Title: Physiological Ecology
1Physiological Ecology
2Outline
- Introduction to Ecology
- Evolution and Natural Selection
- Physiological Ecology
- Behavioural Ecology
3Physiological 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
4Physiological Ecology
- Nutrient and Energy Transfer
- Endothermy and Ectothermy
- Climate
- Current Climate Change
5Physiological Ecology
- Nutrient and Energy Transfer
- Endothermy and Ectothermy
- Climate
- Current Climate Change
6Nutrient and Energy Transfer
Ch. 6.1 6.6, Bush
7Outline
- Basics of energy
- Photosynthesis
- Trophic Levels
- Efficiency of Energy Transfer
8Outline
- Basics of energy
- Photosynthesis
- Trophic Levels
- Efficiency of Energy Transfer
9Forms 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
10Energy transfer
11Energy source
- The ultimate energy source for (most) life on
earth is the sun
12Outline
- Basics of energy
- Photosynthesis
- Trophic Levels
- Efficiency of Energy Transfer
13Photosynthesis
- What is it?
- Chlorophyll, a necessary pigment
- Variations in photosynthesis
- The fate of carbohydrate
14Photosynthesis
- Synthesis of carbohydrates from CO2 and water
- Sunlight acts as energy source
- O2 is a by-product
15In Chemistry notation
- Energy from sunlight CO2 H2O ? CH2O O2
16Chlorophyll, a necessary pigment
17Pigments absorb light energy
Pigments absorb light energy between 400-700
?m -energy in this range is termed
Photosynthetically Active Radiation (PAR)
18Why are leaves green?
- Pigments cannot absorb light in the green
wavelength region
19The Green Gap
20Why are some plants not green?
- Chlorophyll is missing from some cells, making
the reflectance of other pigments visible
21Fall colour
- the production of chlorophyll requires sunlight
and warm temperatures - in many plants, chlorophyll production stops in
fall and other pigments become visible
22Why 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
23Variations in photosynthesis
- C3 photosynthesis
- C4 photosynthesis
- CAM photosynthesis
24CO2 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
25CO2 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
26C3 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
27C4 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
28The 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.
29CAM 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)
30Unrelated 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)
31Why photosynthesize?
- sugars created from photosynthesis are necessary
for - chemical reactions
- plant functions
- e.g., conduction of water and nutrients up the
stem - growth (biomass)
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33Outline
- Basics of energy
- Photosynthesis
- Trophic Levels
- Efficiency of Energy Transfer
34Energy transfer
35Two 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
36Trophic 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
37Trophic levels examples
38How many trophic levels?
39Exceptions 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
40Food 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
41Food chains versus food webs
Food chains
Food web
42Outline
- Basics of energy
- Photosynthesis
- Trophic Levels
- Efficiency of Energy Transfer
43The 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
44Efficiency 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
45Coniferous versus deciduous forest
46Efficiency of photosynthesis
- Of the energy that is actually absorbed by
chloroplasts, at best about 20 is converted into
sugars
47Plant 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
48Primary 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
49Secondary Productivity
- Secondary productivity the rate at which
consumers convert the chemical energy of the food
they eat into their own new biomass
50Pyramid 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
51Productivity pyramid
52Calculating 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
53Simplifying 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
54Calculating efficiencies
e.g., grasshopper Efficiency 1,000 J /
10,000 J 10 efficient
55Efficiencies
- Herbivores are generally more efficient than
carnivores (7 versus 1) - Ectotherms are more efficient than endotherms (up
to 15 versus 7)
56The 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
57What 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!
58Detritivores and decomposers
59Summary
- 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
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