Energy And Ecosystems, Nutrient Cycles, Succession

Question 1

Producers

Answer 1

Plants and algae photosynthesise
Synthesis a glucose molecule from water and carbon dioxide
Light energy is needed
Light energy is ultimately stored in the bonds of the glucose molecule as chemical potential energy

Question 2

Bio mass definition

Answer 2

All the biological molecules made by the plant and are not immediately used for respiration

Includes cellulose, starch, proteins, lipids etc

Represents the growth of the plant

Question 3

How is biomass measured

3

Answer 3

Mass of carbon

Dry mass

Energy value

Question 4

Practical estimation of dry mass

Answer 4

1 heat in a low temperature oven to evaporate water in the tissues

2 until there is no further change in mass

3 calculate dry biomass

4 carbon content estimated as 50% of dry mass

Question 5

Calculating energy in dry biomass

Answer 5

Dried biomass from a known area is placed in a calorimeter
Dry biomass is then burnt (combusted)
Energy released is used to heat water
Change in water temperature is used to calculate energy released
Energy per square metre per year is calculated

Question 6

Gross primary production

Answer 6

The total amount of light energy captured in photosynthesis and stored in molecules as chemical potential energy

Question 7

Respiration

Answer 7

The amount of energy lost from the plant in respiration. This returns to the environment as waste heat

Question 8

Net primary production

Answer 8

This is the remaining amount of chemical potential energy stored in the biomass of the plant. This can be used for growth and reproduction

Question 9

Reason for only 1-5% of light energy being captured

5

Answer 9

Some light is reflected
Only certain wavelengths are absorbed
Light may not strike chlorophyll and pass straight through the leaf
May be other limiting factors
Some may be transferred into thermal energy

Question 10

Why is NPP important

Answer 10

This is the energy in the new biomass made by the plant
Can be used to make new cells and tissues for growth and reproduction
It is also the part of the light energy captured by the plant that, through plant tissues being eaten; can be transferred to consumers

Question 11

Net production in consumers

Answer 11

Consumers get their energy by ingesting biomass
Some of this is used for respiration by the consumer and is lost eventually as heat to the atmosphere
Some is indigestible so is lost as faeces and some is excreted as Urine
The rest is used to make consumer biomass ie growth
Only the energy in the net production can be passed on to the next consumer

Question 12

Net production equation

Answer 12

N= I - (F+R)

N= net production 
I= chemical energy in ingested food 
R= respiratory losses
F= chemical energy lost to the environment as gardes

Question 13

Trophic level

Answer 13

The feeding position of an organism in a food web

Each layer of pyramid represents the net production at that level

Question 14

Keep food chains short

Answer 14

To maximise food production from an area of land food chains should be kept short
This will reduce energy loses due to respiration and faeces and urine
More food is produced from an area of land if it is used for crop production rather than raising livestock

Question 15

Reduce energy losses by animals in the food chain

Answer 15

Eg if humans intend to eat a cow, to maximise production it is important to ensure as much as possible of food eaten by cow is used for production
Farmers try to minimise the amount of food used by the cow for respiration or that is lost as faeces or urine

Question 16

Reducing respiration in farming

Answer 16

Reduce movement of farming eg battery farming so less energy is wasted in movement and more of their food used in growth

Keep in heated habitats: reduces the amount of food used to keep itself warm

Slaughter the animal once it has completed this growth. Food used after this time will be wasted in maintenance of the animal

Question 17

Simplifying food webs

Answer 17

Pesticides: remove insects and other animal pests that eat the crop
Herbicides: kill weeds which are competitors of the crop plant and so reduce yields

Question 18

How ecosystems work

Answer 18

For organisms to live and grow they need supplies of both energy and matter
In most ecosystems energy ultimately comes from the sun and matter from soil or air

Question 19

Principles of nutrient recycling

3 key processes

Answer 19

Uptake
Feeding.
Decomposition

Question 20

Saprobionta

Answer 20

Micro organisms involved in decomposition

Include bacteria and fungi
Which decompose dead material and faeces

They secret digestive enzymes and absorb the products of digestion

Question 21

Mycorrhizae

Answer 21

Fungi that live in close association with plant roots
Provide a very large surface area for uptake of minerals from the soil
In return for their minerals, the plant provides carbohydrates
An example of mutualism- a relationship between two organism where both benefit

Question 22

Nitrogen cycle
(4 stages)

And why it is needed

Answer 22

Nitrogen fixation
Ammonification
Nitrification
Denitrification

Nitrogen is used to make amino acids and nucleic acids

It has a triple covalent bond which is too strong for nitrogen to be used directly

Question 23

Nitrogen fixation

Answer 23

Nitrogen fixing bacteria covert convert nitrogen from the atmosphere into ammonia which can then be used to make amino acids, proteins and nucleic acids

Animals then use the proteins and nucleic acids

Question 24

Where do nitrogen fixing bacteria live

Answer 24

Some live in the soil but many live in root nodules
In return for providing ammonia, the bacteria receive carbohydrates- mutualism

Only some plants have nitrogen fixing bacteria- legumes
Often these are grown to improve soils as they fix nitrogen which can be used again after the plants are ploughed and decomposed

Question 25

Ammonification

Answer 25

Nitrogen containing compounds in plants and animals and in faeces are used by saprobiont bacteria in the soil
They digest proteins using secreted enzymes and absorb amino acids in which they can use
They then excrete ammonia and ammonium as waste products

Question 26

Nitrification

Answer 26

Ammonia and ammonium compounds are absorbed and used by nitrifying bacteria living in the soil
These release nitrites and then nitrates as a waste product

Question 27

Denitrification

Answer 27

In waterlogged soils there are bacteria that get their energy from absorbing nitrates and converting this into nitrogen gas which is released into the atmosphere

This can only happen in the absence of oxygen

They reduce the amount of soil nitrate and are bad for agriculture

Question 28

Soil nitrates

Answer 28

Soil nitrates are essential for the growth of all plants that do not posses nitrogen fixing bacteria

Question 29

Ways of increasing soil nitrates concentration

Answer 29

Activity of nitrifying bacteria
Lightning: N2 -> NO3-
Artificial fertilisers: NO3- and NH4+ ions
Natural fertilisers: manure-> saprobionts->NO3- ions
Ploughing in plants with nitrogen fixing bacteria -> decomposition-> NO3- ions
Land drainage: reduces activity of denitrifying bacteria

Question 30

Ways of decreasing soil nitrate concentration

Answer 30

Waterlogged soils: denitrification

Harvesting of crops: prevents decomposition and return of nitrates to soil

Question 31

Phosphorus

Answer 31

Needed to make DNA, RNA, ATP and phospholipids

Found in soil in the form phosphate ions

They come from the rocks through weathering processes

Question 32

Phosphate cycle process

7

Answer 32

1. Weathering (from rain on rocks) into the soil
2. Uptake by roots with help of microrrhizae
3. Plants make ATP, DNA, phospholipids etc, eaten by animals
4. Lost in animal waste products
5. Saprobionts decompose detritus and faeces, release phosphate
6. Weathering + carried into water and taken up by algae etc. Sedimentation also occurs in which phosphates become part of the sedimentary rocks on the sea floor
7. Bird guano contains high concentrations of phosphate ions which are often used as fertilisers

Question 33

Eutrophication

Answer 33

Learn

Question 34

Natural cycles

Answer 34

Minerals taken up from soil by plants-> used to make biological molecules-> bacteria and fungi decompose biological mmolecules-> minerals taken up from soil by plants

Question 35

Agricultural cycles

Answer 35

Fertilisers added-> minerals taken up from soils by plants-> used to make biological molecules -> crops and livestock harvested and taken away

No decomposition

Question 36

Fertiliser

Natural or artificial

Answer 36

Artificial: inorganic chemicals, come in powders, pellets and liquid form, water soluble

Natural: manure/ slurry of compost, they decompose slowly to release minerals and are not soluble until decomposed

Question 37

Leaching

Answer 37

Artificial fertilisers are washed off the land when it rain and dissolved ions end up in
This leads to eutrophication

Question 38

Causes of eutrophication (3)

Answer 38

Artificial fertilisers leaching

Phosphates in washing powder in waste domestic water

Raw sewage

Question 39

Succession

Answer 39

The process by which an ecosystem changes over time
Different communities of plants that replace each other in a predictable way
Each community changes the habitat in ways that make it less hostile for the next community of plants
We call each plant community a sere
Each plant community will have its associated community of animal

Question 40

Climax community

Answer 40

Final
Stable and very long lasting
Often a forest

Question 41

How does a primary succession start

Answer 41

Initial condition governed by abiotic variables
Often hostile and subject to large variations
No soil
Few minerals
High light intensity as no shade form plants
Extreme temperatures
Windy

Question 42

Pioneers

Answer 42

Any plants able to cope with hostile conditions

Colonise the habitat

Question 43

Pioneer community

Answer 43

On bare rock- lichens, can survive with little water or nutrient providing soil, they anchor themselves in cracks and can dissolve bare rock to get minerals . Also withstand long periods of drought

On sand dunes- marram grass

Question 44

When lichens die

Answer 44

Decompose to become organic matter
This is the begging of a thin soil able to retain some moisture and to slowly release nutrients through decomposition
Condition become less hostile

Question 45

Moss sere

Answer 45

Mosses and some grasses can now germinate and grow using moisture held by the thin soil
As the mosses and grasses die, decomposition adds to the developing soil

Question 46

Herbaceous sere

Answer 46

In less hostile conditions, plants require more water and can now germinate and grow
Include small herbaceous(non woody) plants, ferns and grasses
They have good seed dispersal, producing large numbers of small wind dispersed seeds and germinate rapidly in thin soil
Out compete the mosses and pioneers for light and space
Tall plants reduce wind speed and light intensity
Helps soil to retain moisture and seeds germinate

Question 47

Shrub sere

Answer 47

Soil has changed significantly
Deeper and contain more humus(decaying matter)
Has a PH closer to neutral
Water availability, light intensity and wind speed improves
Larger shrub plants now grow
Sub climax community forms
Grow fast and out compete lower plants

Question 48

Tree sere

Answer 48

Woody trees grow slowly but become established
Diverse set of niches to supports a large variety of insects and other animals
Complex food web established
Climax community

Question 49

Succession order

Answer 49

Pioneer sere
Moss sere
Herbaceous plant sere 
Shrub, small tree sere
Woodland climax sere

Question 50

Secondary succession

Answer 50

When a climax community is removed by humans or destroyed by natural disaster, community of plants may be lost
Pioneers and possibly other plants from later in the primary succession will re establish and succession starts again
Secondary succession is usually much quicker as there is already well developed soil which may contain lots of seeds

Question 51

Plagioclimax

Answer 51

Human activity often deliberately stops or reserves a primary succession to maintain an earlier stage eg grassland
Often use animal to stop the succession such as by grazing

Question 52

Conservation methods

5

Answer 52

Managing succession

Seed banks

Captive breeding

Protected areas

Fishing quotas

Question 53

Conservation methods

Managing succession

Answer 53

Eg animals grazing

Too many sheep then grassland is reduced so have to have the right number

Question 54

Seed banks

Conservation methods

Answer 54

store of seeds from crop plants and from wild plants is kept in controlled condition- very cold and dry
Preserved so that if a species becomes extinct they can be revived

Question 55

Captive breeding

Answer 55

Breeding of endangered species in a controlled environment

Question 56

Protected areas

conservation methods

Answer 56

National parks and conservation areas

Question 57

Fishing quotas

Conservation methods

Answer 57

Limits placed on number of fish caught to sustain populations