Energy And Ecosystems

Question 1

What is a trophic level

Answer 1

Each stage in a food web

Question 2

What happens to the energy in each trophic level

Answer 2

Majority is lost due to respiration and excretion
Remaining energy is used to form biomass

Question 3

What is biomass

Answer 3

Mass of carbon within the organism

Question 4

What is GPP

Answer 4

Gross Primary Production
Chemical energy stored in plant biomass in a given area/ volume
Total energy resulting from photosyn

Question 5

What is NPP

Answer 5

Net primary production
GPP- energy lost by respiration
Energy left to go towards making biomass

Question 6

How to work out net production of consumers

Answer 6

N = I - F + R

I= chemical energy stored in ingested food (Eaten)
F = chemical energy lost to environment in faeces and urine
R = respiratory losses

Question 7

What units are used in rates of productivity and why

Answer 7

kJ ha-1 year-1
kJ unit for energy
Recorded as per unit area to STANDARDISE the results - environment can be compared, takes into account that different environments will vary in size

PER YEAR - take into account impact seasons (rain, light, temp) = annual average - comparison

Question 8

Why is the nitrogen cycle important?

Answer 8

Nitrogen is within proteins, ATP and nucleic acids

Cannot gain nitrogen through nitrogen gas because of its triple bond which plants and animals cannot break

Microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb

Question 9

What are the key processes of nitrogen cycle

Answer 9

• saprobiotic nutrition and microbes (essential for all other stages) = microbes feeding on dead plant matter/waste
• ammonification
• nitrification
• nitrogen fixation
• denitrification

Question 10

2 ways nitrogen is extracted from atmosphere in soil

Answer 10

Leguminous plants
Nitrogen fixing bacteria in root nodules of plants directly converts nitrogen from atmosphere into ammonia into their roots

Free living nitrogen fixing bacteria within soil which can fix nitrogen into ammonium

Question 11

What is nitrification

Answer 11

Nitrifying bacteria Can oxidise ammonium into nitrites
Oxidise further into nitrates
Absorbed by AT into plant roots (assimilation)
Animal absorb through digestion and absorption

Question 12

Explain saprobiotic nutrition

Answer 12

Have to name nitrogen containing compounds (urea, protein, DNA)
Decomposers break down proteins to release nitrogen
Converts back to ammonium
IF LACK OF O2 in soil = anaerobic denitrifying bacteria convert nitrates back into nitrogen gas
NITROGEN GOES BACK TO ATMOSPHERE

Question 13

Why is phosphorus cycle important

Answer 13

Used in phosphate groups of DNA RNA ATP and phospholipid bilayer
Essential element of life for all organisms

Question 14

Where is phosphorus found

Answer 14

As a phosphate ion in mineral form in sedimentary rock

Question 15

What are the mycorrhizae and why are they beneficial for plant growth

Answer 15

Fungal associations between plant roots and beneficial fungi - acting like extensions of the plant’s root system

• fungi increases the SA for absorption of water and mineral ions
• mycorrhizae acts like a sponge so holds water and minerals around roots
• this makes plants more drought resistant and able to take up more inorganic ions

IMPROVING THE UPTAKE OF RELATIVELY SCARCE IONS

Question 16

Why do plants have mutual relationship with mycorrhizae

Answer 16

Plant provides advantage to fungus, through photosynthesis it creates carbohydrates and share them with fungus

BOTH PROVIDE MUTUAL BENEFIT TO EACH OTHER FOR SURVIVAL

Question 17

Explain the phosphorus cycle
How phosphorus is passed through organisms and rocks and back into the oceans/ soils

Answer 17

Phosphate ions in oceans/ soil
Plants absorbs ions through AT in root hair cells
Animals consume plants to absorb ions
Excretion from animals releases phosphorus back into soil and oceans in form of phosphate ions
ALSO decomposition - excess phosphate ions from waste materials (guano, bones)
These are eroded and released back into soil/ ocean
Deposition - phosphate ions build up to create rocks
Sedimentation - phosphate ions within soil compaction through sedimentation to create sed rocks
Sed rocks eroded and release phosphate ions back to soil/ ocean

Question 18

What are fertilisers
Damage without fertilisers?
Diff fertilisers

Answer 18

Added to soul to replace the nítrate and phosphates ions lost when plants are harvested and removed from nutrient cycles
Continue to do so = plant and soils which are mineral deficient

Natural (manure)
Artificial (inorganic chemicals)

Question 19

How do fertilisers increase productivity

Answer 19

Nitrogen is essential for plant growth (component of amino acids, atp, DNA)
Nitrate ions are readily available = plants develop taller, larger leaves
= increases rate of photosynthesis and improves crop productivity

Question 20

Pros and cons of
natural
artificial fertilisers

Answer 20

-cheaper (free if farmer owns animals)
- extract minerals and proportions cannot be controlled

• (synthetically created) so have exact proportion of minerals plants need
• inorganic substances are more water soluble = more these ions dissolve in water surrounding the soil (advantage) - plant can absorb
• BUT larger quantities are washed away with rainfall = greater impact on environment

Question 21

What is leaching and what causes it

Answer 21

When water-soluble compounds are washed away often into river or ponds

Can be harmful to humans if reaches sources of drinking water

Question 22

What is eutrophication and what causes it

Answer 22

Nitrates leached from fertilised fields stimulate growth of algae in pond - Nutrient concentrations increase in bodies of water

Excessive growth of algae creates blanket on surface (upper layers of water become densely populated with algae) which blocks out light
Plants below cannot photosynthesise and die
Bacteria within water feed and repisé on dead plant matter
= increase in bacteria (all respiring and using up oxygen in the water)

EVENTUALLY - lack of dissolved oxygen in water which means fish and aquatic organisms die (no oxygen for respiration)