5.3-4 energy in ecosystems

Question 1

define producer

Answer 1

autotrophs - make their own food from photosynthesis

Question 2

define primary secondary and tertiary consumer

Answer 2

primary - animals that eat the producer
secondary - usually eat anima material
tertiary - eats secondary consumers

Question 3

define tropic level

Answer 3

the positions occupied by a species in a food chain

Question 4

define biomass

Answer 4

a chemical store of energy and the total mass of living material

Question 5

3 steps of measuring dry mass

Answer 5

1. try a tissue in an oven set to 40-80 degrees as too high could burn sample
2. weigh the samples at regular intervals until the mass becomes constant
3. once the mass becomes constant all the water will have evaporated

Question 6

how to measure biomass

Answer 6

mass of carbon present in the biomass can be calculated using a calorimeter.
burning the biomass and measuring the energy given off as heat tells you how much energy is in the biomass

Question 7

define productivity of an ecosystem

Answer 7

the rate of generation of biomass

Question 8

define GPP

Answer 8

gross primary productivity is the total amount of chemical energy converted from light energy by plants

Question 9

4 reasons why not all the light energy from the sun is converted to chemical energy

Answer 9

1. reflected
2. transmitted through the leaf
3. the wrong wavelength
4. hits parts of the plant that cannot photosynthesis

Question 10

how much os the GPP is approximately lost to the environment when plants respire and what it is known as

Answer 10

50%
respiratory loss (R)

Question 11

what is NPP

Answer 11

net primary productivity is the energy available to the plant for growth and reproduction

Question 12

how to calculate NPP

Answer 12

NPP = GPP - R

Question 13

how much % of energy is passed to the next trophic level

Answer 13

10%

Question 14

why is only 10% of energy passed to next trophic level (3 points)

Answer 14

• not all food is eaten such as plant roots/bones
• some parts are indigestible so the energy in these parts are returned to the environment as faeces
• some energy is lost to the environment as heat produced during respiration and during excretion of unrine

Question 15

define the net secondary production

Answer 15

the energy that is left and stored in the consumers biomass which is available in the next trophic level N = I(F+R)

Question 16

how to work out the % efficiency of energy transfer

Answer 16

(net production of trophic level / net production of previous trophic level) x100

Question 17

2 ways to increase NPP of crops and NP of livestock by increasing yeilds

Answer 17

• reducing energy lost to pests by simplifying food webs
• reducing respiration of livestock so more energy used for growth so more food is produced in less time

Question 18

3 ethical reasons to not increase NPP and NP

Answer 18

restricts the natural behaviour causing pain through discomfort issues
disease could spread more likely
using pesticides can have a negative impact of the surrounding environment

Question 19

4 steps of the nitrogen cycle

Answer 19

1. nitrogen fixation
2. ammonification
3. nitrification
4. denitrification

Question 20

explain nitrogen fixation

Answer 20

nitrogen gas is reduced by adding H2 to form ammonia
catalysed by nitrogenous enzyme in bacteria

Question 21

explain ammonification

Answer 21

microorganisms that feed on the remains of dead animals and plants known as saprobiotic nutrition
they secrete enzymes breaking down organic molecules which they then absorb (extracellular digestion). Break down amino acids in organic matter converting them into ammonium compounds forming ammonium ions in soil

Question 22

explain nitrification

Answer 22

carried out by specialised bacteria where is converts ammonium compounds into nitrates (oxidised)
energy is released in reactions and bacteria used this to carry out chemiosmosis
(oxidised once to nitrites then again to nitrates)

Question 23

explain denitrification

Answer 23

nitrates are converted into nitrogen gas by bacteria in anaerobic conditions. using nitrate ions as electron acceptors for respiration instead of oxygen which produces nitrogen gas which is released into the atmosphere hence reducing the amount of nitrates in the soil

Question 24

where is phosphorous mostly stored

Answer 24

as the ion PO43- in sedimentary rocks and released where they weather

Question 25

why do plants form a symbiotic relationship with a fungus

Answer 25

as the fungus mycorrhizae can obtain the plant more phosphorus in return for sugars from photosynthesis.
the hyphae of the fungus increase the surface area of the plants root system

Question 26

what is a second major source of phosphate

Answer 26

from sea bird waste known as guano

Question 27

define artificial fertiliser

Answer 27

inorganic (pure chemicals) in the form of powder, pellets or dissolved liquid. Ammonium nitrate is produced by the harder process through nitrogen fixation

Question 28

define natural fertiliser

Answer 28

produced from organic matter such as manure, composted waste, sewage or parts of crops left after harvesting

Question 29

why is crop rotation helpful

Answer 29

as alternating growing crops and having leguminous plants in fields. the leguminous plants will contain nitrogen fixing bacteria which will replace the nitrates lost from the soil and then the plants can be left to decay to recycle other nutrients back into the soil so that is ready for the next crop

Question 30

explain the 6 steps of eutrophication

Answer 30

1. excess mineral ions leaching into ponds or rivers
2. the large amounts of nutrients cause rapid growth of algae
3. large amounts of algae on surface block light and prevent it from reaching the plants below causing them to die
4. bacteria feed on and decompose the dead plant matter
5. large amounts of bacteria use up the oxygen in the water to carry out respiration
6. fish and large aquatic organisms die as there is no longer enough oxygen to survive

Question 31

why is eutrophication less likely with natural fertilisers

Answer 31

as the nitrogen and phosphorus are still part of larger organic molecules which would need to be broken down by saprobionts before are soluble