Evolution Flashcards
Homology/Homologous
sharing traits via a common ancestor
Divergence/decent with modification
over time, similarities between daughter lineages decrease
Tip
end points (modern or extinct)
Nodes
hypothetical common ancestors of species that descended from that branch point
Root
the branch leading to the common ancestor of all the taxa in the tree
Clade
a group of species or genes that include all descendents of an ancestral species or gene
monophyletic
group/clade where all species share a common ancestor
paraphyletic
group where all species share a common ancestor, but some species are excluded from the group
polyphyletic
grouping of lineages more closely related to other species not in the group than they are to each other
phylogram
length of branches can indicate the amount of evolutionary change
dendrogram
tips of the tree are kept the same length from the root and can be used to represent evolutionary time since divergence
polytomy
a phylogenetic tree can have more than two branches from a single node (can show ambiguity)
outgroup
taxonomic unit that branched off in ecolution prior to the common ancestor of all individuals in the ingroup (used to root trees)
bootstraping
analyzes a tree by resampling with replacement (common for nodes)
jackknifing
analyzes a tree by resampling without replacement
ortholog
homologous genes in a different species that arose from a single gene in the last common ancestor of these species
paralog
homologous genes in the same species that are related by duplication of an ancestral gene
gene duplication can lead to
1) non functionalization
2) conservation
3) neofunctionalization
4) specialization
5) subfunctionalization
How many exons usually encode Ig domains?
two
purifying selection
aspect of natural selection that reduces genetic variation and preserves DNA and protein sequences
evidence of purifying selection
dN/dS < 1
neutral selection
dN/dS = 1
positive/darwinian selection
dN/dS > 1
selective sweeps/hitchhiking
reduce variation in regions of the chromosome adjacent to selected sequence
evolution
genetic change in a group of organisms
steps of evolution
1) genetic variation arises through mutation and recombination
2) change in frequencies of genetic variants
types of evolution
anagenesis - evolution in a single lineage over time
cladogenesis - splitting of one lineage into two, speciation
molecular data
1) genetic
2) can be used with all organisms
3) can be applied to huge amount of genetic variation
4) quantifiable
5) provides info about the process of evolution
neutral mutation hypothesis
when selection is important there won’t be a lot of genetic variation
balancing selection
selection that maintains variation
-overdominance - both homozygotes have much greater fitness than heterzygote
-sickle cell vs malaria
species
different types of living organisms
-evolutionary independent group
biological species concept
species is a group of individuals that can interbreed with each other, but are reproductively isolated from members of other species
morphospecies concept
only phenotype
phylogenetic species concept
smallest recognizable group that has a unique evolutionary history
temporal isolation
reproduction at different times of year
ecological isolation
don’t encounter each other/different habitats
behavioral isolation
differences in behavior prevent breeding, mating calls
mechanical isolation
anatomical differences prevent copulation
gametic isolation
can mate but gametes don’t for zygote
speciation
process by which new species arise
allopatric speciation
a geographic barrier splits population
reinforcement
postzygotic isolation mechanisms encourage the development of prezygotic isolation mechanisms
sympatric speciation
speciation without external barrier
difficulties with sympatric
-need genetic differentiation to occur
-nonrandom association of genes can promote speciation but recombination usually breaks up nonrandom association
distance approach
based on overall similarity
maximum parsimony
fewest evolutionary changes since last common ancestor
maximum likelihood/bayesian methods
which phylogeny maximizes probability of obtaining organism’s characteristics
exon shuffling
exons of different genes are exchanged creating genes that are mosaics of other genes
multigene families
a group of genes that share a common ancestor gene and are created from gene duplication and differentiation
whole genome duplication
can happen through polyploidy
-2R hypothesis - early vertebrates went through two rounds of duplication
