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94 Cards in this Set
- Front
- Back
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What is parsimony?
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The most parsimonious explanation for the occurrence of events is the one that assumes the process course found in nature with the least amount of steps.
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What is anagensis?
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Gradual change of ancestral species.
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What is cladogenesis?
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Evolutionary splitting event leads to speciation
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What is polytomy?
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Splitting into more than 2 species: the speciation occurred too quickly to discern which happened first
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What is phylogenetic analysis?
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The study of relationships among species to portray to some degree the real history of evolution
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What are some types of characters used in phylogenetic analysis?
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Morphological
Physiological Molecular Behavior Ecological Geographic |
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Why are characters not static?
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Can change through space and time as a result of selection.
Can change during ontogenic development Can intraspecifically vary: -body size, coloration -can be gender specific: sexual dimorphism -can change due to modification (phenotype= genotype + environment) can get lost/change as a result of preservation/preparation (ex. stuffed animals, specimens stored in ethanol, etc) |
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What is the plesiomorphic character state?
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The ancestral/primitive character.
Arose early in evolution of a taxonomic group In the state shared by organisms proceeding from it |
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What is the apamorphic character state?
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The derived character
The modified version of primitive condition, arose later in evolution New state |
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What is synapomorphy?
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A shared derived character
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What is autopomorphy?
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The uniqued derived character
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What is the cladistic method?
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Builds and tests relationships based on distribution of states of characters.
Created by Willi Hennig |
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What is the geologic time scale?
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Chronologic schema relating stratigraphy to time
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What is radiometric dating?
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Compares radioactive isotopes to decay products
Gives the absolute age of a rock or fossil |
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Explain the concept of molecular clocks/global clocks
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Zuckerkandl and Pauling came up with the idea through studying amino acid differences in hemoglobin lineages.
Their hypothesis was that there is a constant rate of evolution which provides a simple way of estimating phylogeny. Also enables us to estimate the absolute time since different taxa diverged. D= 2rt and t=D/2r D is the proportion of base pairs that differ btwn sequences R is the rate of divergence per base pair per Myr t= time since the species common ancestor |
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Why does a global clock not exist?
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Differences in generation time
Subsitution rates vary greatly across genes Slight differences in efficiency of DNA repairing |
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What is an advantage of molecular clocks?
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Useful because provide rough age estimates of lineages for which little to no fossil data exists.
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What are gene trees?
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Reconstruct phylogeny of a gene by inferring historical relationships among variant DNA sequences of a gene
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Explain homology
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Any similarity between characters due to shared ancestry
Criteria of homology: 1. position in relation to neighboring structures/organs 2. Quality + structure (ex. human teeth and placoid scales of sharks) 3. Continuity connecting 2 dissimilar stages by connecting intermediate stages |
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What are analogous characters?
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Phenotypic similarity due to similarity of function
Ex. bird wing and insect wing |
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What is convergence?
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Non-homologous similarity which evolved due to adaption to the same environmental conditions
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Where is homology seen in molecular biology?
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Mainly genes and proteins
Genes are homologous if they are derived from an ancestral gene Sequence similarity as a criterion for homology *Molecular homology is a statement to the similarity between proteins and genes not necessarily how they are related in evolutionary history |
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Described the different criteria of homologous sequences (orthologous, paralogous, xenologous)
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Orthologous: if separated by speciation event, derived from common ancestor
Paralogous: separated by gene duplication event Xenologous: horizontal gene transfer |
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What are evolutionary reversals?
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The return from a derived character to an ancestral state.
Dollo's law states that this can't happen- wrong |
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Do rates of character evolution differ?
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Yes.
Conservative characters Mosaic evolution |
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Explain what conservative characters are.
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Conservative characters: have little orno change over long periods of time (ex. pentadactyly in humans evolved in amphibians first)
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Explain mosaic evolution.
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Evolution of different characters at different rates within lineage. A species does NOT evolve as a whole, usually features evolve quasi-independently
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What are the consequences of mosaic evolution and conservative characters?
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Every species is a mix/mosaic of plesiomorphic and apomorphic characters, so it's inaccurate to say that a species is more advanced than another
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What is heterochromy?
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Evolutionary change in timing/rate of developmental events.
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Explain paedomorphosis
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Evolution of a more "juvenile"morphology of reproductive adult.
Ex. axolotly reproduces while retaining most of its larval characteristics |
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What is neoteny?
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Type of paedomorphosis
Reducing growth rate of somatic characters (axolotl) |
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What is progenesis?
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Type of paedomorphosis
Cessation of grown at an earlier age Leads to smaller size |
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WHat is peramorphosis?
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Type of paedormorphosis
Delayed maturity that can result in reproduction at a larger size Ex. human brain size evolution |
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What is alternative splicing?
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Can result in several proteins being encoded by a single gene
Ca. 35% of human genes subject to alternative splicing |
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What are gene families
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Groups of genes that are similar in sequence and often have related functions (ex. hemoglobin)
Created by gene duplications Include psuedogenes: sequences that resemble functional genes but differ at a few bp sites and are not transcribed b/c have internal "stop" codons so they are no longer expressed Processed pseudogenes: those that originated by reverse transcriptase from mRNA to DNA that lacked introns, then silencing and more bp changes -> so introns don't match but sequences are recognizably similar |
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What is a haplotype?
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A particular DNA sequence that differs by 1+ mutations from homologous sequences
*If mutation gets fixed- carried by nearly entire population- called a substitution |
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What is a point mutation?
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Alteration of a single base pair. There are 2 different kinds:
Transition: exchange of a purine for a purine or a pyrimidine for a pyrimidine. Transversion: exchange of a purine for a pyrimidine or vice versa. |
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What are synonymous mutations?
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Those that do not have an effect on the amino acid sequence of the polypeptide or protein. This is due to the redundancy of the genetic code, in that 60 codons only code for 20 amino acids.
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What is a nonsynonymous mutation?
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That which results in an amino acid substitution
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What are indels?
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Insertions or deletions. Can be of single base pairs or many. Usually result in frameshift mutations that change the gene product completely, usually causing it to be inactive.
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What is replication slippage?
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Alters the # of short repeats in microsatellites.
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What are transposons? What do they result in?
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Sequences of DNA that can move around to different positions within the genome of a single cell. There are 2 types:
1. Consist of DNA that moves directly from place to place. 2. 1st transcribe DNA -> RNA, use reverse transcriptase to make DNA copy of RNA t insert into new location *Usually result in frameshift mutations that destroy function of the protein |
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What are some mutation causing agents?
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UV-light, X-rays, chemicals
X-rays cause chromosome aberrations Ehtidiobromide intercalates between bases and causes frameshift mutations Mutation rates in birds/mice are elevated in industrial areas Mutation rates of birds after Chernobyl explosion also increased |
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What are selectively natural mutations?
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Those that do not alter their carrier's survival or reproductive success.
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What are homeotic mutations?
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Redirect development of one body segment to another (controlled by Hox genes)
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What is pleiotropy?
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A single gene influences more than 1 character (ex. PKU)
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What are multiple loci?
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One gene 1 gene affects a certain trait.
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What is fitness?
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Capability of an individual to produce viable offspring. If differences in individual genotypes affect fitness, the frequencies of genotypes will change over time/generations
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Explain interchromosomal recombination.
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It is the independent assortment of maternal and paternal homologous chromosomes during meiosis I.
The # of interchromosomal possibilites for recombination depends on # of chromosomes 2^n |
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What is Robertsonian translocation?
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Also called centric fusion. Acrocentric chromosomes lose their small pieces and the large ones fuse together to make metacentric chromosomes.
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What are the general changes of chromosomes throughout evolution?
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Tend to reduce in number
Tend to increase in size |
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What is aneuploidy?
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Unbalance in chromosome complements
ex. Trisomy-21, Monosomy-X |
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What is polyploidy?
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Changes in # of whole sets of chromosomes
Common in plants |
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What are autopolyploids?
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Polyploids with multiple sets of chromosomes from a single species
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What are allopolyploids?
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Polyploids with multiple sets of chromosomes from different species caused by hybridization of closely related species.
But hybrids are often sterile because homologous chromosomes can't pair during meiosis |
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What are polytene chromosomes?
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During interphase, they form when multiple rounds of replication produce many sister chromatids that remain synapsed together (endoreplication).
The metabolic advantage of this is that multiple copies of genes permit a high level of gene expression Ex. salivary glands in drosophila |
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What are lamp brush chromosomes?
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Found in oocytes of most animals except mammals
Meiotic bivalents, each consisting of 2 long strands that form brushlike loops along main axis of chromosome Giant chromosomes in lamp brush form are useful for studying chromosome organization and gene expression since they allow the individual transcription to be visualized Loops = high amount of RNA production, gene expression |
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Define gene copy.
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The # of representatives of a gene without distinguishing allele or sequence differences
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What role does environment play in variation?
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Affects development or expression of many features
Ex. sex determination in turtles ex. consumption of alcohol/drugs during pregnancy |
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What is developmental noise?
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Phenotypic variation from random events at molecular level when both genotype and environmental factors are the same
ex. wing size at right and left side of body on fruit flies |
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Explain maternal effect.
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Refers to effects of a mother on her offspring that are not due to genes
ex. amount of yolk, maternal care, parent's environment |
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What is epigenetic inheritance?
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Refers to changes in phenotype or gene expression caused by mechanisms other than change in DNA sequence.
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What is genomic imprinting?
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The activity of a gene or chromosome that depends on parental origin (about 1% of in mammals)
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WHat is DNA methylation?
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The addition of a methyl group to C of CG doublets, which then gets replicated and methylated state can be transmitted for a few generations
Methyl state reduces/eliminates gene transcription |
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What are some methods to determine whether variation in a characteristic is genetic, environmental, or both?
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1. Phenotypes experimentally crossed and backcross progeny. Mendelian ratios among phenotypes of progeny indicate simple genetic control.
2. Greater resemblance among siblings than among unrelated individuals suggests genetic variation contributes to phenotypic variation. |
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Look over Hardy Weinberg.
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Do it.
Do it. Do it do it do it do it Done. |
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What are the 5 components of Darwin's evolutionary tree?
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1. Evolution as a real historic process
2. Common ancestor 3. Gradualism 4. Multiplication of species 5. Natural selection |
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What are some differences between Lamarck and Darwin?
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L-use and disuse
D- variation L-transmission of acquired characteristics D- inheritance L-Increasing complexity D- differential survival L-No extinction D-extinction L-Independent progression D- branching tree of life |
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What is a similarity between Lamarck and Darwin?
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Adaptive change in lineages ultimately driven by environmental change over long periods of time
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What are adaptations?
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Defines a characteristic that has evolved by natural selection
Also refers to the process whereby members of a population become better suited to some feature in their environment through change in a characteristic that affects their survival or reproduction. |
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What is natural selection?
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Any consisten differences in fitness among phenotypically different classes of biological entities. Exists when there is variation in fitness
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What is sexual selection?
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Refers to competition for mates
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What are the levels of selection?
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Genes: genic selection
Individual organisms: individual selection Populations: within species Species selection |
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Is natural selection due to chance?
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NO.
Natural selection resides in the difference in rates of increase among biological entities that is not due to chance. |
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What is gene hitchhiking?
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The process by which an evolutionarily neutral (or sometimes deleterious) allele or mutation may spread through the gene pool by virtue of being linked to a beneficial mutation.
More generally this can refer to the process which a gene's frequency changes due to selection operating upon linked genes. (Fig. 11.7) |
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What is the handicap hypothesis?
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Proposes that females can asses the quality of a male by his ability to survive despite having a trait that could potentially be detrimental to his health
(Sexual selection) |
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Describe the transmission of selfish genetic elements.
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Selfish genetic elements are transmitted at a higher rate than the rest of the individual's genome and are detrimental to the organism.
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What is meiotic drive?
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Any process which causes some alleles to be over-represented in the games
Ex. haplodiploid arthropods (ants) |
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What is the psr element?
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Paternal sex ratio
Smal chromosome, is transmitted through sperm then causes loss of the paternal chromosomes, except themselves early in development PSR chromosomes convert diploid fertilized eggs (which would normall develop into females) into haploid males that carry a psr chromosomes Eventually: would eliminiate all females. |
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What is an altruistic trait?
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A feature that reduces the fitness of an individual that bears it for the benefit of the population or species. An altruistic traint cannot evolve by individual selection.
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How have altruistic behaviors evolved?
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By kin selection
Kin selection hypothesis: an allele that influences its bearer to spare its siblings' lives will increase in frequency, as sibling carries other copies of the same allele. |
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What is the reason most cannibals tend to avoid eating close relatives?
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Disease hypothesis: Cannibals are at risk of contracting disease, if they share a genetic susceptibility to certain pathogens with these relatives
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For a character to be regarded as an adaptation...
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It must be a derived character that evolved in a response to a specific selective agent
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What is a preadaptation?
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Describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose
Ex. dinosaurs having used feathers for insulation and display before using them to fly |
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What are exaptations, co-options, and preadaptations?
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Related terms referring to shifts in the function of a trait during evolution
Exaptation: penguins using wings for underwater "flight" adaptation: wings modified into flippers |
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Discuss recognizing adaptations, since not all traits of organisms are adaptations
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1. Traits can be necessary consequences of physics or chemistry
2. Traits may have evolved by random genetic drift rather than natural selection 3. A character state may be the result of phylogenetic evolution |
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What should you not expect of natural selection and adaptation?
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1. Necessity of adaptation
2. Perfection: selection can only fix genetic variants with higher fitness 3. Progress: has the connotation of a goal 4. Harmony and balance of nature: selection at the level of genes and individual organisms is "selfish" |
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What are the 3 species concepts?
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1. Morphological
2. Biological 3. Phylogenetic (2&3 are the most commonly advocated) |
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Explain the morphological species concept
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Use of certain morphological characters. Traditionally, this concept was used but the problem is that you can't see convergence and this can lead to errors.
Can also misinterpret variation: ex. if a species has color variation can be mistaken for 2 species Also, characters can disappear or change during ontogeny (ex. frogs and deer) Cryptic species: look similar morphologically, but different species |
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Explain the phylogenetic species concept.
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1. Phylogenetic species is an irreducible (basal) cluster of organisms that is diagnosable distinct from other such clusters, and within which there is a parental pattern of ancestry and descent
2. A species is the smalles monophyletic group of common ancestry |
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Explain the biological species concept
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Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. The shared gene pool gives the species its identity
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What is a semispecies?
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Genetically differentiated groups of populations that are partially, but not fully reproductively isolated
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What is a superspecies?
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A collection of semispecies
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What are some difficulties with the biological species concept?
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-Do allopatric populations belong to the same species?
-Do they interbreed? Captive breeding experiments -If barriers are present, they can independently evolve |
