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Evolution final
notes for evolution final
52
Biology
Undergraduate 4
05/11/2012

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Term
Lamarck
Definition

He focused on inheritance of acquired characteristics.

Independent origins of life and linear progression.

 

Term
Who was Lyell?
Definition

He was a geologist that advanced uniformitarianism which is the idea that history repeats itself.

Darwin and Wallace ideas of evolution via natural selection would stem from Lyell's idea of uniformitarianism.

 

Term
Uniformitarianism
Definition

Is the theory that Lyell advanced that geological processes that we observe today have operated over vast stretches of time and explain the geology of the part and the present.

The major geo. features now are like the same geo. features of the past.

Term
Who is Malthus?
Definition

Malthus influence Darwin.

He had the idea of diminishing returns. Specifically pop'n grow exponentially and food source grows linearly, so eventually pop'ns will run out of food. Darwin realized that this idea could be applied to plants, animals, and human pop'n. Influenced Darwin and Wallace b.c Darwin now has a mechanism. Combined with variation among individuals, struggle leads to natural selection.

Term
Wallace
Definition
The reason why Darwin published. Essentially Darwin and Wallace had the same idea about natural selection. He sent Darwin a letter and then Darwin wrote things down to produce the Origin of Species. Codiscoverer of natural selection. Thought about the idea of natural selection in SE Asia with a malarial fever.
Term
Who is Darwin?
Definition
He wrote the Origin of Species based on 2 principles: natural selection drives evolution and all living things have a common ancestry. Darwin differs from Lamarck b/c he suggests a common ancestor, not suggesting inheritance of acquired characteristics, and not linear progression of forms thru time. He shook society b/c humans have a common ancestry with other things and natural selection which is not a pastoral theory of place.
Term
Natural selection
Definition
the evolutionary process that in which beneficial alleles increae in frequency over time in a pop'n due to increased survival and reproductive success of individuals carrying those alleles. It is a consequence of variation within the pop'n, inheritance, and the differential fitness across indiviuals who have different values for that trait. It is very gradual and depends on chance, short-sighted, probabilistic
Term
Fitness
Definition
Is the expected reproductive succes of an individual relative to other members of the pop'n.
Term
Adaptation
Definition
Is an inherited trait that makes an org. more fit in its env.(both abiotic and biotic) and that has arisen s a result of the direct action of natural selection for its primary function. Example is the cactus. The cactus has a waxy outercoating to absorb water, it also has the ability to store water, and can survive in the high temperatures of the dessert. It also adapted to the biotic factors by evolving spines which is used to protect it from predators. To be an adaptation, a trait mut have been shaped by nature to serve the same primary function that make it beneficial today.
Term
evolution
Definition
is any change across successive generations in the heritable characteristics of biological pop'ns.
Term
vestigial traits or structures
Definition
is a useless or rudimentary version of a body part that was one used by ancestors. Stuctures that were once used by now do not have a function. Examples include pseudogenes, wisdom teeth, appendix, goose bumps, and tonsils. They are important b/c since they are no longer used it can tell us about our ancestors and why or when did they use them. They are important b/c it can tell u how the ancestor looked, what functions were important, and if they look like the ancestor and provide evidence for evolution.
Term
Phylogeny
Definition

is the pattern of relatedness among evolutionary units such as individuals, genes, pop'ns or species

 

Term
phylogenetic tree
Definition
us a graphical representation of a phylogeny in the form of topology. A visual rep. of the pattern of relatedness among evolutionary units.
Term
rooted tree
Definition
has common lineage from which all the species on the tree indicated at the base of the tree. As a result the direction of the tree indicated the passage of time.
Term
unrooted tree
Definition
does nt fully indicate the direction of time, therefore time is not explicit
Term
branch lengths
Definition
are a unit of time. When branch lengths are drawn with different lengths then they rep. the amount of evolutionary change measured as the actual or estimated # of changes in the DNA sequence or other characteris that have occured along a given branch. Some trees like the primate phylogeny have branch tips aligned in which these trees are intended to convey only the pattern of relationships among various species displayed.
Term
Chronogram
Definition
is a tree that does not have branch lengths, so only topology matters.Branch length does not matter.
Term
homoplasy
Definition
a similiar trait tin 2 species and b/c of convergent evolution rather than common ancestry, reconstructing the phylogenies may be misleading. U might think that they have a common ancestor b/c same traits but it is true b/c they have different lineages.
Term
Phylogram
Definition
is a tree that represents evolutionary change with branch lengths.
Term
Chronogram
Definition
is a tree that reps. evolutionary change with branch
Term
Monophyletic
Definition
a taxonomic group consisting of all the descendents of the group's most common ancestor and no other members.
Term
Paraphyletic
Definition
contains the group's most common ancestor by not all of the descendents.
Term
polyphyletic
Definition
do not rep. proper evolutionary clades. A group that does not contain a common ancestor of its member and/ or all the descendents of that common ancestor. Just a few descendents with no common ancestor included.
Term
Saltation
Definition
is the idea that mutation is the major force driving evolutionary change. We see big jumps between character states and this ws right after Mendel's discovery.  This was the major competitor to natural selection as the dominant mode of evolutioanry change in the early 20th century.Driven by mutation and suggest that ir ws constant mutation that cause change and not differential fitness. Natural selection on the other hand is driven by differential fitness.  
Term
Thomas Hunt Morgan
Definition
worked with fruit flies and showed visually how recombination happened. Usign fruit flies he showed that genes were physical things that carried chromosomes. Laid the ground for modern synthesis.Made it possible to build quantitative theories of evolution. He showed what genes were and nody had seen genes. Also, showed physically that genes are on chromosomes and they undergo recombination,
Term
R.A.Fisher
Definition
Laid the foundations for much of modern synthesis(ANOVA and likelihood) and showed Mendelian inheritance could lead to continous variation in traits, which led to his founding of quantitative genetics. Promoted natural selection as the primary cause of evolution.
Term
Sewall Wright
Definition
Proponent of the effects of genetic drift and inbreeding on evolution. Developed adaptive landscape.
Term
adaptive landscape
Definition
convienent metaphor for thinking about how fitness varies according to a combo. of the traits that u have. Tells us how natural selection will move pop'n. Natural selection should cause the pop'n to move uphill(higher fitness). Fitness landscape is a way of thinking of evolution at multiple loi. A heuristic rep. of fitness as a function of genotype and phenotype. (Used by biologist to envision the course of evolutionary change.
Term
J.B.S. Haldane
Definition
showed how easily natural selection could explain observed evolutionary change(peppered moth)
Term
What was Fisher, Wright, and Haldane's important contribution to evolutionary biology?
Definition
Together they were able to use math methods to show that there was no conflict between Mendel and Darwin. Mendel's mechanism of inheritance ws the missing piece of Darwin's puzzle. They used math methods to prove natural selection.
Term
Dobzhansky
Definition
connected the math of the modern synthesis from abstraction to biological reality and studied the genetics of fruit flies in natural pop'ns.
Term
Hardy Weinberg equilibrium
Definition

serves as the null model for the studies of allele frequencies and genotype freqs. in pop'ns.

5 assumptions

1. random mating(genotype freqs. given by allele freqs.

2. no differential survival

3. no mutation(no change in allele freqs. across genes)

4. infinite pop'n size

5. no migration

This model examines a trait encoded by a single locus with 2 alleles A1 and A2 to produce 3 genotypesA1A1,A1A2, and A2A2.

Term
3 LESSONS OF h-w EQUILIBRIUM
Definition

1. evolution will only take place if we violate one of the assumptions of the H-W model.

2. Under random mating, we expect the genotype freqs. from the allele frequencies

3. even if a pop'n is not currently at equilibrium, it can reach H-W equilibrium in 1 generation if assumptions are met.

calculate genotype freqs. by using (p^2+2pq+q^2)

Term
How do we calc. expected ratios of carriers to phenotypically recessive individuals?
Definition
2pq/q^2
Term
Directional selection
Definition

when one allele is consistently favored over another which is freq. independent selection. Selection drive allele freqs. in a single diretion, toward an increasing freq. of the favored allele. Eventually the favored allele will become fixed in a pop'n and it will replace all other alternative allele at the same locus. When an allele becomes fixed then it is said to reach fixation. Recombination can bring the allel together with another gene, the 2 of them together can go to fixation fast.

there are 2 ways to change

1. if we think about one gene at a time, then it can change id the speed on how fast the alleles change(S)

2. dominace pattern can also affect the frequency.

Term
overdominance
Definition
is the freq. independent selection that can act on eone locus wirh 2 alleles. AKA heterozygous advantage, the A1A2 heterozygote has a higher fitness than the homozygotes. So directional, natural selection depends on the current allele freqs. in a pop'n(sickle cell is an example). (Balanced polymorphism). The fitness of heterozygotes is the highest and the fitness does not depend on frequency. Neg. freq. selection, the frequency goes down as it becomes more favored(a higher fitness). Selection changes so it goes to the middle.
Term
balanced polymorphism
Definition
is a stable equilibrium that is polymorphic meaning that both alleles are present. Produced by overdominace and negative freq. dependence.
Term
underdominance
Definition
the A1A2 heterozygotes have a lower fitness than either homozygotes. In this case, natural selection will favor 1 allele over the other but which allele becomes fixed in a pop'n will depend on where the pop'n starts. Unstable equilibrium. Pos. freq. dependence selection pushes it to the closest extreme. If it is at high freq. the fitness goes up and vs.
Term
Genetic Drift
Definition

is the random fluctuation in allele freqs. over time due to sampling effects infinite pop'ns. There are 3 consequences

1. in a finite pop'n, allele freqs. fluctuate over time, even in the absence of natural selection

2. some alleles are fixed, others are lost, and the fraction of heterozygotes in the pop'n decreases over time.

3. Separate pop'ns diverge intheir allele frequencies and in terms of which alleles are present.

 

Term
Genetic drift influences evolution by
Definition

1.removing genetic variation form pop'ns decreasing heterozygousity

2.influencing the probabilty of survival of new mutations

3. acting in conjunction with migration to shift allele frequencies of pop'ns that are newly founded

4. acting during times of reduced pop'n size to shift allele frequencies

Term
Bottle neck effect
Definition

when pop'ns will fluctuate in size over time for an example to climate change

when a pop'n is small, genetic drift will have a larger effect for example increasing the rate at which heterozygousity is lost.

The effective pop'n size iod an actual pop'n is the number of indiviudals in an idealized pop'n(every adult reproduces)that would have the samw amount of genetic drift(measured by decreasing H) as the actual pop'n.

Term
Founder effect
Definition

is the coloniztion of islands typically happens by a small # of individuals

The initial allele frequencies can differ from the source pop'n simply on the basis of which individuals fo the colonization. and insular pop'ns are ussually conducive to drift.

Term
effective pop'n size
Definition
smaller than the census pop'n sizes. Statistical variation in the # of progeny, sex ratios that differ from 1:1, natural selection can increase variation in progeny #, overlapping generations, fluctuations in pop'n size.
Term
assortative mating
Definition
when individuals mate with those of the same genotype and phenotype and has less heterozygotes
Term
dissassortative mating
Definition
individuals tend to mate with those of different genotypes of phenotyes and has more heterozygotes.
Term
linkage disequilibrium
Definition

When statistical associations are present between alleles at the A locus and B locus, then there is linkage disequilibrium.

Migration, mutation, selection,and drift all make this possible, but recombination breaks it down. Physical linkage maintains LD.

Term
epistasis
Definition
the phenomenon in which alleles at 2 or more loci interact in nonadditive wats to determine phenotype.
Term
Natural thoery of Molecular Evolution
Definition
polymorphisms within species and substituitions between species are selectively neutral.(Motoo Kimuri). A controversial proposition,but definately a useful null model.One prediction is that Neutral Theory is that substituitions occur at a constant rate.
Term
Molecular clock
Definition
a technique used for assining realtive or absolute age based on genetic data. Assume that substituitions at neutral loci occur in a clockwise fashion, and so researchers use genetic distances between pop'ns to estimate the time since divergence. It can give more insite and information into the features and characteristics of ancestral background.
Term
Breeders equation
Definition

 R=h^2S

The mean trait value that is the avg phenotype of a continuously valued trait that changes over time as a consequence of natural selection. It relates the narrow sense heritability, the strength of selection measured as S and the consequences of selection measured as R.

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