B14 Flashcards
define fossils
remains of organisms that lived millions (thousands) years ago perserved in rock or ice
(best evidence of evolution)
2 types of fossil records
mummification
rock fossils
why would there be no decay of the organism
lack of heat
lack of oxygen eg in bogs
chemicals that kill bacteria (acid in bogs)
lack of water (deserts)
purpose of mummification
see what the organisms looked like (colour, texture)
extract DNA for analysis and comparison with modern day organisms
4 variety of rock fossils
animal dies and body is buried by sediment
mould fossil
cast fossil
trace fossils
how does body of animal used as fossil record
soft organic parts decay and disappear
hard parts eg bones decay more slowly and replaced by minerals forming rock
what are trace fossils
footprints, burrows and root shapes made by organisms can make casts in the right conditions
why would a fossil record be incomplete?
4 reasons
benefits of fossil record
trace how certain organisms have changed overtime or where change hasn’t occurred
help use reconstruct the ecology, climate and environment million years ago
evolution of horse
early horse lived on swampy ground : short and had 4 well spread toes to avoid it sinking into the mud
evovled as the ground became drier : less toes in contact with ground allowed faster running + grow taller to withstand predators
modern horse = one toe forming hoof to run very fast on hard ground
define extinction
permanent loss of all members of a species
causes of extinction
the environment is no longer suitable for an organism
predators + new diseases
new competitors that are more successful outcompeted for resources
what happen to some species
descendants live on earth eg birds descendants of dinosaurs
