BIOEE 1780 Lecture 29: Lecture 29
7 May 2018
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Formula for Charting Population Growth: N2 = N1 + births + immigrations - death - emigrations
• N1 = current size of the population
• N2 = size of the population in the next time step
Formula for Analyzing the Diversity of Species/Clades: D2 = D1 + originations + immigrations - extinctions
- emigrations
• D = diversity (i.e. the total number of species in a particular clade)
• In many cases, macroevolution is studied on a global scale, rather than in one particular region. This
eliminates immigration and emigration from the equation: D2 = D1 + originations - extinctions
• This data is stratigraphic - you don't have all of the data, so you have to estimate.
o Diversity is tabulated from a stratigraphic range data (usually done in geological stages).
Paleontologists study the morphology of fossils to determine phylogenetic relationships.
Only 10% of living organisms would fossilize.
• The fossil record sample size is small.
• Fossils are biased, commonly fossilizing hard-shelled marine organisms.
o 99.9% of fossils are in 8 phyla
• The fossil record is incomplete.
What do we learn only from fossils about the history of life?
1. The fossil record gives important perspectives on intermediates.
a. Darwin believed that the lack of intermediates was due to the imperfection of the fossil record.
b. Transitional forms/intermediates aren't common, but they are present.
2. Fossils inform biotic history - we can infer that extant species share a common ancestor in the past.
3. Fossils calibrate rates of molecular evolution.
a. Fossils give minimum ages of taxa.
4. Fossils are critical in reconstructing climate history and ancient environments.
a. Examples:
i. Pollen record - allows for reconstruction of plant communities
ii. O isotopes reveal ocean temperatures in the past
iii. C isotopes can provide information about diet
5. Tempo (timing) and mode of evolution through time
a. Tempo = rate at which evolution occurs
b. Mode of evolution = the kind of evolution that's occurring
i. Darwin recognized two modes of evolution:
1. Gradual Change (now known as Anagenesis or Gradualism): the gradual change over
time in morphology; not speciation or lineage splitting
a. Darwin couldn't find evidence of anagenesis in the fossil record. He believed this
was due to the imperfections of the fossil record.
b. Post-Darwin, paleontologists found a few examples of anagenesis.
c. Often, there is little net change over time.
2. Splitting (now known as Cladogenesis): the splitting of lineages
c. Time-Morphology Plot: depicts morphological change through time
i.The tempo is equivalent in these 3 scenarios, because all of the change is observed between the
dashed lines.
ii.In actuality, these won't be perfect lines due to variance within the population.
Document Summary
Formula for charting population growth: n2 = n1 + births + immigrations - death - emigrations: n1 = current size of the population, n2 = size of the population in the next time step. Formula for analyzing the diversity of species/clades: d2 = d1 + originations + immigrations - extinctions. Emigrations: d = diversity (i. e. the total number of species in a particular clade) In many cases, macroevolution is studied on a global scale, rather than in one particular region. This eliminates immigration and emigration from the equation: d2 = d1 + originations - extinctions. This data is stratigraphic - you don"t have all of the data, so you have to estimate: diversity is tabulated from a stratigraphic range data (usually done in geological stages). Paleontologists study the morphology of fossils to determine phylogenetic relationships. Fossils are biased, commonly fossilizing hard-shelled marine organisms: 99. 9% of fossils are in 8 phyla. Pollen record - allows for reconstruction of plant communities.
