Energy/NutrientRelations (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– Heliophyte: sun-adapted plant

Ps

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

Prey Density

Food IntakeRate

LoLo Hi

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:• 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 CostTime: reflects handling prey

• What if 2 prey?• E/T = (Ne1E1-Cs ) + (Ne2E2-Cs )

• 1 + Ne1H1 + Ne2H2

Optimal Foraging Theory

Ne = number prey encountered per unit time

Cs = cost to search for preyH = handling timeE = energy gained by consuming prey

• 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

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?

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 (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 SpeciesFound at different elevationsRainfall amount & variation changes

Lizards biggerwhere 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