Phylogeny and Systematics

1
Chapter 25

• Phylogeny and Systematics

2
Phylogeny

• Evolutionary history of a species or group of
  related species
• Systematics is the science of constructing
  phylogeny

3
Fossils

• Serve as a great tool in determining the ancestry
  of species
• Fossils are formed by sedimentary rock.
• Hardened parts of the organism are replaced with
  minerals and form rock like structures
• Fossils are also things like footprints, animal
  burrows, feces, pollen, etc.

4
Dating Fossils

• Relative Dating identifying organisms and time
  periods based on the types of fossils found
• We define each time period and major events that
  occurred on the Earth with these different layers
  of fossils

5
Geological Time Scale

• History of Earth divided into four eras
• Precambrian Earths origin to 543 mya
• Ends with radiation of most modern animal phyla
  (called the Cambrian explosion)
• Paleozoic 543 mya to 245 mya
• Ends with mass extinctions of many marine and
  terrestrial organisms, radiation of reptiles, and
  origins of mammal-like reptiles
• Mesozoic 245 mya to 65 mya
• Age of Reptiles, flowering plants appear
• Cenozoic 65 mya to present
• Major radiation of mammals, birds, and
  pollinating insects

6
(No Transcript)
7
Absolute Dating

• Age of a fossil is given in years, instead of
  before or after (ie before Mesozoic)
• Radiometric dating measure of certain
  radioactive isotopes in fossils or rocks.
• Each organism contains two types of carbon
• Carbon-12 and carbon-14
• When the organism dies it stops accumulating
  carbon and carbon-14 breaks down into nitrogen-14
• We can then measure the ratio of carbon-14 to
  nitrogen 14 to get the date of the fossil.

8
Absolute Dating

• Carbon dating is used for young fossils
• Uranium dating is used for older fossils

9
Phylogeny and Continental Drift

• History of the Earth helps explain the current
  biogeography (where animals are and are not)
• Continental drift is the major geographic factor
  correlating with the spatial distribution of
  organisms
• Continents drift around on molten lava
• North America and Europe drift apart about 2 cm
  per year

10
Continental Drift

• Causes mountain formation and volcanoes
• Near the end of the Paleozoic era all the land
  masses were together
• Pangea
• Caused life on land and water to be more
  competitive

11
Plate Tectonics
12
Continental Drift

• Pangea then began to break apart during the
  Mesozoic era
• This isolated populations and increased the
  evolutionary arena
• Remember that population isolation is one key in
  speciation
• This explains why we see the same fossils in
  Africa as South America

13
(No Transcript)
14
History of Life Mass Extinctions

• Fossil record details long periods of relatively
  little change with abrupt changes in species
• Due to Environmental Factors
• Biological Factors
• Certain species disappear while others that
  survive change rapidly
• As one species goes extinct it has a great impact
  on other organisms

15
Two Important Mass Extinctions

• Permian mass extinction
• Claimed about 90 of marine species
• 8 out of 27 orders of Permian insects perished
• Occurred around the time of the formation of
  Pangea
• Most active volcano period in the last half
  billion years

16
Two Important Mass Extinctions

• Cretaceous mass extinction
• Doomed more than half the marine life
• Exterminated many plants and all the dinosaurs
• Main theory is that a asteroid or comet hit the
  earth
• Evidence of impact
• Thin layer of iridium in the sediment at the time
  of impact

17
(No Transcript)
18
Systematics Connecting Classification to
Phylogeny

• Systematics tracing phylogeny
• Includes taxonomy which is the naming and
  classification of species or groups of species
• Taxonomy places groups of organisms into
  classifications that reflect their relationship
  to one another

19
Taxonomy

• Each species has a binomial name
• Consisting of its genus and species name
• Leopard (Panthera pardus)
• First letter capitalized and italicized or
  underlined
• We use latin for the names because it is a dead
  language and doesnt change meanings
• Like cool today means good, and 40 years ago it
  meant something cold
• It is also a way to avoid ambiguity
• When we say bear there are many kinds of bears so
  use the species name to refer to the particular
  bear

20
Classification

• We group similar species into the same genus, and
  similar genus into the same family
• Leopard (Panthera pardus) is closely related to
  the african lion (Panthera leo) and the Tiger
  (Panthera tigris)

21
(No Transcript)
22
Phylogenetic Trees

• Reflect the hierarchal classification of
  organisms