4. Ecophysiology of Energy

Definition of ecophysiology

organism-focused subdiscipline of physiological ecology, focusing on the physiological processes that help individual organisms survive

Energy balance

• mainly comes from sunlight

• energy is the property of matter and radiation which it manifest as a capacity to perform work and currency of life

• energy stored= energy in — energy out

Autotrophs

use inorganic energy to store chemical energy in organic compounds

ex: photosynthesis and chemosynthesis

Photosynthesis

chemical reactions which use light energy to reduce carbon in CO2 to produce carbs

Photosynthesis → Limiting factors

• light

• CO2

• H2O

• temperature

• nitrogen

Photosynthesis → Basic chemical equation

6CO2 + 6H2O → C6H12O6 + 6O2

Rubisco

huge protein that’s used in Calvin Cycle to fix (capture CO2 and make it biologically useful) CO2

Rubisco and connection to photorespiration

• rubisco is supposed to bind to CO2 but sometimes binds to O2 with conditions that are

  • high temperature, high O2, and low CO2 concentrations

  • may happen to protect plant from too much light energy and less O2 when photosynthesis evolved

Major photosynthetic pathways, costs and benefits of each

1. C3 photosynthesis

2. C4 photosynthesis

3. CAM photosynthesis

C3 photosynthesis 

normal photosynthesis

C4 Photosynthesis

• Separates dark and light reactions in space 

• in different parts of leaf, costs more energy better than C3 for warm, high-lighted environments

• minimizes photorespiration 

CAM photosynthesis

• separates dark and light reactions in time

• modified version of C4

• water conservation: stomata are open at night (when air is cool and evaporative demand is low) 

• CO2 is stored until daytime, then stomata is closed

• cost= low maximum photosynthetic rate

• favorable= for very dry environments (desert)

Photosynthesis: 

• Tradeoffs between carbon dioxide capture and water loss

• water using efficiency= carbon gained vs lost;

• to increase H2O use efficiency= open stomata less, reduce water lost when opening stomata, get better at using CO2 already in leaf

Photosynthesis

• Tradeoffs ecophysiology of nitrogen

• nitrogen is very limiting in soil and takes lots of carbon and energy to build roots to get nitrogen 

• how should nitrogen (necessary for photosynthesis) be allocated among leaves?

  • put more nitrogen (more photosynthetic enzymes) in leaves, but lose out on light in lower leaves and lose out on occasional sunfleck

Major trade-offs for plants

Leibig’s law of the minimum

• growth is dictated by scarcest (limiting) resource

• not total resource available

• plants should allocate structures to acquiring the most limiting resource 

• ex: trees lives with high CO2 levels, should make more roots because more CO2= water is limited so more roots needed to suck up water

Beer’s Law math problems

Heterotrophs

consume energy from organic compounds which are typically made from autotrophs

Heterotroph

• metabolism

• metabolic rate= rate of energy expenditure

• BMR= basal metabolic rate= minimum amount of energy required to maintain essential function

Heterotroph:

• Respiration

• aerobic= stored chemical energy )in glucose) is broken down to generate ATP in presence of oxygen

• anaerobic= stored chemical energy )in glucose) is broken down to generate ATP in absence of oxygen

ii. Major categories for the use of metabolic energy in animals

• Maintenance  

• thermoregulation

• behavior

• growth

• heat increment of feeding

  • digestion

iii. Limiting factors in respiration

• food (sugars, glucose)

• oxygen

• enzymes

• temperature

  • as temperature rises= respiration decreases bc enzymes and cells break down because life can’t sustain high temperatures

iv. Limiting resources for heterotrophs

• food

• oxygen

• mates

• territory

v. Major trade-offs for animals in energy allocation

• growth vs reproduction

• surviva; vs reproduction

• reproductive tradeoffs

• foraging tradeoff