Energy Flow & Nutrient Cycles

Question 1

How is energy lost at each trophic level?

Answer 1

In things that can’t be eaten (eg bones and faeces), and respiration

Question 2

Food chains

Answer 2

PRODUCERS - plants photosynthesise, converting sunlight energy into energy forms that can be used by other organisms
PRIMARY CONSUMERS - the organisms that eat the producers
SECONDARY CONSUMERS - eat primary consumers (and so on through the trophic levels)
Some energy is lost at every stage

Question 3

Reasons for loss of energy at each tropic level

Answer 3

• Around 60% of the available energy is never taken in by the organism
• plants can’t use all the light energy that reaches their leaves (may be wrong wavelength)
• some parts of organism can’t be digested
• some part of organism aren’t eaten eg bones

Question 4

Gross Productivity

Answer 4

The rest of the available energy that is absorbed by the body

Question 5

Respiratory Loss

Answer 5

30% of total energy available is lost due to respiration

Question 6

Net Producivity

Answer 6

The amount of energy available to become biomass, and is what is available to the next trophic level

Question 7

Net Productivity equation

Answer 7

gross productivity - respiratory losses

Question 8

Percentage efficiency of energy transfer

Answer 8

net productivity of trophic level / net productivity of previous level
answer*100

Question 9

Changes in percentage efficiency throughout the food chain

Answer 9

as you go further up the food chain, energy transfer becomes more efficient
efficiency varies between types of organisms

Question 10

Pyramids of numbers

Answer 10

shows the number of organisms at each trophic level

Question 11

Pyramids of biomass

Answer 11

shows the amount of biomass (in kgm^-2) at each trophic level at a single moment in time

Question 12

Biomass

Answer 12

dry mass of an organism

Question 13

Pyramids of energy

Answer 13

show the amount of energy available in each trophic level in kilo-joules per square meter per year (the net productivity of each trophic level)

Question 14

Natural ecosystem

Answer 14

Hasn’t been changed by human activity

Question 15

Intensive farming

Answer 15

changing an ecosystem by controlling the biotic and abiotic conditions to make it more favourable to crops and/or livestock so that the crops/livestock can have greater net productivity

Question 16

Three ways intensive farming increases productivity

Answer 16

1. increase efficiency of energy conversion
2. remove growth limiting factors
3. increase energy input

Question 17

Examples of intensive rearing of livestock

Answer 17

• kept in warm indoor pens where movement is restricted
• high energy food that is low in indigestible material
• slaughtered young, when more energy is being transferred to biomass

Question 18

Benefits of intensive farming

Answer 18

more food can be produced at lower costs in a shorter space of time

Question 19

Herbicides

Answer 19

kills weeds that provide competition, so crops receive more energy

Question 20

Fungicides

Answer 20

kill damaging fungal infections, so the crops don’t have to use energy fighting infections

Question 21

Insecticides

Answer 21

kill insect pests that eat and damage crops, so less biomass is lost from crops

Question 22

Problems with chemical pesticides

Answer 22

*may kill other insects that aren’t pests *eating lots of primary consumers that all contain some pesticide may adversely affect a secondary consumer *expensive

Question 23

Biological agents used to reduce pest numbers

Answer 23

*natural predators *parasites (lay eggs or live within pests, either killing it or reducing its ability to function

Question 24

Problems with biological agents

Answer 24

*natural predators may become a pest species themselves *biological agents can affect other non-pest species *may be less cost effective than chemical pesticides

Question 25

Integrated system

Answer 25

Using both chemical pesticides and biological agents

Question 26

Fertilisers

Answer 26

replace minerals in the soil

Question 27

Natural fertilers

Answer 27

slurry and sewage

Question 28

Artificial fertilisers

Answer 28

pure chemicals as powders or pellets

Question 29

Problems with fertilisers

Answer 29

*can be washed into rivers *changed nutrients balance of soils *fertiliser amounts needs to be carefully calculated to be cost efficient

Question 30

The carbon cycle (TCC)

Answer 30

Carbon is needed by all organisms to make essential compounds

Question 31

Photosynthesis (TCC)

Answer 31

Carbon is absorbed by plants, and passed on down the trophic levels

Question 32

Decomposition (TCC)

Answer 32

Detritus is broken down by decomposers (eg bacteria) who secrete enzymes which break down the carbon compounds, which are then reabsorbed for use in respiration (saprobiotic nutrition)

Question 33

Saprobiotic Nutrition

Answer 33

Feeding on dead organic matter

Question 34

Respiration (TCC)

Answer 34

Carbon returned to the air during respiration

Question 35

Combustion (TCC)

Answer 35

dead organic matter that isn’t decomposed can be turned into fossil fuels and the burnt, which releases carbon

Question 36

Daily change in CO2 concentration

Answer 36

Concentration falls during day as photosynthesis occurs, but never to zero as respiration occurs all the time

Question 37

Yearly change in CO2 concentration

Answer 37

Highest CO2 concentration in autumn and winter, as there is less plants photosynthesising

Question 38

Global Warming

Answer 38

Caused by enhancing the greenhouse effect

Question 39

What gases augment the greenhouse effect?

Answer 39

Carbon dioxide and Methane

Question 40

Effects of global warming on crop yeild

Answer 40

increase crop yields, as CO2 is a limiting factor, so increasing CO2 could increase crop yield

Question 41

Effects of global warming on insect pests

Answer 41

it depends on the species

Question 42

Effects of global warming on wild animals and plants

Answer 42

some may become more widely distributed, but those adapted to colder temperatures will become less distributed