Energy and ecosytems 3.5.3 (Energy transfers in and between organisms 3.5)

Question 1

What is an ecosystem?

Answer 1

A biological community of interacting organisms and their physical environment.

Question 2

What is the ultimate source of energy for most ecosystems?

Answer 2

The sun.

Question 3

Define primary producers in an ecosystem.

Answer 3

Organisms that produce their own food through photosynthesis, such as plants.

Question 4

What is the role of decomposers in an ecosystem?

Answer 4

Decomposers break down dead organic matter into simpler substances, recycling nutrients back into the ecosystem.

Question 5

What is a trophic level in an ecosystem?

Answer 5

A position in the food chain, such as primary producers, primary consumers, secondary consumers, etc.

Question 6

What is a food chain?

Answer 6

A linear sequence of organisms through which nutrients and energy pass in an ecosystem.

Question 7

What is a food web?

Answer 7

A complex network of interconnected food chains in an ecosystem.

Question 8

What is the 10% rule in energy transfer in ecosystems?

Answer 8

Only about 10% of the energy from one trophic level is transferred to the next trophic level.

Question 9

What is the difference between a food chain and a food web?

Answer 9

A food chain shows a linear sequence of organisms, while a food web shows a complex network of interconnected food chains.

Question 10

What is the difference between a producer and a consumer in an ecosystem?

Answer 10

Producers create their own food through photosynthesis, while consumers obtain energy by consuming other organisms.

Question 11

What is a biotic factor in an ecosystem?

Answer 11

Living components of an ecosystem, such as plants, animals, and bacteria.

Question 12

What is an abiotic factor in an ecosystem?

Answer 12

Non-living components of an ecosystem, such as temperature, water, and sunlight.

Question 13

What is the importance of biodiversity in an ecosystem?

Answer 13

Biodiversity ensures the stability and resilience of ecosystems, as well as providing valuable ecosystem services.

Question 14

What is the difference between a habitat and a niche in an ecosystem?

Answer 14

A habitat is the physical environment where an organism lives, while a niche is the role and position of an organism within its habitat.

Question 15

What is the role of a predator in an ecosystem?

Answer 15

Predators help control the population of prey species, maintaining the balance of the ecosystem.

Question 16

What is Gross Primary Production (GPP)

Answer 16

The chemical energy store in plant biomass , in a given area or volume

Question 17

What is the Net primary production (NPP)

Answer 17

the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

Question 18

What is another word for a decomposer

Answer 18

Saprobiant

Question 19

Between each tropic level how is energy lost

Answer 19

•Majority of energy is lost due to respiration (heat energy) and excretion
• The remaining every is used to form the biomass

Question 20

What is biomass

Answer 20

The total mass of living material in a specific area at a time

Question 21

How can the amount of biomass remaining in an organism be measured

Answer 21

It can be measured in terms of mass of carbon or dry mass of tissue per given area

Question 22

How can an ecosystem be more productive

Answer 22

• depends on the abiotic and biotic factors
• Higher abiotic and biotic factors will maximise rates of photosynthesis
• More carbohydrates being produced in plants
• So more carbon produced into food webs at the start

Question 23

How can net primary production be calculated

Answer 23

NPP = GPP - R

R = respiration
GPP = gross primary production

Question 24

What is NPP in the NPP calculation

Answer 24

The energy left over that is available to the plant to create new biomass and therefore available to the next tropic level in a food web

Question 25

What is the equation for net production of consumers

Answer 25

N = I - ( F+R)

I = chemical energy store in ingested food
F = the chemical energy lost to the environment in faeces and urine
R = Respiratory losses

Question 26

what could the units for rates of productivity include

Answer 26

KJ/ m^2 / day
or KJ / ha ^-1 / year ^-1

Question 27

why are the units recorded per unit area

Answer 27

Per unit area takes into account that different environments vary in size.
- Standardising results to enable comparisons between environments

Question 28

Why are units in KJ

Answer 28

the unit for energy which also includes per unit area and per year

Question 29

Why are units per year

Answer 29

Per year takes into account seasonal variations on biomass
- More representative and enables comparison between environments

Question 30

How might energy be lost in the transfer from the sun to the producers

Answer 30

• Reflection / absorption of the sun by the atmosphere
• Chlorophyll only absorbs scientific wavelengths
• Not all light will fall on chlorophyll
• limiting factors

Question 31

Describe how biomass is formed in plants

Answer 31

• During photosynthesis , plants make organic compounds from atmospheric CO2
• Most sugars synthesised are used by the plant as respiratory substrates
• Rest used to make other groups of biological molecules

Question 32

how can biomass be measured

Answer 32

Mass or carbon or dry mass of tissue per given area

Question 33

Describe how dry mass of tissue can be measured

Answer 33

1) sample dried in an oven e.g. at 100 degrees
2) sample weighed and reheated at regular intervals
3) until mass remains constant

Question 34

Explain why dry mass is more representative than fresh ( wet ) mass

Answer 34

Water volume in wet samples will very but will not affect dry mass

Question 35

Describe how the chemical energy stored in dry biomass can be estimated

Answer 35

Using calorimetry :
1) known mass of dry biomass is fully combusted
2) heat energy released heats a known volume of water
3) increase in temperature of water is used to calculate chemical energy of biomass

Question 36

explain how features of a calorimeter enable valid measurement of heat energy released

Answer 36

• stirrer => evenly distributes heat energy
• Air / insulation => reduces heat loss and gain to and from surroundings
• water => has a high specific heat capacity

Question 37

Explain the importance of NPP in ecosystems

Answer 37

• NPP is available for plant growth and reproduction
• NPP is also available to other trophic levels in the ecosystem, such as herbivores and decomposers

Question 38

What is primary or secondary productivity

Answer 38

The rate of primary or secondary production

Question 39

State the formula for efficiency of energy transfer

Answer 39

Energy or biomass available after transfer / Energy or biomass available before transfer x100

Question 40

Explain why energy transfer between trophic levels is inefficient

Answer 40

• Heat energy is lost via respiration
• Energy lost via parts of an organism that aren’t eaten
• Energy lost via food not digested => lost as faeces
• Energy lost via excretion

Question 41

Explain how crop farming practices increase energy transfer efficiency

Answer 41

• Simplifying food webs to reduce energy / biomass losses to non human food chains e.g.
  • Herbicides kill weeds => less competition
  • Pesticides kill insects => reduce loss of biomass from crops
  • Fungicides reduce fungal infections => more energy to create biomass
• Fertilisers to prevent poor growth due to lack of nutrients

Question 42

Explain how livestock farming practices increase energy transfer efficiency

Answer 42

• Reducing respiratory losses within a human food chain :
- Restrict movement and keep warm => less energy lost as heat from respiration
- Slaughter animal while still growing / young , when most of their energy is used for growth
- Treated with antibiotics => prevent loss of energy due to pathogens
- Selective breeding to produce breeds with higher growth rates