Get out your notebook Write down: – What is one career that collects evidence for evolution? – What is evolution? History of Evolutionary Thought 2 Early Ideas On Earth’s Organisms Aristotle believed species were fixed creations arranged by their complexity Idea lasted 2000 years 3 Early Ideas On Earth’s Organisms Linnaeus – 1st to group similar organisms and assign them Latin names Two word name (Genus species) Known as Binomial nomenclature 4 Lamarck’s Theory of Evolution Jean-Baptiste Lamarck, 1809 One Of First Scientists To Understand That Change Occurs Over Time Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime Said acquired changes were passed to offspring 5 Lamarck’s Theory of Evolution Idea called Law of Use and Disuse If a body part were used, it got stronger If body part NOT used, it deteriorated 6 Lamarck’s Theory of Evolution Inheritance of Acquired Characteristics Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime These Traits Could Then Be Passed On To Their Offspring Over Time This Led To New Species 7 Lamarck’s Theory of Evolution Use & Disuse - Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them Blacksmiths & Their Sons (muscular arms) Giraffe’s Necks Longer from stretching) 8 9 Lamarck’s Theory of Evolution Inheritance Of Acquired Traits – Traits Acquired During Ones Lifetime Would Be Passed To Offspring Clipped ears of dogs could be passed to offspring! 10 Lamarck’s Theory of Evolution Tendency Toward Perfection Organisms Are Continually Changing and Acquiring Features That Help Them Live More Successfully In Their Environment Example: Bird Ancestors Desired To Fly So They Tried Until Wings Developed 11 Lamarck’s Mistakes Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) Genes Are NOT Changed By Activities In Life Change Through Mutation Occurs Before An Organism Is Born 12 What we know now: Phenotype: The physical characteristics that are expressed based on a species’ genes (what we see) Genotype: The DNA/genetic code that determines how an organism looks (we cannot see it). Passed from generation to generation. Phenotype can change during life, but this will never change genotype, so these traits are not inheritable. Evolution and Natural Selection Charles Darwin the Naturalist copyright cmassengale 15 I. Charles Darwin - Charles Darwin is the father of evolutionary theory. - What question is he trying to solve? - Why do populations change over time? Darwin on HMS Beagle It took Darwin years to develop his theory of evolution; eventually published ideas in book entitled On the Origin of Species He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey. A map of Darwin’s voyage The Galapagos Islands Finches on the islands resembled a mainland finch More types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects…) Finches had different types of beaks adapted to their type of food gathering 19 20 Darwin’s Observations Left unchecked, with unlimited resources, the number of organisms of each species will increase exponentially, generation to generation In nature, populations tend to remain stable in size Environmental resources are limited 21 Darwin’s Conclusion • Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals • Only a fraction of offspring survive each generation • Survival of the Fittest 22 Darwin’s Observations • Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike. • Much of this variation between individuals is inheritable. 23 Darwin’s Conclusion • Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals • Called Natural Selection 24 Darwin’s Theory of Evolution •The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection) •New species evolve 25 Evolution - Evolution is when a POPULATION of organisms changes over time - Darwin proposed the idea that evolution happens through natural selection. - Developed from his idea of artificial selection = nature provides variation and HUMANS select variations they find useful Natural Variation and Artificial Selection Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful 27 28 II. Natural Selection - Natural selection is the way evolution happens. That is, natural selection is how organisms change over time. - Natural selection is when nature selects a. organisms with good genes to live and pass on their genes and… b. organisms with bad genes to die out II. Natural Selection - In any population, there are differences between species. - For example: These fish are different sizes, shapes and speeds. - What causes these differences? - Mutations (alterations in DNA sequences) II. Natural Selection - Organisms with helpful traits, such as being fast, survive better in their environment, compared to being slower. II. Natural Selection - Over time, only the organisms with the good genes (in this example, fast fish) will survive and the new population of fish will look very different from their ancestors: Ancestors (Great-Grandparents) New population of fish II. Natural Selection Sometimes called “Survival of the Fittest” - Fitness: the physical traits and behaviors that enable organisms to survive and reproduce in their environment - Common Descent: the idea that all species have common ancestors Darwin’s Theory of Natural Selection 1.Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited 2.Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do No Reproduce 3.Because More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited Resources 4.Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence 5.Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring. 6.Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species 7.Species Alive Today Have Descended With Modifications From Species That Lived In The Past 8.All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent You are Darwin. Explain why and how this change could happen. Finch Beak Size These two finches came from the same ancestor. According to Darwin, how did they come to look different? What would Lamarck had said? Exit Ticket What is the process that natural selection drives called? (Points….1…0…) a. Speciation b. Natural Selection c. Evolution d. Degradation Which one of these is an example of natural selection? (Points…1…0…) a. A snake loses its skin once a month to remove parasites. b. A population of fish with an avian predator gradually changes over time from grey-blue to a green color as the color of the water in their pond becomes greener due to green algae growth. c. A single giraffe stretches his neck every day until it grows longer so that he can eat taller vegetation. d. A dog barks to warn its owner when someone comes to the door. Predict what would happen in the following scenario: (Points…5…4…3…2…1…) There is a large population of wolves. They all have different length fur in their coats. Some have very long, thick fur. Others have very long, thin fur. And still others have short, thin fur. There are no wolves with short, thick fur. Predict what would happen to the wolf population if there was a climate change that caused the temperatures to drop 20 degrees throughout the year. (If you need more room please use the back of this page).