Topic 5—B: Energy Transfer and Nutrient Cycles- 2. Farming Practices and Production

Question 1

What do food chains and food webs show?

Answer 1

• They show how energy is transferred through an ecosystem

Question 2

What do food chains show?

Answer 2

• They show simple lines of energy transfer

Question 3

What are each of the stages in a food chain called?

Answer 3

• Trophic level

Question 4

What do food webs show?

Answer 4

• They show lots of food chains in an ecosystem and how they overlap

Question 5

What are decomposers also part of?

Answer 5

• Food webs e.g. (fungi)

Question 6

What do decomposers do?

Answer 6

• They break down dead or undigested material, allowing nutrients to be recycled

Question 7

What needs to be increased to increase the amount of energy that is available for human consumption?

Answer 7

• Net primary production of crops
• Net production of livestock

Question 8

What are the 2 ways increasing efficiency can be done?

Answer 8

• Simplifying food webs to reduce energy losses
• Reducing respiratory losses

Question 9

Simplifying food webs

Answer 9

• Pests are organisms that reduce the amount of energy available for crop growth and therefore net primary production of crops
• This reduces the amount of energy available for humans
• So by simplifying the food web i.e. getting rid of food chains that don’t involve humans, energy losses will be reduced and the NPP of the crop will increase

Question 10

Examples of chemical pesticides that farmers can use to reduce pest numbers

Answer 10

• Insecticides) These kill insect pests that eat and damage crops. Killing insect pests means less biomass is lost from crops so they grow to be larger which means NPP is greater
• Herbicides) These kill weeds which can remove direct competition with the crop for energy from the sun.

Question 11

What do biological agents do?

Answer 11

• They reduce the numbers of pests, so crops lose less energy and biomass
• This increases the efficiency of energy transfer to humans

Question 12

Examples of biological agents that can be used to reduce the number of pests

Answer 12

• Parasites live in or lay their eggs on a pest insect. Parasites either kill the insect or reduce it’s ability to function
• Pathogenic bacteria and viruses are used to kill pests

Question 13

Reducing respiratory loss

Answer 13

One way that farmers increase the net production of their livestock is by controlling the conditions that they live in so that more energy is used for growth. And less is lost through respiration

Question 14

Examples of ways to reduce respiratory loss

Answer 14

• Movement increases the rate of respiration, so animals may be kept in pens where their movement is restricted
• The pens are often indoors and kept warm, so less energy is wasted by generating body heat

Question 15

What does reducing respiratory loss mean?

Answer 15

• More biomass is produced and more chemical energy can be stored, increasing net production and the efficiency of energy transfer to humans

Question 16

What are the benefits of reducing respiratory loss?

Answer 16

• More food can be produced in a shorter period and often at lower costs

Question 17

Disadvantages of reducing respiratory loss for animals?

Answer 17

• Keeping animals in pens to enhance net production raises ethical issues
• Some people think that the conditions intensively reared animals are kept in cause the animals pain, distress or restricts their natural behaviour so it shouldn’t be done

Question 18

How can farmers maximise NPP?

Answer 18

• Managing abiotic and limiting factors
• Increasing cultivated area and use of monoculture
• Limited space between plants (Increases GPP)

Question 19

How can farmers maximise NP?

Answer 19

• Reduce movement (barn, cage, shed)
• Food provided so no foraging
• Eat digestible food so faeces decrease and more essential molecules for growth
• Keep barn warm (decreases respiratory loss)
• Control protein intake to reduce urea
• e.g. (antibiotics) to reduce pathogens food chain

Question 20

Differences between agricultural and natural ecosystems

Answer 20

• Energy inputs for natural is sunlight but for agricultural it is sunlight/ lamp
• Productivity levels for natural is lower whereas productivity levels in agricultural are higher
• Species diversity in a natural ecosystem is higher compared to agricultural
• Nutrient availability in natural is nutrients cycle within ecosystem but for agricultural nutrients are added e.g. (fertilisers)
• Stage of succession for a natural ecosystem is climax community but for agricultural it’s plagioclimax community (interrupted)