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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?