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Transcript
Theory of Evolution WRITE A DEFINITION: THEORY: • a well-supported testable concept that is backed-up by evidence • Concept has been tested multiple times and is proven EVOLUTION: • gradual change over time; the process by which modern organisms have descended from ancient organisms Ideas that shaped Darwin’s thinking: James Hutton (1795)the EARTH was shaped by geological forces occurring over very long periods of time, and the Earth is millions of years old. Ideas that shaped Darwin’s thinking: Charles Lyell (1830)the geological processes still occurring now have shaped Earth’s features over long periods of time http://www.biologydaily.com/biology/Sir_Charles_Lyell Formation of Earth • The Earth is about 4.8 billion years old • According to science, the Earth was put together piece by piece over the course of about 100 million years Early Earth Atmosphere Earths early atmosphere was made up of 6 main things: • Hydrogen cyanide • Carbon dioxide • Carbon monoxide • Nitrogen • Hydrogen sulfide • water Could you have lived on early Earth? Cooling of the Earth • Not only was the atmosphere not suitable for life the early Earth was VERY hot • About 4 billion years ago the earth began to cool – Rocks formed on the earths surface Formation of water • 3.8 billion years ago the earth cooled even more – Liquid was able to remain on the earths surface forming the first oceans video Free Oxygen • Fossils of prehistoric bacteria have been found in rocks that are dated to be more the 3.5 billion years old • 2.2 b.y.a. Photosynthetic bacteria began producing oxygen as a by product of photosynthesis Free Oxygen • Free oxygen mixed with iron in the ocean forming iron oxide • Oxygen gas started accumulating in the atmosphere, forming the ozone layer • Increased oxygen levels caused some life forms to go extinct and allowed other life forms to evolve Ideas that shaped Darwin’s thinking: Theory of PangaeaAll land was at one time connected Ideas that shaped Darwin’s thinking: Continental driftshifting of the earths continent/ crust divergent convergent Transform Division of Life on Earth • Life on Earth is divided into Eras and Periods – Eras are bigger than periods • Based on fossil evidence – major changes that occurred in the Earth’s climate and geography affected the living organisms Darwin’s Theory of Evolution The Puzzle of Life’s Diversity Chapter 15-1 Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006 Charles DarwinThe person who contributed the most to our understanding of evolution In 1831, he joined the crew of the Beagle as a naturalist for a 5 year voyage around the world. The Fossil Record • Fossil record showed 2 types of organisms – Ones that were similar to animals and plants alive at the time – Ones that were different to animals an plants alive at the time • Why had these species disappeared? – 99% of all species that have ever lived on Earth are extinct Fossils and Ancient Life • What is a fossil? – Hardened remains of plant or animal in rock • Why do scientist use fossils? • Fossils allow us to infer what past life forms were like – Structure – Predator/Prey – Habitat How Fossils Form • After the organism dies the remains must be preserved • The dead organism is buried by sediment – Mud – Sand – dust How Fossils Form • Different types of fossils can be formed – Eggs – Foot prints – Bones – Leaves Relative Dating • Most fossils form in sedimentary rock – formed by the deposition of materials at the Earth’s surface • The age of a fossil is determined by comparing its placement with that of fossils in other layers of rock – Layers of sedimentary rock are built from oldest to newest Index Fossil • Fossils used to define and identify geological time – When the organisms lived • Species that existed for a short period of time over a wide geographic range Radioactive/Radiometric Dating • Uses radioactive elements to determine how old the rock is – Radioactive elements decay at a steady rate – The use of half-lives to determine the age of a To date older rocks you must sample use elements with longer half– Half life: the length of time lives required for half of the Carbon-14 (5,730 years) radioactive atoms to decay Uranium (half-life: 4.47 b.y.) How the fossil record is used • used to show change in organisms over time – Evidence of gradual change • life on earth is divided based on changes in the fossil record – Transitions marked by extinction – Extinction makes new habitats available to species DARWIN WONDERED? Why do Argentina and Australia have different Animals even though they have similar grassland? Why have so many species disappeared? How are these extinct species related to living species? Ideas that shaped Darwin’s thinking: Jean-Baptiste Lamarck (1830)• one of first scientists to recognize living things changed over time and that all species were descended from other species. Lamarck's Hypothesis: 1. Tendency towards perfection 2. Use and disuse 3. Inheritance of acquired traits Tendency Towards Perfection • Innate tendency toward complexity and perfection • Organisms are continuously changing and acquiring traits that benefit them Use and Disuse • By selective use or disuse of organs, organisms acquire or loose traits during their life time • These traits are passed down to offspring The male fiddler crab uses its front claw to attract mates and fight off predators. Through repeated use, the front claw becomes larger. The fiddler passes on this acquired characteristic to its offspring Inheritance of Acquired traits • Acquired traits could be passed on to offspring – Lamarck didn’t know about genes and how traits are inherited. If you lifted weights your whole young adult life, and then you had children, would your kids be more muscular? Inheritance of Acquired traits What’s wrong with Lamarck’s hypotheses? • Individuals DO NOT evolve – You cannot change your DNA • Acquired traits cannot be passed down to offspring • An organisms behavior has no effect on its heritable characteristics What’s right with Lamarck’s hypothesis? Lamarck recognized that organisms are Adapted to their environment What does drive evolution? • Evolution= •Inherited adaption's that accumulate in a population over many generations competition Darwin's greatest influence Charles Darwin spent one month observing life on the Galapagos Islands. There, he encountered some unique animals, such as finches and tortoises. http://www.darwinadventure.com/pictures/galapagos_giantortoise.jpg http://mikebaird.com/ecuador/images/galapagos_off_ecuador_ng_map.jpg A summary of Darwin’s Theory 1. Individual organisms differ and some of the variations are genetic WHY DOES VARIATION MATTER? The Galapagos Islands are close together but have very different climates. • hot and dry, with little vegetation • more rainfall and were rich in vegetation Each island had its own unique Assortment of plant and animal species. Biology by Miller and Levine; Prentice Hall Publishing©2006 Inherited Variation • Inherited variationpassed from parents to offspring How are traits passed from parents to offspring hint: think about meiosis • Crossing over • Random lining up of chromosomes A summary of Darwin’s Theory 2. Organisms produce more offspring then can survive, and many that do survive do not reproduce. – High birth rates and a shortage of resources force organisms into competition Ideas that shaped Darwin’s thinking: Thomas Malthus (1798)• If the human population continued to grow unchecked, there would be insufficient living space and food. • Individuals adjust to limited resources Natural selection • Each individual differs from other members in its species – Each has unique advantages and disadvantages • Natural selection- based on their traits, some individuals are able to survive longer then others – Takes place without human control or direction Organisms cannot change their characteristics or force natural selection… Giant Tortoises of the Galápagos Islands Section 15-1 and on Pinta Island, tortoise necks were somewhere in between Pinta Pinta Island Tower Marchena Intermediate shell Fernandina James Santa Cruz Isabela Santa Fe Hood Island Floreana Isabela Island Hood Saddle-backed shell On the desert-like Hood Island, tortoises had long necks… Dome-shaped shell …while Go to on the lush rainforest of Isabela Island, Section:tortoises had short necks… Natural Selection doesn’t give organisms what they need to survive Artificial Selection • Artificial selection- nature provided the variation and humans selected for the variations they saw useful. – Used to improve crops and livestock (selective breeding) A summary of Darwin’s Theory 3. Because more organisms are produced then can survive, they compete for limited recourses. – Food – Shelter – Space – Mates The struggle for existence • Competition what drives evolution If there is no competition there is no evolution A summary of Darwin’s Theory 4. Each organism has different advantages and disadvantages in the struggle for existence. • Survival of the Fittestthe ability of an organism to survive and reproduce in its specific environment Survival of the Fittest • Fitness is a result of adaption's – Adaptation= inherited characteristics that increase an organisms chance of survival Is the most fit animal always the biggest, strongest and fastest? Survival of the Fittest? Adaptation vs. the ability to adapt • Adaptation- a trait or characteristic that you re born with • Ability to Adapt- How you use your traits or characteristics to survive Individuals DO NOT changes • Individuals are unchanging • Individuals either live or die based on the traits that they inherited from their parents A summary of Darwin’s Theory 5. Species alive today are descended with modifications from ancestral species Review of Darwin’s Theory • Individual organisms differ and some of the variations are genetic • Organisms produce more offspring then can survive, and many that do survive do not reproduce. • Because more organisms are produced then can survive, they compete for limited recourses. • Each organism has different advantages and disadvantages in the struggle for existence. • Species alive today are descended with modifications from ancestral species Review of Darwin’s theory • Adaptations- an inherited trait or characteristic that is passed down from on generation to the next – NOT something gained during your life time! • Acquired traits- are not passed down • The ability to adapt- how an organism is able to use their adaptations to their advantage in order to survive in their environment Conditions for natural selection Conditions for natural selection include: • Variations exist among members of a population • Many more individuals are produced each generation than will survive • Some individuals are better adapted so they survive & reproduce • Members of a population compete for food, space, mates... Evidence for Evolution Fossil Record Geographic Distribution Homologous Body Structures Similarities in Embryology Fossil record Fossil record • The fossil record is a history of life on Earth – The earth is millions of years old • Which scientists proposed this? – Fossils that are found in different rock layers show the evolution of living species over millions of years Fossil Record • Transitional fossils-document various intermediate stages in the evolution of modern species Incomplete Fossil Record • Not all fossils have been found – We are still finding new fossils – The gaps in the fossil record are getting smaller • Not all organisms that ever live become fossilized – Soft bodied organisms are not fossilized – Organisms that don’t die in or by the water are usually not fossilized Geographic distribution • when a population gets separated difference selective pressures will work on the populations and cause changes • Divergent Evolutionpopulations evolve separately – Formation of new species Geographic distribution • The environment selects for specific adaptations – If the environment is the same in 2 different locations we see the evolution of similar but unrelated species – Convergent evolutionevolution of shared traits in unrelated species • Bats and birds Homologous body structures Homologous structures: variations on a body structure that was present in their common ancestor Vestigial Structures • structures or organs that seem to serve no useful function – Human tail bone – Whales tiny pelvic and limb bones – Ostriches wings • vestigial structures show common ancestry with organisms in which the homologous structure is still functional. Similarities in Embryology • The early stages of development are similar in different species – All animals with backbones • The same groups of embryonic cells develop in the same order and pattern – Cause for homologous structures Descent with modification • Natural selection produces organisms that have different characteristics – Species today look different then their ancestors • Common descent: All living organisms are related to one another – A single tree of life links all living organisms