Lecture 3 Outline of Last Lecture I. Finish E. coli & Evolution a. Adaptation definition b. Acclimation definition II. Natural Selection and more on the drunkard’s walk a. Evolution definition b. Natural selection definition c. What must be true for evolution through natural selection to occur? Outline of Current Lecture III. Finish natural selection IV. Evolution of Multicellularity a. Bacteria & Archaea b. Basic Morphology V. Advantages & Disadvantages of Multicellularity a. Characteristics b. Advantages !Current Lecture What must be true for evolution by natural selection to take place? •heritable DNA variation in the population •some phenotypes reproduce more than others •a source of DNA mutations (on going change) •no sexual reproduction necessary! Bio 152 1!!!These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best !used as a supplement to your own notes, not as a substitute. !!!Evolution of Multicellularity **Clicker Question** Why are there still bacteria? •Nothing has out competed them where they live Bacteria & Archaea •single celled organisms •LCA = last common ancestor in the phylogenetic tree •the node at which all current bacteria, archaea & eukaryota have stemmed from •animals, fungi & plants very similar to each other compared to other eukaryotes •“similar” = DNA replication, protein synthesis & metabolism Basic Morphology differences/similarities between bacteria/archaea & eukaryotes Similarities 1. Basic metabolism — energy transduction 2. Biomolecules — DNA, RNA, etc. Differences 1. Size — around 10x as big 2. Nucleus 3. Internal membranes 4. Organelles 5. Prokaryotes can live many more places — more energy sources 6. Multicellular lineages all in eukaryotes !Advantages & Disadvantages to Going Multicellular!Characteristics of Multicellular Organisms (1,4,5,6 in all multicellular organisms, the rest only in some) **eukaryotes can be single celled** 1. Specialized Cells 2. Tissues 3. Organs —functional unit of tissues 4. Cell adhesion molecules 5. Specialized reproductive cells •entirely separate only rarely 6. Regulation cell proliferation & cell death 7. 3D organization —some cells are not in contact with their environment Bacteria can form bio-films, which are large #’s of bacteria embedded in matrix of extracellular polymeric substance that they secrete (slime). They can also separate & live on their own. Why aren’t they considered multicellular organisms? •they secrete slime in order to hold them together — bio-films give them a cell adhesion mechanism •each bacterium regulates its own growth —to be multicellular the aggregation must regulate growth together •they don’t have specialized cells Advantages **Clicker Question** Unicellular chlorella was cultured with O. vallescia. What do these data suggest? •clusters of around 8 chlorella have some kind of fitness advantage •organisms secreted an external!membrane that connected them —this would not have occurred in the wild, it developed in the 40 days that they were clustered. Showed that something in their genes was expressed when they were placed in this situation •Advantage to multicellularity = defense against predators (shown in this experiment) Snowflake Yeast •lab created— selected for “heaviness”, if the yeast didn’t sink then it would go into the bleach and die •“organisms” like to be a specific size — they begin to use apoptosis to manage snowflake size •asexually reproduce •better able to maintain their position and collect food
View Full Document
Unlocking...