chapter 23- ecosystems

Question 1

what is an ecosystem

Answer 1

a natural unit which consists of a defined area and all the communities within it, both abiotic and biotic components an encompasses all their interactions

they are dynamic as they are constantly changing as a result of the organisms present and the conditions

Question 2

what is a habitat

Answer 2

an organisms place of residence, where it lives such as the bottom of a lake in a cave or within a cave hole

Question 3

what is a population

Answer 3

a group of individuals of the same species which occupy a particular habitat at a particular time

Question 4

what is a community

Answer 4

a collection of different populations which occur together in both space and time

Question 5

what is the environment

Answer 5

the set of conditions that surrounds the organisms and encompasses their abiotic and biotic environments

Question 6

egs of abiotic factors

Answer 6

edaphic (soil) factors, light, water availability, temperature, oxygen availability

Question 7

impact of light on an ecosystem

Answer 7

plants are directly as they photosynthesise, greater availability the greater success of plant species, coping strategies eg lower light > broader leaves, reproductive systems that operate when light is optimum, photosynthetic pigments that require less light

Question 8

impact of temp on an ecosystem

Answer 8

plants and ectothermic animals develop quicker then warmer conditions, changing seasons > migration/hibernation/leaf fall/dormancy/flowering

greatest effect is on metabolic enzymes

Question 9

impact of water availability on an ecosystem

Answer 9

lack of > stress > death
eg plants wilt as not turgid and upright and also needed for photosynthesis , cacti are xerophytes that have developed successful strategies to cope with water stress

Question 10

impact of oxygen availability on an ecosystem

Answer 10

in aquatic ecosystems its good to have fast flowing cold water as it contains high conc of o2, if its too warm or too slow the drop in o2 conc > suffocation

in waterlogged soil the air spaces the air spaces between particles are filled with water so reduces o2 available

Question 11

impact of edaphic (soil) factors on an ecosystem

Answer 11

different types have different particle sizes
clay: fine, easily waterlogged and clumpy when wet
loam- diff sizes, retains water but not waterlogged
sandy- coarse, well separated allowing draining, not retain water and easily eroded

Question 12

egs of biotic factors

Answer 12

competition
prey
predators
mutualism/symbiosis
mates
parasitism (int/ext)

Question 13

what is secondary production

Answer 13

energy used to make new consumer tissue (biomass)

Question 14

what is biomass

Answer 14

the mass of all living material present in an ecosystem

Question 15

When a consumer eats a producer what flows between what

Answer 15

biomass flows between trophic levels

Question 16

equation for efficiency

Answer 16

biomass transferred / biomass intake X100

Question 17

what are the 2 types of primary productivity and describe

Answer 17

gross (GPP)- amount of chemical energy as biomass that a producer creates in a given length of time

net (NPP)- amount of chemical energy that is not consumed by respiration (NPP= GPP- resp)

Question 18

how to calculate biomass at each level

Answer 18

biomass present in each organism x total no of organisms in trophic level

Question 19

what are the units for an area of land and for an area of water

Answer 19

land- g/m2
water- g/m3

Question 20

what are some biotic factors that humans could manipulate in order to control an ecosystem/in favour of agriculture

Answer 20

fencing to avoid predation
pesticides to reduce competition
selection of mates (artifical)

Question 21

what are some aboitic factors that humans could manipulate in order to control an ecosystem/in favour of agriculture

Answer 21

watering
drainage (o2)
warmth of greenhouses
warmth of housing animals eg stables/sheds
fertilisers/addition of lime/pH

Question 22

explain why its very rare to find more trophic levels than in this food chain (that requires 5) (2)

Answer 22

total energy available is less at each level, so too little energy is available further up the chain to support higher/more trophic levels

Question 23

calculate the %energy transfer efficiency between algae (53000 kJm-3yr-1) and small aquatic animals (10150)

Answer 23

10150/53000 x100

=19.2%

Question 24

explain why the answer to part a (%energy efficiency) is less than 100% (1)

Answer 24

because energy is transferred to heat/ or respiration inefficiency of metabolic reactions/keeping warm/moving/not all food is digestible eg cellulose/lost in faeces/urine

Question 25

plants absorb nitrogen in the form of

Answer 25

nitrate

Question 26

In the nitrogen cycle, bacteria convert nitrogen gas into...

Answer 26

ammonia

Question 27

The process of converting nitrogen gas into ammonia is known as ...

Answer 27

nitrogen fixation

Question 28

The bacteria that carry out nitrogen fixation are known as.... and 2 egs are

Answer 28

nitrogen fixing bacteria Two examples of these bacteria are Azotobacter and Rhizobium.

Question 29

Azotobacter convert ammonia to .... in the ...

Answer 29

ammonium ions from nitrogen gasin the soil they are free living in the soil, they contain nitrogenase

Question 30

Rhizobium live within the ....... of ..... plants and directly transfer .... to the plant

Answer 30

root nodules of leguminous plants, transfer ammonia they contain nitrogenase

Question 31

what relationship do rhizobium have with legumes

Answer 31

symbiotic/mutualistic

Question 32

egs of legumes

Answer 32

peas, beans and clover

Question 33

In the soil, Nitrosomonas convert the ammonium ions into ... Nitrobacter then convert this nitrogen-containing compound to .... The processes carried out by these bacteria are collectively called ...

Answer 33

nitrite nitrate nitrification

Question 34

nitrogen fixation requires a lot of energy, why?

Answer 34

because the triple bond in N2 takes a lot of energy to break (12ATP)

Question 35

animals make their own nitrogen containing compounds, but where do they get the nitrogen from

Answer 35

by eating plants

Question 36

how is nitrogen returned to the soil by plants and animals and what is this waste fed on by

Answer 36

death and excretion fed on by decomposers

Question 37

Decomposers convert nitrogen-containing compounds eg dna into ammonia. This ammonia is then released into water in the soil, forming…

Answer 37

ammonium ions.

Question 38

what would happen to the nitrogen cycle if there was no way of regenerating nitrogen gas

Answer 38

run out of nitrogen gas any nitrogen that had made its may into soil and other orgs > =H2O > river >ocean much more difficult for plants to obtain nitrate > death

Question 39

what are the reactant and products of nitrogen fixation via rhizobium and azotobacter and is it oxidation/reduction of nitrogen

Answer 39

reactant- nitrogen gas N2 product- ammonia NH3 reduction both aerobic bac

Question 40

what are the reactant and products of nitrification (via nitrosomonas) and is it oxidation/reduction of nitrogen

Answer 40

reactant- ammonium ions NH4+ product- nitrites NO2- oxidation in well aerated soil

Question 41

what are the reactant and products of nitrification (via nitrobacter) and is it oxidation/reduction of nitrogen

Answer 41

reactant- nitrites NO2- product- nitrates NO3- (this is highly soluble in water) oxidation in well aerated soil

Question 42

what are the reactant and products of denitrification via denitrifying bac and is it oxidation/reduction of nitrogen

Answer 42

reactant- nitrates NO3- product- nitrogen gas N2 reduction

Question 43

Denitrifying bacteria (eg...) convert ... to .... when they carry out .....

Answer 43

pseudomonas, nitrates (use as source of energy for resp) to nitrogen gas (released), anaerobic resp/in absence of O2 eg waterloggged soil

Question 44

decomposers are involved in which process

Answer 44

ammonification

Question 45

Plants absorb nitrate to form biological molecules containing nitrogen. what might the plant make from nitrogen?

Answer 45

amino acids nucleic acids

Question 46

Which two processes produce ammonium ions in the nitrogen cycle?

Answer 46

Nitrogen fixation Ammonification

Question 47

An area of land contains two types of soil. One patch of soil is well aerated, whereas the other patch of soil is less aerated. Identical plants are grown in both soils and given the same access to water and sunlight. In the areas where the soil was less aerated, the plants had stunted growth. Suggest why.

Answer 47

Denitrifying bacteria respire anaerobically, so less aerated soil would mean more denitrification. Additionally, there would be less nitrification as nitrifying bacteria respire aerobically. Overall, this leads to less nitrate available in the soil for the plants to absorb for growth.

Question 48

nitrogenfixing bac are a key part of an ecosystem, describe the role of nitfixbac in the nitrogen cycle (2)

Answer 48

nitfixbac convert nitrogen into ammonia which allows nitrogen uptake into organisms plants cant absorb nitrogen form air but they can use ammonia produced from nitfix to make nitrogen containing compounds

Question 49

give examples of processes and activities which can increase the availability of nitrogen and its compounds in the soil (4)

Answer 49

fixing of nit by nitfixbac apply artificial fertilisers urination/defecation of animals, silage, maure lightning causes oxidation of n2 decay of organic matter via saprobionts

Question 52

In the atmosphere, carbon is found in the form of ...

Answer 52

carbon dioxide

Question 53

During photosynthesis, carbon dioxide is converted into organic carbon-containing compounds. What is this process called?

Answer 53

carbon fixation

Question 54

what eats producers in a food chain and transfers carbon-containing molecules

Answer 54

consumers

Question 55

Producers and consumers release carbon dioxide back into the atmosphere through the process of ...

Answer 55

respiration

Question 56

Dead producers and consumers are broken down by organisms called... and describe

Answer 56

decomposers primarily microscopic bacteria and fungi but also toadstools etc feeds via saprophytic digestion (organic to inorganic nutrients)

Question 57

These organisms break down dead producers and consumers in a process called... and describe it

Answer 57

decomposition chemical process in which a compound is broken down into smaller molecules or constituent elements (often in organic form it cannot be use directly so needs to be processed into inorganic which are more usable and so returned to the E)

Question 58

Fossil fuels are burned in a process called.... which releases carbon dioxide back into the atmosphere.

Answer 58

combustion

Question 59

describe how saprobionts obtain their nutrients (3 marks)

Answer 59

they secrete extracellular enzymes onto dead organic matter and digest it extracellularly and then absorb the products/nutrients

Question 60

suggest how the presence of detritivores may cause the activity of saprobionts to increase

Answer 60

increases surface area of dead/decaying matter increases rate or reaction of enzymes /digestion by saprobionts

Question 61

info about nitrogen gas/N2

Answer 61

it is inert (very stable due to the triple bond) so not easy to break down/apart in chemical reactions plants and animals cannot use N2 plants must secure nitrogen in a "fixed" form ie incorportated in compounds eg nitrate ions or ammonia/ammonium ions. bacteria are essential to this process to prevent nitrogen becoming a limiting factor in ecosystems

Question 62

what are detritivores

Answer 62

eg earthworms, beetles, slugs, maggots, woodlice they ingest and digest organic matter which increases the sa for decomposers to act upon

Question 63

in the nitrogen cycle, plants get nitrates, what do the back get

Answer 63

eg carbs like sucrose or glucose