patterns of evolution Flashcards
lecture 12 - Mark Briffa
macroevolution
speciation events or splits from a lineage
microevolution
changes within a species or within a lineage
the fossil record - problems
- new branches should appear to be gradual as microevolutionary changes accumulate
- but in fossil recoed new species appear suddenly
explanations :
- major gaps in fossil record - gradual transitions ar absent
- evolutionary chnages happen suddenly in short bursts
punctuated equillibrium
the idea that evolution occurs in spurts instead of following the slow, but steady path that Darwin suggested
phyletic gradualism
model of evolution which theorizes that most speciation is slow, uniform and gradual
phylogeny
the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms
adaptive radiation
rapid increase in the number of species with a common ancestor, characterized by great ecological and morphological diversity
convergent evolution
the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities
analogous characters
having similarities in functions but different evolutionary origins
homologous characters
derived from the same common ancestor
co-evolution
the process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another
happens when two or more species directly influence each other’s evolution = exert selection pressure on each other
co-adaptations
the process by which two or more species, genes or phenotypic traits undergo adaptation as a pair or group
trilobites and predators ( arms race )
- hard exoskeleton appeared in Cambrain arthropods
- the sea became dangerous at the time
- trilobites under strong selection pressure to avoid predatation
fossils
- transformed body parts
- shell, bones, teeth - activity ( ‘trace fossils’ )
- burrows, footprints - preserved remains ( ‘sub fossils’ )
- shells, remains in amber - organic cheicals
- any body parts
step one : how fossils are formed
body survives long enough after death to undergo fossilisation
- soft parts are destroyed quickly
- few fossils of soft bodied organisms
- even hard parts are likely to be destroyed
step two : how fossils are formed
remains must become buied in sediment at the bottom of a water column
- fossils are only found in sedimentary rocks
the chance of fossilisation depends on proxiity to sediment
- terrestrial = low
- in water/on sediment = medium
- in sediment = high
step three : how fossils are formed
permineralization
- sediement covered by more layers
- compacts into rock - may deform or destory the fossil
(or) - hard minerals leach out and rocks impregnate the remains
- original compounds replaced and leach out
step four : how fossils are formed
exposure ( the ‘unlikely’ event )
- fossil means something dug up
- tectonic pressures can move the fossil around
- re-expose it in a terrestrial area
- can also be lost forever
radio-carbon dating - dating fossils
- 5730 years after death 1/2 the C14 to N14
( C14 half life = 5730 ) - can work out date of death by examining the ratio
- only for fossils up to 40,000 years
volcanic ash - dating fossils
- many sediments contain volcanic ash (‘tephra’)
- Potassium and Argon ( unstable isotopes ) in ash
- decay ore slowly that C14 - fossils older than 100,00 years
paleomagnetic dating - dating fossils
- currents in Earths core change direction of magnetic field ‘normal’/’reserved’
- determines allignment of magnetic particles when rocks form
- age rocks by comparing the polarity to cores of rock from sea bed
relative dating - dating fossils
compare fossils to fossils of known age and other strata that lookk similar
paleontology
study of fossils
Cretaceous
65 - 144 mya
extinction of most dinosaurs
Sinosauropteryx ( dinos )
- melanosomes : contain the pigments in hairs and feathers
