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48 Cards in this Set
- Front
- Back
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Fossils
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Preserved remains, traces of an organism found in rocks
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Comparative anatomy and embryology
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study of structure or embryos of different organisms and looking for similarities/differences that may be used to suggest evolutionary relationships
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Homologous features
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similar structures in organisms that have a common evolutionary origin
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Examples of homologous features
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Forelimbs of vertebrates - have different functions but structure is the same
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Phylogenetic tree
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Shows the evolutionary interrelationships among various species that are believed to have a common ancestor
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Divergent evolution
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The evolution of different species from a single ancestor species
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How are homologous features evidence of divergent evolution?
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Darwin's Finches were very common but they all had different beaks, the beaks reflected the food source of that island. Their beaks caused them to diverge from the original ancestor
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Adaptive radiation
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Rapid divergent evolution resulting in many species
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Analogous features
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Features that serve the same function but have evolved independently
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Example of analogous feature
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Organs in different organisms. Wings of birds and butterflies: serve the same function but the evolutionary relationship between the two are not close
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Convergent evolution
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The independent evolution of structures with similar form and function in unrelated organisms resulting from the influence of similar environmental factors. Starts with two different ancestors but over time, due to environmental pressures, they start to become more similar.
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Example of convergent evolution?
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Australian sugar glider and American flying squirrel
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What does the environment act as?
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The agent of change
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Parallel evolution
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The independent evolution of structures with similar form and function in two closely related organisms. They diverge from a common ancestor but only evolve to a certain point where they continue on a parallel path. Different to divergent evolution, in divergent evolution they continue to evolve further and further apart. whereas in parallel they reach a point of evolution and stay at the same stage
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Examples of parallel evolution?
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Eucalyptus trees
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Von Baer's Law
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General features, which are common to all the members of a group of animals, are developed in the embryo earlier than the more specialised features; which distinguishes the various members of a group.
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Vestigial structure
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A structure that over time has evolved into a non-functional structure
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Example of vestigial structure?
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The appendix in humans
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definition of evolution
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any change in the heritable traits (physical traits or behaviours) within a population across generations
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Population?
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any group of organisms coexisting at the same time and place, that are capable of breeding with each other
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Gene pool?
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all of the alleles at all loci in the population
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natural selection
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differential survival and reproduction of individuals in a population due to trait differences
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artificial selection?
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where a third party e.g. dog breeders, select certain organisms due to favourable characteristics and discard the rest
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genetic drift
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change in the gene pool of a small population due to chance.
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founder effect
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a small group of individuals becomes separated from the larger population, an acute example of genetic drift
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gene flow
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the movement of alleles between populations, due to immigration and emigration. Depending whether the mechanism is stabilising or de-stabilising you will keep the allele frequency between generations OR it will change over generations
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Biological fitness
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relative proportion of fertile offspring left by a fit individual. A fit individual is one that has adaptive features that best suit it to survival in its environment
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7 Factors of evolution
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reproduction, variation, excess potential offspring, selection, adaptations over time, chance effects, divergence and speciation
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Selection and fluctuating fitness
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the alleles for most genetic diseases are found in low frequencies in most populations, but in some populations the allele frequencies for genetic diseases can be high
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example of fluctuating fitness
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sickle-cell anaemia. Normally the allele frequency for sickle cell anaemia is very low, however in areas surrounding the equator it is found to be quite high. This is because malaria cannot grow in sickle cells, therefore people who have sickle cell anaemia are more biologically fit to survive in these areas compared to normal blood celled people
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Heterozygous advantage
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This occurs when an organism is more biologically fit if it has the heterozygous form of an allele variation. This is exemplified by sickle cell anaemia in places such as Indonesia. People with homozygous dominant red blood cells will not be protected against malaria and become very sick, people homozygous recessive sickle cells will become sick from sickle cell anaemia but will not fall prey to malaria. However, if a person has heterozygous for sickle cell they will be protected against malaria and be able to function normally while having both normal red blood cells and sickle cells in their body
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Define speciation
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the formation of a new species
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what steps must occur for speciation?
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1. Physical isolation of populations
2. divergent evolution |
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What are the two models of speciation?
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1. splitting
2. budding |
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Define reproductive isolating mechanisms
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Mechanisms that mean two species are reproductively isolated, they cannot produce viable offspring
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What are the 5 reproductive isolating mechanisms?
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1. Behavioural
2. Structural 3. Hybrid inviability 4. Hybrid sterility 5. Ecological or habitat |
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What is antibiotic resistance?
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Bacteria have certain form and in a population there will be some variations to that form that sets some bacteria apart from the rest. When an antibiotic is applied there are two options: a bacteria will be in a location where he doesn't receive the full does and thus will survive. Or, he has a variation which makes him resistant to the antibiotic. Thus, some bacteria will survive a dosage of antibiotics and will repopulate the population with offspring who are also resistant to the antibiotic
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What is comparative DNA sequencing?
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Looks at how similar organisms are through their DNA. The more similarities in DNA sequencing of two organisms, the closer evolutionarily they are.
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Define biochemistry
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The study of similarities between the biochemistry of organisms, to determine how evolutionarily similar they are. {e.g. enzymes, proteins, bases, other bodily chemicals}
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What is molecular hybridisation and how does it work?
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Uses polymerase chain reaction technology - DNA strand of species A is heated to uncoil and DNA strand of species B is heated to uncoil. One strand from each species is then combined and cooled to create a hybrid DNA strand. The more bases organisms have in common the stronger the molecule will be.
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define biogeography
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studies the evolutionary history of the Earth itself. You can look at fossils found on the Western coast of Africa and the Eastern coast of Australia and determine whether they came from the same origin, thus determining the history of the continents.
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What is stabilising selection?
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The two outliers are eliminated and the middle range is retained
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What is directional selection?
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one outlier on one side is eliminated and the rest is retained. The adaptive phenotype is shifted in one direction and one phenotype is favoured over others.
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Example of directional selection?
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The moths of the industrial revolution. Increased pigmentation allele was favoured so therefore its frequency was increased.
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What is disruptive selection?
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The middle range is eliminated and the outliers retained. Favours two phenotypic extremes at the expense of intermediate forms. The environmental pressures are pushing for divergence
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Example of disruptive selection?
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Darwin's finches. Due to a prolonged drought it resulted in a population that was bimodal for beak size. Competition was so intense that birds able to exploit either small or large seeds were favoured, but intermediate phenotypes were in low numbers.
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Factors favouring gene pool stability?
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large population, random mating, no gene flow, no mutations, no natural selection
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Factors favouring gene pool change?
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small population, assortative mating, gene flow, mutations, natural selection
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