a. the fossil record. the law of succession pygmy armadillo fossil glyptodontfossil diprotodon...
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A. The Fossil Record
The Law of Succession
pygmy armadillo
fossil glyptodont fossil Diprotodon
wombat
The Fact of Extinction
Fig. 22-3 Campbell and Reece
Younger stratumwith more recentfossils
Layers of depositedsediment
Older stratumwith older fossils
Rivers carry sediment into seas and swamps
Fig. 22-15
Bristolia insolens
Bristolia bristolensis
Bristolia harringtoni
Bristolia mohavensis
Latham Shale dig site, SanBernardino County, California
Dep
th (m
eter
s)
0
2
4
6
8
10
12
14
16
18
1
2
3
3
3
1
2
44
Fig. 25-4Present
Dimetrodon
Coccosteus cuspidatus
Fossilizedstromatolite
Stromatolites Tappania, aunicellulareukaryote
Dickinsoniacostata
Hallucigenia
Casts ofammonites
Rhomaleosaurus victor, a plesiosaur
100
mill
ion
year
s ag
o20
017
530
027
040
037
550
052
556
560
03,
500
1,50
0
2.5 cm4.5 cm
1 cm
Fig. 25-5 Campbell and Reece
Time (half-lives)
Accumulating “daughter” isotope
Remaining “parent” isotopeFr
actio
n of
par
e nt
iso t
ope
rem
a in i
ng
1 2 3 4
1/2
1/41/8 1/16
Bias in the fossil record:Preservation biasTemporal bias
Trends in Evolution
Cope's rule: evolution tends to increase body size over geological time in a lineage of populations.
Figure: over the last sixty million years, the average weight of horses has increased ten fold.
Understanding the type of trend (passive or driven) is importantDon’t over-interpret too much about mechanismsSelection can be going on in a passive system or in a driven one…