Alexander S. Berman 4A

 Pages in the IB book: ◦

 Taxonomy = the science of classification: arranging organisms into groups, which provides several advantages: ◦ species identification: members of a species share nearly all the same characteristics ◦ predictive value: groups of related taxa share many common characteristics ◦ evolutionary links: shared derived characteristics are inherited from common ancestors ◦ effective communication: all scientists use the same terminology for taxonomy  Taxonomy uses both morphological and biochemical methods to distinguish homologous structures from analogous structures ◦ avoids the problem of convergence, in which unrelated organisms have similar morphologies, called analogous structures ◦ emphasizes homologous structures which are those derived from a common ancestor

 Every known living organism on earth uses DNA as its main source of genetic information  All proteins found in living organisms use the same 20 amino acids to form their polypeptide chains  Amino Acids have 2 possible orientations: left handed and right-handed. ◦ For all living things on Earth no right amino acids were observed

 Phylogeny- study of the evolutionary past of a species  By comparing the similarities in the polypeptide sequences of certain proteins in different groups of animals one can trace their ancestery  With advances in DNA sequencing, the study of nucleic acid sequences in an organism’s DNA as well as its mitochondrial DNA has been beneficial in establishing biochemical phylogeny.  Changes in the DNA sequences of genes from one generation to another are partly due to mutations and the more differences there are between the 2 species, the less closely related the 2 species are.

 Differences in polypeptide sequences accumulate steadily and gradually over time as mutations occur from generation to generation in a species  By comparing homologous molecules from 2 related species.  Look at the differences between the species ◦ Ie: 3 different species- A, B, C. Comparing DNA sequencing between the 3. Between A and B there are 23 differences. Between A and C there are 123 differences. Therefore, it can be concluded that Species A and B are closer than A and C. (Add a little TOK in there for ya)

 A way to measure differences: DNA Hybridization ◦ Take 1 strand of DNA from species A and a homolgous strand from species B and fuse them together. Where the base pairs connect, there is a match; where they are repelled and do not connect, there is a difference in the DNA sequence and in conclusion no match.

 Cladistics ◦ A system of classification which groups taxa together according to the characteristics which have most recently evolved.  Clade ◦ a taxonomic group of organisms classified together on the basis ofhomologous features traced to a common ancestor.

Analogous CharacteristicsHomologous Characteristics Organisms which may have the same function but they do not necessarily have the same structure and they are not derived from the same ancestor Ones derived from the same part of a common ancestor Fins in aquatic organismsPresence of eyes Analogous ExamplesHomologous Characteristics Wings used for flying are an example: eagles, mosquitoes, bats all use wings to fly. Although these organisms are classified in the animal kingdom, they are certainly not placed in the same clade simply because of their ability to fly The 5 fingered limbs found in organisms like humans, whales or bats. The shape and the # of bones might vary and the function may vary but the general format is the same. Therefore they have a common ancestor Dolphins vs. Sharks. Both have fins but sharks are fish where dolphins are mammals Simple eyes found in certain molluscs such as the Nautilus function as pinhole camera without a system of lenses, whereas highly evolved eyes like those of birds or prey use crystalline lenses, adjustable irises and muscles to help focus on objects at different distances

1. Make a list of organisms which will be included 2. List as many possible characteristics which each organism possesses 1.ie: backbone, hair, opposable thumbs etc 3. Once list has been made there will be one which is common to all of the organisms being studied 1.The ancestral trait is called primitive characteristics 1.Ie: eukaryotic, multicellular, even backbone 4. Make a table that shows the derived characteristics along the top row and the names of the organism in the first column 5. From info presented on the table you can make the cladogram 1.First branch from the bottom belonging to the organism with the fest derived traits. The organims with the most derived characteristics goes to the top of the last branch.

1: all organisms come from a eukaryotic ancestor because based on the table (which wasn’t shown) it is obvious that they are all multi-cellular 2: the cladogram shows that lizards evolved after salamanders because they possess the derived characteristics of claws or nails, which is more evolved than the salamander’s characteristics 3: the observer can deduce from the cladogram on our left that any 2 organisms found on successive branches are more closely related to each other than those found on branches which are separated by one or more nodes ie: chimps are more closely related to mice then they are to perch. Note: see the Jaws line that was drawn? well, everything to the right of that line has jaws while everything to the left doesn’t. it was put in there to show evolution.

 Cladograms are simply hypothesis that are drawn.  New evidence can be added which will “update” the hypothesis

 pa.edu/faculty/farabee/biobk/cladogram_1.gif&imgrefurl= / lass.html&h=377&w=560&sz=26&tbnid=cBUjNOOAnlUv9M:&tbn h=73&tbnw=109&prev=/search%3Fq%3Dcladogram%26tbm%3Di sch%26tbo%3Du&zoom=1&q=cladogram&docid=sK9- KkZ9M8u6MM&hl=en&sa=X&ei=3OMMT4WmPILY0QH- 4djpBQ&sqi=2&ved=0CEgQ9QEwBQ&dur=199 pa.edu/faculty/farabee/biobk/cladogram_1.gif&imgrefurl= / lass.html&h=377&w=560&sz=26&tbnid=cBUjNOOAnlUv9M:&tbn h=73&tbnw=109&prev=/search%3Fq%3Dcladogram%26tbm%3Di sch%26tbo%3Du&zoom=1&q=cladogram&docid=sK9- KkZ9M8u6MM&hl=en&sa=X&ei=3OMMT4WmPILY0QH- 4djpBQ&sqi=2&ved=0CEgQ9QEwBQ&dur=199  &hl=en&sa=N&fhp=1&biw=944&bih=927&tbm=isch&tbnid=hcb nAV661qPr3M:&imgrefurl= dogram&docid=9Y4fHODBdy98fM&imgurl= ctionary.com/images/science/AScladog.jpg&w=456&h=316&ei= KeMMT8n_GqPv0gHclKn2BQ&zoom=1&iact=hc&vpx=283&vpy= 445&dur=6467&hovh=187&hovw=270&tx=196&ty=103&sig= &page=1&tbnh=127&tbnw=183&start =0&ndsp=20&ved=1t:429,r:9,s:0 &hl=en&sa=N&fhp=1&biw=944&bih=927&tbm=isch&tbnid=hcb nAV661qPr3M:&imgrefurl= dogram&docid=9Y4fHODBdy98fM&imgurl= ctionary.com/images/science/AScladog.jpg&w=456&h=316&ei= KeMMT8n_GqPv0gHclKn2BQ&zoom=1&iact=hc&vpx=283&vpy= 445&dur=6467&hovh=187&hovw=270&tx=196&ty=103&sig= &page=1&tbnh=127&tbnw=183&start =0&ndsp=20&ved=1t:429,r:9,s:0 Higher level Biology book, pages