5B Energy Transfer and Nutrient Cycles Flashcards
1
Q
How do plants produce biomass?
A
They photosynthesise
2
Q
What is an ecosystem?
A
All the organisms living in a particular area and all the non-living conditions
3
Q
What are producers?
A
Organisms that make their own food
e.g. plants & algae produce their own food through photosynthesis
4
Q
Why do plants photosynthesise?
A
To make glucose and other sugars
5
Q
What are the sugars produced in photosynthesis used for?
A
- Used in respiration, to release energy for growth
- To make other biological molecules i.e. cellulose - used to make up the plants biomass
6
Q
What is biomass?
A
The mass of living material
Or
Can also be thought of as the chemical energy stored in the plant
7
Q
How is energy transferred in an ecosystem?
A
It is transferred through the living organisms when they eat one another
e.g. primary consumers eat producers etc to form a food chain
8
Q
How can biomass be measured?
A
As dry mass or using a calorimeters
9
Q
How can biomass be measured?
A
In terms of the mass of carbon in an organism
Or dry mass of its tissue per unit area
10
Q
What is dry mass?
A
The mass of the organism with the water removed
11
Q
How is dry mass measured?
A
A sample of the organism is dried, often in an oven set at a low temp
Sample is weighed at regular intervals (e.g. everyday)
Once mass becomes constant you know all the water has been removed
12
Q
What is the typical unit for dry mass?
A
Kg/m^2
The result can be scaled up if needed to give the total population of the area
13
Q
How is the mass of carbon be figured out from the dry mass?
A
The mass of carbon is generally taken to be 50% of the dry mass
14
Q
What is a calorimeter used for?
A
Can be used to estimate the amount of chemical energy stored in biomass
15
Q
What is chemical energy from biomass measured in?
A
Joules (J) or kilojoules (kJ)
16
Q
How do you use a calorimeter?
A
1 - Sample of dry biomass is burnt & energy released is used to heat a known volume of water
2 - Change in temp of the water is used to calculate the chemical energy of the dry biomass
17
Q
What are GPP and NPP types of?
A
Chemical energy stores
18
Q
What is GPP?
A
The total amount of chemical energy converted from light energy by plants, in a given area
19
Q
What does GPP stand for?
A
Gross Primary Production
20
Q
What are respiratory losses (relating to GPP)?
A
Around 50% of the GPP is lost to the environment as heat when plants respire
This is called respiratory losses
21
Q
What does NPP stand for?
A
Net Primary Production
22
Q
What is NPP?
A
The available energy to a plant for growth and reproduction - the energy is stored in the plant’s biomass
It is also the energy available to organisms at the next stage of the food chain
23
Q
What is the formula relating NPP and GPP?
A
NPP = GPP - R
24
Q
What are the units for primary production?
A
kJ/ha/year can also be written: kJ ha^-1 year ^-1
Or
kJ/m^2/year can also be written: kJ m^-2 yr^-1
25
When primary production is expressed as a rate what is this called?
Primary productivity
26
Where do consumers store their biomass?
In their biomass
27
Where do consumers get energy from?
By ingesting plant material or animals that have eaten plant material
28
How much of the consumers’ food is transferred to the next trophic level?
Only about 10%
Around 90% of the total available energy is lost in various ways
29
How is chemical energy lost between trophic levels?
- Not all of the food is eaten (e.g. bones)
- Some are egested as faeces
- Via respriration and urine
30
What happens to the energy (biomass) in a consumer that is not lost to the environment?
The energy that is left is stored in the consumers' biomass & is availble at the next trophic level
This is called the consumers' Net Production
31
What is the formula used to calculate net production?
N = I - (F + R)
```
N = net production
I = Chemical energy in ingested food
F = Chemical energy lost in faeces & urine
R = Energy lost through respiration
```
32
What is the formula used to calculate the efficiency of an energy transfer?
(Net productivity/chemical energy ingested) X 100
33
What do food webs show?
How energy us transferred between organisms
34
What is a food chain?
They show simple lines of energy transfer - each of the stages in a food chain is called a trophiv level
35
What is a food web?
They show lots of food chains in an ecosystem and how they overlap
36
What are decomposers?
They break down dead or undigested material, allowing nutrients to be recycled
Key part of food webs
37
Why are farming practices used?
Most of them aim to increase the amount of energy that is availble for human consumption
38
What are the two ways that farmers try to reduce energy losses?
- The energy lost to other organisms (e.g. pests) can be reduced
- The enrgy lost through respiration can be reduced
39
How can farmers reduce energy losses to other organisms?
By simplifying food webs
40
How do farmers simplify food webs?
Through pest control
41
What are two methods of pest control?
- Chemical pesticieds
| - Biological agents
42
Give two examples of chemical pesticides
- Insecticides
| - Herbicides
43
What do insecticides do?
Kill insect pests that eat & damage crops
Killing insect pests means less biomass is lost from crops, so they grow to be larger - this means NPP is greater
44
What do herbicides do?
Kill weeds - this removes direct competition with the crop for energy from the sun
Can also remove preferred habitat or food source of the insect pests - helps to further reduce their no.s & simplify the food web
45
What are biological agents?
These reduce the no. pests so crops lose less energy & biomass - increases the efficiency of the transfer to humans
46
Give two examples of biological agents
- Parasites
| - Pathogenic
47
What do parasites do (as biological agents)?
Live in or lay their egss on a pest insect - parasites either kill the insect or reduce its ability to function
e.g. some wasp species lay their eggs inside catepillars, the eggs hatch & kill the catepillar
48
What do pathogens do (as biological agents)?
They are disease-causing bacteria and viruses that are used to kill pests
e.g. the bacterium Bacillus thuringiensis produces a toxin that kills a wide range of catepillars
49
Do farmers use chemical pesticides or biological agents?
Both - the intergrated systems combine both biological & chemical methods
The combined effect reduces pesticides even more than either could alone meaning NPP is increased even more
50
What is one method that farmers use to reduce respiratory losses?
Controlling their living conditions to increase net production - so more energy is used for growth & less is lost through respiration
e.g. keeping cows close together
51
What are two ways in which farmers control the livestock living conditions to reduce respiratory losses?
- Movement increases rate of respiration, animals are kept in pens - movement is restricted
- Pens are often indoors & kept warm - less energy is wasted by generating body heat
52
What are the benefits of farmers controlling livestock living conditions?
More food can be produced in a shorter space of time, often at a lower cost (as less biomass is lost as waste products)
This increases net production & the efficiency of energy transfers to humans
53
What are some ethical issues that arise due to farmers controlling livestock living conditions?
Some people think that the conditions intensively reared animant are kept in cause the animals pain, distress or restricts thier natural behaviour
Therefore they shouldn't be done
54
What happens to nutrients when crops are harvested?
They can be lost
55
Where and why do crops take in minerals from?
They take in minerals from the soil as they grow & use them to build their own tissues
56
Why are nutrients lost when crops are harvested?
When crops are harvested they’re removed from the field where they’re grown rather than dying and decomposing there
Mineral ions that they contain are not returned to the soil by decomposers in the nitrogen or phosphorus cycle
57
How can animals/animal products being taken from the land affect the environment?
Phosphates & nitrates are lost from the system when they’re removed
Animals eat grass & plants taking their nutrients
When they’re taken elsewhere the nutrients aren’t replaced through remains or waste products
58
Why are fertilisers added to soils?
To replace lost nutrients
59
Why are fertilisers used?
Adding fertiliser replaces the lost minerals - more energy from the ecosystem can be used for growth
Increases the efficiency of the energy transfer
60
What are the two types of fertilisers?
- Artificial fertiliser
| - Natural fertiliser
61
What are artificial fertilisers?
They are inorganic
They contain pure chemicals (e.g. ammonium nitrate) as powders of pellets
62
What are natural fertilisers?
They are organic matter
They include manure, composted vegetables, crop residues and sewage sludge
63
What happens when too much fertiliser is applied to plants?
The fertilisers can leach into waterways
64
What is leaching?
When water-soluble compounds in the soil are washed away, often into nearby ponds and rivers
e.g. by rain or irrigation systems
65
What can leaching lead to?
Eutrophication
66
When is leaching more likely to occur?
If the fertiliser is applied just before heavy rainfall
67
Why are chemical fertilisers more likely to be leached?
Chemical fertilisers are relatively soluble
This means excess minerals are not used immediately are more likely to leach into waterways
68
Why are natural fertilisers less likely to be leached?
The nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants
This means that their release into the soil for uptake by plants is more controlled & leaching is less likely
69
What is a natural ecosystem?
One that hasn’t been changed by human activity
70
What are saprobionts?
Type of decomposer
71
Is the leaching of phosphates or nitrates more likely?
The leaching of phosphates is less likely than the leaching of nitrates because phosphates are less soluble in water
72
What happens if too much of a particular nutrient is used?
If this happens it can cause crops to die as it changes the balance of nutrients in the soil
73
What is eutrophication caused by?
Excdess nutrients in the soil
74
What is the process of eutrophication?
1 - mineral ions leached from fetilised fields stimulate the rapid growth of algae in ponds & rivers
2 - Large amounts of algae block light from reaching the plants below
3 - Eventually the plants die as they're unable to photosynthesise enough
4 - Bacteria feed on the dead plant matter. Increased no. bacteria reduce the oxygen conc. in the water by carrying out aerobic respiration
5 - Fish and other aquatic organisms die because there isn't enough dissolved oxygen
75
How do saprobionts break down food?
Secrete enzymes & digest food externally (extracellular digestion)
76
How do fungi form a mutualistic relationship with plants?
Fungi attach to plants, the fungi increases surface area so plants can absorb ions and the plant gives the fungi inorganic compounds
77
What are the 4 main parts of the nutrient cycle?
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
78
What is nitrogen fixation?
Nitrogen gas in atmosphere turned into nitrogen-containing compounds
79
What is biological nitrogen fixation carried out by?
Bacteria such as Rhizobium
80
What happens in biological nitrogen fixation?
Turn nitrogen into ammonia which then turns into ammonia ions
81
Where is Rhizobium found?
Inside roots of nodules of leguminous plants
82
What is ammonification?
Nitrogen compounds from dead organisms are turned into ammonia by saprobionts
83
What are examples of nitrogen containing compounds?
Animal waste (urine and feces)
84
What is nitrification?
Ammonia ions in soil converted into nitrogen compounds
85
What is nitrification carried out by?
Nitrifying bacteria
86
What are the stages of nitrification?
Ammonia ions - nitrites - nitrates
87
What is denitrification?
Nitrates in soil converted into nitrogen gas
88
What is denitrification carried out by?
Denitrifying bacteria
89
What are the conditions for denitrification?
Anaerobic conditions in waterlogged soils
90
What is the nitrifying bacteria that converts ammonia ions to nitrites?
Nitrosomonas
| Extra knowledge so don't worry too much about this
91
What is the nitrifying bacteria that converts nitrites to nitrates?
Nitrobacter
92
What do plants and animals need phosphorus?
Make biological molecules such as phospholipids, DNA and ATP
93
Where is phosphorus found?
Rocks and dissolved in the oceans as phosphate ions
94
How does phosphorus taken in by plants?
Assimilated
95
How is phosphate in rocks released into the soil?
Weathering
96
Where do plants take phosphorus from?
The soil through there roots
97
How is phosphorus transferred from plants to animals?
Eaten, food chain
98
How are phosphate ions lost by animals?
Waste, secretion
99
What part do saprobionts play in the phosphorus cycle?
Break down organic compounds (dead animals, urine and feces), releasing phosphate ions into the soil
100
Where does weathering of rocks release phosphate ions to?
Seas, lakes and rivers
101
What happens to phosphate ions in the sea?
Taken up by aquatic producers (algae), then passed on to birds
102
What is the waste of birds called?
Guano, contains high proportion of phosphate ions
