13.Energy And Ecosystems

Question 1

What do organisms in any ecosystem rely on?

Answer 1

A source of energy to carry out all their activities

Question 2

What is a producer

Answer 2

Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide, and mineral ions

Question 3

What are consumers

Answer 3

Obtain energy by feeding on other organisms rather than using their own energy of sunlight directly.
Primary consumers-plants
Secondary consumers-eat primary
Tertiary consumers-eat secondary

Question 4

What are saprobionts

Answer 4

Decomposers - break down complex materials in dead organisms into simple ones. Releasing valuable minerals and elements in form that only plants can absorb, work carried out by fungi and bacteria

Question 5

What is a food chain

Answer 5

Describes feeding relationship in which producers are eaten by primary consumers, etc etc
each stage is called tropic level
Arrows show direction of energy flow

Question 6

What are food webs

Answer 6

Shows all the consumers and their food sources, all organisms within an ecosystem will be linked to others in the food web

Question 7

What is biomass

Answer 7

• Total mass of living material in specific area at a given time.
• Fresh mass easy to get but varying amounts of water make it unreliable
• dry mass small sample not representative, organisms killed

Question 8

How can the chemical energy stored in dry mass measured?

Answer 8

Calorimetry -

Question 9

How much energy is captured by green plants from sun

Answer 9

Less than 1%

Question 10

Why is most of sounds energy not converted to organic matter by photosynthesis

Answer 10

• over 90% sun energy reflected back into space by clouds etc
• not all wavelengths of light can be absorbed and used in photosynthesis
• light not fall on a chlorophyll molecule
• factors may limit rate of photosynthesis

Question 11

What is gross primary production

Answer 11

The quantity of the chemical energy stored in plant biomass at at given time in a given area

Question 12

What is net primary production

Answer 12

The chemical energy store left after plants have used 20-50%

The chemical energy store left after the losses to respiration have been taken into to account

Question 13

What’s the equation for npp

Answer 13

Net primary = gross primary — respiratory losses

Production production

Question 14

What is the low percentage of energy transferred at each stage due to

Answer 14

• Not all of organism not consumed
• some parts consumed not digested so lost in faeces
• some energy lost as excretory materials
• energy losses as heat or respiration

Question 15

What is the net production of consumers equation

Answer 15

N = I - (F+R)

I is chemical energy store of ingested food
F is energy lost in faeces and urine
R is energy lost is respiration

Question 16

What does the relative inefficiency of energy transfer between trophies levels explain

Answer 16

• Why only 4/5 trophics levels as not enough energy to sustain more
• total mass of organism in particular place (biomass) is less higher trophic levels
• total amount of available energy is less at each stage

Question 17

What’s the equation for percentage efficiency

Answer 17

Energy available after transfer
————————————— x 100
Energy available before transfer

Question 18

What do all nutrient cycles have in common

Answer 18

One simple sequence:

• nutrient taken up by producer as inorganic molecules
• producer incorporates nutrient into complex organic molecules
• when producer eaten, nutrients passes into consumers
• nutrients passes along the food chain when these animals are eaten
• when they die, complex molecules are broken down by saprobiontic microorganisms that release nutrients in original simple form

Question 19

What percentage of air is nitrogen?

Answer 19

78%

Question 20

What are the four main stages in nitrogen cycle

Answer 20

Ammonification
Nitrification
Nitrogen fixation
Denitrification

Question 21

What happens during ammonification

Answer 21

• Production of ammonia from organic nitrogen containing compounds such as proteins, nucleic acids
• ammonia forms ammonium ions in soil

Question 22

What happens in nitrification

Answer 22

-two stages of oxidation reaction

Ammonium to nitrite
Nitrite to nitrate

Question 23

What are the two stages of the oxidation reaction in nitrification

Answer 23

Oxidation of ammonium ions to nitrite ions

Oxidation of nitrite to nitrate ions

Question 24

How do farmers raise the productivity of nitrifying bacteria

Answer 24

As require oxygen, soil can’t get clogged

Soil must be aerated by ploughing, and good water drainage so oxygen isn’t forced out by water

Question 25

What is happens during nitrogen fixation

Answer 25

Process by which nitrogen gases is converted into nitrogen containing compounds

Carried out industrially and natural through lightening.
Two types by micro organisms:free living nitrogen fixing bacteria, mutualistic nitrogen fixing bacteria

Question 26

What does free living nitrogen fixing bacteria do

Answer 26

Reduce gaseous nitrogen to ammonia, which they use to manufacture amino acids. Nitrogen rich compounds then released from them when they die

Question 27

What do mutualistic nitrogen fixing bacteria do

Answer 27

Live in nodules on roots of plants, obtain carbohydrates from plant and plant acquires amino acids from bacteria

Question 28

What happens during denitrification

Answer 28

• Soils waterlogged, low oxygen conc. microorganisms present changes
• fewer aerobic, more anaerobic denitrifying bacteria
• convert soil nitrates into gaseous nitrogen.
• reduces availability of nitrogen containing compounds for plants.
• soil must be most aerated to prevent build up of denitrifying bacteria

Question 29

Where is the main reservoir of phosphorous found?

Answer 29

In mineral form

Question 30

What is the phosphorus cycle

Answer 30

1-weathering and erosion of rocks helps phosphate ions become dissolved and available for absorption by plants which incorporate it into biomass
2-phosphate ions pass into animals which feed on plants.
3-excess phosphatebions excreted by animals, accumulate in waste material
4-death of plants and animals, decomposers break them down releasing phosphate ions back into water or soil, some ions remain as bone that are very slow to breakdown.
5-phosphate ions in excreta released by decomposition are transported by streams and rivers into lakes n oceans where form sedimentary rock

Question 31

What is the role of mycorrhizae in nutrient cycles

Answer 31

Associations between certain types of fungi and roots of plants.
Vastly increases surface area for water absorption and minerals
Extensions of root system
Acts like sponge
Improves uptake of relatively scarce ions such as phosphate ions

Mutualistic with plant, plant gets water, fungus gets organic compounds

Question 32

Why are fertilisers needed

Answer 32

• Replace mineral ions in soil that have been absorbed

- As plants don’t decompose in place they grow, and animals don’t either

Question 33

What are the two types of fertilisers

Answer 33

Natural organic fertilisers - dead and decaying remains of plants and animals as well as animal wastes eg manure slurry and bone meal

Artificial inorganic fertilisers - mined from rocks and deposits, converted into different forms and blended together. Always contain nitrogen phosphorous and potassium

Question 34

How do fertilisers increase productivity

Answer 34

• Nitrogen is essential for amino acids
• amino acids essential for growth
• when nitrates readily available plants likely to develop earlier, taller, greater leaf area
• increases rate of photosynthesis, improve crop productivity

Question 35

How has the use of nitrogen containing fertilisers become detrimental

Answer 35

• Reduced species diversity-nitrogen rich soils favour grasses and nettles and other rapidly flowing species, out compete other species
• leaching-pollution of water courses
• eutrophication-caused by leaching of fertiliser into watercourses

Question 36

What’s leaching

Answer 36

-Process by which nutrients are removed from the soil.
Rainwater dissolves any soluble nutrients, such as nitrate ions and carry them deep into soil, out of reach of plant.
-leached nutrients end up in water courses.
-negative effect on humans if drinking water, prevent oxygen transport in babies and links to stomach cancer

Question 37

What is eutrophication

Answer 37

Process by which nutrient concentrations increase in bodies of water
Occurs mostly in fresh water lakes

Question 38

What’s the process of eutrophication

Answer 38

1-low conc of nitrate, limiting factor in plant and algal growth
2-as nitrate ion conc increases as result of leaching, ceases to be limiting factor, populations grow
3-algae bloom, absorbs light
4-light is limiting factor for plants below surface
5-dead organisms used as food, saprobiontic bacteria grow
6-require oxygen, demand increases, oxygen conc reduced, nitrates released from organisms
7-oxygen is limiting factor, without aerobic organisms less comp for anaerobic organism
8-anaerobic further decompose dead material, releasing toxic wastes eg hydrogen sulphide making water putrid