Biodiversity Through Earth History

1
Chapter 13 Biodiversity Through Earth History
2

• evolution
• natural selection
• adaptation
• extinction
• View diversity as dynamic
• rate of change in number origination -
  extinction
• of species on earth rate
  rate
• logistic growth

3
(No Transcript)
4
Data here indicate that species diversity of
marine organisms has increased exponentially over
the last 600 million years - seems to disagree
with logistic growth curve (no steady state is
approached) These data are not trusted - they
may simply mean that the analysis can be done
only on sedimentary rocks we have access to
(Dev., Ter.) - the more volume of sediment we
have the more species we find - not a good
measure of diversity
5
Data on the number of new appearances of marine
invertebrates of a given age (namely, as they
appeared) by phyla-classes-orders taxonomic
levels. Compare to previous data - no
exponential growth is observed when looking at
the evidence this way
very productive periods
6
Marine invertebrate fossils indicating diversity
through geological time - time history of
order-family-genus diversity. Five major
perturbations over the past 500 m. y. Largest
mass extinction at end of Permian, 251 m. y. ago
- Best researched extinction (dinosaurs) is the
Cretaceous-Tertiary (K-T), 65 m. y. ago. Fossil
record indicates high taxonomic levels are less
affected, lower taxonomic levels recover rapidly
from mass extinctions - biota of Earth is rather
resilient. Mass extinctions cause great losses
but stimulate origination.
65 my
440 my
360 my
251 my
206 my
7
Location of the Chicxulub impact crater
Support for meteorite impact as a cause for the
K-T mass extinction frequency of collisions of
large objects with Earth.
Size of impact crater
Evidence supporting meteorite impact and its
effect on plants at the K-T boundary
8
Impacts may be with comets and with asteroids.
Comets are in stable orbit around the Sun in the
Oort cloud region, mainly. Asteroids (made of
minerals) are around the Sun in the asteroid
belt.
Mass extinctions seem to occur once every 100 m.
y. More precisely there is a 26 m.y periodicity
in the fossil record, again suggesting
extraterrestrial causes for extinctions
9
Gravitational disturbances might send comets or
asteroids our way? You are on your own with any
of these hypotheses!
10
A CLOSER LOOK - The K-T Strangelove Ocean