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Chapter 7
Energy relations
Energy sources and trophic biology:
light, organic molecules, or inorganic
molecules
Announcements?
• Meetings?
Energy sources and trophic
biology
• Photosynthesis = autotrophic
– Plants, bacteria, protists
Energy sources and trophic
biology
• Chemosynthesis = autotrophic
– Bacteria
Energy sources and trophic
biology
• Consume organic matter =
heterotrophic
– Bacteria, fungi, protists, animals, plants
Trophic diversity across biological kingdoms
Figure 7.2
3 biochemical pathways for
photosynthesis:
• C3
• In dry environments:
– C4
– CAM
Different photosynthesis
types in different
environments - C3
•
•
•
•
Cool/moist, low light environ
Energy efficient
Less efficient water use
Less efficient CO2 uptake
Different photosynthesis
types in different
environments - C4
•
•
•
•
Hot/dry, high light environ
Less energy efficient
More efficient water use
More efficient CO2 uptake
Different photosynthesis
types in different
environments - CAM
•
•
•
•
Desert - succulents
Less energy efficient
Most efficient water use
Efficient CO2 uptake at NIGHT
Energy Relations In Plants
(All measured by CO2 flux)
• Gross Photosynthesis (Pgross )
– Total amount of CO2 fixed into glucose
• Respiration (R)
– Total amount of glucose utilized for energy
• Net Photosynthesis (Pnet )
– Pgross - R
Generalized Light Response Curve
+
0
Compensation
Point
Saturation
Point
Irradiance
Figure 7.21
Contrasting
photosynthetic
response curves
Light response curve:
• 1 = range of irradiance where P
limited by low light
Light response curve:
• 2 = optimum irradiance (max Pnet)
Light response curve:
• 3 = range of irradiance where P
limited by high light; breaks down
photosynthetic apparatus faster than
repaired
Light Response Curves
C4 Plant Species
Sugar Cane
Sorghum
Corn
+
0
-
C3 Species Have Higher
Pnet in Low Light
Irradiance
C3 Plant Species
Trees
Wheat
Algae
Light response curve for
different species
Generalized Nutrient Response Curve
Saturation
<<<< Deficiency >>>>
Toxicity >>>>
Optimum
Nutrient Concentration
Nutrient Response Curves
MicroNutrient
Fe
MacroC
Mn
Nutrient
O
Zn
H
RequiredCu
in small quantities
Required in large quantities
P
Mo
K
Become toxic
at
higher
Rarely
toxic
at
concentrations
B
N
concentrations
that
occur
in
Nature
Cl
S
.
Mg
.
Ca
Nutrient Concentration
Energy/nutrients usually in
limited supply
• Environment-plant relations:
– Photosynthesis only with appropriate T,
light, water, nutrients (based on
climate/soil)
Energy/nutrients usually
limited supply
• Plant-Herbivore relations
– Plants are numerous
– Easy to find, catch
– Low nutritional value
– Available seasonally
Energy/nutrients usually
limited supply
• Plant-Herbivore relations
– Plants use physical and chemical
defenses
• Thorns
• Toxins
• Digestion-reducing compounds
Energy/nutrients usually
limited supply
• Predator-Prey relations:
– Prey animals less numerous than plants
– difficult to find, catch
– Higher nutritional value
Energy/nutrients usually
limited supply
• Predator-Prey relations:
– Evolution of defenses by plants and
prey animals
– NS pressure on herbivores/predators to
evolve alternative methods
Energy/nutrients usually
limited supply
• Detritivores:
– Majority of food plant material
Predation
1 search
2 recognition
3 catching
4 consumption
Table of adaptations
• Pred activity
• Searching
• Pred
adaptation
• Sensory
acuity
• Prey counter-adaptation
• Improved sensory
acuity
• Space out
• Search where
• Polymorphism
prey are
abundant
• Search image
Table cont.
• Pred activity • Pred adaptation • Prey counteradaptation
• Warning signals,
• Recognition of• Learning
mimicry
prey
Table cont.
• Pred activity
• Pred adaptation
• Catching
• Improved motor
skills
• Weapons of
offense
• Prey counter-adaptation
• Improved motor skills,
startle responses,
aggregation formation
• Weapons of defense
Table cont.
• Pred activity
• Pred adaptation
• Handling prey • Subduing skills
• Prey counter-adaptation
• Active defense, tough
integument, autotomy
• Toxins
• Detoxification ability
Anglerfish:
Frogfish:
Cryptic against rocky background.
Lure to attract prey.
Harris Hawk
To detect small prey, extremely good
eyesight. For capturing prey, has sharp
beak and talons.
SEA ANEMONES poisonous tentacles.
Counter-adaptation, CLOWNFISH coat
themselves with chemical inhibitor prevents anemone stings, avoid
predation from anemone and other fish.
FLOUNDER
Lies on one side of its body - prevents
shadow. Chromatophores modify color to
match background. Throws sand on the
top of their flattened body to increase
concealment.
What do these
BUTTERFLIES
mimic?
Some INSECTS resemble twigs in
physical structure and behavior.
They can branch off a limb and
remain motionless.
AUSTRALIAN
TAWNY
FROGMOUTH
Resembles part of the tree in
which it rests. This bird is
active at night and remains
motionless during dayight
hours.
GRAY TREEFROGS occur as
two different color morphs
within the same population: a
brown morph...
. . . and a green morph.
EASTERN CORAL
SNAKE
is highly venomous
Predators generally avoid snakes with
a bright banding pattern of black,
yellow, and red. ~ 70 spp. of New
World snakes have this "coral" type
of banding.
Warning signals need not always be
visual. RATTLESNAKES possess a
highly venomous bite and give a
warning noise with their rattle.
Warning signals can be olfactory:
SKUNKS- warning coloration and bad
odor warn predators. Spray temporarily
blinds close predators; offensive odor
lingers long after discharge.
MONARCH BUTTERFLY feeds as larva
on milkweed plants - contain toxins.
Toxins are sequestered in tissues of
adult. Distinctive colors of adult
Monarch warns birds not to eat them.
VICEROY (left)
closely resembles
Monarchs.
Although not
distasteful, birds
avoid Viceroy.
Katydids employ two types of defense. First,
coloration resembles leaves - crypsis
decreases chances of detection.
If detected, second line of defense decreases
probability of being captured - it hops away.
PEACOCK BUTTERFLY from Ireland
has spots resembling eyes. These
"eyes" frighten away
insectivorous birds.
Squids deter predation by
forming a group. Group
formation may decrease per
capita predation risk in
number of ways: selfish herd
behavior, confusion effects,
or by having more individuals
on look out for approaching
predator. This may explain why large
ungulates travel in herds.
ELK have keen sense of smell, good
hearing, and are swift runners to
avoid most predators. If trapped in
deep snow, antlers are a match for
most predators.
Turtles have tough integument which is
virtually impenetrable. BOX TURTLES
have broad hinge across plastron, allows
them to completely close shell so tightly
- not even a knifeblade can be inserted.
Six-lined Racerunner has a bright
colored tail that distracts predators
from its head. When caught, the tail
breaks off allowing the lizard to
escape = AUTOTOMY.
HEDGEHOGS are covered with sharp
spines similar to the porcupine.
When attacked, they curl up into a
ball exposing a sphere of spines.
LIONFISH have long, poisonous
spines that are used as a defense
against predators.
POISON ARROW FROGS of C. and S.
America produce mucous covering - one
of most potent natural poisons known.
Mucous used by native people to poison
arrow points. Frog has warning coloration.
Counter-adaptations of prey
• 1. Crypsis:
–Increases recognition time
–Only have to make prey less
profitable than other prey item
2. rarity
• Most predators eat more than
one type of prey
• Most target more common
species, or PT (= apostatic
selection)
• Example: prey choice of bird
Optimal foraging theory
• Maximize benefit/cost ratio of energy
• Natural selection should result in traits
that allow species to shift behavior /
growth patterns to maximize efficiency
of resource acquisition under changing
environmental conditions
Optimal “Foraging” by Plants
Environment
Optimal Growth Pattern
Low light
Produce more leaves
(less roots)
Limited water
or nutrients
Produce more roots (less
leaves)
Optimal foraging
• Herbivores, carnivores
– Optimize foraging by:
• Minimize energy/water use in search, chase,
subdue, eating prey
• Select prey based on availability and value
Size of pumas and their prey
Figure 7.19
Fig 7.25
Optimal foraging theory
predicts maximum energy
intake
• But, many studies do not find
animals behave optimally
• Why?