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
Sexual selection wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Natural selection wikipedia , lookup
Evolutionary history of life wikipedia , lookup
Punctuated equilibrium wikipedia , lookup
Evidence of common descent wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Theistic evolution wikipedia , lookup
Population genetics wikipedia , lookup
History of Evolutionary Thought • Species- a group of organisms that can interbreed and produce fertile offspring. • Before 1850, most people believed… – The earth was formed by supernatural events – Earth never changes. – The earth was only a few thousand years old. – Each species was made by a divine creator. – Each species was made to fit its environment. – Species never changed and did not go extinct. Charles Darwin • 02/12/1809 – 4/19/1882 • At age of 22, sailed on • “HMS Beagle” to Galapagos islands Believed God created each species to match its habitat and a species never changed. Charles Darwin cont. • Five year journey, he • made observations and recorded them in a journal. Darwin began to doubt that species remained “constant.” James Hutton and Charles Lyell • Founders modern geology. • The crust of the earth has • • been slowly changing over time. Some of earth’s formations have taken millions of years to form. The earth is older than what people thought. George Cuvier • Species can go extinct. • Proved this studying fossils. • Ex.) Mammoth fossils • The earths crust is “layered” with fossils. • Deeper crust = older fossils Jean Baptiste Lamarck • Species change over time. • Species can “acquire” traits in their lifetime. • Ex.) Big muscles. • These traits can be passed to offspring. • Right idea, wrong explanation. Alfred Russell Wallace • Studied different species around the world. • There is a constant struggle for food. • Weaker individuals will die out. • Survival of the fittest. Thomas Malthus • Applied Wallace’s concept • • • • to humans living in London. Population growth was very high. People were dying due to starvation and disease. The environment cannot support everyone. This applies to all species. Lamark Species do change Wallace Sent copy of his essay to Darwin Darwin realized these were same ideas he had Malthus Population ideas apply to all species… Darwin felt ideas applied even more directly to plants and animals Lyell Earth old enough for change to occur, causing Darwin to question if life could change as well? Charles Darwin • In 1859, Darwin published “The Origin of Species.” Major points of Darwin’s book: • Organisms have traits that help them survive. • Species do change over time. • These gradual changes may cause one species to change into new species. • African apes are close genetic relatives of modern humans. Darwin’s Theory – Evolution by Natural Selection What causes evolution? • Evolution is the GENETIC change in members • • • • • • of a species over time. Darwin’s most important insight was that members of a species vary. Ex) Livestock Farmers use variation in artificial selection or “selective breeding” Nature provides the variation, humans select and breed useful variations to improve crops, etc. Later, Darwin stated reason for why species in nature change… Called “natural selection” … Natural Selection • Natural Selection is the “process” that drives evolution. • Process by which individuals that are better suited to their environment survive and reproduce most successfully. Natural Selection 1.) Every species contains variety. Causes? 2.) Living things face a constant struggle for existence. Why? 3.) Only individuals that survive can reproduce. “Survival of the fittest”? Adaptation? 4.) Results in changes in the gene pool. How is genetic change measured? 5.) Entire species is now better suited for survival. HOW? If not? Darwin’s Theory – Evolution by Natural Selection Natural Selection (Review) • Variation (caused by genetics)= neck length • More individuals than can survive= competition for leaves in trees • Members with best adaptation will survive and • reproduce – long neck Results in genetic change= frequency long neck allele increasing and short neck allele decreasing • Results in next generation of the species being “genetically better” than the previous generationnumber of giraffes with long neck more prevalent in population Evolution and Natural Selection “Misconceptions” • Q: Why is variation important? • A: Variation is key because the environment an organism lives in is constantly changing -ex) England- factories/pollution -What if amongst the moths there was no variation… only peppered no dark… -Result might have been… EXTINCTION Evolution and Natural Selection “Misconceptions” • Q: What is an adaptation? -adaptation is NOT a process by which organism “changes” to survive -It is incorrect to say… “When the environment changed the dark moths were the best at adapting and remained hidden from the birds.” -It is also incorrect to say… “The moth population adapted to the environment after the pollution increased and thus lived.” Evolution and Natural Selection “Misconceptions” • A: An adaptation is a trait an organism is born with that because of what the environment is like it increases the organism’s chances of surviving -peppered moths could not consciously change their color from peppered to dark -this is what you are implying if you write “the dark moths were the best at adapting to …” -NO organism can change its genetic traits (DNA) Evolution and Natural Selection “Misconceptions” • Q: Definition of evolution is- genetic change in a species over time… What does genetic change refer to? -It is understood that an organism can NOT change its DNA …so how does genetic change apply… • A: Genetic change means changes in allele frequency in the gene pool, which lead to changes in genotypic frequency, and then changes in phenotypic frequency as well Evolution and Natural Selection “Misconceptions” • Q: Entire species is better suited … means… • A: “The entire population of the species is now better suited for survival.” • Q: How would this apply to the peppered • moths? A: The species of moths is now better suited for survival because the population consists of mostly dark moths. Evolution and Natural Selection • The definition of evolution is … -genetic change amongst members of a species -this is happening in the population in terms of the alleles causing changes in both genotypic and phenotypic frequencies… Evolution and Natural Selection • We can describe the genetic change amongst the population two ways… • Directional selection vs. balancing selection • Both terms describe how the allele frequencies are changing as a result of natural selection… Evolution of Peppered Moths… Genetic Change Amongst the Peppered Moth Population 1.2 1 Allele Frequencies 0.8 p 0.6 q 0.4 0.2 0 Year 1 Year 3 Year 5 Year Year 7 Year 9 Evolution of Peppered Moths… • Frequency of the dominant allele (p or peppered) decreased • Frequency of the recessive allele (q or dark) increased • This is directional selection Directional Selection • Frequency of an allele is pushed in one direction without opposition Sickle Cell Anemia: The Puzzle • Recessive disease originated in Africa • Africa 1/100 aa • United States 1/500 aa • Why has natural selection not acted against the sickle cell allele (a) in Africa to reduce its frequency? Genetic Change Amongst the African Population Allele Frequeny 1.2 1 0.8 p 0.6 q 0.4 0.2 0 1 2 3 Year 4 5 Balancing Selection • Two opposite forces affect the allele in a population • Allele frequency may vary year to year, but over time usually remains same (value) ex) sickle cell allele (aa) – lethal - death by sickle cell = decrease ex) sickle cell allele (a) – favorable - (Aa) resistant to malaria = increase ex) no sickle cell allele (AA) – lethal - death by malaria = decrease How Species Form? • Natural selection favors variations that increases a species survival. • If environment changes, natural selection will occur. • Can members of a species change enough to form a new species? • Speciation- generation of a new species How Species Form? • Ecological Races (subspecies) – Populations of the same species that differ genetically because they have adapted to different living conditions. – Still members of same species. Why might members of same species be separated? • Different groups of subspecies may • • • become isolated from each other. Isolation makes it difficult for members of the same species to mate. Geographic Isolation Populations separated into different environments due to geographical features (mountains, canyons, bodies of water, etc.) Speciation cont. • When geographical isolation prevents • interbreeding for long periods of time, populations in different places become increasingly different due to different environments. Eventually if the groups can no longer mate and create fertile offspring, they will be considered separate species. Macroevolution • Evolutionary relationships on a “large scale” • Scientists attempt to explain diversification of life • Scientists attempt at determining how living • organisms on Earth are related to each other “Common Ancestor” • Ex) Charles Darwin said… “Humans and apes shared a common ancestor” “Modern day whales had a distant ancestor that lived on land and walked on four limbs” Evidence of Evolution • Fossil Evidence • Structural Evidence • Developmental Evidence • DNA Evidence What is a fossil? • Any traces of dead organisms. • Organism must be buried by sediment. Usually happens in swamps, mud, tar pits, or the ocean bottom. • “Hard stuff” fossilizes. What can fossils tell us? • A glimpse into the history of an organisms • • past. Transitional species = “intermediate forms” Ex.) Whale evolution Structural Evidence • Comparing the way two organisms are put • together to determine if related or share common ancestor. Homologous Structures: structures that are similar in structure differ in function. Analogous structures= pertain to the various structures in different species having the same appearance structure or function but have evolved separately thus do not share common ancestor. Structural Evidence cont. • Vestigial structures: Structures reduced in size and have no present function; “remants of organism’s past” Developmental Evidence • Compares embryos of different species to determine • how closely organisms are related and whether or not might share a common ancestor. Longer early stages of development are similar between organisms= more closely related Fish Fish Salamander Tortoise Chicken Rabbit Rabbit Human DNA Evidence • DNA evidence supports the other three. • If species change over time, their DNA will also change. • Similar organisms=similar DNA sequences • More similar DNA = more closely related.