Karteikarten
Macroevolution - genetics
Karten in diesem Stapel (18)
- 1adaptive radiation: lineage rapidly diversifies with newly formed lineages evolving different adaptationsadaptive radiation in horses:
- major participant in modern evolutionary synthesis
- dispelled myth that evolution of horse was linear process
- grasses became more common (energy rich food) helped with evolution - 2Hyracotherium - earliest horse-like forms - more dog like - small brain case - teeth flattened, gridning molars - shortness of tooth crowns indicates browsing not grazingin N.america - phyletic line led to horse genus Equus
- in Eurasia, line led to modern capris, rhinos + other off-toes
separate evolutionary paths = consequence of isolation of continents resulting from continental drift - 3Miohippus (evolved from Hyracotherium) - larger animal - big brain case/different forefeet - one branch gave rise to true horses (Merychippus)Merychippus
- true horse line (arose in miocene)
- larger-bodied animal (exploration of more open habitat)
- major change in tooth structure - 4selective forces shaping horse evolution: grasses: - very tough, high silica content - apical meristem close to ground - both adaptations against herbivory - high-crowned teeth-adaption against wear from silicaSpring foot
- feet hoofed
- strong elastic ligaments bound toe bones to main leg bones
- spring-foot more efficient mechanism
- suspensory ligament provides lift to limb - 5decedents of Merychippus - at least 6 separate lines developed (only one led to modern horse) - horses eventually became extinct over whole of new world (reappeared during spanish conquistadors)domestic horse (Equus caballlus)
- example of hybridisation
- doesn't have single, simple origin
- modern horse originated form 77 wild mares (different in their mtDNA) - 6adaptive radiation triggers: - space - selection - innovation - habitat fragmentation - sexual selectioncolonising populations likely to evolve rapidly
speciation = both anagenesis & cladogenesis
Anagenesis = species formation without branching of evolutionary line of descent
Cladogenesis =specie formation by evolutionary divergence from an ancestral form.
founding populations initially small -> likely to undergo genetic drift - 7founding pops subject to different selection pressures compared to parent: - few/no competing, related species - no/few predators - larger islands & lakes spatially more heterogeneous: allopatric speciation more likelyDarwin's finches:
- beak form correlated with diet
- divergences in beak form -> character displacement among secondarily simpatico populations
- evolution driven by competition for shared resources
- genetic drift - 8Coelacanths - big carnivorous fish - arose in Devonian - lobed fins suggest link to early tetrapod lineagemass extinction = loss of >70% of species
- 94 major global extinctions: 1. end of ordovician 2. end of permian (wiped out 95% spp) 3. end of triassic (wiped out whole animal class) 4. end of cretaceous (K-T event - wiped out dinosaurs) 6th mass extinction: underway due to human activities (over-hunting, fragmentation...)K-T event
- end of cretaceous
- extinction of dinosaurs
- due to impacts of shower of giant meteorites or mantle plume eruption
mass extinction resulted from:
- relatively short-erm acid rain
- long term atmospheric barrier to solar radiation - 10Pimm: with continuing deforestation, 50% of worlds animal & plant app will be extinct in <50 yearsO'ahu tree in hawaii
- all species endangered
- main threat from predatory snail (was introduced to control giant African land snail) - 11Climate change - implicated decline of amphibians - global arming predicted to result in rising levels + acidification of oceans 100% coral reef predicted to become extinct (also threatened by commercial dealers)continental drift:
earths surface = thin curst
- convection currents causing movement
evidence: same fossils found on different continents
effects:
- land masses split & join up with others
- terrestrial fauns + floras become isolated
- isolated seas join up with oceans - 12Ice age - triggered by rise of mosses (chemical weathering of rocks reduced atmospheric CO2) 1. extinction of species (Mass extinction) 2. formation of barriers to movement 3. splitting of populations & subsequent speciationGlacial refugia (region where flora and fauna survived during ice age)
- species sub-populations become isolated due to:
extension of glacial finger
formation or arid areas
lowered sea levels
water locked up in ice - 13Symbiosis = living together, physically close association between different species types: - mutualism (+/+ effect) - parasitism (+/- effect) - parasite benefits - commensalism (0/+ effect) - one benefits, other receives no harmcoevolution -> moths & sloths
sloths = nutrient poor diet, slow lifestyle (diet difficult to digest)
- algae in sloth fur highly digestible & lipid-rich
- sloths consume algae-gardens
- moths specialised to colonise sloth fur
- moths carry nutrients, increasing nitrogen in sloth fur which fuels algal growth
- sloths transport moths to ovipositor sites in dung (facilities reproduction of moth) - 14mutualism = 2-way selection resulting in coadaptation parasitism = 2-way selection resulting in counter adaptationbees: 20,000 spp known (9 families)
- wouldn't become bees without flowering plants (still be unspecialised wasps_
- couldn't have divorced without angiosperm also diversifying
- insect pollination not only driving force in angiosperm diversification (herbivores & abiotic factors also important)
*most bee-flower relationships = non-obligate - 15Cospeciation = as host spectates, so does associated specialist mutualist or parasite evidence: - tree topologies of mutualist/hosts match perfectlysystems exhibiting cospeciation:
- system where parasites/mutualist physically very close associated with host
- obligate parasites & mutualists
- vertically transmitted parasites - 16reasons for non-congruence: - cospeciation - failure to speciate - duplication - extinction host switching (incomplete, with extinction/speciation/both)functional genomics = study of function of genes + other parts of the genome
comparative genomics = analysis & comparison of genomes of different species
- aim = gain insights into how organisms have evolved - 17Regulatory (homeotic) genes: How genes = master control genes - conductors of gene 'orchestra' - involved in embryogenesis - control differentiation along longitudinal body axis in most species - control différentiation of limbs along axisrole of Hox gene:
- know whereabouts it is in body
- active builder genes in region
- builder genes can construct structures such as: antennae, legs or wings appropriate to specific part of body:
- mutations in these genes occurred during evolutionary past
- mutations can be highly maladaptive
*Hox is highly conserved - 18How gene of amphibious (non-vertebrate) - neural crest cells absent in amphioxus - implanted amphibious Hox garments into mice/chick embryos - regulated development of neural crest *phenotypic expression of homeotic gene depends on what body it lives in - homeotic genes themselves are being regulated (transcriptional cascade)some homeotic genes retain original overall function e.g. controlling eye development
homeotic genes give animals great flexibility for evolving drastically new body plants/organs
(doesn't allow the evolution of some body plans)
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- Karteikarten am Macroevolution - genetics , erstellt von michaela minkin am 22/05/2018.
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