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Physiological Ecology

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Title: Diversification of dioecios angiosperms Author: Jana Vamosi Last modified by: Jana Created Date: 7/10/2001 3:23:30 PM Document presentation format – PowerPoint PPT presentation

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Title: Physiological Ecology


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 O2CO2 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
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33
Outline
  • Basics of energy
  • Photosynthesis
  • Trophic Levels
  • Efficiency of Energy Transfer

34
Energy transfer
35
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

36
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

37
Trophic levels examples
38
How many trophic levels?
39
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

40
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

41
Food chains versus food webs
Food chains
Food web
42
Outline
  • Basics of energy
  • Photosynthesis
  • Trophic Levels
  • Efficiency of Energy Transfer

43
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

44
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
45
Coniferous versus deciduous forest
46
Efficiency of photosynthesis
  • Of the energy that is actually absorbed by
    chloroplasts, at best about 20 is converted into
    sugars

47
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

48
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

49
Secondary Productivity
  • Secondary productivity the rate at which
    consumers convert the chemical energy of the food
    they eat into their own new biomass

50
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

51
Productivity pyramid
52
Calculating Ecological Efficiency
  • Lindeman Efficiency
  • -can be seen as the ratio of assimilation between
    trophic levels
  • energy (growth respiration) of predator
  • energy (growth respiration) of food species

53
Simplifying Ecological Efficiency
  • Production Efficiency
  • -can be seen as the ratio of biomass production
    between trophic levels
  • energy (growth respiration) of predator
  • energy (growth respiration) of food species

54
Calculating efficiencies
e.g., grasshopper Efficiency 1,000 J /
10,000 J 10 efficient
55
Efficiencies
  • Herbivores are generally more efficient than
    carnivores (7 versus 1)
  • Ectotherms are more efficient than endotherms (up
    to 15 versus 7)

56
The Lost energy
  • First Law of Thermodynamics
  • energy cannot be created or destroyed it can only
    change form
  • Second Law of Thermodynamics
  • as energy changes form it becomes more
    disorganized. I.e., ENTROPY increases
  • Energy quality index
  • lightgtchemical bondgtmovement,heat

57
What happens to the rest of the energy?
  • used to do work (cell processes, activity,
    reproduction)
  • Lost as heat (entropy)
  • not consumed or not assimilated
  • decomposers eventually get this!

58
Detritivores and decomposers
59
Summary
  • Virtually all energy comes from the sun this
    energy is never destroyed, it just changes form
  • Photosynthesis converts light energy into
    chemical energy
  • All other trophic levels depend on photosynthesis
    for life
  • Organisms vary in their ability to extract energy
    from the trophic level below them but most
    efficiencies are below 15, leaving much for
    detritivores

60
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