13 energy and ecosystems

Question 1

what are producers?

Answer 1

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

Question 2

what are consumers?

Answer 2

organisms that obtain their energy by consuming other organisms

Question 3

what are primary consumers?

Answer 3

consumers that directly eat producers (green plants)

Question 4

what are secondary consumers?

Answer 4

consumers that eat primary consumers

Question 5

what are saprobionts?

Answer 5

organisms that break down complex materials in dead organisms into simple ones, releasing minerals that can be absorbed by plants

Question 6

what are trophic levels?

Answer 6

stages in the food chain

Question 7

what is biomass?

Answer 7

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

Question 8

equation for net primary production

Answer 8

net primary production = gross primary production - respiratory losses

Question 9

what is gross primary production?

Answer 9

total quantity of the chemical energy store in plant biomass

Question 10

what is net primary production?

Answer 10

chemical energy store which is left when respiration losses have been take into account

Question 11

4 reasons why a low percentage of energy transferred in ecosystems

Answer 11

• some of the organism is not consumed
• some parts are consumed but not digested so lost in faeces
• lost in excretory material e.g urine
• lost as heat from respiration and lost to the environment

Question 12

what percent of the atmosphere is nitrogen?

Answer 12

78%

Question 13

how are nitrate ions absorbed by plant roots?

Answer 13

active transport

Question 14

what are the four main stages in the nitrogen cycle?

Answer 14

ammonification, nitrification, nitrogen fixation and denitrification

Question 15

what is ammonification?

Answer 15

the production of ammonia from organic nitrogen containing compounds (e.g urea and proteins) by saprobionts

Question 16

what is nitrification?

Answer 16

the conversion of ammonium ions into nitrate ions by nitrifying bacteria (aerobic), carried our in two stages:

1) oxidation of ammonium ions to nitrite ions
2) oxidation of nitrite ions to nitrate ions

Question 17

how to farmers raise productivity (nitrification)?

Answer 17

nitrifying bacteria are aerobic so:

• keep soil aerated by ploughing
• good drainage prevents air spaces being filled with water

Question 18

what is nitrogen fixation?

Answer 18

nitrogen gas is converted into nitrogen-containing compounds, carried out by free-living nitrogen fixing bacteria and mutualistic nitrogen fixing bacteria (nodules)

Question 19

what is denitrification?

Answer 19

convert soil nitrates into gaseous nitrogen by denitrifying bacteria (anaerobic), occurs when soils become waterlogged and have low oxygen concentration

Question 20

what is phosphorus used for?

Answer 20

ATP, phospholipids and nucleic acids (DNA)

Question 21

which farming practices can increase efficiency in food chains?

Answer 21

farming animals: reduce respiratory losses by reducing movement and heating enclosures
framing plants: simplify food webs by removing weeds and pesticides

Question 22

which 4 forms of inorganic molecules and ions containing nitrogen are found in biological systems and the physical environment?

Answer 22

• atmospheric nitrogen gas
• ammonium ions
• nitrates
• nitrites

Question 23

how is phosphorus found in the environment?

Answer 23

found as phosphate ions in mineral form in sedimentary rocks

Question 23

how is phosphorus found in the environment?

Question 24

why are mycorrhizae beneficial for plant growth?

Answer 24

• fungi increases surface are for water and mineral absorption
• acts like a sponge so holds water and mineral around the roots
• makes plants more drought resistant and able to take up more inorganic ions

Question 25

what is the relationship between plants and mycorrhizae?

Answer 25

mutualistic - plant benefits from improved water and inorganic ion uptake while fungus receives organic compounds from the plant

Question 26

what are natural (organic fertilisers)?

Answer 26

consist of dead and decaying remains of plants and animals as well as animal waste

Question 27

what are artificial (inorganic) fertilisers?

Answer 27

mined from rocks and deposits and converted into different forms, contain nitrogen, phosphorus and potassium

Question 28

what are the negative effects of nitrogen-containing fertilisers?

Answer 28

• reduced species diversity: nitrogen rich soils favour the growth of grasses and other rapidly growing species which out-compete many other species which did as a result
• leaching
• eutrophication

Question 29

what is leaching?

Answer 29

the process by which nutrients are removed from the soil:

• rain water dissolves soluble nutrients and carry them deep into the soil beyond the reach of plant roots
• they find their way into watercourses which can have harmful effects if they get into a source of drinking water

Question 30

what is eutrophication?

Answer 30

the process by which nutrient concentration increases in bodies of water

Question 31

what are the stages of eutrophication?

Answer 31

1) fertilisers move into lake because excess has been used
2) fertiliser in water makes again grow on the bottom and top
3) no light can get to plants at a the bottom because too much algae on top (algal bloom)
4) plants at the bottom die and are decomposed by saprobionts which require oxygen so conditions become anaerobic
5) fish die because no oxygen

Question 32

equation for net production of consumers

Answer 32

N = I - (F + R)

I - energy ingested in food
F - energy lost in faeces and urine