Energy and ecosystems

Question 1

What is the source of energy for ecosystems

Answer 1

sunlight

Question 2

How do plants use sunlight to produce energy

Answer 2

By photosynthesis, they use sunlight in producing organic compounds such as glucose

Question 3

Biomass

Answer 3

total mass of living material in a specific area at a given time

Question 4

producers

Answer 4

photosynthetic organisms that manufacture organic substances using light energy, water and carbon dioxide

Question 5

consumers

Answer 5

organisms that obtain their energy by feeding on other consumers rather than using the energy of sunlight directly

Question 6

What organisms are consumers

Answer 6

Animals

Question 7

Primary consumers

Answer 7

Those that directly eat producers- first in the chain of consumers

Question 8

Secondary consumers

Answer 8

Animals that eat primary consumers

Question 9

Tertiary consumers

Answer 9

Animals that eat secondary consumers

Question 10

Saprobiants

Answer 10

a group of organisms that break down the complex materials in dead organisms into simple ones. In doing so they release valuable minerals and elements in a form that can be absorbed by plants and contribute to recycling

Question 11

Food chain

Answer 11

describes a feeding relationship in which the producers are eaten by the primary consumers. These in turn are eaten by secondary consumers and in turn tertiary consumers.

Question 12

Trophic level

Answer 12

Each stage in a food chain

Question 13

what do the arrows in a food web/chain show

Answer 13

direction of energy flow

Question 14

Food webs

Answer 14

most animals do not rely on a single food source and within a single habitat many food chains will be linked together to form a food web

Question 15

how is biomass measured

Answer 15

using dry mass per given area in a given time

Question 16

Calorimetry

Answer 16

a sample of dry material is weighed and is then burnt in pure oxygen within a sealed chamber called a bomb. The bomb is surrounded by a water bath and the heat of combustion

Question 17

How much of the sun’s energy is converted by plants into organic matter

Answer 17

1-3%

Question 18

Why is most of the sun’s energy not converted into organic matter

Answer 18

-90% of the suns energy is reflected back into space by clouds or absorbed by the atmosphere
-not all wavelengths of light can be absorbed and used for photosynthesis
-light may not fall on chlorophyll molecule
-a factor such as low carbon dioxide levels might affect the rate

Question 19

Gross primary production (GPP)

Answer 19

The total quantity of the chemical energy store in plant biomass in a given area or volume in given time

Question 20

How much GPP is used in respiration

Answer 20

20-50%

Question 21

net primary productivity (NPP)

Answer 21

The chemical energy store that is left when the losses to respiration have been taken into account

Question 22

What is NPP available for

Answer 22

plant growth and reproduction

Question 23

How much NPP is used by primary consumers

Answer 23

10%

Question 24

How much NPP is used by secondary and tertiary consumers

Answer 24

20%

Question 25

What is the reason for a low % of NPP being transferred

Answer 25

-some of the organism is not consumed
-some parts can be consumed but not digested (faeces)
-some energy is lost in excretory materials (urine)
-energy lost as heat from respiration

Question 26

How is net production of consumers calculated

Answer 26

N=I-(F+R)

Question 27

What does the inefficiency of energy transfer between trophic levels explain

Answer 27

-most food chain only have 4 or 5 trophic levels because insufficient energy is available to support a large enough breeding population
-the total mass of organisms in a particular place is less at higher trophic levels
-the total amount of energy available is less at each level as one moves up the food chain

Question 28

Summarise the common features of all nutrient cycles

Answer 28

• Nutrient taken up by producers as simple inorganic molecules
• Producer incorporates nutrient into complex organic molecules
• Nutrient passed on to consumers when producer is eaten
• Nutrient passed along food chain to other consumers
• When organisms die the complex molecules are broken down by saprobiontic microorganisms (decomposers) and nutrient is released in it’s original simple form to be recycled

Question 29

Describe the features of the nitrogen cycle

Answer 29

-Living organisms required source of nitrogen to manufacture proteins and nucleic acids, most are unable to access the nitrogen from the atmosphere.
-Plants obtain nitrogen by active transport from nitrate ions in the soil
-Animals obtain nitrogen containing compounds by consuming other organisms
-Microbes return nitrate ions to the soil through decomposition

Question 30

process of the nitrogen cycle

Answer 30

-few organisms can convert nitrogen gas into compounds useful to other organisms in a process known as nitrogen fixation
-These organisms can be free-living or live in a relationship with certain plants
-Most plants obtain their nitrogen by absorbing nitrates from the soil through their root hairs by active transport.
-They then convert this to proteins which is passed to animals when they eat the plant
-On death, sabrobiants break down these organisms releasing ammonium which can then be oxidised to form nitrite ions by nitrifying bacteria.
Further oxidation by the same type of bacteria forms nitrate ions.
-These ions may be converted back to atmospheric nitrogen by the activities of dentrifying bacteria.

Question 31

Ammonification

Answer 31

Ammonification: production of ammonia from organic nitrogen containing comounds by sapprobiontic organisms.

Question 32

Nitrification

Answer 32

Nitrification: nitrifying bacteria carry out oxidation reactions to convert ammonium ions into nitrites and then nitrates

Question 33

Nitrogen fixation

Answer 33

Nitrogen Fixation: nitrogen gas is converted into nitrogen containing compounds in a variety of ways. Haber process, lightening, by nitrogen fixing bacteria. There are two type of nitrogen fixing bacteria: free living bacteria which convert nitrogen gas into ammonia. Mutualistic nitrogen fixing bacteria live in the root nodules of legumes and obtain carbohydrates from the plant whilst providing a supply of amino acids they have fixed from nitrogen gas.

Question 34

Denitrification

Answer 34

Denitrification: anaerobic denitrifying bacteria reside in waterlogged soil and convert nitrates into gaseous nitrogen

Question 35

Describe the features of the phosphorous cycle

Answer 35

Phosphorus stored in phosphate ions in sedimentary rock
Weathering and erosion of phosphate in rock, ions dissolved in water
Phosphate ions taken up by plant roots and incorporated into biological molecules
Feeding and digestion by consumers
Phosphate ions in animal waste and remains of animals
Decomposition by saprobionts
Washed back into the sea and incorporated into sedimentary rock

Question 36

Explain the roles of saprobiontic organisms in nutrient recycling

Answer 36

Saprobiontic organisms (decomposers) break down complex molecules in consumers and producers when they die and release the nutrient in its original simple to be taken up by producers

Question 37

Why are fertilisers needed

Answer 37

crops are grown repeatedly and intensely on the same area of land and minerals are not returned to the same area of land so can limit the rate of photosynthesis. fertilisers added to the soil to replace the nitrate and phosphate ions lost when plants are harvested to remain productivity.

Question 38

natural ferilisers

Answer 38

consist of the dead and decaying remains of plants and animals (manure)

Question 39

strengths of natural fertilisers

Answer 39

they are cheaper because farmers have access to animals

Question 40

limitations of natural fertilisers

Answer 40

the exact minerals in them cannot be controlled

Question 41

artificial fertilisers

Answer 41

inorganic chemicals made from the elements nitrogen, phosphorus and potassium

Question 42

strengths of artificial fertilisers

Answer 42

-created to contain exact proportions
-water soluble so they’re easy to absorb

Question 43

limitations of artificial fertilisers

Answer 43

-as they’re water soluble more dissolve in the water surrounding the soil so larger quantities are washed away and therefore have a greater effect on the environment

Question 44

What does research suggest about fertilisers

Answer 44

a combination of natural and artificial fertilisers gives the greatest long-term increase in productivity. However it’s important that minerals are added in appropriate quantities as there is a point at which further increases in the quantity of fertiliser no longer results in increased productivity

Question 45

suggest a reason why after a certain point the addition of more fertiliser no longer improves the productivity of crops

Answer 45

another factor is limiting photosynthesis such as light or CO2 so only the addition of this factor will increase photosynthesis and hence productivity

Question 46

How do fertilisers increase productivity

Answer 46

Plants require minerals to grow such as nitrogen which is an essential component of amino acids. Where nitrate ions are available plants are likely to develop earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and improves crop productivity

Question 47

What are the effects of nitrogen-containing fertilisers

Answer 47

-reduced species diversity- nitrogen rich soils favour the growth of grasses, nettles and other rapidly growing species which outcompete many other species
-leaching
-eutrophication

Question 48

leaching

Answer 48

process by which nutrients are removed from the soil and water soluble compounds are washed away into the rivers or ponds. here they may have a harmful effect on humans if the river or lake is a source of drinking water

Question 49

eutrophication

Answer 49

the process by which salts build up in bodies of water

Question 50

process of eutrophication

Answer 50

-nitrates leached from fertilisers field stimulate growth of algae in ponds
-excessive growth of algae creates a blanket on the surface of water which blocks out light
-as result plants cannot photosynthesise and die
-bacteria within the water feed and respire on the dead plant matter
-results in an increase in bacteria which are all respiring and using up the oxygen within the water