* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Theory of Evolution
Survey
Document related concepts
Sexual selection wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Natural selection wikipedia , lookup
Theistic evolution wikipedia , lookup
Saltation (biology) wikipedia , lookup
On the Origin of Species wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
Paleontology wikipedia , lookup
The Expression of the Emotions in Man and Animals wikipedia , lookup
Evolutionary history of life wikipedia , lookup
Transitional fossil wikipedia , lookup
Transcript
Darwin's Theory of Evolution Unlocking Darwin’s Mysterious Idea Darwin’s Voyage of Discovery Darwin’s Epic Journey He was born February 12th 1809 This year we celebrate his 203rd birthday!! Darwin developed the biological theory of evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors In 1831, he began a 5 year voyage on the HMS Beagle that would change his life. Observations Aboard the Beagle Species Vary Globally Different, but similar, animals inhabited separate, but similar, habitats That some similar environments have very different animals. (Kangaroos in Australia but not England) Species Vary Locally Different, yet related, animals occupied different habitats within a local area Exs. – Tortoises and Birds in the Galapagos Islands varied from island to island Species Vary Over Time Some fossils of extinct animals were similar to living species Ex. – Extinct giant armored Glyptodont is similar to and lived in the same area as the Armadillo Giant Ground Sloth Modern Sloth Putting the Pieces of the Puzzle Together Darwin thought about the patterns he’d seen on his voyage He realized that there were many similarities between the animals he’d seen There was evidence that suggested that species were not fixed and that they could change by some natural process Ideas That Shaped Darwin's Thinking An Ancient, Changing Earth The Earth is very ancient and is continuously changing. – Hutton and Lyell helped scientists see that the Earth is millions of years old. – The geologic processes that shaped the Earth happen very slowly and are still happening today. Hutton and Geological Change Hutton proposed that rocks form very slowly and are changed by forces that twist, lift and fold them He also realized that mountains can be worn down by rain, wind, heat and cold In order for these events to occur, he concluded that the Earth must be more than a few thousand years old Lyell’s Principles of Geology Believed that the geological processes we see today must be the same ones that shaped Earth millions of years ago There needed to be enough time in Earth’s history for these changes (like a river carving out a canyon) to take place He agreed with Hutton that the earth was much older than a thousand years Cuvier was an anatomist who studied fossils. Noticed that some fossils indicate that organisms in the past were very different from living organisms of today. Older fossils differed more from living species than younger fossils. Abrupt changes in the fossil record shows evidence of mass extinctions. Darwin’s Observations While in South America, Darwin witnessed an earthquake that was strong enough to lift the rocky shoreline 3 meters out of the sea – with mussels and other sea life clinging to it Later, he observed fossils of marine animals in mountains thousands of feet above sea level Lamarck’s Evolutionary Hypotheses Proposed that the use or disuse of organs caused organisms to gain or lose traits over time. These new characteristics could be passed on to the next generation. Ex. - A water bird’s long legs happen because the animal kept wading in deeper water to get food. Evaluating Lamarck’s Hypotheses Lamarck’s hypotheses were incorrect in many ways We know that traits acquired during a lifetime cannot be passed on to offspring Evaluating Lamarck’s Hypotheses However, Lamarck was one of the first to: – Suggest that species are not fixed – Explain that evolution uses natural processes – Recognize that there is a link between an organism’s environment and its body structures Lamarck’s work paved the way for later biologists, including Darwin Darwin’s Ideas Descent with Modification – Every species-living and extinct- must have descended by reproduction from preexisting species and that species must be able to change over time. Natural Selection – The mechanism for descent with modification Darwin’s Reasoning Overproduction – More offspring can be produced than can survive to maturity. – The environment limits the populations of all organisms by causing deaths or by limiting births – Based concept on the ideas of Malthus who speculated that human populations are limited by war, famine and disease. Genetic variation: individuals have different traits in any population and some of these traits are inherited. Struggle to Survive: individuals compete with each other. Some variations improve an individual’s chance to survive and reproduce. These favorable variations are called adaptations. Differential Reproduction – Organisms with the best adaptations survive and reproduce. Those without die. – Over time, favorable adaptations increase in the population. – Nature changes species by selecting traits (parents) that are passed on to the next generation. Artificial Selection In artificial selection, nature provides the variations, and humans select the ones they find useful Darwin knew that variation occurs in wild species as well as domesticated species He realized that that natural variation provided the raw material for evolution Artificial Selection Darwin Presents His Case Darwin wanted to gather as much evidence as he could to support his ideas before he made them public In 1858, Darwin read an essay by Alfred Wallace whose thoughts about evolution were almost identical to his! In order to not get “scooped”, Darwin decided to present his work at a scientific meeting in 1858 along with some of Wallace’s essay The next year, Darwin published his complete work on evolution: On the Origin of Species Evolution by Natural Selection Struggle for Existence – From Malthus’ theory of supply and demand, Darwin reasoned that if more individuals are produced than can survive, they will have to compete for food, living space and other necessities of life – Darwin described this as the struggle for existence Evolution by Natural Selection Variation and Adaptation – Individuals have natural variations among their inheritable traits – Some variations are better suited to life in their environment than others – Fast predators capture prey more efficiently – Prey that are faster, better camouflaged or better protected avoid being caught. Variation and Adaptation – Any heritable characteristic that increases an organisms ability to survive and reproduce in its environment is called an adaptation – Examples of Adaptations: • • • • Tiger’s claws Camouflage colors Plant structures Avoidance behaviors Adaptations Survival of the Fittest Darwin felt that there must be a connection between an animal’s environment and how it survives Ability to survive and reproduce in a specific environment is called FITNESS Fitness depends upon how well an organism is suited for its environment Fitness is a result of ADAPTATION Good adaptations allow organisms to survive and are passed on to their offspring. Good fitness: Reproduce Low Fitness: Few offspring/extinction Darwin thought that this seemed very similar to artificial selection He referred to “survival of the fittest” as Natural Selection Survival means more than just staying alive. It means reproducing and passing adaptations on to the next generation Natural Selection: Nature chooses Artificial selection: Man chooses Favorable characteristics are inherited over several generations. Artificial Selection (Breeding Livestock) Natural Selection (Bird of Paradise Mating Display) Natural Selection Natural Selection Natural Selection is the process by which organisms with variations most suited to their local environment survive and leave more offspring Natural Selection occurs in any situation in which more individuals are born than can survive Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment. Common Descent Natural selection produces organisms with different structures than their ancestor, different niches, and new habitats. Each living species has descended, with changes, over time. The Evolution of the Horse If we look back far enough we could find the common ancestors of all living things. A single “tree of life” links all living things This is known as the principle of common descent. Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years. Today, fields like genetics and molecular biology support Darwin’s basic ideas about evolution Biogeography Darwin recognized the importance of pattern in the distribution of life Biogeography is the study of where organisms live now and where they and their ancestors lived in the past Two biogeographical patterns are significant to Darwin’s theory: Closely Related but Different This is a pattern in which closely related species are different in slightly different climates To Darwin, the biogeography of the Galapagos species suggested that populations on the island had evolved from mainland species Over time, natural selection on the islands produced variations among populations that resulted in different, but closely related, island species Darwin noticed that all the birds he had collected throughout the Galapagos were all finches Lines of Evidence: Geography Distantly Related but Similar This is a pattern in which very distantly related species develop similarities in similar environments Darwin noted that similar ground-dwelling birds inhabit similar grasslands in Europe, Australia and Africa. Differences in body structures indicate that they evolved from different ancestors, but similarities provide evidence that similar selection pressure caused species to develop similar adaptations Geographic Distribution of Living Species The Age of Earth and Fossils The Age of Earth Darwin viewed the fossil record as core evidence of evolution He proposed that Earth was hundreds of millions of years old, instead of a few thousand He argued that countless species of many different forms had appeared on Earth, lived for a long time and then vanished From viewing the remains found in rock layers, it was observed that species indeed changed over time. Lines of Evidence: Transitional Forms, Page 1 of 2 The Age of Earth and Fossils The Age of Earth – Half a century after Darwin published his theory, scientists discovered radioactivity – Scientists now use radioactivity to establish the age of rocks and fossils – Radioactive dating indicates that the earth is about 4.5 billion years old, which supports Darwin’s idea that the Earth was very old The Age of Earth and Fossils Recent Fossil Finds – During Darwin’s time, not enough intermediate fossils had been found to document the evolution of modern species from their ancestors – Since Darwin, paleontologists have discovered hundreds of fossils that identify intermediate stages in the evolution of many different groups of modern species – Exs: • Whales • Dinosaurs Birds • Fish Four-Legged Animals Comparing Anatomy and Embryology In Darwin’s time, scientists noted that all vertebrate limbs had the same basic bone structure But some were used for crawling, some for climbing, some for running and others for flying Homologous Structures Same Structure, Different Function What does it show? Evidence of a common ancestor Homologous Structures Darwin proposed that animals with similar structures evolved from a common ancestor with a basic version of that structure Similarities and differences among homologous structures help determine how recently species shared a common ancestor Homologous structures have also been found in plants Analogous Structures The clue to common descent is common structure, not common function NOT inherited from a common ancestor. Analogous Structures – Body parts that share a common function , but not structure – Same function, Different structure Exs. – The wing of a bee and the wing of a bird Analogous Structures Vestigial Structures Vestigial structures are those structures that are similar but are reduced in size and remain unused Humans have a vestigial structure. Can you name it? Vestigial pelvis and femur in a modern whale. Vestigial Structures Embryology Embryology is the study of the early stages of development of an organism Researchers noticed a long time ago that vertebrate embryos look very similar The same groups of embryonic cells develop in the same order and in similar patterns Embryology Vertebrate embryos have fold of tissue in the neck region called gill pouches In fish these develop into gills In human these same pouches develop to form inner ear bones. Embryology Lines of Evidence: Molecular Evidence Similarities in early development suggest a common ancestor Genetics and Molecular Biology Biochemists study and compare chemicals found in living things (DNA and Proteins) The genetic code is nearly identical in almost all organisms This is powerful evidence that all organisms evolved from common ancestors that shared this code DNA Sequencing