trophic dynamics

Question 1

important for?

Answer 1

• Really important for the cycling of energy, carbon, nutrients among organisms in an ecosystem

Question 2

trophic structure?

Answer 2

Feeding relationships among organisms in a community or ecosystem

Question 3

food chains?

Answer 3

• Describe transfer of energy and sometimes nutrients through trophic levels
  
  • Traces fate of a packet of energy from the time it enters the ecosystem to when it leaves

Question 4

energy transfer between levels: describe (10% rule, limits)

Answer 4

• Relatively inefficient w/ 10% rule - 10% of the energy from the sun is captured by PP, then 10% of that goes to primary consumers, and so on
  
  • # of trophic levels and energy content in each are limited by inefficient transfer of energy up plant based food chain (and NPP)
  • Extracted energy from consumption not 100% efficient, metabolic costs with digestion and food processing
  • Loss of energy when foraging

Question 5

overall PP pattern? what depends on PP

Answer 5

• Overall pattern that more PP = more herbivore production
  
  • Secondary production is dependent on PP
  • Secondary production = energy contained within heterotrophs
  • Graph shows energy contained in the secondary producers going up
  • Size of first trophic level will determine all the rest

Question 6

food webs?

Answer 6

• Interconnected feeding relationships (transfer of energy and nutrients) in a community
  
  • Lots of simplifications made, bias towards things that are easy to measure, hard to determine
  • Difficult to analyze the networks but interesting patterns

Question 7

terrestrial vs aquatic systems? look at graph

Answer 7

• Aquatic systems - inversion in biomass
  
  • Same amount of PP in both, but difference in the biomass
  • Aquatic system energy flow - high rate of consumption, easy by which biomass is digested
  • Reducing some of the stresses that threaten herbivores, you are able to get a greater efficiency - management can increase the energy the trophic level contains

Question 8

how do herbivores negatively effect PP

Answer 8

○ Direct damage and consumption
○ Reduce photosynthetic capacity (indirect/future cost)
○ Impair function
○ Loss of nutrients
○ Consumption of seeds and fruits
Includes defenses (costly)

Question 9

plant defenses - 2 types

Answer 9

○ Constitutive; produced continuously in the background - ex. Comparison- our immune system always has background processes
○ Induced: increase rapidly in response to herbivory - can be physical or chemical - thorns, hairs, toxins

Question 10

plant defenses costs

Answer 10

• Tradeoff between defenses and new growth
  
  • Best predictor of future herbivory is current herbivory - plant responds by producing more defenses in the future
  • Either defense can be very costly - up to 30% of energy is dedicated to defense

Question 11

plant defense graph?

Answer 11

○ Shows tannin production - deter based on taste + digestibility
○ Negative linear relationship - plants that produce more tannins are producing less leaves - tradeoff