Energy transfers

Question 1

Where do plants get their CO2 from to make carbohydrates?

Answer 1

Atmosphere or water

Question 2

Where is most energy lost to between each trophic level?

Answer 2

Respiration and excretion

Question 3

After energy is lost, what is the remaining energy used to make?

Answer 3

Biomass

Question 4

What factors maximise rate of photosynthesis?

Answer 4

Light, green plants, warmth and plenty of water

Question 5

What is GPP?

Answer 5

Gross Primary Production is the chemical energy stored in plant biomass, in a given area or volume. It is the total energy resulting from photosynthesis.

Question 6

What is NPP?

Answer 6

Net primary production (NPP) is the chemical energy stored in plant biomass taking into account the energy that will be lost due to respiration (R).

NPP = GPP – R

Question 7

What is the formula to work out the net production of consumers?

Answer 7

N= I - F + R

I = the chemical energy stored in ingested food F = the chemical energy lost to the environment in faeces and urine R = respiratory losses.

Question 8

What are the units for rate of productivity and why are they useful?

Answer 8

kJ ha–1 year–1

It is recorded as per unit area to standardize the results to enable environments to be compared- it takes into account that different environments will vary in size. The units are also per year to take into account the impact seasons will have on rain, light, and heat – it provides an annual average to allow fair comparisons between environments.

Question 9

What is a producer?

Answer 9

A producer is a photosynthetic organism that can manufacture organic substances, using light energy, water, carbon dioxide and mineral ions 

Question 10

what is a consumer?

Answer 10

consumers are organisms that obtain their energy by feeding on other organisms, rather than using the energy of sunlight directly.

Question 11

What is a saprobiont?

Answer 11

Saprobionts or a group of organisms that break down the complex materials in dead organisms into simple ones - majority of this is carried out by fungi and bacteria

Question 12

What do the arrows on a food chain show?

Answer 12

Direction of energy flow

Question 13

What kind of energy is sunglight conserved as in plants?

Answer 13

Chemical energy

Question 14

what are the units of biomass? 

Answer 14

grams per square metre (for an area like grassland or seashore)

g m-2

grams per cubic metre (for volumes like ponds or oceans)

g m-3

Question 15

How is the chemical energy store in dry mass estimated?

Answer 15

By using calorimetry

Question 16

Why is only a small % (1-3%) of the Sun’s energy converted to organic matter?

Answer 16

• over 90% of the Sun’s energy is reflected back into space by clouds and dust or absorbed by the atmosphere
• not all wavelengths of light can be absorbed and used for photosynthesis
• light may not fall on a chlorophyll molecule
• a factor, such as low carbon dioxide levels, may limit the rate of photosynthesis

Question 17

Roughly how much of the NPP can be used by primary consumers for growth?

Answer 17

10%

Question 18

What are the reasons for low percentage of energy transferred to each stage?

Answer 18

• some of the organism is not consumed
• Some parts I consume to it cannot be digested and are therefore lost in faeces
• Some of the energy is lost in excretory materials, such as urine
• Some energy losses occur as heat from respiration and lost to the environment. These losses are high in mammals and birds because of the high body temperature. Much energy is needed to maintain their body temperature when heat is constantly being lost to the environment.

Question 19

why do food chains rarely have more than four trophic levels?

Answer 19

• Insufficient energy is available to support a large enough breeding population at trophic levels higher than this
• The total mass of organisms in a particular place (biomass) is less as higher trophic levels
• The total amount of energy available is less as each level as one moves up a food chain

Question 20

How does keeping animals in confined spaces increase energy-conversion rate?

Answer 20

• movement is restricted and so less energy is used in muscle contraction
• The environment can be kept warm in order to reduce heat loss from the body
• Feeding can be controlled so the animals receive the optimum amount and type of food for maximum growth with no wastage
• Predators are excluded so that there is no loss to other organisms in the food web