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Chapter 7 Changes Over Time Changes Over Time Section 7-1: Darwin’s Theory Pages 224-231 What important observations did Darwin make on his voyage? How did Darwin account for the diversity of species and the differences between similar species? How does natural selection lead to evolution? Chapter 7 Changes Over Time 5.1 Natural Selection Charles Darwin Simple Definition of Evolution -- Change over time. Classical Definition of Evolution – Common decent of all life upon earth from a single ancestor as a result of mutations and natural selection. Molecules to man theory. Microevolution – Small changes within a species. Macroevolution - Major changes from one kind of animal into another Chapter 7 Changes Over Time Charles Darwin (cont.) Darwin explored South America and its remote islands, such as the Galapagos, on the HMS Beagle during a 5 year journey. Chapter 7 Changes Over Time 5.1 Natural Selection Darwin’s Observations Darwin made observations about the diversity and uniqueness of organisms. Many of the animals on the Galapagos were similar, but not the same as organisms in mainland South America. Darwin reasoned that perhaps the organisms in the Galapagos originally came from South America and over time, they had evolved or changed. Chapter 7 Changes Over Time Chapter 7 Changes Over Time 5.1 Natural Selection Tortoises Darwin found giant tortoises on all the Galapagos Islands, but nowhere else. He reasoned that each new population changed slightly, or evolved, to fit its unique environment on the island. Chapter 7 Changes Over Time Changes Over Time Natural Selection Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species. Although resources are limited, animals often produce more offspring than could survive. Sometimes changes occur in genes and a new trait is created. Chapter 7 Changes Over Time Changes Over Time Overproduction, Variations, Competition and Selection Genetic variations (differences in traits) among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce. Natural selection does not give a new species what it needs to survive Natural selection merely chooses for a trait that is already there. Over time, it may make a trait better or more distinct but it does not create it. Chapter 7 Changes Over Time Finches Darwin was also impressed by the diversity of finches on the Galapagos. He reasoned that the finches changed over time because they adapted to the different habitats and food sources on the islands. Chapter 7 Changes Over Time Chapter 7 Changes Over Time Galapagos Finches Chapter 7 Changes Over Time Sharpbeaked Ground Finch Chapter 7 Changes Over Time Large Ground Finch Chapter 7 Changes Over Time Warbler Finch Chapter 7 Changes Over Time Galapagos Woodpecker Finch Chapter 7 Changes Over Time Chapter 7 Changes Over Time Chapter 7 Changes Over Time Chapter 7 Changes Over Time Chapter 7 Changes Over Time 6.2 Species change over time. Reviewing Darwin’s theory of natural selection and evolution. Copy the red sections down on a clean sheet of paper Natural Selection Notes Four principals of natural selection are • OverproductionMore offspring are produced than can survive Chapter 7 Changes Over Time 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • Overproduction • Genetic VariationThere may be slight variations in the offspring. Chapter 7 Changes Over Time 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • Overproduction • Genetic Variation • Competition – The offspring Compete for survival in their unique environmental conditions. Chapter 7 Changes Over Time 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • Overproduction • Genetic Variation • Competition • Selection - Those with the best traits for a particular environment (adaptations) will survive and reproduce. This is commonly called “survival of the fittest.” More fish with the beneficial notch survive to reproduce Chapter 7 Changes Over Time Darwin’s Theory of Natural Selection Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species. Two factors that lead to natural selection – Genetics and the environment Chapter 7 Changes Over Time Virtual Labs- How can natural selection be modeled? http://www.glencoe.com/sites/common_assets/scie nce/virtual_labs/LS16/LS16.html http://science.discovery.com/interactives/literacy/da rwin/darwin.html Chapter 7 Changes Over Time Environmental changes can affect populations. III. Environmental changes can affect populations. A. Population size is limited by environmental conditions. B. Populations increase through births and immigration. C. Many factors limit population size. 1. Competition 2. Predators 3. Disease 4. Catastrophic events D. The survival of a species depends on its ability to adapt to change. 1. How Extinction Happens Chapter 7 Changes Over Time Environmental changes can affect populations. III. Environmental changes can affect populations. A. Population size is limited by environmental conditions. B. Populations increase through births and immigration. C. Many factors limit population size. 1. Competition 2. Predators 3. Disease 4. Catastrophic events D. The survival of a species depends on its ability to adapt to change. 1. How Extinction Happens