rest of Unit 7

Speciation

one species splits into 2/more due to genetic divergence & reproductive isolation, punctuated(branch from parent and change a little) Gradual(species diverge steadily)

Microevolution

small scale changes in allele frequencies in a population (beak size)

Macroevolution

large scale changes above species level, formation of new species

Species

organisms that can interbreed and produce fertile offspring, cant with other groups

Reproductive Isolation

gene flow(allele movement from migrating and interbreeding) stops b/c populations become genetically different and cant reproduce with each other

Hybrids

offspring produces from 2 different species that are weak, infertile, cant survive well

Prezygotic barriers

prevents fertilization from happening b/c of different mating times, behaviors, physical incompatibility, gametes cant fuse

Postzygotic Barriers

after fertilization, hybrid cant survive or reproduce, offspring are weak

Habitat Isolation

prezygotic, species live in different habitats and dont meet, water & land snakes

Temporal Isolation

prezygotic, species breed at different times of day, season, year

Behavioral isolation

prezygotic, different courtship behaviors prevent mating

Mechanical Isolation

prezygotic, physical differences prevent mating/pollen transfer

Gametic isolation

prezygotic, sperm and egg cant fuse

Reduced hybrid viability

postzygotic, hybrid offspring cant develop/survive well

Reduced hybrid fertility

postzygotic, hysbrid is healthy but sterile

Hybrid breakdown

postzygotic

Allopathic Specistion

physical barrier separates a population, stops gene flow(Grand Canyon)

Sympatric Speciation

no physical barrier, pop live in same area but gene flow is reduced-> Polyploidy(cell division errors, reproductively isolated), Sexual selection(mate preference differences, only mate with similar ), Habitat differentiation(pop uses different resources in same area, dont mate)

Autoploidy

organism had extra chromosome sets from same species, chromosome number doubles, gametes are diploid instead of haploid, fertilization creates tetraploids- new species fertility restored

Hybrid Zones

region where 2 different species interbreed, making hybrids, can reinforce separate species, merge species, or stabilize distinct species

Punctuated Equilibria

species show long period of little change or brief rapid evolutionary changes

Common ancestor

species from where 2/more species evolved, all groups after inherit traits from it

Sister taxa

groups that are each others closest relatives, share most recent common ancestor with no one else

Character(trait)

heritable feature to classify organisms

Phylogeny

evolutionary history of a species family tree(hypothesis) showing are organisms are related with common ancestors, tree cannot determine time/dayes, species evolve from another’s which is better/more evolved

Systematics

classifies organisms and determines their relationships with traits to build trees

Taxonomic categories

Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain(species more specific and related)

Rotating Branches

no new evolutionary relationships,

Basal Taxon

lineage that diverged earliest from the root

Homologous Structures

shows evidence of being related

Analogous Structures

similar solutions to similar problems but not related

Convergent evolution

unrelated organisms evolve similar traits bc they live in similar environments and face similar natural selection, but don’t share a recent common ancestor, makes analogous structures

Homologies

phenotypic/genotipic similarities bc of shared ancestry, even with mutations- homolgies can be identified by aligning dna sequences for matching regions

Clade

group with one common ancestor and all its descendants(common ancestry)Monophyletic(common ancestor and all its descendants) Paraphyletic(has common ancestor, but only some descendants, some missing) Polyphyletic(has organisms from different lineages and not the most recent common ancestor)

Derived characters

make clades, traits that are evolutionary, unique to a group, not found in older ancestors

Backbone

shared ancestral characters, backbone evolved before mammals, found in many groups

Branch lengths

can show amount of genetic change/evolution or time when species diverged

Occams Razor

choose simplest explanation, maximum parsimony(choose tree with fewest evolutionary changes and fewest mutations)

rRNA Genes

rRNA evolve slowly, study ancient relationships

MitochondrialDNA

mtDNA evolves quickly, study recent evolutionary events

Orthologous genes

shows common ancestry because they are the same genes in different species that diverged after speciation

Paralogous genes

genes in the same genome(species) that arose from gene duplication then diverged

Molecular clocks

method to estimate when species/genes diverged by measuring how quickly DNA changes accumulate, counting DNA differences-estimate how long ago a species shared a common ancestor Othrologous(count # of DNA differences is proportional to time since speciation) Paralogous(# of dna differences is proportional to time since gene duplication

Horizontal gene transfer

organisms transfer genes to each other with reproduction through viruses, plasmids, cell fusion, genes move sideways, Prok genes move through plasmids, Euk gets bacteria like genes