Phylogeny and classification D.5.5-D.5.10 Phylogeny and classification http://www.youtube.com/watch?feature=player_embedded&v=F38BmgPcZ_I

Linking Classification and Phylogeny Evolutionary relationships in branching phylogenetic trees -- Called a cladogram

LE 25-9 Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Species Genus Panthera Mephitis Lutra Canis Family Felidae Mustelidae Canidae Order Carnivora

Cladogram Each branch point represents the divergence of two species

Evolutionary Relationships/ phylogeny is depicted in an evolutionary tree/ cladogram Evolutionary relationships in branching trees

Evolutionary Relationships/ Phylogeny is depicted in an Cladogram Nodes show that groups share a common ancestor & evolved from this ancestor

Evolutionary Relationships/ Phylogeny is depicted in an Cladogram Each branch point represents the divergence of two species Branching

Evolutionary Relationships/ Phylogeny is depicted in an Cladogram Carnivora Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) lupus (wolf) Species Genus Family Order Felidae Mustelidae Canidae Lutra This evolutionary tree shows that leopards, skunks, otters, dogs, wolves all share a common ancestor. What other conclusions can you make form this phylogenic tree? Common Ancestor

How many common ancestors does G and H have? Evolutionary Relationships/ Phylogeny is depicted in an Cladogram How many common ancestors does G and H have? three How many common ancestors does G and E have? TWO Which pair are more closely related G and H OR G and E? G and H share more ancestors.

In the below evolutionary tree which groups are more closely related J and K OR J and H? J and K are more closely related because they share two common ancestors I, A. And J and H only share one common ancestor, A

Evolutionary Trees/ Phylogenies also show relative time. The top of the tree being more recent. The bottom showing the distant past

D.5.5 Define Clade and cladistics A cladogram depicts patterns of shared characteristics among taxa A clade is a group of species that includes an ancestral species and all its descendants Cladistics studies resemblances among clades

D.5.5 Define Clade and cladistics Cladistics: a System of classification which groups taxa together according to the characteristics which have most recently evolved. Used to decide how close a common ancestor is, researchers look at how many primitive and derived traits the organism share.

IB Objective D.5.10 Discuss the relationship between Cladograms & Classification: Classification traditionally based on morphology/ physical characteristics ; While Cladistics is based on molecular differences/base sequences/amino acid sequences. This is a strength of cladistics because it maintain objectivity; Cladistics is based on probability but improbable events do occur, so relationships can be wrong; and this is thus a weakness of cladistics; Clades includes ancestral species/descendants from that species; The Members of clade share set of features not found in more distant relatives; Cladogram is a tree-like diagram where nodes/branches represent the splitting of (two) new groups from a common ancestor; Different cladograms can represent same relationships in a group; Cladogram timescale not necessary; Classification based on cladograms is often same as traditional classification; However, in some groups, cladograms have led to revised classification;

A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

LE 25-10a Grouping 1 Monophyletic

A monophyletic group = CLADE

D.5.7 Outline methods to construct cladograms and the conclusions that can be drawn from them How cladograms are made Make a list of all the organisms which will be included in your cladogram List the characteristics each organism possesses

Then you make a table like the one below: D.5.7 Outline methods to construct cladograms and the conclusions that can be drawn from them: How cladograms are made Once the list is made the characteristics common to all organisms this trait is considered a primitive trait. Then you make a table like the one below: Multicellular Vertebral column Hair placenta total sponge ✓ x 1 sailfish 2 wombat 3 elephant 4

STEP 5: USE DATA TABLE TO CONSTRUCT A VENN DIAGRAM

STEP 6. CONVERT VENN DIAGRAM TO A CLADOGRAM

D.5.7 Outline the conclusions that can be drawn from them Cladograms are constructed to show evolutionary relationships between organisms Organisms at the bottom are the earliest ones Organisms at the top of the branch are considered the most recent. Biochemical evidence (DNA Similarities) can be used instead of physical characteristics

Organisms at the bottom are the earliest ones Cladograms are constructed to show evolutionary relationships between organisms Organisms at the bottom are the earliest ones Organisms at the top of the branch are considered the most recent. Drosophila Lancelet Fish Amphibian Bird Human Rat Mouse Cenozoic Mesozoic Paleozoic 65.5 251 542 Neoproterozoic Millions of years ago

Human Mushroom 30% Tulip 40% Percentage differences between sequences Comparison of possible trees 15% 20% 5% 10% 25% Tree 1: More likely Tree 2: Less likely Biochemical evidence (DNA Similarities) can be used instead of physical characteristics

LE 25-15ab Sites in DNA sequence 1 2 3 4 5 6 7 Biochemical evidence (DNA Similarities) can be used instead of physical characteristics I II Species III IV I II III IV Bases at site 1 for each species Base-change event

LE 25-16 Lizard Bird Mammal Four-chambered heart Mammal-bird clade Lizard-bird clade

D.5.6 Distinguish with example between analogous characteristics and homologous characteristics In constructing a phylogeny/ cladograms, one needs to distinguish whether a similarity is the result of homology or analogy Homology is similarity due to shared ancestry Analogy is similarity due to convergent evolution

D.5.6 Distinguish with example between analogous characteristics and homologous characteristics Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages

Assignment. Make two cladograms: First cladogram–PLANTS (topic 5.5) show the evolutionary/ phylogenic relationships between bryophytes, filicinophyta, coniferophyta, angiospermaphyta Second Cladogram – Animals (topic 5.5) show the evolutionary/ phylogenic relationships between porifera, cnidaria, platyhelminthes, Annelida, Mollusca, Arthropoda.

IB Practice Test Question 1 Define the term clade. (1)

IB Practice Test Question 1 -- Answer A clade is a group of related organisms sharing a common ancestor / a group of organisms containing an ancestor and all of its descendants

IB Practice Test Question 2 Suggest two reasons for using cladograms for the classification of organisms.(2)

IB Practice Test Question 2 -- Answer Methods used to prepare cladograms use a different approach from traditional classification/taxonomy; Cladograms show ancestral relationships; Cladograms reflect how recently two groups shared a common ancestry; cladograms are (objective/accurate because they are usually) based on molecular differences (e.g. differences in DNA/ RNA Proteins); Cladograms should be considered as a good complement to traditional classification;

IB Practice Test Question 3 Using examples, distinguish between analogous characteristics and homologous characteristics.(4)

IB Practice Test Question 3 -- Answer Analogous Structures: [2 max] similar structures but different (evolutionary) origins / different basic structure but same function; e.g. vertebrate and invertebrate eyes / insect and human legs; Accept any other valid example. Homologous Structure: [2 max] structures are of similar origin / same basic structure but different functions; e.g. pentadactyl limbs in vertebrates; Accept any other valid example.

IB Practice Question 4 The cladogram below shows the classification of species A to D. Deduce how similar species A is to species B, C and D. (2)

IB Practice Question 4 -- Answer A is most similar to B; A is equally similar to C and D; A is least similar to both C and D;

IB Practice Test Question 5 Outline the evidence provided by DNA for the common ancestry of living organisms. (2)

Practice Test Question 5-- Answer all living organisms use DNA as genetic/hereditary material; genetic code is universal (e.g. nitrogenous bases code for proteins); The idea that mutations accumulate gradually in DNA; and thus the more differences there are in DNA between species the longer the time it has been since those species shared a common ancestor;

IB Objective D.5.10 Discuss the relationship between Cladograms & Classification: Classification traditionally based on morphology/ physical characteristics ; While Cladistics is based on molecular differences/base sequences/amino acid sequences. This is a strength of cladistics because it maintain objectivity; Cladistics is based on probability but improbable events do occur, so relationships can be wrong; and this is thus a weakness of cladistics; Clades includes ancestral species/descendants from that species; The Members of clade share set of features not found in more distant relatives; Cladogram is a tree-like diagram where nodes/branches represent the splitting of (two) new groups from a common ancestor; Different cladograms can represent same relationships in a group; Cladogram timescale not necessary; Classification based on cladograms is often same as traditional classification; However, in some groups, cladograms have led to revised classification;