Biol 415 Exam 1

Microevolution

change in genetic composition over time

Macroevolution

large changes in form and function over time

Darwin’s theory of evolution

evolution occurs as descent with modification, all species share a common ancestor, and changes occur through natural selection

descent with modification

change in inherited traits over generations

Lamarck’s theory of evolution

adaptation occurs through inheritance of acquired changes, microbes are continually generated spontaneously and are evolving from simple to complex

Wallace’s theory of evolution

common ancestry and natural selection

homologous traits

traits that are similar due to inheritance from a common ancestor

adaptations

traits that have evolved by natural selection

inheritance of acquired characteristics

evolutionary idea that use/disuse of body parts can lead to changes in an individuals lifetime that can be passed on to offspring

heritability

the extent to which offspring resemble their parents more than an individual chosen randomly from the population

fitness

a measure of how well an organism function in a given environment/ a function of survival and reproductive success

sexual selection

selection for traits that provide a mating advantage

genetic drift

changes in frequency of alleles due to chance events

blending inheritance

the evolutionary idea that traits from mom and dad would mix together to produce a phenotype that is a mixture of mom’s and dad’s phenotype

The Modern Synthesis

the merging of natural selection with particulate inheritance into a new theory that hereditary information is encoded in genetic material called genes

Tenets of the Modern Synthesis

genetic variation arises by chance due to mutations,

\-there are two levels of recombination of homologous chromosomes during meiosis,

\-most beneficial mutations cause slight changes in phenotype

\-evolutionary change tends to be slow and gradual

\-populations evolve by changes in gene frequency brought by genetic drift, gene flow and natural selection

\-speciation occurs gradually when population are reproductively isolate by geographic barriers

Igneous rock

solid rocks formed from molten lava

sedimentary rock

layered deposits of sediments hardened under pressure

metamorphic rock

rocks changed with heat and pressure

how are igneous rocks dated

radioactive decay

how are sedimentary rocks dated

bracketing between igneous formations

how is organic material dated

decay of carbon-14

drawbacks to 14C dating

small half life, can only be used for fossils 50-60 ky old

biomarker

distinctive molecule only produced through biological activity

biomarker example

okenane molecule only produced by purple sulfur bacteria

evolution

change over time

Edicaran period

570-540 mya, almost all fauna from this period went extinct within 40 my

Cambrian Period

541 mya, diversification of life, most existing animal lineages evolved during this period

fossil trackways

fossilized imprints of footprints that show the organisms gait and can thus be linked to extant organisms

mutation

any change to the genomic sequence, the origin of genetic variation

ploidy

number of copies of unique chromosomes in a cell

gene expression

process by which information from a gene is transformed into product

allele

alternate form of a gene occurring at a specific locus on a chromosome

synonymous mutation

a change in a nucleotide that does not change the amino acid specified by the codon

non-synonymous mutation

a change in a nucleotide that changes the amino acid specified by the codon

nonsense mutation

change in a nucleotide that results in an early stop codon

frameshift mutation

addition or deletion of a nucleotide that changes the reading frame of the codons

germline mutations

mutations that affect the gametes and are heritable

somatic mutations

mutations that affect the cells of the body and are not heritable

recombination

exchange of alleles between homologous chromosomes to generate variation

independent assortment

random sorting of chromosomes as they line up prior to cell division, increases genetic diversity of offspring

Unequal crossing over

something goes wrong and leads to a deletion event in one homolog and a duplication event in the other homolog

Transposable Elements

parasitic pieces of DNA that jump all over the genome, possibly causing gene disruption via frameshift mutations, non synonymous mutations, or nonsense mutations

genotype

genetic makeup of an individual

phenotype

observable, measurable characteristic as the manifestation of the genotype of an organism

polyphenic trait

the ability of one genotype to produce multiple phenotypes depending on environment

Quantitative trait

traits influenced by multiple genes that generate a normal distribution, aka continuously varying traits

morphogen

signaling molecule that flows btw nearby cells to alter the expression of target genes

Phenotypic Plasticity

changes in phenotype produced by a single genotype in different environments that allows an organism to tailor to their environment

polygenic trait

Multiple genotypes produce the same phenotype

systematics

scientific study of biological diversity

taxonomy

theory and practice of classifying organisms

cladistics

phylogenetic grouping based on shared characteristics (synapomorphies)

comparative method

comparing of two different lineages who share the same trait not due to relatedness in order to study how that trait evolved

phylogenetics

the study of evolutionary relationships

phylogeny

the evolutionary history of a lineage

phylogenetic tree

a visual representation of a phylogeny

clade

a common ancestor and all of its descendants

phenetics

phylogenetic grouping based on overall similarity

monophyletic group

same as a clade, all descendants of a MRCA

paraphyletic group

grouping that contains some but not all descendants of the MRCA of the group

polyphyletic group

multiple monophyletic groups that don’t include the common ancestor

apomorphy

a trait shared by only some members of a clade but not all

synapomorphy

derived character state shared by an ancestor a its descendants

symplesiomorphy

shared ancestral state that evolved a long time ago that multiple clades can have in common

what types of traits are phylogenetically informative

synapomorphies

what types of traits are not phylogenetically informative

apomorphies, symplesiomorphies, homoplasies

homoplasy

similarities due to anything other than common decent, convergent evolution

convergent reversal

evolutionary changes back to an ancestral condition

tree length

sum of overall characters in a phylogenetic tree

parsimony

the simplest explanation or the least number of character state changes is the most likely correct

polytomy

inability to determine relatedness of some members based on parsimony consensus tree

mutational saturation

when so many mutations have occurred that you can’t see them anymore due to masking or reversion to original state

exaptation

a trait originally evolved for a certain function, but natural selection co-ops it to preform a new function

outgroup

a group closely related but not the same as the in-group in order to serve as a basis of comparison

coalescence

the process of going back in time to the MRCA

species tree

phylogeny of a species depicting ancestor-descendent relationship of species

gene tree

phylogeny of DNA sequence at a particular locus, depicts the genealogy of alleles

lineage sorting

when alleles of unlinked loci can sort differently into lineages isolated by speciation

bootstrapping

statistical measure to determine the level of support for each node

multi regional model of human origins

the hypothesis that Homo sapiens evolved gradually across the entire old world from an older species of hominin

out-of-Africa model of human origins

the hypothesis that Homo sapiens evolved in Africa alone, and that other hominin fossils represent extinct sister clades

evolutionary substitution

the complete replacement of one nucleotide by another in a population

neutral theory of molecular evolution

Kimora’s theory that most evolution at the molecular level is neutral and that neutral mutations become fixed at a regular, clock-like rate

Beneficial mutations

mutations governed by positive selection and drift

deleterious mutations

mutations governed by purifying selection and drift

neutral mutations

mutations governed only by genetic drift

observations of neutral theory

\-rates of a.a substitutions in proteins are high

\-more variation and heterozygosity in wild pop’s to be explained by selection alone

\-distant species have large number of differences in cytochrome c gene

\-important parts of genome evolve more slowly

1/2N

probability of a new allele becoming fixed

1-(1/2N)

probability of a new allele going extinct

u

neutral mutation rate, # of new mutations/locus

1/Ne

probability of a new mutation becoming fixed

uNe\*(1/Ne)=u

the rate of allele fixation in populations is equal to the rate at which new mutations appear in individual genomes

caveats to the molecular clock

convergence, homoplasy, and mutational saturation

2u

the rate at which two species diverge

D

the total amount of differences between two species

u=D/2t

neutral mutation rate

positive selection

only mutations that have an effect on the gene are selected for; selection for nonsynonymous mutations

neutral drift

some mutations have an affect, some don’t

purifying selection

selection removes any mutations that have an effect, selection for synonymous mutations