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Transcript
Evolution Charles Darwin (English Scientist ) • Ideas 1st to be published • HMS Beagle – South America and South Pacific 5 year journey – Organism diversity led to curiosity about relations – Galapagos • Species-unique but similar • Led to idea of change over time (spent 22 years studying) • Ideas supported by fossil evidence Galapagos Unique Adaptations • Galapagos finch – Beak feed on Cacti • Galapagos Tortoises – Largest in body size and shape • Galapagos marine iguanas – Eat algae on ocean bottom (unusual food for reptile) – Large Claws-slippery rocks Charles Darwin • Base on Thomas Malthus idea “Human population grows faster than Earth’s food supply” Darwin realized organisms: – Struggle to survive – Struggle for food – Compete for space – Escape predators – Find mates – Find shelter Darwin and pigeons • Breed and watched survival • Traits--vary depending on size and inheritance • Artificial Selection-breed organisms with specific traits Darwin and Natural Selection • Mechanism for change in population • Organisms with certain variations, survive, reproduce, and pass their variations to next generation. • Organisms without variations less likely to survive and reproduce. Natural selection gradual process by which biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment. Darwin-how species change over time • Organism produce more organisms than can survive (fish millions of eggs) • Individuals in a population have variations (different color, size, speed) • Individuals with useful variations survive and pass traits (speed) • Overtime-offspring with certain variations make up most of population and may look different from ancestors. Darwin Determined that species did not arise independently; rather species are descendants of other species. Alfred Russell Wallace • Studied in Indonesia and Amazon River • Introduced Theory of Evolution • “Useful variations will tend to increase, unuseful or hurtful variations to diminish” • Some qualities of an individual may allow it to outlive another w/o qualities; pass qualities to offspring. Lamarck’s Model • Jean Baptiste de Lemarck • Individuals change due to environmental influences; organisms adapt based on individual needs • Acquired changes passed to offspring • “Use and disuse”- stronger is used; weaker if not used; overtime modified due to use or disuse; disuse may disappear. Relationship of work by Lamarck, Wallace and Darwin • Darwin refuted Lamarck’s hypothesis that individuals change to meet needs due to environmental stress and that these acquired characteristics • Wallace work overshadowed by Darwin; Now some celebrate Wallace more – Jointed presented to scientific community Visualizing Evolution Evolution difficult to observe – Short scale of human life – Contradictory to faith – Interpretations of data Evidence for Evolution • • • • • • Structural Physiological Fossils Anatomy Embryology Biochemistry Structural adaptations • Special structures and body parts • Mimicry • Camouflage Structural Adaptations-develop over millions of years • Size of teeth • Claws • fingers Mimicry—Structural adaptations that enables one species to resemble another. • Batesian- a species without any special defense mechanism mimics another species that predators avoid. (Same warning signs –coloring, pattern—no defenses—chemicals, spines) • Mullerian- more than one species with similar defense mechanisms all have the same coloration (Same warning signs and same defenses) Mullarian Mimicry-avoid being eaten; pass on genes Camouflage • Adaptation-blend in with surroundings Darwin’s idea of natural selection ex Mole Rat • Current animals probably resemble African rock rats • Ancestors avoided predators-size of teeth and claws • Ancestors survived passes variations to offspring • Over time-modern mole rat—blindness evolved b/c no survival advantage. Physiological Adaptations-(some rapid) • Changes in metabolic process – Bacteria that resist antibiotics – Insects and weeds resistant to chemicals that kill them. Fossils • Record of early life and evolutionary history • Still incomplete recordjigsaw puzzle • As become more complete, sequence of evolution more clear Anatomy • Homologous Structuresstructural features with a common evolutionary origin • Similar arrangement or function or both Anatomy • Analogous (aka “convergent”) Structures-Do not have common evolutionary (evolved independently) origin but similar in function Anatomy • Vestigial Structure-Body structure with no function in present day organism (ancestor’s may have used) – Eyes on blind mole-rat and cave fish – Forelimbs of ostrich Embryo • Earliest stage of growth and development of plants and animals. • Similarities among young embryos suggest evolution from a distant, common ancestor. Biochemistry • DNA and RNA comparisons • Determine evolutionary relationships b/w species • 1970s RNA and DNA nucleotide sequencing to construct evolutionary diagrams. Mechanism for Genetics and Evolution • Genetics used to explain variation among individuals of a population • Studies of the complex behavior of genes in populations-population genetics • Populations, not individuals evolve. Natural Selection acts on range of phenotypes in populations Gene Pool All the alleles of the populations genes. Allele frequencyPercentage of any specific allele in a gene pool. Genetic equilibrium Population in which the frequency of alleles remains the same over generations • Affect small populations • Observed in small human populations that have been isolated • Can result in an increase of an allele in a small population (Amish) Genetic Drift Alteration of allelic frequencies by chance events Disrupts Equilibrium Genetic Equilibrium Disturbances • Gene Flow-transport of genes by migrating individuals – Leaves-genes lost from gene pool – Enter-genes added to gene pool • Mutations, genetic drift and gene flow may significantly affect the evolution of small and isolated gene pools (island) • Natural selection most significant factor to change a gene pool. Natural Selection acts on variations • Variations can be inherited and they are controlled by alleles • Allelic frequencies in a pop’s gene pool will change over generations due to natural selection. • Three types of natural selection: Stabilizing, directional and distruptive Stabilizing selection • Natural selection that favors average individuals in a population Directional Selection • Natural selection favors one of the extreme variations of the trait Disruptive selection • Individuals with either extreme of a trait’s variation. Speciation • When members of similar populations no longer interbreed to produce fertile offspring within natural environment. – Geographic isolation – Reproductive isolation – Polyploid Geographic isolation • Physical barrier divides population – Prevents interbreeding between 2 groups • Founders Effect