Chapter 13 - Energy and ecosystems

Question 1

what is the initial source of energy for organisms

Answer 1

sunlight

Question 2

how is energy passed between organisms

Answer 2

biomass

Question 3

what are producers

Answer 3

photosynthetic organisms that manufacture organic substances using light water co2 and minerals

Question 4

what are consumers

Answer 4

organisms that get their energy from feeding on other organisms

Question 5

what are primary consumers

Answer 5

consumers that eat producers

Question 6

what are secondary consumers

Answer 6

those that consume primary consumers

Question 7

what are saprobionts

Answer 7

organisms that break complex material in dead organisms down into simple molecules

Question 8

what is a food chain

Answer 8

a feeding relationship in which producers are eaten by primary consumers they are eaten by secondary consumers who are eaten by tertiary consumers

Question 9

what is each stage in a food chain called

Answer 9

a trophic level

Question 10

what is a food web

Answer 10

many overlapping food chain

Question 11

what is biomass

Answer 11

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

Question 12

why is it better to measure the dry mass

Answer 12

the presence of water in an organism varies dependent on conditions

Question 13

why is such a small percentage of the suns energy used in photosynthesis

Answer 13

reflected by clouds
not all wavelengths of light can be used in photosynthesis
light may not fall on chlorophyll
limiting factors may reduce photosynthesis

Question 14

what is gross primary production

Answer 14

the total quantity of chemical energy stored in plant biomass at a given Time

Question 15

what is net primary production

Answer 15

the chemical energy that remains when the loss of energy used in respirations has been accounted for

Question 16

what is the equation for net primary production

Answer 16

net primary production = primary production - respiratory losses

Question 17

why is such a low percentage of energy transferred between trophic levels

Answer 17

not all of the organism is consumed
some parts are consumed but can’t be digested so are lost in faeces and urine
heat is lost through respiration

Question 18

why are fertilisers needed especially in agriculture settings

Answer 18

normally plants would die and decompose, returning their nutrients to the soil
in agriculture the plants are removed before they can decompose so the nutrients must be returned in another way

Question 19

what are natural fertilisers

Answer 19

consists of the dead and decaying parts of plants and animals

Question 20

what are artificial fertilisers

Answer 20

NPK fertillisers

mined from rocks and deposits and combined to produce the right ratio for the crop

Question 21

how do fertilisers increase productivity

Answer 21

plants grow healthier and photosynthesise more

Question 22

what is nitrogen used for

Answer 22

dna amino acids and atp

Question 23

what are some of the detrimental effects of nitrogen fertilisers

Answer 23

leaching, eutrophication, reduced species diversity (nitrogen favouring species out-compete others so diversity decreases )

Question 24

what is leaching

Answer 24

the process by which nutrients are removed from the soil

Question 25

describe the process of leaching

Answer 25

rainwater dissolved minerals and leached it into water courses and drain into fresh water lakes this can cause eutrophication and illness in humans if water is contaminated

Question 26

describe the process of eutrophication

Answer 26

in most lakes, nitrate ions act as a limiting factor for algal growth. leaching increases the concentration of nitrate ions so they are no loner limiting. an algal bloom develops. this prevents light from reaching lower depths. plants and algae at these depths die. saprobionts break down dead plant matter. saprobionts use up oxygen and release co2. Oxygen becomes limiting for aerobic respiration and so fish and plants die. there is less competitions for anaerobic organisms who decay the material turning the water putrid

Question 27

describe the phosphorus cycle

Answer 27

phosphate ions in rocks are released by weathering. plants absorb phosphorous through their roots. mycorrhizae increase the rate of absorptions. phosphate ions are transferred through the food chain as organisms consume one another. phosphate ions are lost from animals in waste products. when these animals and plants fie, saprobionts break down complex material into the soil to be absorbed by plants. weathering rocks releases phosphate into water sources which is taken up by aquatic producers

Question 28

what is the role of mycorrhizae in the phosphorus cycle

Answer 28

it forms a mutualistic relationship with plants- plants benefit from the increased uptake of phosphorus and the mycorrhizae benefit form organic materials from the plant

Question 29

what is denitrification

Answer 29

nitrates in the soil are converted into nitrogen gas by denitrifying bacteria under anaerobic conditions

Question 30

what is nitrogen fixation

Answer 30

nitrogen gas in the atmosphere is converted into nitrogen-contaminating compounds by bacteria

Question 31

what are the two microorganisms involved in nitrogen fixation

Answer 31

free living bacteria
reduce nitrogen gas into ammonia which they use to produce amino acods
mutualistic bacteria

Question 32

what is nitrification

Answer 32

amino is oxidised to nitrate ions which are oxides to nitrate

Question 33

why do nitrogen compounds easily leach through the soil

Answer 33

they are soluble