Biodiversity The Road to the Six Kingdoms of Life
How the 6 kingdoms came about At first, only two kingdoms were recognized Then Haeckel proposed a third kingdom Protista (where protists had both plant & animal qualities) 4 th Fungi were grouped together since they did not carry out photosynthesis
Carl Woese Six Kingdom Scheme Includes the Archaebacteria
Modern Classification Techniques
Taxonomy Taxonomy becomes very important in other fields of Biology, such as the study into species evolution. Taxonomists may attempt to determine the evolutionary history of groups of organisms. Scientists may compare characteristics of different species living today with each other and with extinct species There are several types of evidence that scientists use to classify and organize organisms.
Evidence Used (i) Fossil Records (relative and radioactive dating) (ii) comparative anatomy ( Structural Info.) (iii) comparative embryology (iv) biochemical information ( DNA / Proteins ) (v) cellular structure (vi) behavior
(i) Fossil records Radioactive dating The age of a fossil is determined using either: relative age Or absolute age relative age - sedimentary rock forms in layers so the approximate age of a fossil can be determined in relation to the age of the rocks the fossil is found in.
the oldest layers are found at the bottom, and the younger layers are on top. the age of a fossil can be approximated by the rocks layer it is found in.
Absolute Age The absolute age of a fossil or rock can be found through radioactive dating. - A radioactive isotope (atom with additional neutrons) breaks down into a new element at a known rate called a half-life. (the time it takes for ½ of a radioactive sample to break down). See Page 113.
Carbon Dating Half - life Useful range C14 ----------> C12 5730 yrs 60 000 yrs note: for fossils too old for carbon dating, an isotope with a longer half - life must be used: Isotope U235 K40 U238 half - life 700 million years 1.25 billion years 4.5 billion years
Try This Sample Problem: If you had a fossil with 2 units of C14 left in it and you determined that in the living organism (or one that is similar) has 16 units of C14. Use the following method to find the absolute age of the fossil:
Method 1: 1. Determine amount of C14 left in fossil. 2. Determine amount of C14 in a living organism of the same size and type living today. 3. Calculate the number of half-lives needed to reduce the C14 in the living organism to the amount that is left in the fossil. 4. Multiply by the half - life (in this case, 5730 years ) by how many half lives have passed to determine the age of the fossil.
(ii) comparative anatomy Comparing the anatomy of organisms indicates a common ancestry because of: homologous structures - structures having a common ancestry but with different uses in various species. Eg. Similar bone structure of the forelimb of a bat, whale, horse and human suggests these different species have a similar evolutionary origin. Page 113,114 & 664
analogous structures - body parts of organisms that do not have a common evolutionary origin but perform similar functions. Eg. insect wings and bird wings are similar in function but not in structure. Page 665
- vestigial organs - small or incomplete organs (or bones) that have no apparent function in one organism but do have a function in another species. - This indicates evolutionary origin from a common ancestor. Page 665 Eg. Human ear muscles, Human appendix, Hip bones in whales, Human tail bone, Leg bones in snakes, and Forelimbs in the flightless ostrich
iii) Comparative Embryology Comparing the embryos of organisms can indicate a common ancestry with other types of living organisms because of similar stages of embryonic development. (eg. gill slits and tail in human embryos indicates humans share common ancestry with birds, reptiles and fish) Page 665
(iv) biochemical information ( DNA / Proteins ) Comparing the biology of one species with another at the molecular level (DNA & Proteins) can indicate a common ancestry. Page 115 - human proteins (amino acid sequences) have more in common with chimpanzee proteins than frog proteins. - pig or bovine insulin is similar enough to humans that it can be used to treat human diabetes.
(v) cellular structure Studying structures of cells gives clues to their evolutionary history. - Remember only two basic types of cells prokaryotic and eukaryotic (review p. 106) - fossil evidence has shown the first life forms were prokaryotic (similar in appearance to bacteria) and existed approximately 3.5 billion years ago -eukaryotes appeared only about 1.5 billion years ago - multicellular organisms only 700 million years ago
(vi) behavior - how organisms are adapted and function in their environment is called behavioral adaptations - eg. include migration, courtship displays, foraging behavior - it is believed that these adaptations have evolved in response to changes in environmental conditions - the favorable adaptations were passed on to the offspring - note: Biofact p.706
How have classification systems improved as a result of these modern techniques? - through the use of these techniques, organisms once thought to be closely related, have been found not to be related and vise versa.
Phylogeny and Phylogenetic trees
Phylogeny and Phylogenetic Tree A hypotheses about the evolutionary history of an organism. The roots of the phylogenetic tree show the oldest ancestral species. The upper ends of the branches show current species. Each fork represents the adaptation that changed the common species into two new species. Use the example on page 116.
Homework PAGE 121: 1, 2, 5,6, and 12