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Evolution
change in a population over time
Darwin’s postulates
environment, competition, variation, and artifical
environment postulate
any modification b/c of environment aspects (food availability/type, climate/weather changes, and natural disasters)
competition postulate
any modification to species b/c of struggle for resources (predation and intraspecic), diseases, and fitness
variation postulate
modifications to species b/c of genetics (inheritable changes b/c of reproductive techniques)
artificial selection
modifications via selective breeding
Genetic variation
what drives differences within population?
macrovariation
changes over long periods of time (ex. reptiles- birds)
microvariation
small changes over fast period (ex. bacteria and finch beaks)
Mutations, sexual reproduction, and gene expression
What are the three reasons for genetic variation
mutations
unpredictable changes, can be detrimental or beneficial, and most common in bacteria/viruses
sexual reproduction
different gamete combinations, crossing over/independent assortment, and low mutation rates b/c of checkpoints, telomeres, and enzymes
genetic duplication
mostly harmful if not occuring in plant, can expand genomes, and can create new species (b/c self-fertilization)
Comparative Anatomy, fossils, biogeography, and molecular comparisons
What is the evidence for evolution?
Homologous structure, analogous structure, and vestigial strucutures
What are the different types of comparative anatomy?
Homologous structure
anatomically similar but different functions + usually b/c of divergent evolution (mammalian forelimbs + arthropod appendages)
divergent evolution
interbreeding species diverged into two or more evolutionary groups (common ancestor)
convergent evolution
species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures (do not share ancestor)
analogus structure
anatomically different but similar function b/c of convergent evolution (shark + dolphin tails, vertebrae vs invertebrate eyes, limb regneration
vestigial structures
had role in ancestor but no longer has use; usually gets smaller b/c cannot remove (whales + boa constrictors having hip bone + appendix, tailbones in apes/humans, and goosebumps)
fossils
direct evidence of change over time, shows intermediates btwn extict and extant or groups, and can show transitions in body forms (ex. aracharoptrxy/birds, tiktaalik/amphibian-reptile, and horses + whales)
Biogeography
past + present distribution of species, island species most closely related to mainland, fossil distribution b/c of tectonic plates, and leads to closely related species on different continents (ex. monkeys in S America, africa, and asia; jaguar + leopard; camels form N America to Africa/Asia + S America
Molecular Comparisons
genetic similarities in DNA/AAs, can be used to create phylogenic trees + infer when spieces diverged, supported + moderized Darwin’s Theory (Ex. humans + chimpanzes diverged 6mya and share 99% of DNA)
biological species concept
populations have members capable of producing viable offspring
phylogenic species concept
species in a single line of decent form + stay that way (doesn’t get supported well)
Anogenic + Cladogenic
What are the two forms of speciation?
Anogenic
gradual change of one species to a new form, # of species doesn’t change
Cladogenic
two or more species share an ancestor; alloptric and sympatric
allopatric
geographic isolation b/c of different pressures and common in islands/land bridges
sympatric
speciation occurs in close proximity, polyploidy in plants (extra genes); (song birds and cichlids w/ various species in lake victoria)
allopatric and sympatric
what are the types of cladogenic?
reproductive isolation
how a species remains pure
prezygotic and postzygotic
2 categories of reproduction isolation
habitat/ecological, temporal, behavioral, mechanical, and gametic isolation
what are the types of prezygotic barriers?
hybrid invariability, hybrid breakdown, and hybrid sterility
What are the types of postzygotic barriers?
habitat/egological isolation
temporal isolation
timing of mating (ex. plants fertilizing at different times)
behavioral isolation
different mating rituals (mainly in birds)
mechanical isolation
physically different and won’t work
gametic isolation
mating occurs but eggs and sperm cannot fuse (common in fish)
hybrid invariablity
doesn’t make it past embryonic phase and most common (bulldog and leopard frogs)
hybrid breakdown
hybrid survives but offspring have reproductive issues (sunflowers)
hybrid sterility
hybrid cannot reproduce (mules, zebroids, liger, and tigons)