Transcript lect8cut
Energy/Nutrient Relations (Ch. 7) Lecture Outline • 1) Major methods of gaining energy • 2) Limitations on energy gain – Plants – Animals Plants • Light curve….Photosynthetic rate vs. light (photon flux density). Note Pmax at Isat • Pmax = max. rate • Isat = light amt. when system saturated Fig. 7.20 Plants • Adiantum: fern in deep shade – Sciophyte: shade-adapted plant • Encelia: desert Ps – Heliophyte: sun-adapted plant Lite Plants • Sun/shade plant Pmax and Isat values • Highest Pmax? • Highest Isat? Fig. 7.21 Lecture Outline • 1) Major methods of gaining energy • 2) Limitations on energy gain – Plants – Animals What limits animal food intake? • Search time: find prey • Handling time: subdue & process prey Hi Food Intake Rate Lo Lo Hi Prey Density Animal Functional Response Curves • Holling: 3 functional responses (how food intake varies with prey density) Fig. 7.22 Animal Functional Response Curves • Type 1: Linear – Little search or handling time (rare) – Ex, filter feeders Feather duster worm Fig. 7.22 Animal Functional Response Curves • Type 2: Rate increases faster than density – Partially limited by search/handling time – Common! Fig. 7.22 Animal Functional Response Curves • Ex, moose feeding Fig. 7.23 Animal Functional Response Curves • Ex, wolf feeding Fig. 7.24 Animal Functional Response Curves • Type 3: S-shaped curve (rare) – 1) Prey find safe sites at low density – Or, – 2) Predator needs to learn to handle prey efficiently Optimal Foraging • Principle: organisms cannot simultaneously maximize all life functions. – Choose prey to maximize energy gain Optimal Foraging Optimal Foraging Theory • • • • • • • • Model: Ne = number prey encountered per unit time Cs = cost to search for prey H = handling time E = energy gained by consuming prey Can calculate energy intake per unit time: E/T E/T = (Ne1E1-Cs )/(1 + Ne1H1) 1 refers to prey species 1 E: Energy gain minus Cost Time: reflects handling prey Optimal Foraging Theory • What if 2 prey? • E/T = (Ne1E1-Cs ) + (Ne2E2-Cs ) • 1 + Ne1H1 + Ne2H2 Ne = number prey encountered per unit time Cs = cost to search for prey H = handling time E = energy gained by consuming prey Optimal Foraging Theory • What if 2 prey? • E/T = (Ne1E1-Cs ) + (Ne2E2-Cs ) • 1 + Ne1H1 + Ne2H2 • If optimal foraging: prey choice maximizes E/T – Ex: if 2 prey, prey #2 eaten if E/T for both prey > E/T for prey #1 only Optimal Foraging Theory • Does it work? • Ex, bluegill sunfish Optimal Foraging Theory • Values calculated for prey in lab • Daphnia (water fleas), damselfly larvae, midge larvae damselfly midge water flea Optimal Foraging Theory • Prey abundance documented (top) • Equation predicts optimal prey size (mid) • Fish stomachs examined (bottom) • Does it work? • Yup... Optimal Foraging By Plants? Optimal Foraging By Plants? • Allocation to leaves, stems & roots • Principle of Allocation: Energy allocated to obtain resource in shortest supply – Do plants allocate to resource in shortest supply? – Where we see this before? Optimal Foraging By Plants? • Allocation to leaves, stems & roots • Principle of Allocation: Energy allocated to resource in shortest supply – Do plants allocate to resource in shortest supply? • Where we see this before? Optimal Foraging By Plants • Ex, N in soil Fig. 7.26 THE END (material for knowledge demo #1) Population Genetics & Natural Selection (Ch. 4) Who?? Darwin • Proposed most important mechanism evolution: natural selection • Key points? (BIOL 1020) Natural Selection (BIOL 1020) • Organisms over-reproduce (competition). • Offspring vary. – Some differences heritable (transmitted between generations). • Higher chance survival/reproduction: pass favorable traits to offspring Define adaptation Natural Selection (BIOL 1020) • Organisms over-reproduce (competition). • Offspring vary. – Some differences heritable (transmitted between generations). • Higher chance survival/reproduction: pass favorable traits to offspring • Adaptation: Genetically determined trait with survival and/or reproductive advantages (improves “fitness”) • Key: Trait heritable Gregor Mendel • Discovered genes (heritable units). – Alternate forms: alleles. – Some (dominant alleles) prevent expression others (recessive alleles) Define…. Evolution by Natural Selection • Adaptation: Genetically determined trait with survival/reproductive advantages (improves “fitness”) – Genotype: Alleles for trait – Phenotype: Expression of trait. May be affected by environment. • Phenotypic plasticity: ability phenotype to change based on environment Evolution by Natural Selection • Adaptation: Genetically determined trait with survival and/or reproductive advantages (improves “fitness”) • Depends on heritability (h2) trait (how “well” transmitted) h2 = VG / VP • VG: Variability due to genetic effect • VP: Total variability phenotype Evolution by Natural Selection • Heritability: h2 = VG / VP • VG: Variability due to genetic effect • VP: Total variability phenotype • Phenotype influenced by both genes and environment • Or, VP = VG + VE Evolution by Natural Selection • Modified equation: h2 = VG / (VG + VE) • h2 ranges 0-1 • If VG small, little heritability • If VE large (lots phenotypic plasticity), little heritability How measure? Measuring heritability • Linear Regression: Fits line to points – – – – Equation line: Y = m X + b m = slope (regression coefficient) b = Y intercept Regression coefficient: measures h2 Variation Within Species • Many species’ populations differ • How much variation due VG vs. VE? – Clausen, Keck, Hiesey (CA plants) How test VG vs. VE? Variation Within Species • Common garden experiment: Grow same location. Variation Within Species – Differences remain: genetic variation (VG) – Differences disappear: phenotypic plasticity (VE) Result? Variation Within Species • Found differences. • Populations form ecotypes: locally adapted to environment – Same species (can interbreed) Variation Within Species • Do animal populations vary locally? • Chuckwalla (Sauromalus obesus) – Herbivorous lizard (desert SW). Variation Within Species Found at different elevations Rainfall amount & variation changes Lizards bigger where more rain Due to better environment (VE) or genetic (VG)? How test? Variation Within Species • Chuckwalla “Common garden” expt. • Genetic differences! Variation Within Species • Genetic differences suggest adaptations • Experiments: can show natural selection in populations? Experiments: who am I? Adaptive Change in Lizards • Genus Anolis (anoles) • Hundreds species New World • Length hind leg reflects use vegetation • Perch diameter Anolis carolinensis Adaptive Change in Lizards • Experiment: lizards from 1 island (Staniel Cay) put on islands with different vegetation • Do they evolve (limb size changes)? Staniel Cay Adaptive Change in Lizards • Positive correlation (after 10-14 yr) between vegetation and change morphology • Is this natural selection in action? Adaptive Change in Lizards • Positive correlation (after 10-14 yr) between vegetation and change morphology • Is this natural selection in action? Probably. But genetic change not shown Adaptation by Soapberry Bugs • Soapberry Bug (Jadera haematoloma) feeds on seeds • Beak pierces fruit walls Soapberry Bugs • Feeds on native or introduced plants (fruit size varies) • Feed on bigger fruits: longer beaks • How test if differences genetic? Soapberry Bugs • Raise bugs on common foods--beak length differences persisted • Bugs adapted to different hosts: natural selection