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