Energy and ecosystems

Question 1

List the trophic levels of a food chain

Answer 1

producer/autotroph
primary consumer
secondary consumer
tertiary consumer
predator/quaternary consumer

Question 2

Why are ecosystems dynamic?

Answer 2

The species are all interdependent and so a change in one population will affect others

Question 3

Gross primary productivity GPP (unit)

Answer 3

Total quantity of chemical energy stored in plant biomass, in a given area/volume over a given time (kJ/m^2/yr)

Question 4

Net primary productivity

Answer 4

Chemical energy store left after losses due to respiration (20 - 50%), so available for growth + reproduction
NPP = GPP - R

Question 5

List causes of loss of energy through a food chain

Answer 5

• respiratory losses
• excretion of waste
• indigestible parts, natural death of organism -> broken down by saprobionts

Question 6

Equation for net production of consumers

Answer 6

N = I - (F + R)
I is ingested chemical energy
F is losses in waste
R is losses in respiration

Question 7

What is calorimetry?

Answer 7

Combusts material to determine energy stored in dry organic matter -> insulated container to ensure all energy released used to heat water for accurate temp. reading
1 calorie = energy needed to raise 1g of water by 1 degree

Question 8

Why is only 1-3% of Suns energy captured in green plants and used to make organic matter?

Answer 8

• reflection 90%
• not all light wavelengths absorbed
• light may not hit chlorophyll
• limiting factors

Question 9

How do farmers improve primary productivity?

Answer 9

-pesticides/herbicides
-fertilisers
-greenhouse
-artificial lighting
-irrigation

Question 10

How do farmers improve secondary productivity?

Answer 10

• restrict movement
• use of antibiotics
• controlled temp/environment
• controlled diet: optimal nutrients for biomass

Question 11

Nitrogen fixation

Answer 11

N2 gas converted to ammonia by nitrogen fixing bacteria
-> free living
-> mutualistic, living in root nodules of leguminous plants

Question 12

Ammonification

Answer 12

Nitrogen compounds in waste or dead organisms converted into ammonium compounds by saprobionts

Question 13

Nitrification

Answer 13

Two stage aerobic process of oxidation by nitrifying bacteria:
- ammonium to nitrites (NH4+ to NO2-)
- nitrites to nitrates (NO2- to NO3-

Question 14

Denitrification

Answer 14

Anaerobic process of converting nitrates in soil to N2 gas
eg waterlogging increases denitrification, decreasing nitrate levels as lack of O2

Question 15

Mycorrhizae

Answer 15

Mutualistic associations between between the roots of plants + certain types of fungi, larger SA enables increased uptake of water + mineral ions, fungi receive carbs in return

Question 16

Why are fertilisers necessary?

Answer 16

As crops grow they absorb minerals from soil, when harvested mineral content in soil becomes depleted. So farmers replenish minerals w/ fertiliser (natural or synthetic)

Question 17

Leaching

Answer 17

process by which nutrients are removed from soil due to being dissolved in rain

Question 18

Steps of eutrophication

Answer 18

1. fertiliser added
2. rain dissolves minerals -> leaching
3. algal bloom
4. aquatic plants die as light blocked by algae
5. saprobionts respire dead plants/algae aerobically using up O2 -> anoxic conditions (death)

Question 19

How do dissolved phosphate ions end up in oceans, lakes and soils?

Answer 19

• erosion of phosphate ions in rocks and waste/guano
• use of fertilisers
• excretion by animals