Evolution exam 1

Coynes theory of evolution

"life on earth evolved gradually beginning with one 'primitive' species - perhaps a self-replicating molecule - that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species and the mechanisms for most (but not all) of evolutionary change is natural selection"

evolution by natural selection then is a combination of randomness and lawfulness

-random mutations that generate an array of variation -a lawful process that orders this variation, keepin the 'good' and winnowing the 'bad'

important points about natural selection

1. adaptation happens over many generations -if an individuals phenotype changes during it's lifetime, that is not an adaptation -individuals don't ADAPT. what adapts? POPULATION *natural selection acts on individuals but its consequences occur in populations 2. natural selection acts on phenotypes, but evolution is simply changes in allele frequencies - if you don't have heritability, then you don't have evolution 3. natural selection has no goal, it isn't forward-looking 4. while selection acts on existing traits, new traits CAN evolve ex: exaptation: a trait has evolved a novel use that didn't exist in the ancestor so the trichomes are use as a defense mechanism for butterworts but when they were removed, it increased them being eaten by 18% (the adaptation was the trichomes?) secondary adaptations can arise eventually making brand new structures. 5. natural selection does not lead to perfection. species do not perfectly adapt. 6. natural selection does not occur to benefit a population / species.

Darwins 4 postulates

1. individuals in population must vary 2. variation has a genetic basis (heritable) 3. more individuals are produced than can survive 4. survival and reproduction are non-random... individuals that survive and reproduce most are those with favorable variations IF ALL ARE TRUE. then natural selection can occur

structural mutation: duplication

2nd copy of a gene or genes is inserted into the genome can result in a "gene family" with several different copies of orginial locus ex: globin gene family

Population

A group of individuals that belong to the same species and live in the same area at the same time

biological evolution

Change in allele frequency of a species or population over time seeks an understanding of the origin and maintenance of biological diversity *this may or may not result in a change in the mean phenotype of a population most dna doesn't code for anything.. more later

postulate 2: heritability in the finches

so when looking at the mid-parent and offspring beak size from before and after the drought you can see that the sizes of the beaks from parent to offspring is relatively in the similar ballpark. as drought occurred, the size of peak from the parent decreases but as well as the offspring. (positive regression slope)

darwins first and second chapter showed what>

that individuals in a population MUST vary

What is evolution?

the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. "Evolution is 'only' a theory. (Coyne p.14)" scientific use of the word differs greatly from the more common use of the word. In scientific terms it is well thought and well supported group of propositions meant to explain facts about the real world.

with-in species polymorphism ?????

variation is inherited, not only caused by the environment

postulate 1: is the finch population variable

yes, on the chart there are small beaks, ranging to large beaks. -main measure of genetic variation in a quantitative trait... HERITABILITY: proportion of all variation due to genetic differences among individuals (broad sense) for the finch experiment: you would measure the mid-parent length of beak and compare it to the offspring (when grown) and compare the sizes of the beak.

postulate 3: do individuals vary in their success at surviving and reproducing?

yes. the drought had killed 84% of the finches why? food abundance went down what about the food that was left? seeds increased in both size and hardness - the tribulus cistoides began to dominate (their beaks being able to break open the seeds, lead to their success to survive)

structural mutations

affect more than 1 DNA base deletions: occur when a segment of chromosome is left out small and not in a gene? not a problem in a gene and not a multiple of 3? frameshift

Natural selection is a process...

alleles that produce better adaptations become more frequent over time requires these things: variation (it exists) -heritability (comes from mutation) -more offspring produced than can survive -genetic variation must affect individuals probability of leaving offspring coyne pg 117

postulate 4: are survival and reproduction nonrandom

as we saw, the large beaked finches were the only ones able to break the seeds and eat (t. cistoides) therefore, the big beaked birds survived better

another example of testing natural selection

beak size in the finches. all the birds are all close relatives but differ in beak size and shape. interspecific differences results from diet.

jerry coyne

change alone cannot explain the marvelous fit between individuals and their environment ...and it doesn't mutation = random filtering of that variation by natural selection that produces adaptations and natural selection is manifestly not random natural selection is the nonrandom survival of random variants - dawkins

inversions: structural mutations

chromosome breaks in 2 places and is flipped around. humans and chimps have about 1500 inversions fixed in one species of the other. result in duplications and deletions after meiosis and also postzygotic isolation: which leads to reproductive isolation posting barriers for the species

testing the hypothesis of natural selection

darwins 4 postulates -individuals in population vary -variation is heritable -individuals vary in their success at surviving and reproducing -survival and reproduction is nonrandom (each of these are testable)

structural mutation continued

deletions; cystic fibrosis occurs with a deletion of 3 bases in a sodium channel gene

so where does genetic variation come from

dna mutations genes (interspersed throughout chromosomes) are composed of dna and mutations can arise in a number of ways

mutation rates

dna replication is riduculously accurate but varies across orgainsms insertion/deletion rate is 1/17th the rate of base subsitiutions in flies gene duplication? 1.2 X 10-7 (1 out of 10 million) for C. elegans

effects of mutations

effects on fitness (number of offspring organism leaves in next generation lethal: deadly deleterious: harmful to survival and reproduction (most and most recessive) 1% reduction in fitness on average in humans neutral: have no fitness effect beneficial: helpful to survival and reproduction lethal and deleterious mutations WAY outnumber beneficial mutations -natural selection acting on small amount of beneficial mutations prevents population decline

biological evolution continued

evolution (sometimes) may cause increased complexity but organisms don't become more advanced. Ex: fleas and lice loss of wings or tapeworm loss of digestive tract

coynes 6 components of that summary

evolution, gradualism, speciation, common ancestry, natural selection, and non-selective mechanisms of evolutionary change

reciprocal translocations

exchange of chromosome segments between two NONhomologous chromosomes 2 found between chimps and humans ex: chromosome 4 and 20 transolcate segments

Evolution as a theory

for a theory to be considered scientific, it must be testable and make verifiable predictions

chromosomal fusions and fissions

fusion: 2 nonhomologous chromosomes joined (chromosome 2 in humans) fissions: chromosome splits - 14 and 15 pre-primate results in changes in chromosomal numbers

germ line mutations vs somatic mutations

germ line: cells that form gametes (in most animals) somatic: (not passed on) all the other tissues of the organism

1st statement on the importance of variation in natural selection

heritable variation is important for evolution to occur. - "no one supposes that individuals of the same species are cast in the same mould. these individual differences are important for us, for they are often inherited.. and they thus afford materials for natural selection to accumulate"

mutation rates per gene

higher than per nucleotide genes have lots of nulceotides protein-coding loci in humans and fruit flies= u=10'5 and u= 10-7 mutation rates per genome higher than per gene humans have 3 billion base pairs mutation rate u=10-8 about 3 dozen new point mutations scattered throughout genome

synonymous and non-synonymous

most 1st and all 2nd site subsitutions are NONsynonymous and most 3rd sites are synonymous -results in different evolutionary rates

Example of darwins 4 postulates going into play

moths: Biston Betular 1. individs in population must vary -black and white moths occur in same population 2. Variation has genetic basis (heritable) -a single gene codes for difference AA, Aa, aa 3.more individs are produced than can survive -many more moth eggs are produced, many moths are eaten by birds before they reproduce 4. survival and reproducion are non-random -pre-industrial (white moths more fit) post-industrial (black moths more fit bc of the dirt produced and left on trees new the factories) kettlewell results: different survivorship on different backgrounds, results in increase of melanic form, change in freq in industrial areas (black alleles increased in freq)

4. Another prediction of common ancestry

organisms fall naturally into hierarchical system of grouping -evolution predicts and requires this ex: larger groups of organisms that share some homologous feature can be divided into smaller groups that share more and more features in common

furthermore on phenotypic change

phenotypic change from one gen to another may not be evidence of evolution ex: human height why? because human height has occurred in changing environments

effects of mutations on pheotypes

pleiotropy: single gene mutation affects multiple traits ex: dwarfism caused by achondroplasia decreases bone length in many parts of the body decrease in lifespan ex: cats with blue eyes are invariably deaf

mutations: ultimate source of variation

point mutations: single base is changed -must be in gene to effect physical change types: synonymous and nonsynonymous ex of nonsynonymous: sickle cell anemia, mutation on the 2nd position of codon causing sickling

allele frquency

proportion of gene or random bits of DNA copies in a population that are a given allele ex: A % versus a %

whole- genome duplication

rare in animals but common in plants (speciation)

1. Evolution

"a species undergoes genetic change over time" "change in allele frequencies over time" Do we see this? absolutely, and even the most ardent creationists can't and don't debate this

3./4. speciation/ common ancestry

"flip sides of the same coin" all of life on earth shares a common ancestor and diversity arose through "speciation" predictions: all of life should share some fundamental traits, homologies (shared derived characters) common to all of life -DNA code -Biochemical pathways -transcription and translation machinery

5. Natural selection

Natural selection is both revolutionary and disturbing bc: it explains apparent design in nature by a purely materialistic process that doesn't require creation or guidance by supernatural forces " -coyne and that was darwins big IDEA

continued structural mutations: insertions

insertions: segment of DNA added insertion not a multiple of 3 and in a gene? -frameshift (insertion adds 3 base pair so for it to be frameshift it would just be 1 base pair) multiple of 3? potentially problematic. ex" huntington's disease caused by 3-6 bp insertions in the huntington gene

2. phenotypic change (usually gradualism)

it takes several (thousands of) generations of large-scale phenotypic change to occur do we see it? absolutely. Ex: changes in # of ribs across eight trilobite lineages BUT not all species change at the same rate. why? and what are the reasons for it? speciation, character change, and stasis coyne says "if evolution meant one gradual genetic change within a single species, we'd have only one species today"

Example between m nasutus and m guttatus (plants)

m. nasutus flowers are smaller flowers and adapt better to drier areas than the m guttatus flower. Thus the nasutus flower, flowers earlier and for a shorter amount of time. their adaptation is the earlier flowering time. So then you can test whether the plants shift thier flowering time in response to drought: answer is yes they do. post drought plants flowered earlier than pre-drought plants. -variation is inheritable and heritable (hybrids are intermediate) -is survivorship random from the drought? YES some flowered = survived, and some died before flowering

micro- and marco- evolution

mircoevolution: small-scale genetic/phenotypic changes within a population marcoevolution: large-scale results of genetic changes in populations: speciation and the evolution of large scale trends within species traits