1. Topic 5.1 Evidence for Evolution
Essential idea: There is overwhelming evidence for the evolution of life on Earth.
Diagram incorrect, used for comic relief

2. 5.1 Evidence for Evolution
Nature of science: Looking for patterns, trends and discrepancies—there are common features in the bone structure of vertebrate limbs despite their varied use. (3.1)
Understandings
Evolution occurs when heritable characteristics of a species change
The fossil record provides evidence for evolution
Selective breeding of domesticated animals shows that artificial selection can cause evolution
Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
Populations of a species can gradually diverge into separate species by evolution
Continuous variation across the geographical range of related populations matches the concept of gradual divergence
Applications and skills
Application: Development of melanistic insects in polluted areas
Application: Comparison of the pentadactyl limb of mammals, birds, amphibians, and reptiles with different methods of locomotion

3. U 5.1.1 Evolution occurs when heritable characteristics of a species change
What is evolution?
Changes in species over time
What are acquired characteristics?
Develop during the lifetime of an individual
What are heritable characteristics?
Passed on from parent to offspring
What is the mechanism for evolution?
Natural selection

4. U 5.1.2 The fossil record provides evidence for evolution
Sequence in which fossils appear matches the sequence in which they would be expected to evolve
Bacteria and algae  fungi and worms  land vertebrates
Sequence fits with ecology of groups
Ex: plants before animals
Many sequences of fossils are known which can show common ancestry
Ex: horses

6. U Selective breeding of domesticated animals shows that artificial selection can cause evolution
What is artificial selection?
Selection controlled by humans
Examples?
Dogs, mustard plant derivatives

7. U Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
What are homologous structures?
Same structure different function
Supports common ancestry
What are analogous structures?
Same function different structures
What are vestigial structures?
Reduced structures that serve no function

8. U 5.1.5 Populations of a species can gradually diverge into separate species by evolution
What is speciation?
When a species becomes so separated it cannot interbreed and produce viable offspring
What is an example of how speciation can occur?
Geographic and physical isolation

9. U Continuous variation across the geographical range of related populations matches the concept of gradual divergence
What is gradualism?
Gradual changes in organisms over time
What is punctuated equilibrium? (HL 10.3)
Sudden changes in fossil record

10. A 5.1.1 Development of melanistic insects in polluted areas
What is melanistic?
Dark varieties of light colored insects
Peppered moth
Explain what occurred with the peppered moths during the Industrial Revolution?

11. A Comparison of the pentadactyl limb of mammals, birds, amphibians, and reptiles with different methods of locomotion
Crocodiles (reptiles) walk or crawl on land and use their webbed hind limbs for swimming
Penguins (birds) use their hind limbs for walking and their forelimbs as flippers for swimming
Echidnas (mammals) use all 4 limbs for walking and also use their forelimbs for digging
Frogs (amphibians) use all 4 limbs for walking and their hindlimbs for jumping
Differences can be seen in the relative length and thicknesses of the bones
Some metacarpals and phalanges have been lost during the evolution of the penguin’s forelimb
Same bones, in the same relative positions

12. Bone structure
Forelimb
Hindlimb
Single bone in the proximal part
humerus
Femur
Two bones in the distal part
Radius and ulna
Tibia and fibula
Group of wrist/ankle bones
carpals
Tarsals
Series of bones in each of 5 digits
Metacarpals and phalanges
Metatarsals and phalanges

13. 5.4 Cladistics
Essential idea: The ancestry of groups of species can be deduced by comparing their base or amino acid sequences.

14. 5.4 Cladistics
Nature of science: Falsification of theories with one theory being superseded by another—plant families have been reclassified as a result of evidence from cladistics. (1.9)
Understandings
A clade is a group of organisms that have evolved from a common ancestor
Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein
Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor
Traits can be analogous or homologous
Cladograms are tree diagrams that show the most probably sequence of divergence in clades
Evidence for cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species
Applications and skills
Application: Cladograms including humans and other primates
Application: Reclassification of the figwort family using evidence from cladistics
Skill: Analysis of cladograms to deduce evolutionary relationships

15. U 5.4.1 A clade is a group of organisms that have evolved from a common ancestor
What is a clade?
Group of organisms that evolved from a common ancestor
They can be large or small

16. U 5.4.2 Evidence for which species are part of a clade can be obtained from…
What is the most objective evidence organism belong in a clade?
Gene sequences and amino acid sequence of proteins
Species that have a recent common ancestor will have numerous similarities in their genomes
Whereas some species might look alike but diverged from a common ancestor

17. How do differences in DNA and amino acid sequences happen? Mutation
U Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor
How do differences in DNA and amino acid sequences happen?
Mutation
Mutations occur at a constant rate so they can be used as a molecular clock
This can be used to figure out when a species split from its common ancestor

18. U 5.4.4 Traits can be analogous or homologous
What are homologous structures?
Same structure different function, supports common ancestry
Human arm and cat arm
What are analogous structures?
Same function but evolved independently, convergent evolution
Human eye and octopus eye
We can use amino acid based evidence to see if organism are related

19. U 5.4.5 Cladograms are tree diagrams that show the most probably sequence of divergence in clades
What is a cladogram?
Tree diagram based on similarities and differences between the species in a clade
What are they based on?
Amino acid sequences
Principle of parsimony indicates the most probable sequence of divergence in clades
What are nodes?
Branching points on cladograms, represents a hypothetical ancestral species

20. Cladogram

21. Cladogram

22. U Evidence for cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species
Construction of cladograms and identification of clades is known as cladistics
They used to classify organisms based on morphology but this is not always accurate
With advances in technology and using amino acid sequenced, some groups have been reclassified

23. A 5.4.1 Cladograms including humans and other primate
What are the closest relatives to humans?
Chimpanzees and bonobos

24. A 5.4.2 Reclassification of the figwort family using evidence from cladistics
Scrophulariaceae or figwort family
It had over 275 genera and more than 5000 species
One research project looked at the base sequences of three chloroplast genes in a number of species
They found out that the species in the figwort family were not a true clade and that five clades had incorrectly be combined into one family
Figwort family was reclassified
Less than half of the species have been retained in the family
It went from the being the 8th largest angiosperm group to the 36th

26. S 5.4.1 Analysis of cladograms to deduce evolutionary relationships
Sequence of splits at nodes is hypothetical sequence in which ancestors of clades diverged
Some cladograms have numbers to indicate number of differences in genes or amino acid sequence
Some cladograms are drawn to scale
Cladograms are not proof and caution should be used