Ecosytems

Question 1

Define Ecosystem!

Answer 1

1. group of biotic factors and their interaction with the aboitic environment!

Question 2

Define Population vs Community vs Niche

Answer 2

1. Pop. = ALL organisms of a single species in a habitat
2. Com. = All populations interacting in ecosystem
3. Niche = role of each species in ecosystem , how individual organism fits into ecosystem!

Question 3

How can we describe ecosystems in general + WHY?

Answer 3

1. they are DYNAMIC, changing all the time
2. abiotic and biotic factors constantly changing, dying and growing….

Question 4

3 main types of ecosystem changes?

Answer 4

1. Cyclic = ecosystem change REPEATED over time periods e.g tides / pred-prey cycle…
2. Directional = single-direction changes, longer lasting than lifetime of organisms…..
3. Erratic = no rhythm/direction, unpredictable e.g. weather..

Question 5

Define BIOMASS and UNITS for both (2 ways…)

Answer 5

• dry mass of STORED WITHIN LIVING TISSUE of organism, NOT INCLUDING water [Kg year-1 m-2]
  OR
• chemical energy stored within organism [Kj year-1 m-2]

any units = given AREA per UNIT TIME

Question 6

Why is not ALL glucose from photosynthesis fixed into biomass?

Answer 6

1. Plant will respire using produced glucose ITSELF
2. Plant not constantly photosynthesising at all moments
3. Reflected radiation from leaves
4. Unsuitable wavelengths + missed chloroplasts
5. Additional limiting factor for phostosynthesis

Question 7

Why is TRANSFER OF BIOMASS inefficient?

Answer 7

1. Indigestable parts of animal left behind
2. Waste excretion
3. USED UP in metabolic processes
4. Lost as heat during movements!

Question 8

Difference with pyramid of numbers and biomass

Answer 8

1. NUM = not always pyramid shaped, due to width determined by number, and organism SIZE considered (oak tree….)
2. BIOMASS = ALWAYS pyramid shaped, due to mass of organisms decreasing further in trophic levels

Question 9

how to measure biomass in trophic levels?

Answer 9

1. Calorimetry!
2. Burning sample of dry mass, heating water sample and calc temp change in calorimeter

Question 10

Define Gross Primary Productivity and Net Primary Productivity

Answer 10

1. GPP = rate at which plants convert light into chemical energy via photosynthesis [sunlight conversion to glucose]
2. NPP = amount of carbon retained in ecosystem which primary consumer can access [conversion into useable biomass for NEXT consumer]

Question 11

Methods of improving Net Primary Productivity…

Answer 11

• Plant Light Banks + Greenhouse = rate of photosyntheisis increase
• Pesticides/Herbicides = crop yeild increase and less competition [survival chance increased]
• Selective Breeding = selecting most efficient
• Fertiliser = nitrates provided…

Question 12

Methods of improving Net Secondary Productivity…

Answer 12

1. Antibiotics = reduces energy lost due to immune responses when infected
2. Zero Grazing = minimises movements to maximise energy allocated to muscle production
3. Steriods = faster increase of muscle in meats

Question 13

Why are fungi known as saprotrophs?

Answer 13

1. Secreting enzymes out into waste material
2. THEN material digested outside fungi, absorbed into fungi body

Question 14

What is purpose of Nitrogen Cycle?

Answer 14

1. to convert inert, unuseable nitrogen in atmosphere, into reactive, nitrogen compounds!
2. Shows how compounds transfers between different biotic and abiotic factors, and to allow them to use nitrogen compounds ..

Question 15

Describe and Explain Nitrogen Fixation

Answer 15

1. Where nitrogen is chemically combined to form reactive nitrogen compounds, such as AMMONIA, AMMONIUM IONS, AMMONIA COMPOUNDS
2. Occurs via Lightning Strikes (natural NO2), Haber Process (processed fertiliser)
3. NITROGEN FIXING BACTERIA = Aztobacter&raquo_space; soil-living, N2 into NH3
   Rhizobium&raquo_space; root nodule-living of leguminous plants, reduces N2 into NH3 under anaerobic conditions, while recieving carbohydrates in return !!

Question 16

Describe and Explain Ammonification

Answer 16

1. Organic waste/Dead matter contains Urea
2. NH3 formed, which THEN becomes NH4+ ions!
3. Occurs through decomposing organisms

Question 17

Describe and Explain Nitrification

Answer 17

1. Chemoautotrophic bacteria in soil, where ammonium ions converted into useable nitrogen compounds
2. NITROSOMONASS&raquo_space; oxidising NH4+ into nitrites (NO2-)
3. NITROBACTER&raquo_space; oxidising NO2- into NO3- (nitrates)
4. AEROBIC CONDITIONS for maximum oxidation, well aeriated soil
5. NO3- USEABLE AND ABSORBED by plants via roots…..

Question 18

Describe and Explain Denitrification

Answer 18

1. Where nitrates (NO3-) in soil converted into N2 gas via REDUCTION of denitrifying bacteria, as part of respiration sources of oxygen, via nitrates..
2. under ANAEROBIC CONDITIONS, e.g. waterlogged soil, peat bogs…..

Question 19

Describe and Explain Assimilation

Answer 19

1. Process of incorperating the produced nitrates and ammonia from nitrogen fixation and nitrification
2. Plants = absorbed via roots and used in protien manufacture and DNA nucliec acids…