Lecture 6 Flashcards
4 requirements for life
- metabolism
- response to stimuli
- homeostasis
- reproduction with potential for error
are viruses alive?
no, lack metabolism and homeostasis, cannot reproduce without host cell
fossil
a preserved remnant/ evidence of organisms that lived in the past
strata
distinct layers in rock
why is our understanding of the diversity and distribution of past life is biased and incomplete?
fossils more likely to form if hard, aquatic, inshore, and decomposing organisms absent after death
3 types of fossils
- trace fossils (evidence of behaviour)
- cast (minerals fill space in sediment where organism decayed)
- petrified (tissues replaced by minerals)
ichnology
study of trace fossils
sub-fossil
high % organic material (thin carbon film, amber, tar, peat, frozen)
relative dating
done via sedimentary stratigraphy, can’t tell how long ago fossil was created but can tell which fossil came 1st, 2nd, etc
index/indicator fossils
help to read incomplete or scrambled layers, existed for a brief time with wide geographic distribution
geologic time scale
created based on the appearance and disappearance of major taxa, major events correlated with changes in eon, era, period or epoch
radiometric dating
measurement of radioactive isotopes in fossils or rocks to determine absolute dates for geologic time scale
Carbon 12
common, 6 neutrons
Carbon 14
8 neutrons, decays to N-14
half-life
when 50% of atoms in a given amount of radioactive substance have decayed