Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Darwin & Evolution by Natural Selection Cactus eater Insect eaters Seed eaters Bud eater 2006-2007 Charles Darwin • Proposed a way how evolution works – How did creatures change over time? – by natural selection • Collected a lot of evidence to support his ideas – 1809-1882 – British naturalist Darwin’s Life • Darwin took a convoluted path on his way to developing his theory. • His first career was to be a doctor, but he could not stand being around blood • He then studied to be a pastor- his plan was to preach and study nature as a hobby • After completing school, he was invited to serve as a doctor/naturalist on an incredible voyage Introducing… the trip that changed it all… • In 1831, Darwin set sail on the Beagle for a voyage around the world • During his travel, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time = The Theory of Evolution • Darwin was interested in the diversity of organisms in specific areas and the specific locations species inhabited – How are there so many different organisms and why do they live in specific areas? • Darwin used these observations to scientifically explain the diversity of life on this planet. Voyage of the HMS Beagle • Invited to travel around the world – 1831-1836 (22 years old!) – makes many observations of nature • main mission of the Beagle was to chart South American coastline Robert Fitzroy Darwin found…clues in the fossils During his trip, Darwin found: Evidence that creatures have changed over time present day Armadillos Darwin asked: ancient Armadillo Why should extinct armadillos & modern armadillos be found on same continent? Voyage of the HMS Beagle • Stopped in Galapagos Islands – 500 miles off coast of Ecuador Galapagos Recently formed volcanic islands. Most of animals on the Galápagos live nowhere else in world, but they look like species living on South American mainland. 800 km west of Ecuador Darwin found…many unique species Darwin asked: Why were these creatures found only on the Galapagos Islands? The Galapagos Islands • Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands. – Why were these close islands inhabited by similar organisms that appeared slightly different? – Did these species evolve from a common ancestor after being isolated to different islands needing different survival skills? Pinta Island Intermediate shell Hood Island Saddlebacked shell Isabela Island Dome-shaped shell Darwin found… birds Darwin found: Many different birds on the Galapagos Islands. He thought he found very different kinds… But Darwin found… a lot of finches Darwin was amazed to find out: All 14 species of birds were finches… But there is only one species of finch on the mainland! Darwin asked: If the Galapagos finches came from the mainland, why are they so different now? Upon closer examination, Darwin found: The differences between species of finches were associated with the different food they ate. Simplified version of what happened Original Group of finches migrated to islands with some variation in beak characteristics. different beaks are inherited variations The beaks serve as adaptations that help birds compete (or reduce competition) for food Best suited birds survive & reproduce pass on the genes for those more fit beaks over time nature selected for different species with different beaks Original Species separated into many new species Relationship between species (beaks) & food From 1 species to 14 species… Warbler finch Cactus finch Woodpecker finch Sharp-beaked finch Small insectivorous tree finch Large insectivorous tree finch Small ground finch Cactus eater Insect eaters Medium ground finch Seed eaters Vegetarian tree finch variation Bud eater natural selection for best survival & reproduction Large ground finch Not Just Finches Original And then he thought…. and thought some more…. • Over the next 20 years Darwin spent much of his time thinking about the differences he had observed in living organisms during his travels. – He found that all the organisms he had sampled on the Galapagos, were distinct species different from those found on the mainland. – There were also different species found on each island in most cases. Darwin’s Hobbies… • Darwin also saw that humans choose organisms with specific characteristics- Breeding organisms with specific traits in order to produce offspring with identical traits is called artificial selection. • He spent a lot of time studying varieties of pigeons that had been bred • Darwin hypothesized that there was a force in nature that worked like artificial selection. – This force would “work” on the differences between organisms, just like a breeder picks out the best specimens to breed. The tipping point. • Finally in 1858, Darwin received a letter from another Naturalist- Alfred Russel Wallace. • Wallace was a naturalist that had spent a lot of time in the Amazon, and the Malaysian Archipelago – He, like Darwin had noticed the variations in animals between islands and the main lands • Wallace’s letter detailed an idea he had been considering: – Species change overtime, this change occurred in order for organisms to adapt to their environment. • Wallace had independently arrived at the same conclusions that Darwin had considered. The founders of Evolutionary Theory • Darwin realized it was time to publish his work. • He presented some of his own conclusions, along with a paper written by Wallace at a scientific meeting. • Within 18 months, Darwin had published: On The Origin of Species Evolution by Natural Selection • It was proposed that living things evolve as the result of: – Natural Variation – The struggle for existence – The survival of the fittest – The descent with modification Peacock tail evolution: http://www.pbs.org/wgbh/evolution/library/01/6/l_016_09.html Natural Variation • Darwin and Wallace both stated that organisms in nature had variation – Differences among individuals of a species What do we know? • Populations are a mix of different individuals • How do we know this? OBSERVATION Variation Struggle for Existence • Darwin was convinced artificial selection worked in nature as the result of overproduction and competition for resources = struggle for existence – Overproduction- organisms produce more young than the environment can support – Competition for resources- members of each species compete regularly to obtain food, living space, mates, and other necessities of life Survival of the Fittest • Fitness= an individual’s ability to survive and reproduce in it’s environment • Fitness results from adaptations – Adaptations = inherited characteristics that increase an organism’s chance of survival – = “Survival of the Fittest!” Survival & Reproduction of the fittest …the fittest! the traits that help an organism fit the environment better to survive & reproduce Survival & reproduction of the fittest bug… Natural Selection • Survival of the fittest = Natural Selection! – Traits are being selected and increasing over time (over many generations without human influences) • Over time, natural selection results in changes in the genetics of a population. These changes increase a species’ fitness in its environment. What determines survival? • Natural Selection- the environment removes individual that are not fit enough to survive – traits that help individuals survive • • • • survive predators survive disease compete for food compete for territory Adaptations – traits that help individuals reproduce • attracting a mate • compete for nesting sites • successfully raise young Survival & Reproduction of the Fittest Summary of Darwin’s Theory • Individual organisms in nature differ, and some variation is inherited • Organisms in nature produce more offspring than can survive and reproduce • Members of each species compete for limited resources • Unique organisms have different advantages and disadvantages in the struggle for existence • Individuals best suited to their environment survive and reproduce, passing the characteristic to their offspring. Individuals without the characteristic die • Species change over time due to natural selection… new species arise and others disappear • Species alive today have descended with modification from species of the past • All organisms on Earth are united by a common descent Darwin proposed natural selection as the mechanism of evolution • In summary: • Darwin saw natural selection as the basic mechanism of evolution • Survival of the Fittest: Darwin concluded that individuals best suited for a particular environment are more likely to survive and reproduce than those less well adapted – As a result, the proportion of individuals with favorable characteristics increases – Populations gradually change in response to the environment • Organisms without these variations are less likely to survive and reproduce.