Other evidence of evolution

Chp 11

fossil

any preserved trace of an organism that lived long ago

wet, acidic soil- effect on fossilisation

minerals in bone dissolved and no fossilisation occurs

soil with no oxygen- effect on fossilisation

complete preservation of soft tissues and bones

alkaline soil- effect on fossilisation

minerals in bones not dissolved- produces best fossils

rapid burial effect

prevents decomposition and mechanical damage to fossil

location of fossil

often found near water bodies- buried by sediment so not destroyed by erosion

artefacts

objects made by humans. stone tools, carvings, cave paintings

absolute dating

actual age of specimen

relative dating

comparison of fossils to determine whether one sample is older or younger

radioisotope dating

absolute dating method to determine age of fossils, that measures the original radioactive material that decays at a known rate

parent isotope

unstable radioactive isotope present at the start

daughter product

product formed from radioactive decay

half-life

time for half of the radioactive parent material to decay

potassium argon dating

absolute dating method using the known rate of decay of radioactive potassium-40 to form calcium-40 and argon-40

half-life of potassium-40

1.25 billion years

uses of potassium-argon dating

for volcanic rock and material. can only date rocks over 100,000 yrs, most useful over 200,000 yrs

radiocarbon dating

absolute dating method based on radioactive decay of radioactive isotope of carbon-14 to nitrogen

carbon-14 origination (radiocarbon dating)

present in atmosphere. when alive, carbon continually exchanged with environment. with death, exchange stops, carbon-14 decays

half-life of carbon-14

5730 years

uses of radiocarbon dating

recent, once-living organic material, useful up to 50,000 years old

limitations of radiocarbon dating

need to account for C-14 : C-12 ratio of atmosphere when organism alive, can only be for relatively recent remains. C-14 amount becomes very small

stratigraphy

study of layers/strata of sedimentary rock. if sequences of layers similar, are likely to be same age

principle of superposition

in layers of sedimentary rock, the layers at the top are younger than those beneath them

index fossils

fossil that are widely distributed and present for a limited period of time. used in relative dating of stratigraphy

embryology

comparing early stages of development of organisms

homologous structures

structures in different species that are similar, but used in different ways

vestigial structures

structures that no longer fulfil origin purpose or have a reduced function

embryology comparison

human, chickens and fish embryo have slits, arches in necks, tails. indicate common ancestor

homologous structure comparison

pentadactyl limb of four-limbed vertebrates. wings of birds, leg of horse, feet of reptiles and human hand have similar structure

vestigial structure - nictitating membrane

transparent third eyelid for protection (birds). in humans - pinkish membrane at inner corner of eye. unable to fulfil original function