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 P max at I sat P max = max. rate I sat = light amt. when system saturated Fig. 7.20

Plants Adiantum: fern in deep shade –Sciophyte: shade-adapted plant Encelia: desert –Heliophyte: sun-adapted plant Ps Lite

Plants Sun/shade plant P max and I sat values Highest P max ? Highest I sat ? 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 Prey Density Food Intake Rate Lo Hi

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: N e = number prey encountered per unit time C s = 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 = (N e1 E 1 -C s )/(1 + N e1 H 1 ) 1 refers to prey species 1 E: Energy gain minus Cost Time: reflects handling prey

What if 2 prey? E/T = (N e1 E 1 -C s ) + (N e2 E 2 -C s ) 1 + N e1 H 1 + N e2 H 2 Optimal Foraging Theory N e = number prey encountered per unit time C s = cost to search for prey H = handling time E = energy gained by consuming prey

What if 2 prey? E/T = (N e1 E 1 -C s ) + (N e2 E 2 -C s ) 1 + N e1 H 1 + N e2 H 2 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 Optimal Foraging Theory midge damselfly water flea

Prey abundance documented (top) Equation predicts optimal prey size (mid) Fish stomachs examined (bottom) Does it work? Yup... Optimal Foraging Theory

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)

Organisms over-reproduce (competition). Offspring vary. –Some differences heritable (transmitted between generations). Higher chance survival/reproduction: pass favorable traits to offspring Natural Selection (BIOL 1020) Define adaptation

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 Natural Selection (BIOL 1020)

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 (h 2 ) trait (how “well” transmitted) h 2 = V G / V P V G : Variability due to genetic effect V P : Total variability phenotype

Evolution by Natural Selection Heritability: h 2 = V G / V P V G : Variability due to genetic effect V P : Total variability phenotype Phenotype influenced by both genes and environment Or, V P = V G + V E

Evolution by Natural Selection Modified equation: h 2 = V G / (V G + V E ) h 2 ranges 0-1 If V G small, little heritability If V E 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 h 2

Variation Within Species Many species’ populations differ How much variation due V G vs. V E ? –Clausen, Keck, Hiesey (CA plants) How test V G vs. V E ?

Variation Within Species Common garden experiment: Grow same location.

Variation Within Species –Differences remain: genetic variation (V G ) –Differences disappear: phenotypic plasticity (V E ) 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 (V E ) or genetic (V G )? 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 yr) between vegetation and change morphology Is this natural selection in action?

Adaptive Change in Lizards Positive correlation (after 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