Energy and ecosystems

Question 1

What is meant by an ecosystem

Answer 1

a form of a biological community containing all living an non living factors

Question 2

2 ways organisms obtain energy

Answer 2

Plants can obtain energy from the sun

some organisms consume other organisms to obtain energy

Question 3

2 ways biomass can be measured

Answer 3

the mass of carbon or dry mass of tissue per given area

chemical energy store in dry biomass can be measured using calorimetry

Question 4

Structure of a food chain

Answer 4

producer –> primary consumer –> secondary consumer –> tertiary consumer

Question 5

How do plants use energy

Answer 5

To synthesise sugars which are used either as respiratory substrates or to form other biological molecules which form the biomass of the plant

Question 6

2 ways energy is lost through trophic levels

Answer 6

respiration

excretion

Question 7

what is gross primary production

Answer 7

the chemical energy store in plant biomass in a given area or volume

Question 8

What is net primary production

Answer 8

the chemical energy store in plant biomass after respiratory losses have been accounted for

Question 9

What is net primary production used for

Answer 9

plant growth and reproduction but is available for other trophic levels such as herbivores or decomposers

Question 10

Net production formula

Answer 10

N = I - (F + R)
I = chemical energy store in food
F = chemical energy lost by excretion
R = respiratory losses

Question 11

How is rate of primary/secondary production measured

Answer 11

as biomass in a given area in a given time

Question 12

What are Saprobionts and an example

Answer 12

organisms that digest their food externally then absorb the products

fungi are saprobiotic

Question 13

What is mycorrhizae and what does it do

Answer 13

Fungal associations between plant roots and fungi

provides a large surface area for uptake of water and inorganic ions

acts like a sponge so can absorb and hold water and minerals easily

Question 14

What type of relationship do plants and fungi have

Answer 14

mutualistic, as the plant provides the fungi with carbohydrates and the fungi provides the plants with water and inorganic ions

Question 15

The 4 steps of the nitrogen cycle and why is it important

Answer 15

Nitrogen fixation

ammonification

nitrification

denitrification

needed to create DNA, RNA, ATP etc

Question 16

Describe nitrogen fixation and where are nitrogen fixing bacteria found

Answer 16

nitrogen fixing bacteria convert atmospheric nitrogen to ammonium ions

these bacteria are either free living in the soil or have a mutualistic relationships with leguminous plants and live in their root nodules

Question 17

Describe ammonification and what organisms carry this out

Answer 17

Organic nitrogen from decomposition of proteins, DNA , urea etc are converted to ammonium ions which are released into the soil

carried out by Saprobionts, bacteria or fungi that can digest waste extracellularly

Question 18

Describe nitrification

Answer 18

ammonium ions in the soil are oxidised to nitrites then nitrates by nitrifying bacteria

2 STEP OXIDATION

Question 19

Describe denitrification and what organisms carry this out

Answer 19

Converts nitrogen compounds back into nitrogen gas

not as useful as nitrogen gas cant be absorbed by plants

carried out by anaerobic denitrifying bacteria

Question 20

The role of fertilisers and the two types

Answer 20

replace the nitrates and phosphates lost by harvesting plants and removing livestock

natural or artificial fertilisers

Question 21

examples of natural fertilisers and the advantages/disadvantages

Answer 21

manure, peat, seaweed, guano

cheaper, or free if from own livestock

exact minerals and proportions cant be controlled

Question 22

the advantages/disadvantages of artificial fertilisers

Answer 22

they contain exact amounts of minerals, they are more water soluble so higher absorption of inorganic ions

can lead to leaching and eutrophication

Question 23

what is leaching

Answer 23

the washing of water soluble compounds into bodies of water

the leaching of nitrogen fertilisers can lead to eutrophication

Question 24

stages of eutrophication

Answer 24

leaching of nitrates can cause algae growth on the surface

excessive algae growth restricts light intensity underwater, so aquatic plants cant photosynthesis and can die

aerobic bacteria feed on the dead plant matter and respire, using up the oxygen in the water

fish and other aerobic organisms die due to lack of oxygen

Question 25

6 steps of the phosphate cycle

Answer 25

environmental conditions cause the release of phosphate ions from rocks into soil or bodies of water

plants take up the phosphate ions to synthesise organic materials

animals eat the plants and use the ions to synthesise organic materials

animals will die and decompose returning phosphate ions to the soil

bacteria in the soil break down the phosphate into inorganic ions (mineralisation)

inorganic forms of phosphorous can end up in waterways again and be taken up by plants