Transcript Evolution
Evolution Charles Darwin and The Origin of Species What do you think of when you hear the word “EVOLUTION” Science? Animals? Evolution is a very complex and controversial issue. This lesson is an introduction to the theory of evolution and natural selection as Humans? presented by Charles Darwin Change? Charles Darwin? Religion? Survival? Fossils? Extinction? Charles Darwin (1809-1882) ► He was an English Naturalist ► He traveled around the world on his ship, the Beagle ► Studied species and fossils in the Galapagos Islands and around the world ► Why did some species survive while others became extinct? ► Natural selection ► Published The Origin of Species in 1859 Darwin’s Theory ► Darwin's theory of evolution has four main parts: Organisms have changed over time, and the ones living today are different from those that lived in the past. Furthermore, many organisms that once lived are now extinct. The world is not constant, but changing. Change is gradual and slow, taking place over a long time. This was supported by the fossil record, and was consistent with the fact that no naturalist had observed the sudden appearance of a new species. All organisms come from common ancestors by a process of branching. Over time, populations split into different species, which are related because they are descended from a common ancestor. Thus, if one goes far enough back in time, any pair of organisms has a common ancestor. This explained the similarities of organisms that were classified together - they were similar because of shared traits inherited from their common ancestor. It also explained why similar species tended to occur in the same geographic region. The mechanism of evolutionary change is natural selection. Natural Selection ► “I have called this principle, by which each slight variation, if useful, is preserved, by the term of natural selection.” – Charles Darwin - The Origin of Species ► Darwin's theory of natural selection holds that variation within species occurs randomly and that the survival or extinction of each organism is determined by that organism's ability to adapt to its environment. On The Galapagos Islands ► ► ► ► ► Darwin found mockingbirds that were similar to ones that were native to Chile, but differed slightly from island to island He studied different species of finches and the slight variations in their beaks He noticed that the shapes of tortoise shells also varied slightly from island to island He found fossils of animals that had recently become extinct He kept a journal and collected fossils and specimens for further study Darwin’s Finches ► ► ► ► ► These are some of the finches that Darwin studied on his voyage Though they are all finches, their beaks distinguish them from one another Some finches developed short, strong beaks that made it possible for them to crack nuts Some developed long, fine beaks to reach insect larvae in tiny holes This is an example of how these finches adapted to their environment to survive (natural selection) Darwin’s Finches Darwin believed that all of the different finches came from a common ancestor and that their differences were a result of natural selection Example of Natural Selection Peppered Moth Moths can camouflage with trees to avoid being eaten by birds. ► There were light moths and dark moths living near English industrial cities in the 19th century The dark moths stood out on the light colored trees and were more likely to be seen and eaten by birds ► Thus, there were many more light colored moths than dark colored moths. ► As English factories produced more and more soot, the trees turned a darker color. This was able to camouflage the dark moths, but not the light moths THEN, the light moths stood out on the dark trees and were more likely to be seen and eaten by birds! ► Thus, there were more dark colored moths than light colored moths. Because the dark moth was able to camouflage it was able to avoid being eaten. If the light colored moth is not able to adapt to its environment then it will eventually become extinct. Camouflage ► ► ► Many animals have evolved to resemble the environment around them. This makes it very difficult for predators to find them and eat them, thus increasing their chance of survival. It also makes it easier for predators to sneak up on prey. Can you spot them? Brimstone Butterfly Camo Moth Stick Bug Large Fly Lion Preying Mantis Seal Patterns of Evolution ► ► ► ► Darwin believed that natural selection can ultimately lead to the formation of new species. Sometimes many species evolve from a single ancestral species. Similarities in skeletal and muscular structure of Hawaiian honeycreepers led scientists to conclude that the 23 species of honeycreepers evolved from one ancestral species. Such an evolutionary pattern, in which many related species evolved from a single ancestral species, is called adaptive radiation. Adaptive Radiation ► Adaptive radiation most commonly occurs when a species of organisms successfully invades an isolated region where few competing species exist. If new habitats are available, new species will evolve. Divergent Evolution Red Fox Divergent evolution is the process of two or more related species becoming more and more dissimilar. ► Example: The red fox and the kit fox ► The red fox lives in mixed farmlands and forests, where its red color helps it blend in with surrounding trees. The kit fox lives on the plains and in the deserts, where its sandy color helps conceal it from prey and predators. The ears of the kit fox are larger than those of the red fox. The kit fox's large ears are an adaptation to its desert environment Kit Fox ► Similarities in structure indicate that the red fox and the kit fox had a common ancestor. As they adapted to different environments, the appearance of the two species diverged, or became more and more different. Convergent Evolution ► ► ► Convergent evolution is the opposite of divergent evolution In convergent evolution, unrelated species become more and more similar in appearance as they adapt to the same kind of environment. Frogs and Chameleons are examples of convergent evolution because although they are different amphibians, they have both developed harpoon-like tongues to catch insects Co-evolution ► Co-evolution is the joint change of two or more species in close interaction. Predators and their prey sometimes co-evolve; parasites and their hosts often co-evolve; plant-eating animals and the plants upon which they feed also co-evolve. ► One example of co-evolution is pollination of orchids by African moths. These species co-evolve because the moths depend on the flowers for nectar, and the flowers depend on the moths to spread their pollen so that they can reproduce. ► The relationship between the moth and the orchids is mutually beneficial because they help each other survive. Why is This Important? ► Divergent, convergent and co-evolution are different ways organisms adapt to the environment. These are examples of how the diversity of life on earth is due to the ever-changing interaction between a species and its environment. Extinction ► ► ► Extinction is the disappearance of an entire species If a species does not have the genetic traits to survive in its environment, then the species will eventually become extinct forever Some examples of extinct animals are: Galapagos Tortoise Bali Tiger Dinosaurs Thylacine Steller’s Sea Cow Quagga Laughing Owl Dodo Bird Reasons for Extinction ► ► ► ► ► Rarity- when there are very few animals of a species left (Galapagos Tortoise) Inbreeding- when animals mate too much within their own group the offspring become less able to survive and adapt in a healthy way Hybridization-When two animals from different sub-species mate, they might pass on genes that are less healthy (Quagga-half horse half zebra) Gradual loss of habitat- When an animal's habitat is slowly destroyed and they have nowhere to live. (Bali Tiger) Long-term environmental trends- Scientists think that dinosaurs became extinct because of a slow cooling of the earth Reasons for Extinction ► ► ► ► ► ► Catastrophe- Volcanic eruption, dramatic change in climate, tsunami, etc. Extinction or reduction of mutualistic population- If two species are dependent on each other, then the endangering of one also endangers the other Competition- When a new species is introduced to a habitat, then the stronger of the two species will be more likely to survive. Predators-When the population of a species of predator in a habitat suddenly increases, the population of their prey decreases Disease- If a particular sickness spreads quickly throughout a particular species, then many may die before they can reproduce Hunting and collecting- Hunters have been largely responsible for the endangerment of many animal species. Applications ► Knowledge about evolution and natural selection has benefited our society in many ways, and has helped make numerous technological advances, especially in the field of biology and medicine Using Darwin’s theory of natural selection, scientists have been able to identify the desirable traits which would improve the probability of survival in certain species It has helped scientists and doctors in treating viruses and diseases. FOR EXAMPLE ► ► Did you know that when a doctor gives you antibiotics, you need to continue taking them until all of the pills are gone, even if you start to feel better? When a doctor gives you antibiotics, they start to fight of the bacteria in your body, little by little. It starts with the weak bacteria, and eventually kills the strongest bacteria. BUT, if you stop taking your medicine, then it is only the STRONG bacteria that are left in your body. That means that they will continue to reproduce and become stronger and stronger, and it will be much harder for the medicine to kill them. This is an example of natural selection because the strong bacteria survives and grows. Conclusion ► Darwin’s observations have made a great impact in the scientific community. Because of his observations, we are better able to understand why some species survive and some die. ► We are also better able to take precautions to protect species that are endangered. ► Lastly, we can understand the diversity in the world around us and learn to appreciate it. References ► http://www.lucidcafe.com/library/96feb/darwin.html ► http://outreach.mcb.harvard.edu/teachers/Summer06/BethMick/TheoryEvolution.ppt#264,9,EVID ENCE OF EVOLUTION ► wikipedia.com ► http://www.globalchange.umich.edu/globalchange1/current/lectures/selection/selection.html ► http://people.rit.edu/rhrsbi/GalapagosPages/DarwinFinch.html ► http://bioweb.cs.earlham.edu/9-12/evolution/HTML/converge.html ► http://biol1114.okstate.edu/study_guides/scenarios/5-galapagos/images/adaptive_radiation.gif ► http://en.wikipedia.org/wiki/List_of_examples_of_convergent_evolution#Reptiles ► http://www.pbs.org/wgbh/evolution/extinction/index.html ► http://images.google.com/imgres?imgurl=http://sciencegnus.com/Quagga.jpg&imgrefurl=http://s ciencegnus.com/Extinct%2520Animals.html&usg=__jvKRAbOBBqLDKizo6r_GeeZqXo8=&h=301&w =400&sz=10&hl=en&start=1&um=1&tbnid=XgWOxV3IPxCzGM:&tbnh=93&tbnw=124&prev=/ima ges%3Fq%3Dextinct%2Banimals%26hl%3Den%26rls%3Dcom.microsoft:en-us%26um%3D1 ► http://library.thinkquest.org/J002558F/extinction.htm