1. Phylogeny and Systematics How do we classify organisms?

2. Review So far we have looked at:
1. The history of ideas surrounding how organisms change.
2. Darwin’s ideas of change and how natural selection works
3. Genetic basis of natural selection
4. How new species can arise

3. Now ask the question:
How do we organize our knowledge about species and put that into some meaningful classification?
Determine the phylogeny - the evolutionary history of a species or group of species.

4. First step: Naming organisms
Binomial nomenclature:
Invented by Carl Linnaeus
Every species has two names:
Genus & species
e.g. Homo sapiens

5. An aside:
A couple of rules about using species names:
1. They are always underlined or in italics
2. The name of the genus is always capitalized but the species name never is.
3. It’s a name like yours - you don’t refer to a species as ‘the’ Homo sapiens - just Homo sapiens.
4. The plural of species is species and the plural of genus is genera (NOT ‘genuses’)

6. Hierarchical Classification
Species name for a leopard
Genus for all leopards and their relatives
Family for all cats
Order for all carnivorous mammals
Class for all fur-bearing animals
Phylum for animals with spinal columns
Kingdom for all organisms without photosynthesis
Domain for all organisms with eukaryotic cells

7. This information can also be presented as a phylogenetic tree:

8. How are trees constructed?
Based on different kinds of homologous structures called ‘characters’:
Shared primitive characters: those structures that are shared with larger related groups - e.g. all vertebrates share a backbone
Shared derived characters; those structures that are shared by a smaller group (or clade) - e.g all mammals share milk production

9. A simple classification of vehicles:
Imagine that you have sampled a number of objects and found
the following characteristics:
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine

10. A simple classification of vehicles:
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
What are the shared primitive and derived characters?
Wheels - primitive (all have them)
wheels

11. A simple classification of vehicles:
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
What are the shared primitive and derived characters?
Wheels - primitive (all have them)
Engine - possessed by 3 of 5
No engine
Engine
wheels

12. A simple classification of vehicles:
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
What are the shared primitive and derived characters?
1 wheel
2 wheels
Wheels - primitive (all have them)
Engine - possessed by 3 of 5
Wheels - objects with no engine have either 1 or two wheels
No engine
Engine
wheels

13. A simple classification of vehicles:
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
Box
No box
What are the shared primitive and derived characters?
1 wheel
2 wheels
Wheels - primitive (all have them)
Engine - possessed by 3 of 5
Wheels - objects with no engine have either 1 or two wheels
No engine
Engine
Box - objects have a box on the back or not
wheels

14. A simple classification of vehicles:
Glass
Enclosed
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
Box
No box
What are the shared primitive and derived characters?
1 wheel
2 wheels
Wheels - primitive (all have them)
Engine - possessed by 3 of 5
Wheels - objects with no engine have either 1 or two wheels
No engine
Engine
Box - objects have a box on the back or not
Box - glassed in or enclosed
wheels

15. A simple classification of vehicles:
SUV
Van
A simple classification of vehicles:
Glass
Enclosed
2 wheels, no engine
4 wheels, gas engine, glassed box on back
4 wheels, gas engine, no box on back
4 wheels, diesel engine, enclosed box on back
1 wheel, no engine
Car
Box
No box
Unicycle
Bicycle
What are the shared primitive and derived characters?
1 wheel
2 wheels
Wheels - primitive (all have them)
Engine - possessed by 3 of 5
Wheels - objects with no engine have either 1 or two wheels
No engine
Engine
Box - objects have a box on the back or not
Box - glassed in or enclosed
wheels

16. Shared primitive and derived characters?
SUV
Van
Glass
Enclosed
These change depending on the level
of classification you are talking about
e.g. Wheels are a shared primitive character of all vehicles
but the engine is a shared primitive character for the truck, car and SUV.
Car
Box
No box
Unicycle
Bicycle
1 wheel
2 wheels
No engine
Engine
wheels

17. How are trees constructed?

18. History of Life on Earth

19. Hypothesized stages in the appearance of life
Abiotic synthesis of organic molecules
Polymerization of small molecules into larger ones
Formation of polymers into protobionts
Origin of a self-replicating molecule (protobiont)

20. Kinds of evidence used: Fossil Record

21. Dating Fossils
If fossils are used to establish the history of life, there must be a way of telling how old they are.
Radiometric dating
-use radioisotopes
- not stable and will change (or decay) into
other kinds of isotopes
e.g. carbon-14 (C14)
Nitrogen-14 (N14)
Parent isotope
Daughter isotope

22. Dating Fossils Sequence of events Original level (C14)
Stops accumulating carbon (C14)
Original level (C14)
Ancient creature dies
C14 begins to decay and is replaced by N14

23. Dating Fossils Sequence of events Ratio of C14 : N14 ( )
Stops accumulating carbon (C14)
Original level (C14)
Ancient creature dies
C14 begins to decay and is replaced by N14
Ratio of C14 : N14 ( )
= time since the animal died (and radioisotope decay began)

24. Molecular Clocks Number of sequence changes Time since groups diverged
timing evolutionary events by looking at rates of change of sequences in genes
these sequences change at constant rates
Number of sequence changes
Time since groups diverged

25. All other plants and animals Algae and first invertebrates
History of Life
What does the fossil record and dating fossils tell us
about the history of life on Earth?
Oldest rocks
Oldest eukaryotes
All other plants and animals
Origin of earth
Oldest cell fossils
Algae and first invertebrates

26. History of Life

27. History of Life Key events Origin of prokaryotes Orgin of eukaryotes
Origin of multicellular
eukaryotes

28. 1. Origin of Prokaryotes
Prokaryote - a type of organism lacking a membrane-enclosed nucleus and membrane-enclosed organelles.
= bacteria
Oldest known fossils - stromatolites - bacterial mats

29. 2. Origin of Eukaryotes
Eukaryote - a type of organism with a membrane-enclosed nucleus and membrane-enclosed organelles.

30. 2. Origin of Eukaryotes
Endosymbiosis

31. 2. Origin of Eukaryotes
Endosymbiosis
Animals and
Fungi
Plants

32. 3. Origin of Multicellular Eukaryotes
First multicellular organisms
Colonial
-show cellular differentiation

33. Tree of Life (very simplified!)
Bacteria
Universal
ancestor
Archaea
Protista
Plants
Eukarya
Amoebas
Fungi
Animals