Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
173 Cards in this Set
- Front
- Back
|
On the Origin of Species - Charles Darwin |
- book containing 2 main points, 1. species change over time and 2. natural selection is the main cause of evolution - book was for the common audience it contained many proofs and gave him the credit of being the founder of natural selection |
|
|
Descent with modification |
- Term Darwin used to describe evolution |
|
|
1. Species Change Over Generation |
- Belief that cumulative changes over time could lead to speciation |
|
|
2. Natural Selection is the cause of evolution |
- how well individuals are adapted to their environment causes the gradual change within the species |
|
|
Theory - Scientific Definition |
- Hypothesis that has been confirmed, or create using observation and experiment - the best explanation for a set of phenomenon |
|
|
Evolutionary Though Before Darwin - Plato |
- believed that 2 worlds existed a perceived world and a ideal world - allowed no room for evolutionary thinking as the perfect version already exist |
|
|
Perceived World |
- the world we experience because of our senses it was believed to be an illusion of the ideal world |
|
|
Ideal World |
- the world that our senses were incapable of perceiving it was thought to be the perfect world - ex) Plato believed that all the variation we see amongst individuals within a species was an illusion of an original "perfect," individual |
|
|
Evolutionary thought before Darwin - Aristotle |
- ranked species in a hierarchy, and believed that every species were made to fill some void on it - implied evolution was not possible as there is no vacancies in his rankings |
|
|
Natural Theology |
- the study of nature with the intent of better understanding god - explained species adaptations as god creating all species to perfectly fit their environment implying evolution was not possible |
|
|
Carolus Linnaeus |
- natural theologist who invented taxonomy |
|
|
Taxonomy |
- binomial naming system with a 7 tiered classification system |
|
|
Modern Scientific Names |
- genus and species name - always underlined or italicized - generic name is capitalized while the specific name is not ex) Piranga rubra |
|
|
Scientific Names before C.Linnaeus |
- polynomial names that could be up to 12 latin words long |
|
|
Authority |
- scientific name that includes the name of the taxonomist that gave the organism its name ex) Piranga rubra Daudin - the name is capitalized but not italicized |
|
|
Third Species Name |
- given to species that have sub species (different races of the same species) it is italicized but not capitalized |
|
|
sp. |
- term given when you know the genus but not the specific name ex) Piranga sp. |
|
|
spp. |
- term given when there is more than one species within the genera |
|
|
Common Names |
- capitalized only if they come at the beginning of a sentence or a proper name ex) American herring gull |
|
|
Hierarchical Classification - Taxonomy |
- 7 level classification system, each level is referred to as a rank - ever species has a taxa (name) at every rank - Domain -->Kingdom --> Phylum --> Class --> Order --> Family --> Genus --> Species |
|
|
Domain |
- similar Kingdoms |
|
|
Kingdom |
- similar phylums |
|
|
Phylum |
- similar classes |
|
|
Class |
- similar orders |
|
|
Order |
- similar families |
|
|
Family |
- similar genera |
|
|
Genus |
- similar species |
|
|
Species |
- similar individuals |
|
|
Additional Classification Levels - Taxonomy |
- can be created using prefixes super, sub and infra - super > sub > infra |
|
|
Linnaean Classification |
- based on morphology - much more accurate than Aristotle's technique - ex) grouped flying fish with fish based on anatomy |
|
|
Aristotle Classification |
- based on function - ex) grouped flying fish with birds |
|
|
Fossils |
- impression of extinct organisms that have mineralized in rocks - usually do not resemble organisms alive today and can be found in strange places ex) sea shells on top of mountains |
|
|
Palaeontology |
- the study of fossils |
|
|
Georges Cuvier |
- french palaeontologist that made 3 important observations of fossils - 1. they occur in sedimentary rock layers - 2. each layer of rock has different sets of fossils - 3. fossils in older layers are different from fossils in newer layers - also created the theory of catastrophism |
|
|
Catastrophism |
- theory that periodically species would be wiped out by a major natural disaster and replaced by similar species from the surrounding environment - some new species are created supernaturally - does not agree with evolution - agrees with theologist |
|
|
James Hutton |
- created the theory of gradualism |
|
|
Gradualism |
- theory they geological features are created from slow geological processes ex) canyons forming from erosion - these processes have to occur over great lengths of time to create dramatic results |
|
|
Charles Lyell |
- created the theory of uniformitarianism |
|
|
Uniformitarianism |
- theory suggesting that the same geological processes that have been acting in the past are still acting now - this supports and expands James Hutton's theory of gradualism - suggests the Earth is very old, older than the 6000 years biblical scholars had predicted |
|
|
Jean Baptiste de Lamarck |
- first scientist to support the theory of evolution - use the fossil record as evidence that species gradually change over time - believed that changes occurred because species consciously responded to their environment by developing adaptations |
|
|
Lamarck's Principles of Nature |
- Use + Disuse - inheritance of acquired characters |
|
|
Use + Disuse |
- using organs would cause them to grow and strengthen and if they weren't used they would shrink and eventually disappear |
|
|
Inheritance of Acquired Characters |
- losses and gains made through use and disuse are passed on through generations |
|
|
August Weismann |
- disproved Lamarck's principles of nature using an experiment where he would cut off the tails of mice for 23 generations, the fact that tails still appeared after all these generations disproved Lamarck. |
|
|
Charles Darwin |
- natural scientist that created the theory of evolution by natural selection |
|
|
Darwin's Observations - S. America |
- differences between organisms in Europe and S. America were not due to climate - similar species are geographically close - new fossil species ex) miniature horse strange because horse were not native to S. America - species change with geographical distance - realized the Earth must be much older than 6000 ya |
|
|
Darwin's Observations - Australian Mammals |
- majority of Australian mammals are marsupials while everywhere else they are placentals - Australian mammals were ecologically equivalent to placentals - one reason for this could be Australia's isolation suggesting all marsupials are descended from one common ancestor - not because marsupials are better suited for Australian environment - 2 main theories to explain why marsupials are dominant mammals in Australia |
|
|
Dominant Australian Mammal (Marsupials) - Theory 1 |
- inland sea separated marsupials and placentals allowing only marsupials to cross the bering land bride spread through out the americas to antarctica and Australia - by the time the sea had dried up placentals had followed the same path but Australia already had become too isolated |
|
|
Dominant Australian Mammal (Marsupials) - Theory 2 |
- pre-historic Australia was much hotter and marsupials had an evolutionary advantage as they have lower BMR and are able to terminate pregnancy readily when resources are low therefore placentals were outcompeted - placental mammal fossils have been recovered in Australia - placental mammals have to invest a lot more in their offspring |
|
|
Dominant World Mammal (Placental) - Theory |
- outside of Australia monotremes and marsupials were out competed by placentals. - placental offspring is much more independant |
|
|
Invasive Species |
- species that are not native to the environment and compete with the native species directly by predation or indirectly by competing for resources |
|
|
Convergent Evolution |
- when unrelated species evolve into similar forms as a result of inhabiting very similar ecological niches - main reason marsupial and placental mammals can be considered ecologically equivalent |
|
|
Theory of Plate Tectonics |
- the lithosphere is segmented into several interlocking plates that are floating on the mantle leading to changes in geography overtime - as plates move apart molten rock fills the gap - as plates collide ones goes under to melt the other rises into a volcano/mountain |
|
|
Bering Land Bridge |
- land bridge connecting eastern Russia with Alaska that has appeared and disappeared several times over the Earth's history |
|
|
Darwin's Observation - Galapagos Islands |
- marine and land iguana's different from the mainland variety - 5 different varieties of mocking birds that are actually 5 different species, similar to the mainland species and different from island to island - 13 different variations of finches all similar to the mainland one - Tortoises with variation in shell shape from island to island |
|
|
Marine Iguanas |
- from the galapagos islands, had webbed fleet and flattened tails to help them swim, could also hold breath for long periods of time |
|
|
Land Iguanas |
- from the galapagos islands, differed from the mainland ones in coloration resembling the blackish color similar to the volcanic rock of the island |
|
|
Finches |
- found 13 different variations similar to the mainland one - all had different sized beaks corresponding to the food source of their island - as different individuals had become stuck on certain island they had changed over time to be better adapted to the food available on the island leading to speciation |
|
|
Tortoises |
- found on the islands, from island to island they had different shell shapes to better accommodate the food sources available - ones grazing on lower plants had dome shapes while ones grazing on higher plants had saddle shaped shells |
|
|
2 main Reasons Darwin thought species have the ability to evolve |
- 1. Artificial Selection - 2. Essay written by Rev. T.R. Malthus |
|
|
Artificial Selection |
- humans choose individuals to breed who have certain traits that are desired and continue this process to amplify that desired phenotype - this can lead to new breeds ex) all dogs are descended from the grey wolf - ex) all cruciferous vegetables (broccoli, brussel sprouts, cauliflower, kale + cabbage) are different lineages of the artificially selected wild mustard weed |
|
|
Rev. T.R. Malthus - Essay |
- wrote an essay stating humans have the capacity for explosive population growth but don't achieve it because of limited resources which leads to war, famine, diseases, factors that keep the population in check - Darwin thought a similar struggle for resources occur in nature and derived that only those best suited for their environment live long enough to reproduce |
|
|
Natural Selection |
- nature favours individuals that by chance are best suited for their environment, these individuals are more likely to survive and reproduce and greater numbers than those with out the favoured traits |
|
|
Evolution |
- gradual changes amongst populations in order for them to be better suited for their environment |
|
|
Basic Anatomy of a Plant |
- consists of nodes, internodes, axillary bud, terminal bud |
|
|
Plant - Nodes |
- regions where leaves develop and grow |
|
|
Plant - Internodes |
- regions of stem that are segmented by nodes |
|
|
Plant - Axillary Bud |
- part of the node that is able to give off a second branch with its own nodes and internodes |
|
|
Plant - Terminal Bud |
- node found at the end of the stem it can either continue on as an internode to have the stem grow or, become a flower to cease stem growth. |
|
|
Alfred Russel Wallace |
- published a short academic paper on natural selection intended for a scientific audience, this was before Darwin had published his own work on the topic. - it was vague and contained few lines of evidence |
|
|
Ernst Mayer |
- evolutionary biologist who summarized Darwin's theory as 3 inferences based on 5 observations |
|
|
Ernst Mayer - Observation 1 |
- all species can reproduce and increase geometrically if all the offspring survive |
|
|
Geometric Increase |
- increasing by a common factor ex) 2,4,8,16,32 |
|
|
Ernst Mayer - Observation 2 |
- populations usually remain stable in size |
|
|
Ernst Mayer - Observation 3 |
- resources available to a population are limited ex) food, nesting etc. |
|
|
Ernst Mayer - Inference 1 |
- individuals compete for survival, only a fraction of them survive to reproduce |
|
|
Ernst Mayer - Observation 4 |
- no 2 individuals in a population are identical |
|
|
Ernst Mayer - Observation 5 |
- some variation is heritable and passed on to offspring - individuals tend to resemble there parents |
|
|
Ernst Mayer - Inference 2 |
- survival of the offspring depends heavily on its genome - individuals who have received traits that are most advantageous in their environment are more likely to live and reproduce |
|
|
Ernst Mayer - Inference 3 |
- unequal ability to survive and reproduce leads to a gradual change in population over time (evolution) |
|
|
Subtleties of Natural Selection |
- 1. smallest unit capable of evolution is a population - 2. fitness - 3. Natural selection can only act on existing variation - 4. Natural selection can only act on heritable variation - 5. Natural selection is not progressive |
|
|
1. Smallest unit capable of evolution is a population |
- individuals are not able to change their own genetic make up they are stuck with what they are born with - over time a population can change in its genetic make up |
|
|
2. Fitness |
- relative capability to reproduce compared to other individuals in the population - this greatly depends on the environmental context ex) polar bears are fit in the arctic but not in forest environment - survival is important but in terms of only allowing you to reproduce ex) individuals who live shorter lives but produce more offspring may be more fit than those living long lives and producing few offspring |
|
|
3. Natural Selection can only act on existing variation |
- not able to create variation that comes from the random processes (mutation, crossing over, + segregation) - simply eliminates variations that are not suited for the environment - natural selection is unable to create a perfect organism ex) pigs with wings are more fit but doesn't happen because they don't have the requisite genes |
|
|
4. Natural Selection can only act on heritable variation |
- natural selection can not eliminate external factors that create variation ex) chemical leading to frogs with 6 legs stay in high frequency |
|
|
5. Natural selection is not progressive |
- does not always lead to increased complexity, there is no goal other than to allow individuals to better survive and reproduce in their environment - ex) snakes are more simple than lizards so you would think they are the ancestors when really lizards are snakes lost legs |
|
|
Evidence of Evolution by Natural Selection - Microevolution |
- 1. Drug resistance - 2. Pesticide resistance - 3. Industrial melanism - 4. Guppy colouration |
|
|
1. Drug Resistant HIV - Microevolution |
- uses enzyme reverse transcriptase - drug used to inhibit function of wild type reverse transcriptase - under normal conditions the mutant version was unfit - under selection pressure it became more fit - cocktail of drugs are used not to treat HIV to prevent the occurence of a resistant strain |
|
|
2. Pesticide Resistance - Microevolution |
- since the introduction of insecticides the number of resistant insects has exponentially increased - insecticide did no create resistant strain natural selection favoured it |
|
|
3. Industrial Melanism - Microevolution |
- Peppered moths have 2 morphs a light and dark one, when environment is polluted dark one becomes more fit because the tree's used to camouflage become darker, the opposite it true when pollution in the environment decreases |
|
|
4. Guppy Colouration - Microevolution |
- found in mountain pools, males are brighter than females and increase in brightness the higher up you go in elevation - this is because in lower elevation adults and offspring are under predation therefore being too bright leads to lower fitness - in higher elevations only offspring are under predation therefore male adults tend to be brighter to attract more mates |
|
|
Microevolution |
- evolution within a species ex) drug + insect resistance, industrial melanism, guppy coloration - people who oppose evolution usually agree with microevolution |
|
|
Macroevolution |
- evolution leading to speciation or creation of new genera and families - ex) biogeographical evidence, ring species, homologies and vestigial structure |
|
|
Evidence of Evolution by Natural Selection - Macroevolution |
- 1. Biogeographical Evidence - 2. Ring Species - 3. Structure, Embryological + Molecular Homology - 4. Vestigial Structures - 5. Fossil Record |
|
|
- 1. Biogeographical Evidence |
- Evidence gathered from the distribution of species - species located close to one another seem to be more often related than species located far apart even if they look more similar - ex) alpine trees in N. america resemble the ones in S. america but are distantly related, the S. american alpine trees are more closely related to the rain forest trees - species can look very similar but be distantly related due to convergent evolution |
|
|
- 2. Ring Species |
- species distributed in a ring shape because of some physical barrier - ex) salamanders at the north of a mountain range split into coastal and inland varieties, the further south you go the more different the salamander become even to the point of being different species suggesting greater isolation from one another |
|
|
3. Structural Homology |
- similarity in structures of organs in organisms that have very different functions suggesting a common origin ex) pentadactyl limb |
|
|
Pentadactyl Limb |
- limb common to all the vertebrates consisting of a humerus, radius, ulna and carpals - all the limbs within vertebrates are adapted for different functions - all vertebrates have the same set of bones because it was the starting point for natural selection to work on - lobe finned fish have been found with what would be the starting material for the pentadactyl limb |
|
|
Mammalian Skull |
- all mammals consist of a skull made of 28 skull bones of different shapes and sizes - skull of human and chimps consist of the 28 skull bones all in the same location - this indicates that the ancestor of all mammals had 28 skull bones the shape and size of these bones different in different lineages |
|
|
3. Embryological Homology |
- organisms with very different adult morphology look very similar in embryological development, alleles for controlling embryological development are shared between these organisms from a common ancestor - ex) animals such as humans and chickens have gills during embryological development because we still carry alleles from our aquatic ancestors |
|
|
4. Vestigial Structures |
- structures that had functioned in our ancestors but not longer function now - reduction in the size of these structures are often common - ex) whale hip bones are similar to the ones found in terrestrial animals with hind legs, whales did not lose legs due to use and disuse but those with smaller and smaller legs had a greater advantage in swimming |
|
|
3. Molecular Homology |
- shared traits at the molecular level |
|
|
What determines traits |
- traits are determined by proteins that are encoded by DNA via RNA |
|
|
Genetic Code is Universal |
- proteins from a human cell are coded for by the same DNA sequence that would be found in any other organism |
|
|
Genetic Code is Arbitrary |
- during translation amino acids do not directly bind to the mRNA codon they are attached to the tRNA that is complimentary to the mRNA - any tRNA can carry any amino acid |
|
|
Amino-Acyl tRNA Synthetase |
- enzyme that prevents the random pairing of amino acids and tRNA, they join an amino acid with its corresponding tRNA - contains 2 active site that almost guarantees the amino acid and tRNA pairing is correct - mutations in theses enzymes could potentially alter the genetic code and lead to greater rates of mutations than any other mechanism |
|
|
Conserved Traits |
- traits that have been maintained through out evolutionary time because they are so crucial to life - ex) the genetic code is a highly conserved trait |
|
|
Genetic Code |
- conserved trait that is evidence all living organisms come from a single common ancestor - if species were created separately and specifically they should all have their own genetic codes |
|
|
5. The Fossil Record |
- the order in which fossils appear supports the theory of evolution - there is a gradient of change in organisms in the fossil record |
|
|
Missing Links |
- fossils found that would be between to taxa ex) reptiles with bird like feathers |
|
|
Intermediate Link Between Fish and Amphibians |
- shared characteristics of both, had amphibian like head on a fish body - head allowed to turn back and forth which is advantageous on land |
|
|
Evolution of Humans |
- can be seen in the fossil record starting 4mya - gradual flattening of the face and increase in brain size - if these variations live simultaneously they would not be found sequentially as they are |
|
|
Blending Theory of Inheritance |
- early theory of inheritance before Mendel - the most common theory of inheritance in the 1900s - it rejected natural selection - ex) white x black moth = grey moth, even if the black moth would have an advantage according to blending theory it would disappear over generations - how could a rare mutant pass on alleles to become dominant if blending theory of inheritance was accurate |
|
|
Gregor Mendel |
- proved that the theory of blending inheritance was inaccurate - white and black alleles in moths do not create grey alleles and the black alleles can appear in later generations - hi findings were rediscovered after his death and unified with evolution to explain genes |
|
|
Population Genetics |
- study of the change in genetic make up of a population over time - explains evolution using mendelian genetics - the study of evolution at its smallest scale |
|
|
Population |
- grouping of individuals of the same species located within the same arbitrary area - individuals within a population are more likely to breed amongst them selves than with individuals from other populations |
|
|
Gene Pool |
- all the alleles of every gene from every individual within a population |
|
|
Fixed Allele |
- the only allele that exists for the gene, therefore all individuals are homozygous at that particular locus |
|
|
Allele Frequency |
- the number of alleles of interest divided by the number of total alleles at that locus |
|
|
p |
- frequency of the dominant allele |
|
|
q |
- frequency of the recessive allele |
|
|
Genotype Frequency |
- number of individuals with the genotype of interest divided by the total number of genotypes |
|
|
Phenotype Frequency |
- number of individuals with the phenotype of interest divided by the entire amount of individuals |
|
|
Hardy-Weinberg Equation |
- p^2 + 2pq + q^2 = 1 - this equation can be used to predict genotype frequencies if you know the allele frequencies |
|
|
Rule of Multiplication |
- the probability of 2 or more independent events occuring together is the product of their individual probabilities - ex) odds of flipping heads once is 0.5, but flipping it twice is 0.5 x 0.5 = 0.25 |
|
|
p^2 |
- frequency of the homozygous dominant genotype |
|
|
q^2 |
- frequency of the homozygous recessive genotype |
|
|
- Rule of addition |
- the probability of a single outcome occurring in 2 or more ways ex) there are 2 different ways an individual can be heterozygous for a gene q x p and p x q |
|
|
New definition of evolution |
- the change in allele and/or genotype frequencies of a population |
|
|
Genetic Structure |
- allele and genotype frequencies of a population |
|
|
Hardy-Weinberg Equilibrium |
- when a population is not undergoing evolution the genotype frequencies are expected to remain constant from one generation to another |
|
|
Causes of Evolution |
- there are 5 main mechanisms which occur for evolution to take place - 1. Genetic Drift - 2. Gene Flow - 3. Mutation - 4. Non-random mating - 5. Natural Selection - if none of these 5 are acting then the population is said to be under H-W equilibrium |
|
|
Hardy-Weinberg Assumption #1 |
- all individuals in the population have equal abilities in reproducing - genotype does not affect reproductive success - this is very rare in nature |
|
|
Selection against Recessive Phenotypes |
- can't eliminate the recessive allele as it can be concealed and carried on by heterozygotes |
|
|
Elimination of Rare Alleles |
- since these alleles are so uncommon the rate of elimination of these alleles is usually matched by the rate of production |
|
|
Heterozygote Advantage |
- when being heterozygote is associated with higher fitness than being either homozygous dominant or recessive - this phenomenon allows harmful recessive alleles to maintain high frequencies ex) CF |
|
|
Sickle Cell Anemia |
- genetic disorder caused by 2 copies of a recessive allele, even though it is lethal the allele maintains high frequencies because of heterozygote advantage - having this disorder leads to high death rates as it alters an amino acid in the hemoglobin protein, upon exposure to acidic conditions they clump and push the blood cell into sickle form which can't readily move through blood vessels |
|
|
Heterozygote Advantage - Sickle Cell Anemia |
- individuals who are heterozygotes at this locus are resistant to malaria - the malaria parasite has to get into red blood cells to feed before proliferating, this creates high acidic conditions and pushes certain blood cells to sickled state which are recognized by the immune system and eliminated |
|
|
Tay-Sachs Disease |
- having both copies of the recessive allele leads to having a dysfunctional hexomsaminase A, it is 100% lethal - used to be common amongst eastern European jews - heterozygotes for these locus have been seen to be resistant to TB but the mechanism behind this is yet to be known |
|
|
Hexosaminase A |
- lysosomal enzyme that is used to break down fats in the brain |
|
|
Cystic Fibrosis (CF) |
- individuals with both recessive alleles have a defective CFTR protein that does not pump enough chloride out therefore water can't leave, this leads to the mucous lining the air and digestive pathways to become thick and sticky - the recessive allele remains in high frequencies in the population because of heterozygote advantage |
|
|
CFTR Protein |
- protein found in the membranes of cells that line the air and digestive pathways, they pump chloride out which leads to the pumping of water out via osmosis |
|
|
Heterozygote Advantage - Cystic Fibrosis |
- heterozygotes for the disorder have been seen to be resistant to cholera - cholera bacteria produces a toxin that causes the CFTR protein to become overactive, pumping excess chloride and therefore excess water out into the digestive pathway, this can lead to fatal diarrhea - heterozygotes have dysfunctional CFTR proteins therefore the binding of this toxin does not create excess chloride and water pumping |
|
|
Phenylketonuria (PKU) |
- recessive allele produces a mutant protein that is responsible for breaking down phenylalanine - build up of phenylalanine can lead to degeneration of the nervous system if not treated potentially leading to learning disabilities - recessive allele maintains a high frequency because of heterozygote advantage |
|
|
Heterozygote Advantage - Phenylketonuria PKU |
- women who have been observed to be heterozygotes for this trait have lower miscarriage rates - this is because phenylalanine is responsible for breaking down a fungal toxin ochratoxin that can cause spontaneous abortion, they have moderately higher levels to prevent this. |
|
|
Selection Against Dominant Alleles |
- eliminates the allele faster than recessive alleles are eliminated because dominant alleles are associated with the corresponding phenotype in both homozygous dominant and heterozygotes therefore there is no where for the allele to hide from natural selection - there is a potential for complete elimination for the dominant allele - genetic disorders in humans are rarely caused by dominant alleles as natural selection had eliminated them much more conveniently |
|
|
Huntington's Disease |
- genetic disorder caused by a dominant allele, both homozygous dominant and heterozygotes are affected - causes the degeneration of the nervous system ex) loss of motor control, memory, and personality change - symptoms are not present until 35-45 and it is fatal 15-20 years after its onset - frequency of this harmful allele has remained stable because it does not produce lethal affects until late adult hood by which time most individuals have already reproduced |
|
|
Dwarfism |
- genetic disorder caused by a dominant allele - homozygous dominant are die early on and heterozygotes are able to lead a normal healthy life, including being able to reproduce the main reason why this allele remains in stable frequencies in the population |
|
|
Selectively Neutral Mutations |
- mutations that have no immediate effect on fitness - may persist in populations over time and build up over many generations - they can become suddenly better for fitness in the future if the environment changes in a way to favour it - older populations will have more accumulated variation than newer ones - important because it provides a population room to evolve |
|
|
Selectively Neutral Mutation Example - Warfarin |
- synthetic pesticide that deactivates vitamin K epoxid reductase - prevents blood from clotting and was used as a rat poison in the 1900s - few rats already had a mutant version of the enzyme that gave them resistance to warfarin and produced the same effect as the wild type enzyme (selectively neutral). - new resistant rat population recovered |
|
|
Hardy-Weinberg Equilibrium - Genes |
- when a population is said to be under HW equilibrium is it in with respect to a specific locus not the organisms entire genome |
|
|
Linked Genes |
- genes located very close to one another on the same chromosome - they behave the same way in terms of HW equilibrium ex) if one of the genes is under selective pressure it is highly likely the other is not in HW equilibrium also |
|
|
Discrete Characters |
- traits that are, "either or", ex) you either have CF or you don't |
|
|
Qualitative Variation |
- variation within discrete characters ex) different morphs of moth either black or white |
|
|
Polymorphism |
- existence of qualitative variation within the population ex) white and black moths |
|
|
Quantitative Characters |
- most characters are quantitative, not qualitative, few individuals have the extreme traits and most have the average one - the traits follow a continuum of variation which can be seen on a normal distribution - the wider the graph the more variation - natural selection can act on quantitative characters in 1 of 3 ways, directional, stabilizing and disruptive selection - these traits are usually polygenic |
|
|
Polygenic |
- several genes coordinate to determine the trait |
|
|
Directional Selection |
- when one of the extremes is being selected against, this leads to decreased genetic variation and a shift in characters |
|
|
Character Shift |
- the change in a populations average for a trait |
|
|
Stabilizing Selection |
- elimination of both extremes, this keeps the average the same but decreases genetic diversity |
|
|
Disruptive Selection |
- eliminates the average, this causes 2 peaks in the normal distribution and can lead to speciation |
|
|
Frequency Dependent Selection |
- when the effect of a trait on fitness depends on its frequency ex) how common the trait is in the population |
|
|
Negative Frequency Dependent Selection |
- as the trait becomes more common it decreases the individuals fitness - this promotes the coexistence of different morphs - ex) as white moths increase in abundance they become eaten more and therefore black moths start increasing to become the dominant and the same thing happens |
|
|
Positive Frequency Dependent Selection |
- as a trait becomes more common it increases the fitness editing out all but 1 morph - ex) in different colours of plant species pollinators favour the most common colour increasing its frequency - ex) purifying selection |
|
|
Predator Mediated Frequency Dependence |
- predators usually hunt the most common type of prey, this leads to negative frequency dependent selection |
|
|
Balancing Selection |
- natural selection maintaining a stable genetic variation in the population which leads to balance polymorphism - ex) negative frequency dependent selection, diversifying selection, heterozygote advantage |
|
|
Balanced Polymorphism |
- the maintenance of 2 or more distinct phenotypes within a population |
|
|
Sexual Selection |
- selection that occurs between interactions within the sexes and with different sexes, there are 2 types intersexual, and intrasexual |
|
|
Intersexual Selection |
- sexual selection that occurs between the sexes, when individuals choose mates based on their phenotypes - in many animals the females invest much more in reproduction than do males causing them to be more choosy when it comes to mates therefore they have a stronger impact on male evolution than males do on female evolution - can lead to sexual dimorphism |
|
|
Sexual Dimorphism |
- when 2 sexes of the same species differ in phenotypes - females are often bland and camouflage while males are brightly coloured - females prefer brighter coloured males even though they are more visible to predators because it is a sign of good health |
|
|
Sexual Selection - Grey Tree Frog |
- females prefer males that have longer calls than shorter ones - experiment showed that males with longer calls actually do have more fit offspring - this proved that female preference did reflect male fitness |
|
|
Negative Frequency Dependent Selection - African cichlid fish |
- there are 2 morphs, a left mouthed and right mouthed - right morph attacks from left and opposite for the left - as the right increases in frequency prey become more aware on the left side therefore decreasing its frequency and increasing the frequency of the left mouthed - this occurs in a cyclic manner causing frequencies to oscillate |
|
|
Intrasexual Selection |
- sexual selection that occurs within a sex ex) male horned sheep compete for mates but fighting with horns - bigger horns leads to stronger males - female choice is not a factor - also leads to sexual dimorphism |
