Energy and Ecosystems

Question 1

Define the term ‘food chain’

Answer 1

Shows the feeding relationship between producers and consumers

Question 2

Define the term ‘food web’

Answer 2

More accurate demonstration of feeding relationships. Links food webs of one habitat together.

Question 3

Define the term ‘producers’

Answer 3

Photosynthetic organisms that produce organic substances using light energy, water , CO2 and mineral ions

Question 4

Define the term ‘primary consumer’

Answer 4

Organism in the food chain that directly obtains its energy by feeding on the producer. The first consumer/ animal in the food chain

Question 5

Define the term ‘secondary consumer’

Answer 5

Second consumer in the food chain. Feeds on the primary consumer

Question 6

Define the term ‘tertiary consumer’

Answer 6

Third consumer in the food chain. Feeds on the secondary consumer

Question 7

Define the term ‘trophic level’

Answer 7

Position in the food chain occupied by a producer or consumer

Question 8

Define the term ‘herbivore’

Answer 8

Plant eating consumer

Question 9

Define the term ‘carnivore’

Answer 9

Meat eating consumer

Question 10

Define the term ‘omnivore’

Answer 10

Consumer that eats both plants and animals

Question 11

Define the term ‘habitat’

Answer 11

The place where an organism normally lives and which is characterised by physical conditions and the other types of organism present

Question 12

Define the term ‘ecosystem’

Answer 12

All the biotic and abiotic components of a particular area

Question 13

Define the term ‘biomass’

Answer 13

The total mass of living material, normally measured in a specific area over a time period

Question 14

Explain how plants synthesise organic compounds

Answer 14

-Photosynthesis
-Using CO2 from the atmosphere or dissolved in water and solar energy
-To make glucose

Question 15

State three ways in which the sugars produced in photosynthesis are used

Answer 15

-Respiration
-To release energy for growth
-To make biological molecules such as cellulose

Question 16

State how biomass is measured

Answer 16

The dry mass of tissue per unit area

Question 17

State the method that is used to measure the total chemical energy store in dry biomass

Answer 17

Calorimetry

Question 18

Describe the method to measure biomass

Answer 18

1. Dry mass is weighed
2. Water tank with a known volume of water at 400oC
3. Dry mass is burnt in a chamber with pure oxygen
4. Measure the temperature change of the water
5. Energy released= chemical energy stored in dry biomass ( j or Kj )

Question 19

Define the term ‘Gross Primary Production (GPP)’

Answer 19

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

Question 20

Define the term ‘Net Primary Production (NPP)’

Answer 20

The chemical energy store in plant biomass taking into account respiratory losses to the environment

Question 21

State the equation to calculate ‘Net Primary Production (NPP)’

Answer 21

NPP= GPP - R

Question 22

What is NPP?

Answer 22

-Energy available to the plant for growth and reproduction
-Energy available to organisms in the next trophic level (including herbivores and decomposers)

Question 23

State the equation to calculate the net production of consumers

Answer 23

N = I - ( F + R )

N= Net production
I= chemical energy in ingested food
F= chemical energy lost in faeces and urine
R= energy lost in respiration

Question 24

State six methods used by farmers to increase energy transfers

Answer 24

-Using chemical pesticides e.g. insecticides and herbicides
-Reducing species diversity through monoculture
-Maximising solar input
-Limiting movement
-Heating the environment
-Protein/ supplement rich diet

Question 25

Explain how using chemical pesticides e.g. insecticides and herbicides increases the efficiency of energy transfers and state two challenges of this farming method

Answer 25

-Increased photosynthesis = increased biomass = increased NPP Challenges: -Eutrophication / pollution -Reduces species diversity

Question 26

Explain how reducing species diversity through monoculture (growth of one species) increases the efficiency of energy transfers and state two challenges of this farming method

Answer 26

-Reduces competition = higher yield of desired crop = more profit Challenges: -Reduces diversity which decreases stability -Drains nutrients from the soil

Question 27

Explain how maximising solar input increases the efficiency of energy transfers and state two challenges of this farming method

Answer 27

-Increases initial energy input = increases GPP = increase in NPP Challenges: -Costly -> energy intensive -Light pollution

Question 28

Explain how limiting movement increases the efficiency of energy transfers and state three challenges of this farming method

Answer 28

-Reduces respiratory losses = more energy to tissues Challenges: -Unethical -Spread of diseases -Antibiotic resistance (to reduce risk of spread of disease which would occur very quickly but as these are given often it leads to antibiotic resistance)

Question 29

Explain how heating the environment increases the efficiency of energy transfers and state two challenges of this farming method

Answer 29

-Reduces losses for temperature control = optimal for growth Challenges: -Costly -Pollution

Question 30

Explain how providing a protein rich/ supplement rich diet increases the efficiency of energy transfers and state two challenges of this farming method

Answer 30

-Increases biomass = increases profits Challenges: -Unethical (artificial) -Costly

Question 31

State three reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem

Answer 31

-Not all of organism is eaten or digested e.g. bone -Some is lost to respiratory losses or as heat lost through movement -Some is lost in excretory processes

Question 32

State two reasons why in natural ecosystems most of the light falling on producers is not used in photosynthesis

Answer 32

-Not all wavelengths of light can be absorbed an utilised -Doesn't have the correct chlorophyll -The light misses the chlorophyll -Other limiting factors

Question 33

State the equation to calculate efficiency

Answer 33

Efficiency= energy available after the transfer / energy available before the transfer x100

Question 34

In natural ecosystems, the efficiency of energy transfers is low. State three reasons why.

Answer 34

-Only energy source is the sun (only 1-3% of light energy absorbed by chlorophyll) -High species diversity= competition -There is a natural climax community -Loss of energy to the surroundings -Recycling of nutrients in the environment -> decomposes utilise some energy as well so there is less available for the consumers

Question 35

Explain why farming cattle is less efficient than farming crops due to energy transfer

Answer 35

-Simpler food chain (crop= just producer , cattle= producer then cattle) -Energy lost between tropic levels -Energy lost via respiration