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
Heritability of IQ wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Group selection wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Human genetic variation wikipedia , lookup
Genetic drift wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Population genetics wikipedia , lookup
Evolution notes Chapters 16 and 17 Variation • Bell curve is commonly seen in populations. Each extreme trait is not as common as the average trait Causes of variations – Mutation (genetically flawed copies of genes) – Recombination (crossing over during meiosis) – Random fusion of gametes (game of chance) Gene Pool • The total genetic information available in a population Hardy Weinberg Genetic Equilibrium (assumption 1) • The Population will NOT EVOLVE IF – No net mutation occur: allele frequency does not change overall because of mutations • Allele frequency is a measure of how often a certain allele exists in a population • If mutations occur; allele frequency could change and evolution occurs Hardy Weinberg Genetic Equilibrium (assumption 2) – Individuals DO NOT leave or enter a population • Immigration = one or more individuals moving into a population • Emigration = one or more individuals moving out of a population • If individuals leave or enter, evolution can occur Hardy Weinberg Genetic Equilibrium (assumption 3) – The population is large • If the population is small, only a small number of organisms may have a certain trait and that trait could easily disappear. Also the addition of a new trait has a higher probability of becoming dominant in a small population • Genetic drift (allele frequency changes in a population) is much more noticeable in small populations Hardy Weinberg Genetic Equilibrium (assumption 4) – Individuals mate randomly • Many species do NOT mate randomly and therefore certain traits will be favorable or become more predominant than others. This causes evolution Hardy Weinberg Genetic Equilibrium (assumption 5) – Selection does not occur • Natural selection (survival of the fittest) is the most significant factor that disrupts genetic equilibrium • Sexual Selection: birds often choose mates based on their color (the more colorful the male, the more attractive). The fiddler crab chooses their male based on the size of their claw. Anoles prefer bright colors on the male’s dewlap Stabilizing Selection • Organisms with the average trait have the highest fitness. This shows a normal bell curve Directional Selection • Organisms with traits that are towards one extreme have the highest fitness. – Giraffes developed longer necks – Anteaters developed longer tongues Disruptive Selection • Individuals with either extreme have a greater fitness than the average trait – Finches of Galapagos island had small beaks that were good for eating small seeds and big beaks for large seeds, but medium sized beaks were too big to get at the small seeds and not strong enough to break apart the big seeds Morphology • Internal and external structural appearance of an organism – Scientists used to use this to classify species – Now they use the biological species concept (a population of organisms that can successfully interbreed) in addition to morphology to classify a species • The many species alive today diverged from a smaller number of earlier species Geographic Isolation • One species becomes separated from some of its members by a barrier like a river, mountain, or a canyon. After many generations they may become so different that they can no longer interbreed. • These fish were separated by the isthmus of panama Reproductive isolation • Even though they could produce offspring, they do not breed in nature due to: – Different mating seasons (wood and leopard frogs) – Different calls (various populations of frogs) – Size variations (large and small breeds of dogs) Speciation • The formation of a new species • Punctuated equilibrium: species remain unchanged for a long time and then suddenly change very rapidly (this is opposite of “gradualism” Hominids • Humans and their immediate ancestors Primates • Anthropoids – Marmosets, monkeys, apes, and humans • Prosimians – Earlier forms of primates like lemurs, lorises and tarsiers Anthropoids • • • • • • Well developed collarbone Rotating shoulder joints Partially rotating elbow Opposable thumbs Similar dental formula Larger cranial capacity Humans • Bipedalism: the ability to walk on two legs • Cup shaped pelvis (to support upright walking) • S-shaped curve in spine (as opposed to a C-shaped curve in chimpanzees) • Shorter aligned toes • Larger brain, adapted for production of complex speech Australopithecus afarensis • “southern ape” of Africa. Lucy was found in 1974. they lived 3 3.9 million years ago • more recent Australopithecines showed increasingly larger cranium and other variations. Not all are thought to be our ancestors; some are believed to have given rise to other apes Homo habilis • Tool maker • Earliest known hominid in our same genus • 1.6-2.5 million years old Homo erectus • Upright human • Found in Java, China, Europe and Africa • Probably the first hominid to travel out of Africa • Lived 1.8 - .5 million years ago • They were hunters, used fire and many lived in caves Homo sapiens • Neanderthal (lived 230,000 – 30,000 years ago) • Had a slightly larger cranium than us – They were slightly shorter but heavy built – Used stone tools, lived in caves – Wore clothing made from animal skin – Were likely killed off by or out competed by modern Homo sapiens