: Evidence of Evolution

Changes Over Time Building Vocabulary After you read the section, write a definition of each Key Term in your own words. - The Fossil Record Key Terms:Examples: petrified fossilFossils that form by minerals replacing remains are called petrified fossils. moldA hollow space in the sediment in the shape of an organism or part of an organism is called a mold. castA cast is a copy of the shape of the organism that made a mold. relative datingScientists use relative dating to determine which of two fossils is older. radioactive datingA technique called radioactive dating allows scientists to determine the actual age of fossils. Key Terms:Examples: radioactive element half-life fossil record extinct gradualism The rocks that fossils are found near contain radioactive elements, which are unstable elements that decay, or break down, into different elements. The half-life of a radioactive element is the time it takes for half of the atoms in a sample to decay. The millions of fossils that scientists have collected are called the fossil record. A species is extinct if no members of that species are still alive. Gradualism proposes that evolution occurs slowly but steadily. Key Terms:Examples: punctuated equilibria The theory of punctuated equilibria accounts for the gaps in the fossil record.

Changes Over Time End of Section: The Fossil Record

Changes Over Time Graphic Organizer An organism dies in water. The organism is buried under sediment. Over millions of years, the sediments harden and become rock, and the hard parts of the organism are replaced by minerals. The fossil becomes exposed on the surface of a rock. Fossil Formation

Changes Over Time End of Section: Graphic Organizer