10.2

Question 1

define trophic level

Answer 1

the position of an organism in a food chain or web which describes its feeding relationship with other organisms

Question 2

what are producers

Answer 2

make food by photosynthesis or chemosynthesis

Question 3

what are primary consumers

Answer 3

organisms that eat producers

Question 4

what are secondary consumers

Answer 4

animals that feed on primary consumers

Question 5

what are tertiary consumers

Answer 5

feed on secondary consumers (top predators)

Question 6

what are the disadvantages of organisms having one food source

Answer 6

any event that reduces its availability can be detrimental to the species

Question 7

what is the role of decomposers

Answer 7

break down the remains of animals and plants and return mineral nutrients to the soil

Question 8

what is a pyramid of numbers

Answer 8

the number of organisms at each trophic level of the food chain

Question 9

what is a pyramid of biomass

Answer 9

represents the biomass of organisms of each trophic level in a food chain

Question 10

what is a pyramid of energy

Answer 10

represents the total energy store of the organisms at each tropic level in a food chain

Question 11

why are only small proportions of energy passed on between the food chain

Answer 11

undigested matter goes to faeces
lost in heat energy due to respiration
waste products such as urea

Question 12

what is the secondary production

Answer 12

the process of making new animal biomass from plant material that has been eaten

Question 13

what is GPP (gross primary productivity)

Answer 13

the rate at which light from the sun catalyses the production of new plant material

Question 14

what is NPP (net primary productivity)

Answer 14

the material produced by photosynthesis stored as new plant body and tissue

Question 15

how do you calculate NPP

Answer 15

GPP-R (respiration)

Question 16

what are the 2 phases involved in the cycling of nutrients in an ecosystem

Answer 16

biotic phase - inorganic ions are incorporated in the tissue of living things
abiotic phase - inorganic ions are returned to the non-living part of the ecosystem

Question 17

what is the role of decomposers in nutrient cycles

Answer 17

feed on droppings and dead bodies, digest them and return nutrients back to the soil in a form which plants can use again

Question 18

what are the best conditions for fast decomposition and why

Answer 18

warm - increase speed of chemical reactions but not too high temperatures otherwise enzymes will denature
moisture - easier to dissolve foods & prevent them from drying out
plenty of oxygen available

Question 19

why is nitrogen important

Answer 19

needed for making amino acids and proteins

Question 20

why can plants not use nitrogen from the air

Answer 20

it is inert thereforE unreactive

Question 21

how are nitrates returned to the soil

Answer 21

urine contains urea which is a break down product from amino acids
proteins are passed out in faces
dead bodies made from proteins
these are then broken down to ammonium compounds which can be oxidised by nitrifying bacteria to convert them to nitrates which plants can reabsorb

Question 22

what are nitrifying bacteria

Answer 22

bacteria which oxidise ammonium compounds to form nitrites and nitrates

Question 23

what are nitrogen-fixing bacteria

Answer 23

bacteria in the soil that can convert nitrogen from the soil air into ammonia that is then converted into nitrates by nitrifying bacteria

Question 24

what are legumes

Answer 24

plants such as beans, peas and clover which have nodules on their roots that are full of nitrogen-fixing bacteria

Question 25

what are denitrifying bacteria

Answer 25

break down nitrates to power the production of ATP producing nitrogen gas as a waste product

Question 26

what is a carbon sink

Answer 26

a reservoir where carbon is removed from the atmosphere and ‘locked up’ in organic or inorganic compounds