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Physiological Ecology

Physiological Ecology. Outline. Introduction to Ecology Evolution and Natural Selection Physiological Ecology Behavioural Ecology. Physiological Ecology. study of species’ needs and tolerances that determine their distribution and abundance

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Physiological Ecology

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  1. Physiological Ecology

  2. Outline • Introduction to Ecology • Evolution and Natural Selection • Physiological Ecology • Behavioural Ecology

  3. Physiological Ecology • study of species’ needs and tolerances that determine their distribution and abundance • species need lots of things: e.g., carbon, nitrogen, amino acids, etc. • we will discuss species needs and tolerances with regards to ENERGY

  4. Physiological Ecology • Nutrient and Energy Transfer • Endothermy and Ectothermy • Climate • Current Climate Change

  5. Physiological Ecology • Nutrient and Energy Transfer • Endothermy and Ectothermy • Climate • Current Climate Change

  6. Nutrient and Energy Transfer Ch. 6.1 – 6.6, Bush

  7. Outline • Basics of energy • Photosynthesis • Trophic Levels • Efficiency of Energy Transfer

  8. Outline • Basics of energy • Photosynthesis • Trophic Levels • Efficiency of Energy Transfer

  9. Forms of Energy • Fuel (chemical bond energy): • nutrients, such as carbohydrates • needed for everything a species does • e.g., growth, movement • Heat: • needed for all chemical reactions • by-product of reactions • Light: • needed by plants to create fuel

  10. Energy transfer

  11. Energy source • The ultimate energy source for (most) life on earth is the sun

  12. Outline • Basics of energy • Photosynthesis • Trophic Levels • Efficiency of Energy Transfer

  13. Photosynthesis • What is it? • Chlorophyll, a necessary pigment • Variations in photosynthesis • The fate of carbohydrate

  14. Photosynthesis • Synthesis of carbohydrates from CO2 and water • Sunlight acts as energy source • O2 is a by-product

  15. In Chemistry notation… Energy from sunlight + CO2 + H2O  CH2O + O2

  16. Chlorophyll, a necessary pigment

  17. Pigments absorb light energy Pigments absorb light energy between 400-700 m -energy in this range is termed Photosynthetically Active Radiation (PAR)

  18. Why are leaves green? • Pigments cannot absorb light in the green wavelength region

  19. The “Green Gap”

  20. Why are some plants not green? • Chlorophyll is missing from some cells, making the reflectance of other pigments visible

  21. Fall colour • the production of chlorophyll requires sunlight and warm temperatures • in many plants, chlorophyll production stops in fall and other pigments become visible

  22. Why is chlorophyll necessary? • Other pigments pass on the energy they absorb to a chlorophyll molecule • When chlorophyll is in an energized state, it is able to turn light energy into chemical bond energy • This chemical bond energy passes through a number of different molecules and then rests within a carbohydrate (glucose) molecule

  23. Variations in photosynthesis • C3 photosynthesis • C4 photosynthesis • CAM photosynthesis

  24. 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

  25. CO2 is turned into sugar with RUBISCO • RUBISCO (short for Ribulose-1,5-bisphosphate carboxylase) is the most important enzyme on Earth • O2 has an inhibitory effect upon photosynthesis because it makes RUBISCO perform PHOTORESPIRATION instead

  26. C3 photosynthesis • CO2 enters passively so stomata have to be open for long periods of time • Majority of plant species use this variation of photosynthesis • C3 plants experience high rates of: • water loss in hot, arid regions • photorespiration where O2:CO2 ratio is high

  27. C4 photosynthesis • Have a special enzyme that actively pumps in CO2 and delivers it to RUBISCO enzyme so: • (1) stomata do not have to be open for long • (2) photorespiration is reduced • Energetically costly • 1-4% of plant species use C4 photosynthesis. • used by species that live in hot, sunny environments with low CO2 • E.g. tropical grasses

  28. The global distribution of C4 plants in today's world • C4 grasslands (orange) have evolved in the tropics and warm temperate regions where C3 forests (green) are excluded by seasonal drought and fire. • C3 grasses (yellow) remain dominant in cool temperate grasslands because C4 grasses are less productive at low temperatures.

  29. CAM photosynthesis • open stomata at night when the air is cool and more humid, thereby reducing water loss • store the CO2 in tissues to be used during the day • storage space is a potential constraint, thus many CAM plants are succulent (e.g. cacti)

  30. Unrelated species with similar physiology -Photosynthetic pathways show CONVERGENT EVOLUTION -CAM found in at least 12 different families -Recent studies say C4 has independently evolved over 45 times in 19 families of angiosperms Cacti (Americas) Euphorbia (Africa)

  31. Why photosynthesize? • sugars created from photosynthesis are necessary for: • chemical reactions • plant functions • e.g., conduction of water and nutrients up the stem • growth (biomass)

  32. Outline • Basics of energy • Photosynthesis • Trophic Levels • Efficiency of Energy Transfer

  33. Energy transfer

  34. Two types of organisms • Autotrophs (producers) • organisms which can manufacture their own food • e.g., plants • Heterotrophs (consumers) • “other feeders” – organisms which must consume other organisms to obtain their carbon and energy • e.g., animals, fungi, most protists, most bacteria

  35. Trophic Levels • Tropic level refers to how organisms fit in based on their main source of nutrition • Primary producers • autotrophs (plants, algae, many bacteria, phytoplankton) • Primary consumers • heterotrophs that feed on autotrophs (herbivores,zooplankton) • Secondary, tertiary, quaternary consumers • heterotrophs that feed on consumers in trophic level below them (carnivores) • Detritivores • bacteria, fungi, and animals that feed on decaying organic matter

  36. Trophic levels examples

  37. How many trophic levels?

  38. Exceptions to the rule? • Carnivorous plants capture and digest animal prey • They are able to grow without animal prey, albeit more slowly • ~600 spp. of carnivorous plants have been described

  39. Food chains versus food webs • Food chain – the pathway along which food is transferred from trophic level to trophic level in an ecosystem • Food web – the feeding relationships in an ecosystem; many consumers are opportunistic feeders

  40. Food chains versus food webs Food chains Food web

  41. Outline • Basics of energy • Photosynthesis • Trophic Levels • Efficiency of Energy Transfer

  42. The energy budget • The extent of photosynthetic activity sets the energy budget for the entire ecosystem • Of the visible light that reaches photosynthetic land plants, 1% to 2% is converted to chemical energy by photosynthesis • Aquatic or marine primary producers (algae) convert 3-4.5% - this difference accounts for why aquatic and marine food chains tend to be longer

  43. Efficiency of Producers One difference among ecosystems is their reflectance. Broadleaf forests reflect up to 20% of visible radiation. Conifer forests reflect only about 5%. Ecosystems with low leaf area (e.g. deserts) absorb very little light. Conifer forests with very high leaf area index can absorb almost 95% or more of the “incident light”

  44. Coniferous versus deciduous forest

  45. Efficiency of photosynthesis • Of the energy that is actually absorbed by chloroplasts, at best about 20% is converted into sugars

  46. Plant biomass – a fraction of total energy • Of the solar energy that is converted into organic molecules in photosynthesis, about 40-50% is lost in the processes of respiration

  47. Primary productivity • Gross Primary Productivity (GPP): • total amount of photosynthetic energy captured in a given period of time. • Net Primary Productivity (NPP): • the amount of plant biomass (energy) after cell respiration has occurred in plant tissues. NPP = GPP – Plant respiration plant growth/ total photosynthesis/ unit area/ unit area/unit time unit time

  48. Secondary Productivity • Secondary productivity – the rate at which consumers convert the chemical energy of the food they eat into their own new biomass

  49. Pyramid of productivity • Energy content of each trophic level • Pyramid has large base and gets significantly smaller at each level • Organisms use energy for respiration so less energy is available to each successive trophic level

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