Trophic Levels and Energy Transfer

Question 1

Trophic structure

Answer 1

The feeding relationships between organisms in a community

Question 2

Secondary production

Answer 2

A heterotroph is an organism that synthesizes its biomass from the consumption of organic tissue

Question 3

Grazing (green) food chains

Answer 3

Energy at the lowest trophic level is acquired through photosynthesis by producers; less than 10% of terrestrial plant tissue is consumed feeding this chain

Question 4

Detrital (brown) food chain

Answer 4

Begins with dead organic materials; leftover biomass to feed other organisms; 90% of terrestrial plant matter becomes detritus feeding this chain

Question 5

Detritivore

Answer 5

Heterotrophs that feed on dead tissues but does not mineralized organic material back into nutrients (i.e. scavengers: vultures); ensure recycling of matter

Question 6

Decomposer

Answer 6

Heterotrophs thar mineralize dead organic material back into inorganic nutrients (simpler compounds) (i.e. fungi or bacteria); ensure recycling of matter

Question 7

Trophic efficiency

Answer 7

Energy is lost with each trophic transfer; rule of thumb: on 10% of energy is transferred

Question 8

Trophic efficiency

Answer 8

TE = Pn/Pn-1 ; biomass in higher level/biomass in lower level

Question 9

Consumption efficiency

Answer 9

CE = the proportion of net productions at one tropic level consumed by the next level
- not all biomass consumed is converted into secondary production (much lost to respiration)

Question 10

Trophic efficiency: Terrestrial vs. Aquatic

Answer 10

Aquatic is more efficient resulting in a steeper pyramid (steeper = more trophic efficient)

Question 11

Bioconcentration

Answer 11

Uptake of contaminants from WATER (organisms that live in water)

Question 12

Biomagnification

Answer 12

Uptake of contaminants from FOOD

Question 13

Bioaccumulation

Answer 13

Uptake of contaminants from all sources (e.g. water, food, air, soil); older organisms have more toxins since contaminants bioaccumulate with age, size, and trophic level

Question 14

Homeorhesis

Answer 14

“Steady flow” (as opposed to steady state); a dynamic system that returns to a specific trajectory instead of a specific point (i.e. succession)

Question 15

Resistance

Answer 15

The ability of a community to remain unchanged when challenged by disturbance; very resistant to disturbance

Question 16

Resilience

Answer 16

A measure of the rate a community can recover following a disturbance

Question 17

Resistance vs. Resilience

Answer 17

• often inverse relationship between resistance and resilience (tropical vs. boreal)
• low resistance related to rapid change following disturbance
• once a high resistance systems fails, it is difficult to bounce back
• high resilience, low resistance; high resistance, low resilience

Question 18

Latitudinal gradients in resistance/resilience

Answer 18

As latitude increases (equator towards polar) resistance decreases, resilience increases; increase in niche breadth from tropics to tundra

Question 19

Niche breadth

Answer 19

Specialists (small niche) vs. Generalists (large niche)

Question 20

Specialists

Answer 20

Cannot cope with wide range of conditions, but very little competition; resilient system is better for specialists (i.e. koala)

Question 21

Generalists

Answer 21

Can cope with wide range of conditions, but lots of competition; resistant system is better for generalists (i.e. raccoon)
- ecosystems with more generalists = more resilient b/c organisms can tolerate more change

Question 22

Hysteresis

Answer 22

The dependence of a state of system on the history of that system; movement between the two stable states depends on previous conditions