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9/8/2011 LAB REMINDERS Biol 112 Lecture 2: Evolution and Natural Selection Natural Selection‐ Darwin’s observations • PICK UP YOUR TICKET FOR THE HMNH. • NEXT WEEK GO to the museum • YOU CAN GO ANYTIME BUT YOUR TA’s will be there during your scheduled lab time (except WED‐ will be there Sunday instead) • If you want help from a TA it doesn’t have to be yours • TURN IN YOUR PIN FROM THE MUSEUM Variation in populations • Variation exists in populations • Most organisms have a higher reproductive potential than observed number of offspring QuickTime™ and a decompressor are needed to see this picture. Pinguicula.org Heritability of traits e.g. of non heritable variation • Hydrangeas grow different colors depending on soil acidity and availability of Aluminum ions. • Natural selection affects individuals with traits that are inherited (passed on from parents through genes) • Some traits vary due to environmental factors. These traits would not be subjected to selection because the variation can’t be passed on to offspring QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. Pink or Blue flowers not a trait that is inherited through genes. Edenscontainer.co m Low pH-acidic High pH-basic 1 9/8/2011 Figure 1.20 Overproduction of offspring Fungus Coral Spawning 1 Population with varied inherited traits 2 Elimination of individuals with certain traits 3 Reproduction of survivors QuickTime™ and a decompressor are needed to see this picture. 4 Increasing frequency of traits that enhance survival and reproductive success Noaa.gov Evolution by Natural Selection • Inference #1‐ Individuals whose inherited traits give them a higher probability of surviving and reproducing in a particular habitat leave more offspring than others • Inference #2 This unequal ability of individuals to survive and reproduce leads to an accumulation of these traits in a population over generations Summary of Natural Selection • 1. There is variation of traits (morphological, proteins, transcription factors‐ turn genes on/off) in populations • 2. Differential reproduction‐ A trait allows an individual to survive better and/or reproduce more will produce more offspring • 3. If that trait is heritable (is based on genetics) more individuals in the population will have that trait in the next generation. • 4. Natural selection increases adaptations to an environment over time. Green warbler finch Certhidea olivacea Gray warbler finch Certhidea fusca Bud-eater Seed-eater COMMON ANCESTOR Insect-eaters More points to remember about natural selection Warbler finches Figure 1.22 Sharp-beaked ground finch Geospiza difficilis Vegetarian finch Platyspiza crassirostris Mangrove finch Cactospiza heliobates Tree finches Insect-eaters -Evolution occurs at the level of population : INDIVIDUALS DON’T EVOLVE -Environments are variable between regions different adaptations may be more or less advantageous in different areas Large tree finch Camarhynchus psittacula Small tree finch Camarhynchus parvulus Cactus-flowereaters Seed-eaters Ground finches -Environments also change over time resulting in populations of species adapting to these new conditions. This may give rise to new species Woodpecker finch Cactospiza pallida Medium tree finch Camarhynchus pauper Large cactus ground finch Geospiza conirostris Cactus ground finch Geospiza scandens Small ground finch Geospiza fuliginosa Medium ground finch Geospiza fortis Large ground finch Geospiza magnirostris 2 9/8/2011 Figure 22.13a Direct Observations of Evolutionary Change FIELD STUDY Soapberry bugs MRSA Pesticide resistance in insects Soapberry bug with beak inserted in balloon vine fruit Figure 22.13b RESULTS MRSA‐Methicillin‐resistant Staphylococcus aureus Beak 10 On native species, southern Florida 8 Number of individuals 6 4 2 0 Museum-specimen average 10 QuickTime™ and a decompressor are needed to see this picture. On introduced species, central Florida 8 6 4 2 0 6 7 8 9 Beak length (mm) Figure 22.14 2,750,000 10 11 • S. aureus is a common bacteria found on skin • Antibiotics (Methicillin) use to kill off most S. aureus by inhibiting a protein used in the cell wall. • Those that survived had a variation in the protein used to make the cell wall that allowed them to survive and reproduce in the presence of methicillin • MRSA strains are now resistant to many antibiotics 1 250,000 base pairs Pesticide resistance in insects 2,500,000 Chromosome map of S. aureus clone USA300 500,000 Major pest on potato crops Key to adaptations 2,250,000 Methicillin resistance Ability to colonize hosts 750,000 Why? Live on plants with high toxicity thus have existing variation in toxic tolerance Increased disease severity 2,000,000 Increased gene exchange (within species) and toxin production 1,750,000 1,500,000 QuickTime™ and a decompressor are needed to see this picture. Populations have become resistant to 52 different pesticide compounds 1,000,000 High fecundity Colorado potato beetle Complicated life cycle 1,250,000 3 9/8/2011 Evidence for evolution • • • • • • • 1. Homology 2.Hierarchial organization of life 3. Embryological similarities 4. Vestigal characters 5.Convergence 6. Fossils and intermediate forms 7. Geographic distributions Homology is similarity resulting from common ancestry Figure 22.15 Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat © 2011 Pearson Education, Inc. • Comparative embryology reveals anatomical homologies not visible in adult organisms • Evolutionary trees are hypotheses about the relationships among different groups • Homologous traits are used to infer relationships in a tree • Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data Pharyngeal pouches Post-anal tail Chick embryo (LM) Homologies and “Tree Thinking” Human embryo Figure 22.16 © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Convergent Evolution QuickTime™ and a decompressor are needed to see this picture. • Convergent evolution is the evolution of similar, or analogous, features in distantly related groups • These traits often evolve under similar selective pressure or in similar habitats. © 2011 Pearson Education, Inc. 4 9/8/2011 Figure 22.18 Eyes in cephalopods and vertebrates‐ they function similarly (form images) but differ in structure. Marsupial NORTH AMERICA Sugar glider QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. AUSTRALIA Flying squirrel Placental Figure 1 Eye development and degeneration. Vestigial organs • Organs derived from an ancestor that no longer have a function (or a much reduced function). – Some cave dwelling species still have eyes even though they aren’t functional Y Yamamoto, W R Jeffery Science 2000;289:631-633 Published by AAAS • The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time • Fossils can document important transitions. For example, the transition from land to sea in the ancestors of cetaceans Other even-toed ungulates Hippopotamuses †Pakicetus †Rodhocetus QuickTime™ and a decompressor are needed to see this picture. Common ancestor of cetaceans †Dorudon Living cetaceans 70 © 2011 Pearson Education, Inc. 60 50 © 2011 Pearson Education, Inc. 40 30 20 10 Millions of years ago 0 Key Pelvis Femur Tibia Foot 5 9/8/2011 Fig. 3. Biogeographic reconstructions. Biogeography • Biogeography, the geographic distribution of species, provides evidence of evolution • Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift • An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved E C Teeling et al. Science 2005;307:580-584 Published by AAAS © 2011 Pearson Education, Inc. QuickTime™ and a decompressor are needed to see this picture. 6