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Macroevolution (Fossil Record (layers reveal relative ages of fossils -…
Macroevolution
Fossil Record
documents the rise and fall of different groups of organisms over time
based mostly on sedimentary rock layer sequence - strata
new groups rise via gradual modification of preexisting organisms
helped develop a geologic record of earths history - but its incomplete
layers reveal relative ages of fossils - can be more accurate with radiometric dating
radiometric dating - measures decay of radioactive isotopes
Rise and fall of organisms
group of organisms rises when more new species appear than are lost to extinction
Plate Tectonics
continents are part of great plates of Earth's crust that float on hot, underlying portion of mantle
Continental Drift - movements in mantle cause continents to move slowly over time
consequences
alters habitats
climate change due to new location
Promotes allopatric speciation on grand scale
Helps explain puzzles about geographic distribution of extinct organisms
cause extinction + new opportunities for organisms surviving a change
supercontinents have formed and broken into different configuartions
Mass Extinctions
elimination of a large number of species throughout earth, the result of global environmental changes
consequences
disrupts interactions in an ecological community
extinction - that evolutionary lineage is gone forever
Takes millions of years to recover levels of diversity
promotes adaptive radiations - new groups of organisms fill empty niches and diversify
Adaptive Radiations
period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities
Typically Happens
after mass extinction
major evolutionary innovation
diversification from another group of organisms: when groups face little competition from other species
migration to new locations
Changes in morphology
caused by changes to developmental genes. ex. Hox genes
developmental genes highly conserved between species
high degree of conservation indicates that gene is important for survival
Changes that can occur
Change in gene sequence (mutation)
duplication + divergence
changes in gene regulation
when + where + how long a gene is expressed and allowed to function
Heterochrony - evolutionary change in rate or timing of developmental events
definition
broad pattern of evolution above the species level
what it can tell us
speciation has been affected by both small scale factors and large scale factors
new forms arise by slight modification of existing forms
Can observe trends in the fossil record