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Observing Variation in Traits • Copy the following chart into your notes: Animal Bird Fish Dog Snake Rabbit Means of locomotion Trait used for locomotion • • Look at each picture and determine the means of locomotion for each animal and write it in the chart. (How do they get around?) Then determine what trait is used for their specific type of locomotion and write it in the chart. Charles Darwin • • • • From England A naturalist (studied natural history) Sailed all over the world on the H.M.S. Beagle Made numerous observations & collected evidence that led him to propose the Theory of Evolution Darwin’s Curiosity 1. 2. 3. 4. He found it interesting that many so plants and animals are remarkably well suited to their environment He was impressed by the many different ways organisms survived and how they produced offspring He was puzzled by where different species lived and did not live, even though environments are similar. (for example, why were there no rabbits in Australia, even though there were plenty of suitable environments for rabbits?) He collected fossils and eventually realized that some fossils belonged to species that had disappeared, and he wanted to know why and how they might be related to living species. To find the answers to these questions and so many more, Darwin made many, many OBSERVATIONS. . . The Galapagos Islands • Influenced Darwin the most • Islands were close together but had very different climates • Fascinated by the land tortoises and the various different, yet similar birds • He noticed that the characteristics of many plants & animals varied noticeably among the different islands of the Galapagos On the Origin of Species • Darwin used his observations in combination with other scientific developments of his time to develop ideas and theories about why species were so diverse • Eventually, he published his work in a book called On the Origin of Species. • In this book, he introduced the concepts of natural selection and evolution Inherited Variation & Artificial Selection • Variation – how things are different from each other; not just in looks, but also in structure and behavior • Darwin observed that individuals within a species are different. For example, human beings are members of the same species, but we are all different. Some plants of the same species produce larger fruit than others, and some cows produce more milk than others. • Darwin also learned that these differences can be passed down from parents to offspring – this is called inherited variation • Darwin noted that plant and animal breeders would only breed the individuals with the most beneficial traits, so that they could produce new individuals with those same beneficial traits • This is called artificial selection – In artificial selection, nature provides the variation, and humans select those variations that they find useful Artificial Selection Exercise • http://wps.prenhall.com/wps/media/objects/ 486/498193/CDA1_1/CDA1_1a/CDA1_1a.htm • http://wps.prenhall.com/wps/media/objects/ 486/498193/CDA1_1/CDA1_1b/CDA1_1b.htm Evolution by Natural Selection • Darwin saw that people could force evolution, but wanted to see if it occurred naturally (in nature, without humans interfering) • He soon learned that nature also has a form of selection, or a way of selecting which traits are passed down and which ones are not • He identified 3 main processes that worked in nature to select specific traits to be passed down: 1. The struggle for existence 2. The survival of the fittest 3. Descent with modification • Defined – members of each species compete regularly to obtain food, living space, and other things necessary for life. • Causes of this struggle: – High birth rates lead to over population – Shortage of life’s basic needs or resources • Examples: – Predators that are faster catch more prey than the slower – Prey that are faster or better camouflaged can better avoid being caught Survival of The Fittest • Fitness – the ability of an organism to survive & reproduce in a specific environment • Fitness is a result of adaptations • Adaptation – any inherited characteristic that increases the organism’s chance for survival • Successful adaptations make the organism better suited for their environment and therefore increase the organism’s chances of survival and reproduction • Since fitness is a result of adaptations, the better the adaptation, the higher the fitness Survival of The Fittest • Those with higher fitness levels are more likely to survive and reproduce, and their traits will be passed on • Those with lower fitness will die and leave few, if any, offspring and their traits will not be as likely to be passed on • Darwin called this Natural Selection because the traits that get passed down are, in a way, selected by nature, or they are selected in a natural way. • Natural Selection takes place without human control or direction • Over time, natural selection results in more favorable traits being passed down and this increases the fitness of the whole population and species. • Natural Selection cannot be seen directly. It is seen by the changes in populations over many generations Examples of Natural Selection • Peppered Moth - Many times a species is forced to make changes as a direct result of human progress. Such is the case with the peppered moth (Biston betularia). Up until the Industrial Revolution, these moths were typically whitish in color with black spots, although they were found in a variety of shades. As the Industrial Revolution reached its peak, the air in London became full of soot, and the oncewhite trees and buildings that moths used for camouflage became stained black. The birds began to eat more of the lighter-colored moths because they were more easily spotted than the darker ones. Over the course of a few months, dark moths started appearing in the area and lighter moths became scarce. Once the Industrial Revolution peak passed, lighter moths made a comeback. Examples of Natural Selection • Pesticide-Resistant Insects - The more a pesticide is used, the greater the chance that the insects targeted will develop immunity to the chemical. Pesticide resistance is not only very common, but it also usually happens rather quickly. Sometimes all it takes is a single generation. Imagine that a group of insects survives the pesticide and is able to reproduce. More likely than not, the offspring will be resistant to the pesticide from birth. Those that are not immune will die, while the strongest will survive. Since many insects reproduce quickly, several generations can be born within months or even weeks. By the time a few generations have passed, all insects are likely to be resistant to the pesticide. Survival of the Fittest • http://www.gamvak.com/Kids_Games/Survival-Of-The-Fittest • Conduct the following activities to see who “wins” 1. Play Simon Says – demonstrate ability to follow directions. 2. Musical Chairs – demonstrate reaction time 3. Sprints – demonstrate speed 4. 3 legged race – demonstrates teamwork Add up points. The students with the higher numbers have higher fitness and are therefore more likely to survive and reproduce. Descent with Modification • Darwin realized that since adaptations were passed down, there was reason to believe that species today might look different than their ancestors • Descent with Modification – – every living species has descended , with some changes, from other species over time – All living things are related to each other – Common descent – all species, living and extinct, came from common ancestors Evidence of Evolution • Fossil Record: the remains of ancient life that are found in rock layers and give us a history of life on Earth • Geographic Distribution of Living Species: Darwin realized that there were species that were similar, yet different. He realized that similar animals in different locations were the product of different lines of evolutionary descent. • Homologous Body Structure: Homologous structures may not necessarily perform the same function but they share a common ancestral origin. • Similarities in Embryology – embryos or early stages of many animals are very similar; cells develop in the same order even though they end up being very different Summary of Darwin’s Theory • Darwin’s Theory of Evolution is summarized as follows: – Individual organisms differ and some of these differences (variation) is heritable – Organisms produce more offspring than can survive, and many do not survive to reproduce – Because more organisms are produced than can survive, they compete for limited resources – Individuals best suited for their environment survive and reproduce more successfully, and they pass their traits to their offspring, causing species to change over time. – Species that are living today are descended with modification from a common ancestral species that lived in the distant past.