4.2 energy flow

Question 1

how is chemical energy converted from sunlight stored?

Answer 1

stored in carbon compounds (organic molecules) and is transferred to heterotrophs via feeding

Question 2

trophic level

Answer 2

The position an organism occupies within a feeding sequence.

Producers always occupy the first trophic level in a feeding sequence
Primary consumers feed on producers and hence occupy the second trophic level
Further consumers (e.g. secondary, tertiary, etc.) may occupy subsequent trophic levels

Question 3

food chain (what it shows + an example)

Answer 3

shows the linear feeding relationships between species in a community

Arrows represent the transfer of energy and matter as one organism is eaten by another (arrows point in direction of energy flow)
The first organism in a food chain is always a producer, followed by consumers (primary, secondary, tertiary, etc.)

carrot plant -> cottontail rabbit -> feral cat - red fox
(must be species name and not just cat or dog.)

Question 4

Not all energy stored in organic molecules is transferred via heterotrophic feeding – some of the chemical energy is lost by:

Answer 4

1. Being excreted as part of the organism’s faeces
2. Remaining unconsumed as the uneaten portions of the food
3. via heat
4. and respiration

Question 5

The chemical energy produced by an organism can be converted into a number of forms, including:

Answer 5

1. Kinetic energy (e.g. during muscular contractions)
2. Electrical energy (e.g. during the transmission of nerve impulses)
3. Light energy (e.g. producing bioluminescence)

Question 6

why is energy transformations in living organisms never 100% efficient?

Answer 6

1. Most of the energy is lost to the organism – either used in respiration, released as heat, excreted in faeces or unconsumed
2. Typically energy transformations are ~10% efficient, with about 90% of available energy lost between trophic levels
3. The amount of energy transferred depends on how efficiently organisms can capture and use energy (usually between 5 – 20%)
   (aquatic is higher <20%)

Question 7

biomass

Answer 7

is the total mass of a group of organisms 0 consisting of the carbon compounds contained in cells and tissues

Question 8

biomass can be used to measure

Answer 8

canoe used by scientists to measure the amount of energy added to organisms as biomass as carbon compounds store energy.

Question 9

why is the number of potential trophic levels limited?

Answer 9

1. biomass diminishes along food chains w the loss of carbon dioxide, water and waste products to the environment.
2. as energy and biomass is lost between each level of a food chain, higher trophic levels receive less energy/biomass from feeding, thus need to eat larger quantities to obtain sufficient amounts of energy.
3. as they need to eat more, they expend more energy and biomass hunting fro food
4. if energy required to hunt for food exceeds energy available from the food eaten, the trophic level becomes unviable.

Question 10

pyramid of energy (what it is and how to draw + in what units)

Answer 10

is a graphical representation of the amount of energy at each trophic level of a food chain. is expressed in units of energy per area per time - kJ m^-2 year^-1

1. pyramids of energy will never appear inverted as some of the energy stored in one source is alw lost upon transfer
2. each level should be roughly 1/10th of the size of the preceding level (as energy levels are approx. 10% efficient).
3. the bottom level will always represent the producers, w subsequent levels representing consumers (pri, sec, etc.)