Ecosystems

Question 1

What is an ecosystem?

Answer 1

Consists of all living things in a specific area along with non-living physical components they interact with

Question 2

What are examples of biotic factors affecting an ecosystem?

Answer 2

• numbers and type of plants and animals
• competition among organisms for essentials e.g food, territory, and mates
• dynamics of predator and prey relationships
• role of diseases and parasites within ecosystem

Question 3

How does light intensity affect an ecosystem?

Answer 3

Influences growth and behaviour of photosynthetic organisms as light is required for photosynthesis

low light photosynthetic organisms develop larger leaves or use pigments adapted to low light conditions while organisms that cannot adapt may die

Question 4

How does temperature affect an ecosystem?

Answer 4

Affects activity of enzymes regulating metabolic and reproductive activities

in warm conditions plants and ectothermic animals may develop faster and changes can trigger migration, hibernation or dormancy

Question 5

How does water availability affect an ecosystem?

Answer 5

Critical for most cellular activities, for maintaining cellular osmotic balance, and photosynthesis

lack of water can lead to drought stress, cellular damage, wilting in plants, and reduced photosynthesis rates leading to death

Question 6

How does O2 availability affect an ecosystem?

Answer 6

Vital for survival of aerobic organisms as need it to release energy

low O2 can lead to suffocation of aerobic organisms especially those in slow moving water or waterlogged soils

Question 7

How does soil type affect an ecosystem?

Answer 7

Influences soil’s drainage capabilities and nutrients it can offer to organisms

different soil types e.g sand and clay have different particle sizes affecting drainage properties and types of organisms they can support

Question 8

What are trophic levels?

Answer 8

Stages in food chain or food web representing movement of biomass and energy through various organisms

Question 9

What are producers?

Answer 9

Organisms make their own food via photosynthesis converting light energy into chemical energy

Question 10

What are primary consumers?

Answer 10

Herbivores consuming producers for food

Question 11

What are secondary consumers?

Answer 11

Organisms consuming primary consumers for food

Question 12

What are tertiary consumers?

Answer 12

Organisms consuming secondary consumers for food

Question 13

What are saprobionts?

Answer 13

Organisms decomposing complex materials in dead organisms into simpler substances to obtain food and release nutrients back into ecosystem

Question 14

What is a food chain?

Answer 14

Sequence of organisms connected by feeding

Question 15

What is a food web?

Answer 15

Complex network of interconnected food chains within ecosystem

Question 16

What is biomass?

Answer 16

Total mass of living material present at particular time in specific place or within certain organisms

Question 17

How is biomass measured?

Answer 17

Land = gm-2
Sea = gm-3

Question 18

How do you use calorimetry to measure biomass?

Answer 18

1) dry biomass sample until mass remains constant to obtain

2) weigh dry mass

3) burn dry mass in calorimeter

4) measure volume and temp change of surrounding water

5) use values to calculate estimate of heat energy released from burnt biomass

Question 19

What is gross primary production?

Answer 19

Total amount of solar energy plants convert into organic matter storing it as chemical energy within biomass

Question 20

What is net primary production?

Answer 20

Chemical energy available to next trophic level after accounting for respiratory losses (energy converted into biomass)

Question 21

How do you calculate net primary production?

Answer 21

Gross primary production - respiratory losses

Question 22

What factors contribute to energy loss at each trophic level?

Answer 22

• not all solar energy captured by leaves or is correct wavelength for photosynthesis
• factors e.g water availability can limit photosynthesis
• energy lost during photosynthetic reactions
• not all parts of biomass edible or digestible by consumers
• energy lost as heat during movement or respiration
• energy lost in excretory materials e.g urine and faeces

Question 23

How can agriculture affect ecosystems?

Answer 23

Creates simple food chains by reducing number of trophic levels ensuring as much energy as possible transferred into biomass that can be eaten by humans

Question 24

What is ecological efficiency?

Answer 24

Efficiency at which biomass or energy is transferred from 1 trophic level to next as a percentage

Question 25

What is the equation for ecological efficiency?

Answer 25

Energy/biomass available for transfer ÷ energy/biomass available after transfer x 100%

Question 26

What is assimilation by producers like plants?

Answer 26

When producers absorb useful substances and incorporate them into other compounds that aid survival

Question 27

What is nitrogen fixation?

Answer 27

Converts atmospheric nitrogen N2 into compounds like ammonia NH3

Question 28

What can atmospheric nitrogen be fixed by?

Answer 28

- Rhizobium - Azotobacter - lighting - artificial fertilisers

Question 29

What is ammonification?

Answer 29

Converts organic nitrogen-containing compounds in dead organisms or waste into substances e.g NH3 or ammonium ions (NH4+)

Question 30

How does ammonification make substances available to plants?

Answer 30

1) death or excretion by living organisms releases nitrogen-rich organic substances e.g urea, proteins, nucleic acids, and vitamins 2) saprobionts decompose these into simpler substances e.g NH4+ 3) NH4+ can be absorbed and assimilated by plants

Question 31

What is nitrification?

Answer 31

NH3 and NH4+ are oxidised to nitrites (NO2-) then to nitrates (NO3-) which plants can absorb through roots and assimilate

Question 32

What are the 2 bacteria involved in nitrification and what do they do?

Answer 32

Nitrosomonas = oxidise NH3 and NH4+ into NO2- Nitrobacter = further oxidise NO2- into NO3-

Question 33

What is denitrification?

Answer 33

Converts NO3- back into N2 under anaerobic conditions

Question 34

Why is the nitrogen cycle important?

Answer 34

Vital for recycling N essential element for life on Earth ensuring vital biological molecules needed by organisms e.g proteins, DNA and RNA

Question 35

What are the key processes in the carbon cycle?

Answer 35

Photosynthesis = plants absorb CO2 from atmosphere and convert into organic molecules Consumption = C passed through food chains as organisms consume other organisms Respiration = organisms use O2 and carbs to release energy, releasing CO2 back into atmosphere Decomposition = dead organic matter broken down by microorganisms releasing CO2 into environment Formation of fossil fuels = C stored in dead organic matter doesn't decompose due to high temps and pressure transforms over millions of years into fossil fuels Combustion = burning of fossil fuels reacts stored C with O 2releasing CO2 into atmosphere Weathering = C stored in sedimentary rocks released back into environment through weathering processes Volcanic activity = tectonic plate movements lead to release of CO2 from volcanic eruptions

Question 36

What is succession?

Answer 36

Process by which ecosystems change over time due to changes in environment causing plant and animal species present to change

Question 37

What is primary succession?

Answer 37

Occurs on newly formed or exposed land with no soil or organic material (e.g. fresh volcanic lava)

Question 38

What is secondary succession?

Answer 38

Occurs in areas where existing community has been removed leaving soil intact but with no plant or animal species (e.g. an area that has experienced a forest fire)

Question 39

What are the 3 types of communities?

Answer 39

- pioneering - intermediate - climax

Question 40

What are the stages of succession?

Answer 40

1) colonisation by pioneer species 2) condition alteration by pioneer species 3) intermediate community settlement 4) intermediate community diversification 5) climax community development

Question 41

What are the pioneer species and what do they do?

Answer 41

Can cope with extreme initial conditions and contribute organic matter helping soil formation and making environment more hospitable for other species e.g lichen or algae

Question 42

What are the intermediate species and what do they do?

Answer 42

Intermediate species (secondary colonisers) move in when soil improves and continue to modify environment e.g fern plants

Question 43

What are climax communities?

Answer 43

Stable ecosystems with balanced equilibrium of species characterised by small number of dominant plant and animal species that are rarely replaced by new species

Question 44

What are adaptions of a pioneering species?

Answer 44

- ability to reproduce asexually - seeds that are dispersed by wind - rapid germination - ability to photosynthesise - nitrogen fixation to enrich soil - extreme condition tolerance

Question 45

What are the features of a pioneer community?

Answer 45

- low biodiversity - unstable - fastest growth rate

Question 46

What are the features of a intermediate community?

Answer 46

- increasing biodiversity - more stable - slower growth rate

Question 47

What are the features of a climax community?

Answer 47

- high biodiversity but lower than intermediate - most stable - slow growth rate

Question 48

What is deflected succession?

Answer 48

When human activity interrupts normal sequence of succession preventing ecosystem from reaching natural climax community instead reaching a plagioclimax

Question 49

What are examples of activities that can cause deflected succession?

Answer 49

- continuous grazing or trampling by domesticated animals and livestock - clearing native vegetation for planting crops - burning land to clear forests

Question 50

What is Lincolns index?

Answer 50

Total individuals in 1st sample x total individuals in 2nd sample ÷ number of recaptured marked individuals