Tracing Evolutionary History

1
(No Transcript)
2
Tracing Evolutionary History

• Chapter 15

3
Macroevolution and the fossil record

• Macroevolution consists of the major changes in
  the history of life
• The fossil record chronicles these changes, which
  have helped to devise the geologic time scale
• Studying fossils in rock strata in an area can
  show long-term evolutionary change in an area,
  measured in eras
• Eras are time periods that are marked by mass
  extinctions
• Replaced by species that diversified from the
  survivors

4
(No Transcript)
5
The Age of Rocks and Fossils

• The sequence of fossils in rock strata indicates
  the relative ages of different species
• Radiometric dating can gauge the actual ages of
  fossils
• Once an organism dies it stops accumulating
  carbon and the carbon starts to decay, carbon-14
  decays at a specific rate called the half-life
• Determine how much is left

6
Continental Drift

• Continental drift is the slow, incessant movement
  of Earths crustal plates on the hot mantle

7

• This movement has influenced the distribution of
  organisms and greatly affected the history of
  life
• Continental mergers triggered extinctions
• Separation of continents caused the isolation and
  diversification of organisms

8
The Impact of Tectonic Plates

• Plate tectonics, the movements of Earths crustal
  plates, are also associated with volcanoes and
  earthquakes
• Californias San Andreas fault is a
  boundarybetween two crustal plates

9

• By forming new islands, volcanoes can create
  opportunities for organisms
• Example Galápagos
• But volcanic activity can also destroy life
• Example Krakatau

10
Mass Extinction and Diversification

• At the end of the Cretaceous period, many
  life-forms disappeared, including the dinosaurs
• These mass extinctions may have been a result of
  an asteroid impact or volcanic activity
• Every mass extinction reduced the diversity of
  life
• But each was followed by a rebound in diversity
• Mammals filled the void left by the dinosaurs

11
How did some survive?

• Pure Luck-
• Less affected area
• Adaptation-
• Already adapted to new environment
• In a similar environment
• Able to rapidly adapt to the new environment
• Little adaptation needed
• May have already had adaptations and used them to
  serve other purposes

12
Evolutionary Trends

• Evolution is a trend not a preordained
  destination
• Depending on conditions, one species may prevail
  over another
• It does not mean one species is better than
  another
• Evolutionary trends may reflect unequal
  speciation or survival of species on a branching
  evolutionary tree

13
(No Transcript)
14
Phylogeny

• Phylogeny is the evolutionary history of a group
  of organisms
• Represented in trees that trace the evolutionary
  relationships between species
• Fossils can help fill in the history, but the
  tree is not certain
• Represents the most likely hypothesis based on
  available evidence

15
(No Transcript)
16
Systematics

• Systematics includes taxonomy, naming and
  classification of species and groups of species
• Use binomial names
• The first name, the genus, covers a group of
  related species
• The second name refers to a species within a
  genus
• Genus and species Homo sapiens

17
Systematics

• Also group
• them into
• broader
• categories
• Domain, kingdom, phylum, class, order, family,
  genus, species
• Sometimes it is difficult and there is debate
  over placement

18
(No Transcript)
19
Homology vs. Analogy

• Homologous structures are evidence that organisms
  have evolved from a common ancestor
• In contrast, analogous similarities are evidence
  that organisms from different evolutionary
  lineages have undergone convergent evolution
• Their resemblances have resulted from living in
  similar environments

20
Molecular Biology and Systematics

• Anatomical characteristics are still the mainstay
  of classification, but molecular biology is now
  being used to identify similar species
• The evolutionary split of species correlates to
  the accumulation of differences in their DNA
• The more recently two species split from each
  other the closer their DNA sequences are

21
(No Transcript)
22
Molecular Biology and Systematics

• Used in species that are very distantly related
  and have very few structural similarities

23
Molecular Biology and Systematics

• Used in species that are very distantly related
  and have very few structural similarities
• DNA and protein analysis
• Amino acid and nucleotide sequences in electronic
  databases are used for comparison
• Regions of genomes that change at a constant rate
  can be used to show divergence when no fossils
  are found

24
Scientists try to make classification match
evolutionary history

• Clades are evolutionary branches that consist of
  an ancestral species and all of its descendants
• Cladistic analysis is often a search for the
  simplest hypotheses about a species evolutionary
  history
• Cladistic analysis tends to be more objective
  than classical methods

25

• Phylogenetic tree according to cladistic analysis
• Phylogenetic tree according to classical
  systematics

Class Reptilia
26
Classification is a work in progress

• For several decades, systematists have classified
  life into five kingdoms

27

• A newer system recognizes two basically
  distinctive groups of prokaryotes
• The domain Bacteria
• The domain Archaea
• A third
• domain, the
• Eukarya, includes all kingdoms
• of eukaryotes

28

• Classification systems are not fixed and are
  changed as further information becomes available
• These classifications are a system developed by
  man, not by nature and are therefore hypotheses