12.4

Question 1

Primary producers:

Answer 1

able to produce organic materials from the inorganic molecules carbon dioxide and water, in photosynthesis - green plants

Question 2

Primary consumers:

Answer 2

organisms that eat plants and obtain their energy from respiring molecules obtained from plants

Question 3

Secondary consumers:

Answer 3

organisms that feed on primary consumers

Question 4

Trophic levels:

Answer 4

the different levels in a food chain

Question 5

Decomposers:

Answer 5

bacteria and fungi

break down animal faeces and dead bodies

Question 6

Detritivores:

Answer 6

animals such as earthworms, millipedes and woodlice

Question 7

Biomass:

Answer 7

the plant tissue made in photosynthesis/the total mass of living organisms in a community

Question 8

Only about 1% of the energy from sunlight that falls on a plant is actually used in photosynthesis for 3 reasons:

Answer 8

1) Some of the light = wrong wavelength - only red and blue can be used in photosynthesis (680 & 700)
2) Some doesn’t land on a chloroplast and gets transmitted through the leaf
3) Some is lost as heat

Question 9

Only about 5-10% in plant tissues is passed onto primary consumers for 2 reasons:

Answer 9

1) Large amount of plant tissue is composed of lignin and cellulose which cannot be digested by enzymes in animal’s guts
2) Parts of the plant aren’t available to be eaten, e.g. the roots of trees or grass

Question 10

About 10-20% of the energy in primary consumers is passed onto secondary consumers. This is higher than the transfer at the previous stage because:

Answer 10

1) Animal tissue is made mainly of proteins and fats, which have a higher energy value than plant tissue
2) Animal tissue is more digestible than plant tissue

Question 11

Transfer of energy is still not very efficient from PC-SC as..

Answer 11

some parts of animal, e.g. bones and hooves aren’t readily available

Question 12

At every trophic level, organic molecules are used in respiration to produce ATP for processes such as:

Answer 12

muscle contraction
synthesis of large molecules
active transport

Question 13

The energy in organic molecules used in respiration is lost as:

Answer 13

heat

Question 14

Carbon offsetting, e.g. planting trees - take in CO2 in photosynthesis and use this to produce organic molecules that form plant tissue - plant tissue made in photosynthesis is…

Answer 14

biomass

Question 15

CO - this carbon dioxide is released again if the biomass in the tree is…

Answer 15

burned as a fuel or decomposed by decomposers

Question 16

CO -however, because these trees take many years to grow, the carbon dioxide is locked up or…

Answer 16

sequestered in the biomass of trees for many living years