Energy And Ecosystems

Question 1

What is an ecosystem?

Answer 1

A group of living organisms and non living things and the interrelationships between them

Question 2

What are worms bacteria and fungi all examples of?

Answer 2

Decomposers or detrivitours

Question 3

S__________ are a type of decomposer

Answer 3

Saprobionts

Question 4

Why is measuring biomass somewhat inaccurate? What is done to improve accuracy?

Answer 4

Different organisms will have varying levels of water at any one time
Use dry mass

Question 5

What is dry mass measured in?

Answer 5

gm^-2 on land

gm^-3 in air or water

Question 6

What is an alternate way of measuring biomass to simple weighing ?

Answer 6

Bomb calorimetery

Burn sample in a water bath, measure the temperature change within the bath

Question 7

Give the percentage of the suns energy converted by plants

Why is it so low?

Answer 7

1-3%
90% relfected by clouds
Chlorophyll cant absorb all wavelengths
Requires light to hit chlorophyll may just miss

Question 8

Give four factors that make consumers inefficient within a food chain

Answer 8

Respiration
Faeces
Urine
Not all of them are consumed e.g. Bones

Question 9

What is gross production?

Answer 9

The total amount of energy converted into organic matter

Question 10

What is net production?

Answer 10

The amount of energy available to the next trophic level

Question 11

How do you work out net production?

Answer 11

Gross production - respiratory losses

Question 12

Give three general effects that come from the inefficiency of food chains

Answer 12

Max 5 trophic levels
Higher levels have reduced biomass
Reduced total energy at higher levels

Question 13

How do you work out the percentage efficiency of the movement up a trophic level?

Answer 13

(Energy available after / energy available before) x 100

Question 14

Give the down falls of a pyramid of number

Answer 14

Not accounted for size or biomass

So varrying that comparison is impossible

Question 15

Give the downfalls of a pyramid of biomass

Answer 15

The organisms must be killed
Small sample = unrepresentative
Not all year round doesnt show seasonal variation

Question 16

What is the basic role of agriculture?

Answer 16

To increase productivity

Question 17

How does agriculture attempt to increase gross primary production? ( i.e. In plants)

Answer 17

Increase light levels = plants grow all year
Increase water levels through irrigation needed for dependent reaction
Increase temperature= faster photosynthesis (to extent)

Question 18

How do you decrease respiratory losses in live stock?

Answer 18

Restrict farming
Keep warm
Harvest before adulthood

Question 19

Why does weeding increase productivity of a crop?

Answer 19

Reduces competition for the crop

More nutrients

Question 20

Why do pesticides increase net primary production?

Answer 20

Pests damage the crop, this damage needs to be repaired, takes up energy

Question 21

How is gaseous nitrogen turned inti other nitrogen forms?

Answer 21

Lightening strikes
Harber process
Nitrogen fixing bacteria - reduction of nitrogen to ammonia

Question 22

What is the process of ammonification?

Answer 22

Where ammonium is produced from ammonium containing molecules e.g. Urea

Question 23

What type of organisms are responsible for ammonification?

Answer 23

Saprotrophs

Ammonium ions form in the soil due to their release of ammonia

Question 24

What is nitrification?

Give the steps in which it happens

Answer 24

Nitrifying bacteria
Oxidise ammonium to nitrite ions (NO2-)
The pn oxidised further to nitrate ions (NO3-)

Question 25

Why is it crucial to have aerobic conditions in agriculture?

Answer 25

Nitrification is an aerobic process

In anerobic conditions denitrifying bacteria flourish

Question 26

What is a nitrite ion?

Answer 26

NO2-

Question 27

What is a nitrate ion?

Answer 27

NO3-

Question 28

What do denitrifying bacteria do?

Answer 28

Produce Nitrogen gas and nitrogen oxides

Question 29

Why are fertilisers needed?

Answer 29

In crop plants minerals are taken up 
Plants harvested and removed 
No decomposition 
Minerals removed 
Fertilisation adds minerals back to the soil

Question 30

What are natural fertilisers?

Answer 30

Dead or decaying organisms or wastes

Bone meal

Question 31

What are artificial fertilisers?

Answer 31

Where mined rocks or laboratory synthesised chemicals are blended into a mix

Question 32

Give three problems with fertilisers?

Answer 32

Reduced biodiversity (fastest growing favoured which increases competition for other plants)
Leaching rain dissolves nutrients which can percolate into groundwater stores (linked to stomach cancer)
Eutrophication

Question 33

Describe how eutrophication occurs

Answer 33

Lack of NO3- is a limiting factor for algae blooms in rivers
Leaching of NO3- leads to more alage
Growth on surface (algae bloom) limits light to lower depths
Lower plants die as they cant photosynthesise
Saprotrophs feed off dead organisms uses oxygen so [oxygen] reduce
Positive feedback as more dead matter from fish dieing due to anerobic conditions
Further nitrates released from dead organisms

Question 34

Why is the phosphorus cycle crucial?

Answer 34

Needed within organisms for ATP

Question 35

How does most phosphorus exist? Where?

Answer 35

Phosphate ions - PO4^3-

Found in sedimentary rock and can hence be removed by erosion

Question 36

Starting with rocks describe the phosphorus cycle

Answer 36

Erosion removes phosphorus
Into dissolved phosphate ions within water bodies
Plants absorb it
Animals get it through feeding on plants
Animals excrete it - ends up back as dissolved in water supplies
Or forms bones and shells
Bones and shells deposited will either dissolve or form sedimentary rocks

Question 37

What are mycorrhizae and what do they do?

Answer 37

Fungi that have a mutualistic relationship with plant roots
They increase surface area allowing increased absorption of water and minerals
In return in recives organic molecules