Ecosystem Ecology & Energy Transfer Pt. II

Basic ideas (to remember) 

• Only some organisms can produce organic molecules from inorganic ones 

• 1st law of thermodynamics not only explains input/output of solar energy in planet, but also explains:

solar energy captured and turned into chemical energy. 

Energy flows through the food web and is captured by others. 

2nd Law of Thermodynamics

“As energy is transferred or transformed, more and more of it is wasted”

or

“In procethe ss of energy transfer, some energy is dissipated (entropy) as heat.”

Autotrophs

Produce organic molecules (ex; glucose) using external energy source. 

• Are energetic foundation to EVERYTHING. 

Autotrophs types

• Photoautotrophs - Capture wavelength of sunlight and use to drive photosynthesis 

• Chemoautotrophs - Specialized bacteria capable of harnessing energy from organic chemicals via chemosynthesis. 

Chlorophyll and Rubisco

• Chlorophyll - captures protons

• Rubisco - an enzyme in plants, catalyzes the fixation of CO2. (common) 

Indian Pine

Not an autotroph, it lacks chlorophyll (NO photosynthetic). Instead, it gets energy from parasitizing certain fungi that live in mycorrhizal mutualism near the trees. 

• Lives in dark forests. 

The Parasitic Rafflesia (the corpse flower)

Not an autotroph. Infected host vines develop buds (grow to cabbages size) Trees shrews eat and spread seed on elephants feets.  

• NO roots, shoots, stems, or leaves (parasitic plant that lives in south Asia) 

Kleptoplasty (sea slugs)(Elysia timida)

Are capable of using photosynthesis using chloroplast from plants eaten.

Chemoautotrophs (examples)

• Sulphur bacteria - Acidithiobacillus thioxidans

• iron bacteria - Thiobacillus ferroxidase

• found in hot springs, acid mine drainage.

• Energy comes from inorganic Sulphur, atmospheric carbon, and ammonium sulphate for nitrogen. 

Heterotrophs

Must feed on other organisms (to fix energy in ecosystems) 

Heterotroph types

• Herbivores 

• Omnivores 

• Carnivores 

• Detritivores (detritus - feeding on dead)

• Decomposers 

Classification levels for feeding 

Primary, secondary, tertiary, quaternary 

Primary Production (types)

• Gross primary production (GPP) - Rate of solar energy capture.

• Respiration (RA) - Rate which sugar is burned to produce energy.

• Net Primary production (NPP) - NPP=GPP-RA.

Photosynthetic Pathways 

• C3 photosynthesis (Most common) 

• C4 photosynthesis 

• CAM photosynthesis 

C3 Photosynthesis 

It is the least energy-expensive under optimal conditions, but can be wasteful due to photorespiration.

C4 Photosynthesis

More energy expensive than C3 but more efficient under high light and temp conditions.

CAM Photosynthesis

It is the most energy-expensive due to the temporal separation of CO2 uptake and fixation, but it is the most water-efficient. 

Flow of energy through consumers

1) Ingestion

2) Assimilation 

3) Egestion 

4) Respiration 

5) Production 

Equations for efficiency of energetic transfer of heterotrophs 

• Consumption efficiency (CE) 

(food ingestion)/(Food produced) 

• Assimilation efficiency (AE) 

(A/I) 

• Production efficiency (PE) 

(P/A) 

Most levels of trophic levels primary producers can support

4-5 trophic levels.

Biomass pyramids depend on what?

Reproductive potential and longevity of trophic levels

• In aquatic systems, primary producers have short longevity compared to secondary producers. 

Food Chain

Linear representation of feed interactions

2 primary food chain ecosystems

1) Plants - Sit at base of grazing food chain.

2) Detritus - Sits at the base of the detrital food chain. Material is fed on by decomposers. 

Food Web 

Complex representation of all feeding interactions (energetic transfer) 

Top-Down Control (food web)

Predators control herbivores which in turn control primary producers

Bottom-Up Control (food web)

The presence or absence of mineral nutrients determines community structure, including the abundance of primary producers.