fossils Flashcards
1
Q
fossils
A
the ‘remains’ of organisms from millions of years ago which are found in rocks
2
Q
gradual replacement by minerals
A
- things which don’t decay easily e.g teeth and bones can last a long time when buried
- eventually replaced by minerals as they decay, forming a rock-like substance shaped like original part
- surrounding sediments turn to rock but fossil stays distinct inside the rock and eventually someone digs it up
3
Q
from casts and impressions
A
- an organism is buried in a soft material e.g clay
- clay later hardens around it and organism decays, leaving a cast of itself e.g footprints, burrows, rootlet traces
4
Q
from preservation in places where no decay happens
A
- in amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive
- in glaciers its too cold for decay microbes to work
- peat bogs are too acidic to work
5
Q
why can’t scientists be certain about how life began?
A
- many early forms of life were soft-bodied, which means that they have left few traces behind - traces there were have been mainly destroyed by geological activity
6
Q
what can we learn from fossils?
A
how much or how little different organisms have changed as life developed on Earth
