Energy And Ecosystem

Question 1

🔴️ How does intensive rearing increase net productivity

Answer 1

1 Movement is restricted so less energy is used

2 Kept warm inside so less heat loss and no predators

3 Some livestock are genetically selected for higher productivity

4 Fed on controlled diet so higher proportion of digested food absorbed

5 Some are killed when young so more energy transferred to biomass

Question 2

🔴️Describe and explain why the efficiency of energy transfer is different at different stages

Answer 2

1 Some light from the sun is reflected as it’s isn’t of an appropriate wavelength

2 The efficiency of photosynthesis Is approx 2%

3 Energy is lost as part of the plants is not eaten. And some is lost in faeces/ urine

4 It may be lost as heat to the environemt

5 The efficiency of transfer to consumer is greater than transfer to producers as 10% of energy is absorbed

6 The efficiency is lower in warm blooded animals as energy is used to maintain temp

7 Carnivores use more of their food than herbivores

Question 3

🔴️Why do food chains rarely have more than 5 trophic levels?

Answer 3

• some energy is lost at each trophic level in the food chain due to respiration
• less energy is available to be passed on in the next food chain

Question 4

🔴️ Advantages of biological control

Answer 4

• Specific to one pest
• Only 1 application needed as it reproduces
• Pests don’t get resistance
• No chemical residues left
• Keeps pests population consistently low
• Can be used in organic farming

Question 5

🔴️Disadvantages of biological control

Answer 5

• Doesn’t eradicate pest completely
• Slow acting
• May become the pest itself

Question 6

Why do native organisms become the dominant species in a new environment

Answer 6

• They have few consumers
• They out compete the other organisms for resources e.g light

Question 7

How farming practices increase the productivity of agricultural crops

Answer 7

1. Fertilisers are added to soil e.g nitrates
2. Nitrogen for protein and phosphorus for DNA
3. Pesticides and biological agent prevents consumption of crop;
4. Herbicides remove competition;
5. Selective breeding of crops
6. Glass houses enhance conditions temp/CO₂/ light;
7. Ploughing aerates soil which allows nitrification

Question 8

How do we use Integrated control

Answer 8

• Uses biological control more and minimal pesticide
• It controls pest population instead of eradicating it

1. Monitor area and look for pests
2. Mechanically remove pests if present
3. Supply initial dose of pesticide as it is fast acting
4. Then apply biological control .
5. These will increase in number over time and provide long term control
6. Reapply pesticides whenever there is an uncontrollable outbreak

Question 9

Describe the carbon cycle?

Answer 9

• Carbon Dioxide removed from atmosphere by plants by photosynthesis
• Carbon Dioxide removed from atmosphere by ocean (CO₂ dissolves in ocean)
• Plants and animals respire returning CO₂ to the atmosphere
• When plants die they’re broken down by decomposers which respire,returning CO₂ to the atmosphere
• Combustion of fossil fuels returns CO₂ to the atmosphere
• Evaporation of the ocean returns CO₂ to the atmosphere

Question 10

Effects of global warming?

Answer 10

• Melting of polar ice caps: extinction of polar bears
• Rise in sea level could lead to coastal flooding, reducing crop productivity
• Intense whether conditions, changing the distibution of organisms
• The life cycle of insect pests would change as they adapt
• Changes proportion of organisms as only xerophytes survive due to the changed rainfall patterns

Question 11

Ways in which energy is lost between primary and secondary consumers.

Answer 11

• Heat loss to environment by respiration
• movement e.g running (muscle contraction)
• faeces due to indigestible material
• inedible parts as not all eaten;
• excretion e.g urine

Question 12

Reasons why very little of the sunlight energy falling on the leaves of a plant can be used

Answer 12

• Some light may have wrong wavelength
• Reflected;
• Misses chloroplasts
• May be other limiting factor

Question 13

Why does deforestation reduce the diversity index of an area cleared in by deforestation

Answer 13

• deforestation removes many habitats
• less variety and quantity of food
• so fewer species can live there

Question 14

Explain the potential benefit of applying a fertiliser containing ammonium nitrate [((NH₄)(NO₃)] rather than one containing KCN.

Answer 14

• ammonium nitrate contains more nitrogen per molecule than potassium nitrate;
• nitrate ions in fertiliser is absorbed immediately;
• nitrifying bacteria convert ammonium to nitrate so more nitrate made
• the KCN fertiliser would provide only the initial release of potassium nitrate

Question 15

Disadvantages of chemical control

Answer 15

• Non-biodegradable so may store in tissues;
• Non-specific as it may kill predators of pests;
• Builds up in food chain (bioaccumulation)
• May develop resistance;
• Not cost-effective as needs to be reapplied

Question 16

if pigeons consume a poison, how can eagles die from eating pigeons

Answer 16

• accumulation of posion within tissue
• poison is non-biodegradable
• eagles eat large numbers of birds;
• biomagnification leads to a high concentration of poison which kills eagles;

Question 17

Describe and explain the effects of monoculture on the environment.

Answer 17

• Other plant species removed so reduction in biodiversity
• Less variety of food
• Less habitats so less organisms can live there
• Reduces soil fertility so more fertilisers required;
• Could lead to large scale crop failure if new disease emerges ,

Question 18

How can an ecosystem become more stable?

Answer 18

• Have more species (biodiversity)
• More variety of food sources
• More niches/habitats

Question 19

Factors that need to be considered before using an organsim as a biological control

Answer 19

• Specificity: Only affects target species;
• Can survive in conditions of use;
• Ability to work on a large scale;
• Can the produced on a large scale;

Question 20

Explain how regular use of a pesticide could result in a resistant pest population

Answer 20

• Variation in population due to chance mutation
• Some individuals in population acquire allele for resistant so they’re not killed by pesticide;
• These survive when pesticide applied whereas non-resistant ones are killed;
• They reproduce and pass on resistant allele
• This Increases the frequency of resistant allele ;

Question 21

Why isn’t biomass an accurate representation of food availability

Answer 21

• Not all of animal eaten e.g large bones/skin;
• Inedible parts make up different proportions in different organisms

Question 22

3 ways deforestation has increased CO₂ conc?

Answer 22

1. decrease in photosynthesis causes less removal of CO₂
2. burning trees releases CO₂
3. decay of wood by microorganisms releases CO₂

Question 23

How does deforestation reduce biodiversity?

Answer 23

1. loss of habitat for certian species
2. loss of food source
3. fewer plant species due to clearing

Question 24

Why don’t biological control completely eradicate pest

Answer 24

• because biological control never eats all pests;
• as pests diminish so do control agents and vice versa

Question 25

How can we measure the dry mass of an organism?

Answer 25

• Heat at 100 C to evaporate water;
• Weigh and heat until no further change in mass;

Question 26

Why is dry mass better than fresh mass when comparing yield of plants

Answer 26

• Amount of water present will vary;
• This will affect fresh mass but will not affect dry mass

Question 27

Advantages of using integrated control

Answer 27

Biological Agents

• Only needs one application as they reproduce
• Specific;
• Keeps population consistently low;
• Pests do not develop resistance;
• No bioaccumulation;

Chemical pesticides

• Acts quickly;
• Can apply to specific area;
• Can eliminate pests;
• Kills wide range of pests

Question 28

Why does efficiency of food converted to biomass of an organism decrease at a lower temperature

Answer 28

• Lose more heat
• More energy used to maintain body temperature;
• More respiration needed
• More food used in respiration;​
• Less energy to grow

Question 29

As the predator increases why does the mass of prey increases

Answer 29

• Fewer prey as most are consumed by predators
• More food available for surviving prey so they grow more

Question 30

Factors farmers need to consider before investing in a new treatment plan

Answer 30

• How treatment may affect other organisms and environment (yield)
• Cost of substance
• Amount of substance needed for an effect

Question 31

Define biological control

Answer 31

• Use of parasite/predator/pathogen;
• To control numbers of a pest organism;

Question 32

Explain why the increase in the dry mass of a plant over twelve months is less than the mass of hexose produced over the same period.

Answer 32

• some hexose/biomass used in respiration;
• some parts of the plant are eaten;
• some parts lost to decomposers as leaf fall;

Question 33

Why is the dry biomass of plants is always higher than that of animals?

Answer 33

• Plants are producers
• Animals are consumers of plants;
• Loss of energy between trophic levels;
• Due to respiration as heat;
• Less energy available to grow