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EVOLUTION – PART 1: INTRO TO EVOLUTION On the following slides, the pink sections identify the main points; Underlined words = vocabulary! Hyperlinks are in green. Background Image: http://magickcanoe.com/insects/angry-katydid-3-large.jpg This katydid is well adapted to look like the leaves of its habitat. In this unit we will discuss theories of evolution and adaptation that lead to such phenomenon within populations. Background Image: http://magickcanoe.com/insects/angry-katydid-3-large.jpg Sensitivities Due to the sensitive nature of this unit I ask that we keep in mind that evolution can often breed tensions because of religious teachings about the history of life. These theories are part of understanding the world of science. Our scientific discussions will focus on attempting to explain natural phenomena (or events). Differing religious opinions are okay, but religious based theories on the history of life are not the focus of this class. Scientific Theory • Theory in everyday life is different from the scientific theory – i.e. someone has a theory on who will win the Super Bowl. • A scientific theory is an explanation of natural and physical phenomena that is supported by a large body of scientific evidence from multiple, independent researchers. • Unlike hypotheses, theories are well- established and highly reliable – they are subject to change as new information is obtained or technologies developed. Evolution http://www.eurekalert.org/images/release_graphics/yu0926.jpg • The Earth has millions of kinds of organisms with an amazing amount of diversity, yet, we all share similarities, the core of which is DNA. (Every living organism has it!) • How are all these different organisms related to each other? • Evolution, or change in a species over time, is the process by which modern organisms have descended from ancient ones. • For example, the ancient horse a was about the size of a medium dog! Who is Charles Darwin? • The British scientist Charles Darwin is credited the most in our understanding of evolution. • He proposed a hypothesis about the way life changes over time . • That hypothesis, now supported by a larger body of modern evidence, became the theory of evolution. Photograph of Charles Darwin by Maull and Polyblank for the Literary and Scientific Portrait Club (1855). Image After college in 1831, Darwin joined the crew of the ship the H.M.S. Beagle for a voyage around the world for 5 years! http://www.anselm.edu/homepage/jpitocch/genbios/22-05-VoyageOfHMSBeagle-L.gif Darwin Cont. • During his travels, Darwin kept journals, took observations, and made sketches for the variety of species on this planet. • When the ship was anchored, he collected many specimens. – In one single day in the Brazilian rainforest he collected 68 different species of beetles! • When sailing, Darwin took observations of the organisms and kept detailed notes. http://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/St riped.love.beetle.arp.jpg/250px-Striped.love.beetle.arp.jpg Darwin Cont. http://english.people.com.cn/200406/07/images/0606_112.jpg • In his travels, Darwin compared living organisms to fossil evidence that he collected throughout his voyage. • A fossil is the preserved remains of an ancient organism. – Some living organisms he observed looked like preserved fossils, while others were unlike any creature he had ever seen! EX Dinosaurs • His evidence posed more questions. – Why had so many species disappeared? – How are ancient organisms related to modern organisms? http://www.cnn.com/EARTH/9707/17/Galápagos /Galápagos .lg.jpg https://maps.google.com/maps?output=classic Galápagos Islands • Probably his most influential location on Darwin’s journey was the Galápagos Islands off the coast of Ecuador. • The islands had very different climates and very different organisms living there. http://upload.wikimedia.org/wikipedia/commons/a/a1/Gal%C3%A1p agos_tortoise_Santa_Cruz.jpg Darwin learned that each island had a different variety of land tortoises. One island turtle has a long neck and curved opening in the shell to allow for the organism to search for food because of sparse vegetation (or plant life). Yet, another island with a lot of plant life has a turtle that is very close to the ground the with a short neck making it easier to eat. Galápagos tortoises in Alcedo Caldera, Isabela Island Photograph by Frans Lanting "Near the springs it was a curious spectacle to behold many of these huge creatures, one set eagerly travelling onwards with outstretched necks, and another set returning, after having drunk their fill."—October 8, 1835 http://rationalrevolution.net/images/darwin_ape.jpg On the Origin of Species The political cartoon (1861) is just one example of the negative reaction to the theories explained within the book. • Charles Darwin used his notes and other findings to build his theory of evolution; it took him years before he was willing to publish his work because of the drastic controversy it would (and did) cause. • His book, On the Origin of Species [By Means of Natural Selection] was published in 1859. • In it he argued that life has been evolving for millions of years. Five Basic Concepts of Origin • Use the chart to list the 5 themes from On the Origin of Species. 1. Variation Among Species • All species have genetic variation (we now know) caused by differences in the DNA and genes of an organism – EX color of fur; shape of teeth; blood type; hormone levels • Darwin argued that variation was normal and was important. • Characteristics vary and can affect the survival of individuals. http://www.swarthmore.edu/NatSci/cpurrin1/evolk12/gps/images/sad dlestretch.jpg 2. Struggle for Existence • • • • Organisms produce more offspring than can survive. Some that survive do not produce offspring. Organisms are forced to compete for resources. This is called the struggle for existence; members of each species must compete for the necessities of life (food, water, & space). http://eoimages.gsfc.nasa.gov/images/imagerecords/79000/79553/sandy_goe_2012302 _1745_lrg.jpg • Survival affected by short-term natural disasters – EX droughts, fires, floods, snowstorms, hurricanes, etc. • And affected by long-term changes in the environment – EX ice ages, biome shifts, etc 3. Adaptations • Darwin began to realize that organisms have certain characteristics or behaviors that allow them to survive in their environment. • An adaptation is an inherited characteristic (EX a longer neck) that can increase an organism’s chance of survival. • If they live long enough, they will reproduce and pass on their favored genes. http://www.cedar-foundation.org/uploads/images/300%20Turtle.jpg Knowledge Check http://www.pbs.org/wgbh/evolution/library/01/6/images/l_016_02_l.gif The diagram below shows features of the varieties of finches in the Galapagos. How can the diagram help us understand the evolutionary terms like variation and adaptation? Turn and talk to your neighbor. 4. Fitness http://farm1.staticflickr.com/49/125046333_7123c38e73_z.jpg?zz=1 • Some organisms are more suited to their environment due to natural variations in the species. • Darwin used the term fitness to define an individual’s ability to survive and reproduce. • Individuals that are fit to their environment survive and leave more offspring than those who aren’t. 5. Descent with Modification • Living species today are descended (with modifications) from common ancestral species that lived in the past. • Over time, traits [i.e. genes] for less favored characteristics will be eliminated from the gene pool. • Species today, therefore, look different from their ancestors because of historical changes. Sketch, Darwin’s Notebook Branching “Tree of Life” Image Knowledge Check The diagram below shows descent with modifications for modern elephants. How can the diagram help us understand evolutionary terminology like variation and descent with modification? Turn and talk to your neighbor. http://www.zo.utexas.edu/faculty/sjasper/images/22.7.gif What is the gist of the book? • Natural selection is the process by which individuals that are better suited to their environment survive and reproduce most successfully (AKA survival of the fittest). • Organisms that are well adapted will be able to survive. Over time, natural selection leads to changes in the characteristics of a population. • New species develop, increasing biodiversity. – Video – Video 2 Artificial Selection • Darwin understood variation can be a positive thing! – EX dairy farmer would benefit from breeding a cow that produces a lot of milk versus a cow that does not. • He coined the term artificial selection where nature provided the variation and humans selected those variations that are useful – EX a pure breed dog, the best looking horse). – Animation http://www.farmlandthegame.eu/images/animals/Dairy-cows-pict-1.jpg Darwin’s Influences • Many scientific theories and observations in the years before Darwin helped to influence his theories on evolution. • Some scientists long before Darwin came to similar conclusions. • Most people at the time thought Darwin’s opinions too radical to accept at the time. http://www.victorianweb.org/science/darwin/darwin_beard.gif Linnaeus http://www.amentsoc.org/images/carl-linnaeus.jpg • In the 1700s, a Swedish botanist Carl Linnaeus created a categorical system to group animals based on their similarities (still used today). • He rejected the idea that organisms were fixed and did not change. – Book - Systema Naturae, 1735 – Darwin sited Linnaeus’s work in Origin. Hutton • Scottish geologist James Hutton published his hypothesis on the Earth’s geology formed very slowly over time, millions of years and are shaped by natural forces (mainly the weather). – Most Europeans at the time believed that the Earth was only a few thousand years old, but Hutton proposed that the Earth had to be much older. • If the Earth were millions of years old, it would help to explain the SLOW process of evolutionary change. – Book, Theory of the Earth, 1795 http://upload.wikimedia.org/wikipedia/commo ns/thumb/0/0e/Hutton_James_portrait_Raeburn. jpg/220px-Hutton_James_portrait_Raeburn.jpg Erasmus Darwin • Darwin’s grandfather, Erasmus Darwin, an English doctor, posed that life descended from a common ancestor and had grown in complexity over time. – Book, Zoonomia, or The Laws of Organic Life, 1796 http://www.bbc.co.uk/arts/yourpaintings/paintings/erasmus-darwin-1731180219634 • The French scientist Jean-Baptiste Lamarck observed that life changes over time; he argued that traits present in an organism are always passed on to offspring. – EX giraffes stretched their necks to reach food, therefore their offspring inherited the resulting long necks. • Although some of his ideas were flawed, the idea that species change and adapt greatly influenced Darwin. – Book - Philosophie Zoologique, 1809 – Darwin sited Lamarck’s work in Origin. http://en.wikipedia.org/wiki/File:Jean-baptiste_lamarck2.jpg Lamarck http://www.anselm.edu/homepage/jpitocch/genbios/22-x3-Lyell.jpg Lyell • Charles Lyell’s book was published just before Darwin set sail in the Beagle. • In his book, Lyell proposed that scientists can observe the processes that shaped the Earth millions of year ago in the present (volcanoes, earthquakes, etc. all change how the world looks). • Darwin wondered if the Earth can change over time, can species change too? – Book – Principles of Geology, 1830 – Darwin sited Lyell’s work in Origin. Wallace • A contemporary of Darwin, Alfred Wallace, wrote an essay on evolution and the process of natural selection using his studies of plants and animals a year before Darwin published Origins. – Darwin and Wallace both presented their findings at the same scientific conference. – Darwin sited Lyell’s work in Origin. http://io.uwinnipeg.ca/~simmons/16cm05/1116/22-x5-AlfredWallace.jpg Extinction http://www.chrismadden.co.uk/eco/mammoth.gif • Extinction: the destruction of a population. • If an entire population of a species cannot adapt, that species becomes extinct. • 99% of all species that have ever lived are now extinct! • Humans contribute to the extinction of many plants and animals because of pollution, loss of habitat, and poaching. Indian tigers, for example, are a group of tiger species that had an original range from India along Asia's Pacific rim to northern China as well as other sections of Central Asia. Their range today outside of protected areas has been severely limited. "Fragmented Habitat." Science Online. Facts On File, Inc. Web. 30 Jan. 2013. <http://www.fofweb.com/activelink2.asp?ItemID=WE40&SID=5&iPin=SciIllus04661&SingleRecord=True>. • Many scientists say that the earth is currently experiencing a mass extinction crisis. • It is estimated that 1/5 or more of the world’s species will become extinct if the rainforests alone are destroyed, much less the coral reefs of the oceans and other habitats. Mass Extinction Photo courtesy of Donald E. Davis, also in public domain from NASA. • There have been at least 5 mass extinctions during Earth’s history, when a huge % of the living species were destroyed. • At least one of these has been attributed to meteor impact and it’s consequences. – Animation Analyzing the Graphic Chicxulub Crater, Mexico's Yucatan Peninsula 180 kilometre (112 mi) diameter Most scientists now agree that this event 65 million years ago that marked the sudden extinction of the dinosaurs as well as the majority of life then on Earth. Conclusion • Evolutionary theory is constantly changing due to new information that is obtained. – EX The AIDS virus is changing constantly, and the flu vaccine must be modified each year due to changes. • Species change, evolve, over time, and that is happening now. http://evolution.berkeley.edu/evolibrary/images/news/avianswineflu.gif