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Energy and Living Things

Energy and Living Things. Outline. Energy Sources Solar-Powered Biosphere Photosynthetic Pathways Using Organic Molecules Chemical Composition and Nutrient Requirements Using Inorganic Molecules Energy Limitation Food Density and Animal Functional Response Optimal Foraging Theory.

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Energy and Living Things

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  1. Energy and Living Things

  2. Outline • Energy Sources • Solar-Powered Biosphere • Photosynthetic Pathways • Using Organic Molecules • Chemical Composition and Nutrient Requirements • Using Inorganic Molecules • Energy Limitation • Food Density and Animal Functional Response • Optimal Foraging Theory

  3. Energy Flows Through Living Systems Heterotrophs Plants= Autotrophs

  4. Autotroph: ‘self feeder’ - an organism that can gather energy (usually from light) … to store in organic molecules • Photosynthesis • chemosynthesis • Heterotroph: An organism that must rely on other organisms to capture light energy … must rely on breakdown of organic molecules produced by an autotroph as an energy source • Classified by trophic level

  5. Photosynthesis Capture and transfer light energy to chemical bonds Occurs in: Plants Algae Certain Bacteria Not a perfect process – some energy is lost - entropy

  6. How Photosynthesis Works • Light strikes leaf • Energy absorbed by chemical pigments • Absorbed energy drives chemical processes to convert CO2 into larger molecules • First simple sugars – 6 carbon ring structures • Later many molecules of simple sugars joined together to form larger molecules or converted to other compounds • Energy absorbed in building larger molecules, released as they are broken down

  7. Only certain Wavelengths of Light are Used in Photosynthesis • Light Energy Used = ‘Photosynthetically Active Radiation’ or PAR • How Much is absorbed: determined as photon flux density. • Number of photons striking square meter surface each second. • Chlorophyll absorbs light as photons. • Landscapes, water, and organisms can all change the amount and quality of light reaching an area. • Light not absorbed is reflected • Some in PAR + all in green and yellow wavelengths

  8. Wavelengths most useful in driving photosynthesis Absorption spectra of chlorophylls and carotenoids Wavelengths not used - reflected

  9. Fall color • In many plants production of chlorophyll ceases with cooler temperatures and decreasing light • other pigments become visible

  10. Modifications of Photosynthesis for Dry Climates • C3 Photosynthesis • Used by most plants and algae. • CO2 enters leaves BUT water vapor leaves • Poorly adapted to hot dry environments • C4/CAM photosynthesis: Modifications in biochemical processes • Increased efficiency in CO2 absorption • Fewer stomata required/stomata only open during night  decreased loss of water vapor

  11. C3 Photosynthesis CO2 enters passively so stomata have to be open for long periods of time

  12. Why C3 Photosynthesis Doesn’t always work out - CO2 must enter though stomata • stomata (sing., stoma) are tiny holes on the undersides of leaves • CO2 enters and moisture is released • In hot, dry climates, this moisture loss is a problem

  13. C3 grasses (yellow) dominant in cool temperate – C4 plants don’t compete so well there C4 grasslands (orange) have evolved in the tropics and warm temperate regions

  14. C4 Photosynthesis

  15. Photosynthetic Pathways • CAM Photosynthesis • (Crassulacean Acid Metabolism) • Limited to succulent plants in arid and semi-arid environments. • Carbon fixation takes place at night. • Reduced water loss. • Low rates of photosynthesis. • Extremely high rates of water use efficiency.

  16. CAM Photosynthesis

  17. Producers • Herbivores • Animals that eat plants • The primary consumers of ecosystems • Green plants and algae • Use solar energy to build energy-rich carbohydrates • Carnivores • Animals that eat herbivores • The secondary consumers of ecosystems • Omnivores are animals that eat both plants and animals • Tertiary consumers are animals that eat other carnivores • Detritivores • Decomposers • Organisms that break down organic substances • Organisms that eat dead organisms

  18. Efficient Breakdown of Products of Photosynthesis Requires Oxygen • Complex series of reactions, oxygen serves as the terminal electron acceptor • May occur in some organisms w/o oxygen (anoxic conditions) • anaerobic respiration= fermentation • Inefficient • End products vary with organism involved • Ethanol, proprionic acid, lactic acid, etc.

  19. Three Feeding Methods of Heterotrophs: • Herbivores: Feed on plants. • Carnivores: Feed on animal flesh. • Detritivores: Feed on non-living organic matter.

  20. Classes of Herbivores • Grazers – leafy material • Browsers – woody material • Granivores – seed • Frugivores – fruit • Others – nectar and sap feeders • Humming birds, moths, aphids, sap suckers …

  21. Herbivores • Substantial nutritional chemistry problems. • Low nitrogen concentrations – difficulty extracting needed protein/amino acids from source. • Require 20 amino acids to make proteins ~ 14 are must come from diet

  22. How do plants respond to feeding pressures by herbivores? • Mechanical defenses – spines • Chemical defenses • Digestion disrupting chemicals – tannins, silica, oxalic acid • Toxins – alkaloids • More common in tropical species How do animals respond? • Detoxify • Excrete • Chemical conversions – use as nutrient

  23. Digestion Schemes of Herbivores • Require extensive digestive processing • Rumnants – 4 part stomach • Rapid feeding, coarse material is re-milled (regurgitated bolus) after initial fermentation • ‘Chewing their cud’

  24. Coprophagy: expel moist fecal material, re-ingest • 50-80% of fecal material recycled • acts as external rumen • bacterial activity produces B vitamin Cecum is site of much bacterial activity, moist fecal pellets enclosed in protein produced

  25. Carnivores • Predators must catch and subdue prey - size selection. • Usually eliminate more conspicuous members of a population (less adaptive). • act as selective agents for prey species.

  26. European River Otter: Lutra lutra Widest ranging of otters Diet varies with abundance of prey http://itech.pjc.edu/sctag/E_OTTER/Index.htm

  27. Optimal Foraging Theory • Assures if energy supplies are limited, organisms cannot simultaneously maximize all life functions. • Must compromise between competing demands for resources. • Principle of Allocation • Fittest individuals survive based on ability to meet requirements principle of allocation

  28. Optimal Foraging Theory • All other things being equal,more abundant prey yields larger energy return. Must consider energy expended during: • Search for prey • Handling time • Tend to maximize rate of energy intake. • What would a starving man do at an all you can eat buffet?

  29. Optimal Foraging in Bluegill Sunfish

  30. Adaptations of Prey to being preyed upon • Predator and prey species are engaged in a co-evolutionary race. • Avoid being eaten – avoid starving/becoming extinct • Defenses: • Run fast • Be toxic – and make it known • Pretend to be toxic • Predators learn to avoid

  31. Carnivores • Consume nutritionally-rich prey. • Cannot choose prey at will. • Prey Defenses: • Aposomatic Coloring - Warning colors. • Mullerian mimicry: Comimicry among several species of noxious organisms. • Batesian mimicry: Harmless species mimic noxious species.

  32. Mullerian mimicry: Comimicry

  33. Batesian mimicry: Harmless species mimic noxious species

  34. Aposomatic Coloring - Warning colors

  35. Detritivores • Consume food rich in carbon and energy, but poor in nitrogen. • Dead leaves may have half nitrogen content of living leaves. • Fresh detritus may still have considerable chemical defenses present.

  36. Detritivores and decomposers

  37. Review • Energy Sources • Solar-Powered Biosphere • Photosynthetic Pathways • Using Organic Molecules • Chemical Composition and Nutrient Requirements • Using Inorganic Molecules • Energy Limitation • Food Density and Animal Functional Response • Optimal Foraging Theory • Adaptations

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