8A_Evolution

Evolution A process that results in heritable changes in a population spread over many generations
 * biological evolution is change in the properties of populations of organisms that transcend the lifetime of a single individual
 * Biological evolution refers to populations and not to individuals
 * Changes must be passed on to the next generation (is heritable)
 * Can also be defined as change in the frequency of alleles within a gene pool (23 pairs of chromosomes: diploid) from one generation to the next

- Evolution refers to the development of change of characteristics of a line of organisms over time - It is a change, overtime, in the characteristics of pupoulation or of a species - Characteristics change as a consequence of natural election, and hence the characteristics must be those that are inheritable - How you classify things is also based on evolution

Origin of life -> evidence of evolution (homology etc.) -> Theory of Evolution (microevolution, mechanism) -> Reproduction Genetics (Year4)

Inferences: - Common ancestor - Change over time - Heritable change

Theories Full together laws, inferences, hypothesis. observations. A theory can be verified by a mass of facts, but it is still only a proven theory. Theories can never become facts, only explains laws and facts. Gives us a framework for explaining/exploring) a set of phenomenon. Should lead you to make predictions about what would you see if this were true. Can't see it directly, but you can see it's effects. Can be constantly changed and modified and tested. Evolution is a theory!

- Evolution is one of the most important concepts in all of science - Has become a unifying principle (explains connection between experiments) - It is a biological theory and not intended to be useful outside of science (eg. Pokemon) - Explains how new species come about

Charles Darwin
 * a naturalist who was interested in nature
 * at 22, a naturalist/gentlemen-accompier(?) aboard the Beagle (felt like a blind man habing given sight)
 * kept detailed records, collected fossils, drew them, collected samples
 * came to conclusion that all living things are related
 * how?
 * Darwin noticed 13 different species of finches within the different islands of the Galapagos
 * the finches appeared to be related to the only finch found on the mainland of South America
 * the finches all had different beaks that appeared to have different functions
 * An ancestral stock had migrated to the islands where they underwent profound changes under the different conditions of the individual islands, so they could survive and thrive (eg. some have hard and sharp beaks to crack hard nuts/fruits)
 * When Darwin left England in 1831 he accepted the religious dogma of special creation. On his return to England in 1836 he was convinced of the idea of "descent with modification", ie all organisms, including humans, are modified descendants of previously exiting forms of life.
 * Darwin's Dangerous Ideas: from a respected family, trained as a //clergyman//, was then believed that species were all created by God (divine will), went against all of natural history in Britain
 * took him 23 years of work to overcome his doubts, and write 'The Origin of Species' (on natural selection)
 * tied together a lot of things; why biology makes sense.

Natural selection:
 * key mechanism to explain origin of species
 * thinking process
 * Observation 1: Populations have the potential to increase exponentially (parents can have more than one child)
 * Observation 2: Populations are fairly constant in size
 * Observation 3: Natural resources are limited (food, space, water, mates, shelter) (Malthus)
 * Deduction 1: Only some organisms survive. There is a struggle for existence among individuals in a population
 * Observation 4: There is variation within a species, and variation is inherited (eg. in humans: hair, eyes..)
 * Deduction 2: Individuals with favorable variations are more likely to survive and reproduce (successful -> add to gene pool)
 * Deduction 3: Accumulation of variation over many generations is evolution
 * change is driven by environmental pressures (which is why many biologists are worried about global warming)
 * small changes happen in every generation, and these accumulate to form huge changes
 * made of
 * genetic variation
 * is inevitable in a population - caused by, mutation, cross fertilization, environmental influences etc.
 * the meiosis chacteristics that give them an advantage in a certain habitat is passed on to their offspringoverproduction of offspring (individuals in nature usually produce more young than needed to replace the parents, some must die)
 * struggle for existence (food, space, mates)
 * differential survival and reproduction
 * few individuals with advantageous (not best) traits -> frequency of the gene will increase in the gene pool
 * will determine the composition of the gene pool
 * eg. in hummingbirds, a 1 or 2mm difference in beak length can greatly affect how much nectar they can get. Hummingbirds with short bills won't be able to survive, can't reproduce. Eventually all hummingbirds have adapted to the flowers there
 * assumptions made
 * the traits seen must be found in the genes and hence be able to be passed on to the next generation
 * traits arose from random events like meiosis and mutation and not by intent (eg. even if you rebond your hair, your offspring will probably still have a higher disposition for curly hair)
 * 3 categories
 * Stabilizing Selection
 * extreme variations are culled form the population as there is selection against them
 * those with the established (middle range of the curve) adaptive phenotype are retained in greater numbers
 * reduces the variation for the phenotypic character
 * can be seen in the selection pressures on human birth weights
 * Directional Selection
 * associated with gradually changing conditions, where the adaptive phenotype is shifted in one direction and one aspect of a trait becomes emphasized (eg. coloration)
 * eg. peppered moths in England during the Industrial Revolution, who responded to the air pollution...
 * eg. climate change -> more tropical diseases (mosquitoes, malaria) in place like Alaska
 * Disruption or Diversifying Selection

Larmark's Hypothesis on the mechanism of evolution - he speculated that the giraffe's ancestors had stretched their necks in an attempt to get more food, and then passed this trait onto their offspring - A changing environment creates a need for certain features to be developed in order to survive - "Acquired Characteristics": ... - eg. believing that because there is a greater need to be book-smart, this trait will be passed down. (eg. graduates encourage to marry graduates in Singapore in the past). Book-smarts are acquired, not passed down. - difference: - Lamarckian theory was incorrect as the traits acquired by overuse of an organ can be passed down to the next generation - also believed that intent...
 * Larmarck || Darwin ||
 * Environment changes thus creating a "need to change || Variations of inheritable features which already normally exist ||
 * Development of new feature "in order to survive" or "so that one can survive ||  ||

Now: Believe that natural selection is due to sexual attraction, and not environmental pressure. - eg. giraffes fight with their necks to fight for mates - eg. birds that can build the best nests / most colorful / sing the best get the best females

Adaptation and Fitness - Adaptation: any //heritable// trait that suits and organism to its function in its niche

- eg. penguins huddling together to keep warm - It may be structural, physiological, or behavioral - Genetic adaptation has to be functional in the organism's natural habitat - It is not //acclimatization//, which is an organism's ability to adapt //during it's lifetime// to changing environmental conditions - eg. acclimatizing to high altitudes - Fitness: a measure of how well suited an organism is to survive in its habitat and its ability to maximize numbers of offspring to reproductive age - determined by 3 things - survival - fecundity (ability to reproduce) - mating success

Industrial Melanism - where natural selection pressures due to man-made influences have led to color changes in certain species - in the Industrial Revolution in Britain, vast amounts of coal, producing sulfur dioxide that killed off all the lichens. - The gene for dark color wis dominant, once the pressure of predation was removed, this variant quickly spread - (eg. in scotland still lighter colored moths)

Modern: - Antibiotic-resistant tuberculosis

Macroconcept: - Change occurs with time - Identifiable rules - Present depends on past.

look up Francis Collins, Georgia, Kenneth Miller, Niles Eldridge, Eugenia Scott read Wallace's book. See Darwin's Legacy on iTunes read the Flamingo's Smile

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