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

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

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

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

U 5.1.3 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

U 5.1.4 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

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

U 5.1.6 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

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?

A 5.1.2 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

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

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

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

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

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

How do differences in DNA and amino acid sequences happen? Mutation U 5.4.3 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

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

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

Cladogram

Cladogram

U 5.4.6 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

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

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

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