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Biology OCR A > Chapter 23 Ecosystems > Flashcards

Chapter 23 Ecosystems Flashcards

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1
Q

Define ecology

A

The study of relationships between organisms and their environment

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2
Q

Define an ecosystem

A

All the living organisms that interact with each others and all physical factors within the region

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3
Q

What does a dynamic ecosystem mean?

A

Ecosystems are constantly changing with time, also in species distribution, abundance

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4
Q

What are biotic factors and some examples?

A

Living factors:
Interactions between organisms- predation, prey, mutualism, parasitism, competition
Population size
Breeding partners

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5
Q

What are abiotic factors and some examples?

A

Non-living factors:
Light- photosynthesis
Temperature- enzymes
Water Availability- cooling, habitat, reactant
Oxygen Availability- prevented in water logged soil

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6
Q

What are the types of soil and the fancy term for these factors?

A

Edaphic:
Clay- fine particles, easily waterlogged
Loam- different sized particles, retains water but not water logged
Sandy- Coarse particles, doesn’t retain water

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7
Q

What is a trophic level?

A

A stage in a food chain/ web

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8
Q

What is a producer? What is a consumer? What is a decomposer?

A

Producer- Organisms that convert light energy into chemical (usually via photosynthesis)
Consumer- obtain energy by feeding on other organisms
Decomposer- obtains energy from DOM, releasing nutrients back into the soil inorganic to organic, digest externally

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9
Q

What is biomass?

A

Mass of living material present in a place or organism

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10
Q

What is dry mass? What issues surround this? units?

A

Biomass with water removed
Only possible with death and drying of organism- ethics, impact upon ecosystem
Small sample sizes to compensate but less representative
g/m2 or g/m3

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11
Q

How is energy related to biomass? How can it be measured? Units?

A

Biomass is contained as cells and tissues, which store energy
Only a small proportion of food is transferred to energy
Measured via calorimetry, but results in death of organism
Units= KJM^-2Yr^-1

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12
Q

What is ecological efficiency?

A

Efficiency with which biomass/energy is transferred to the next trophic level

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13
Q

What is the efficiency of energy transfer for biomass at the producer level and why is energy lost?

A

Around 1-3%
90% light reflected or transmitted through
Limiting factors of photosynthesis prevent use

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14
Q

What is gross production?

A

Total solar energy converted into organic matter (essentially the products of photosynthesis before respiration)

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15
Q

What is net production?

A

The amount of energy available at the next trophic level

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16
Q

What is the formula for net production?

A

Net Production= Gross Production - Respiratory losses

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17
Q

Why is biomass transfer lost at each trophic level? How much transfers?

A

10%
Not all biomass consumed like teeth
Energy lost via respiration and movement as heat to the surroundings
Egestion- consumes but unable to digest/chemically process material
Excretion- waste product of digestion like faeces and urine

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18
Q

What is the formula for ecological efficiency?

A

(Energy Available after transfer/ Energy available before transfer) x 100

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19
Q

How have human activities manipulated the transfer of biomass within a food chain? PLants

A

Providing favourable conditions, such as pH, temperature, light intensity, for higher amounts of photosynthesis
Removing competition and other predators
Placing humans at lower trophic levels to reduce losses at each stage- simple food chains, plants—humans, or plants—one animal— humans

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20
Q

What are detritivores?

A

Organisms that feed on DOM by breaking it down into smaller pieces and digesting internally
Increase SA for decomposers to digest externally

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21
Q

Why can’t plant use nitrogen gas? How do some bacteria convert nitrogen gas into a more usable form?

A

Nitrogen-Nitrogen triple bond is very strong Plants do not have the enzyme to break it
Azotobacter and Rhizobium contain nitrogenase
N2 + 3H2 —-/ 2NH3

22
Q

How do plants and rhizobium benefit from their symbiotic relationship?

A

Rhizobium lives in root nodules, (Azotobacter free living in soil)
Rhizobium fix nitrogen into ammonia, converted to nitrates, used by plants to make amino acids
Bacteria gain carbohydrates from plants which undergo photosynthesis, so an energy store

23
Q

What are the main stages of the nitrogen cycle, and the bacteria at each stage?

A

Nitrogen-Fixation: Azotobacter and Rhizobium convert N2 into NH3, also carried out by lightening and Haber Process. NH3 dissolves in water to form NH4+ compounds

Nitrification/Oxidation 1: NH3/NH4+ to NO2- by Nitrosomonas

Nitrification/Oxidation 2: NO2- to NO3- by Nitrobacter, which canb e used by plants, to produce protein

Denitrification: NO3- to N2 via denitrifying bacteria in anaerobic conditions, water logged soil

Ammonification: Decomposers convert excretory waste and DOM into ammonia

24
Q

What are the main stages of the carbon cycle?

A

Photosynthesis of plants to produce glucose/carbohydrates
Carbohydrates consumed by consumers
Plants and Animals respire to produce CO2
Decomposers release nutrients from DOM, and respire, releasing CO2
Fossil fuels form from plants/animals, turn to fossil fuels in the absence of decomposers, combustion to release CO2

25
Q

Why do CO2 levels fluctuate naturally?

A

At night photosynthesis stops, but respiration of plants continues, so increases CO2 levels
In winters, days are shorter, so less photosynthesis

26
Q

Why have CO2 levels been increasing and the effect of this?

A

Combustion of Fossil Fuels
Deforestation, and potentially combustion of trees
Ocean Acidification
Leads to global warming, melting of ice caps, flooding, extreme weather

27
Q

What is succession and types of it?

A

Succession- a process in which ecosystems change
Primary: New land, no soil or organic matter present e.g from igneous rock, sand dunes
Secondary: Soil remains, but no plants or animals remain, e.g land post forest fire

28
Q

What is each seral stage?

A

Barren land- Pioneer Species
Intermediate community- secondary and tertiary colonisers, leading to shrubs and small trees
Climax Community

29
Q

What is the pioneer species and how are they adapted in their role?

A

Lichens
First Seral Stage, adapted to barren land
Specially adapted to survive:
- produce a large quantity of seeds/spores
- seeds germinate rapidly
- tolerance to extreme environments
-fix nitrogen and can photosynthesise

When they die, increase the humus (organic component) of the soil so other species can survive

30
Q

What are the components of the intermediate community and how does each stage sustain the next?

A

Secondary colonisers:
Mosses
- able to survive since some humus of the soil, and presence of nitrates, and some water retention
- arrived as seeds

Tertiary colonisers:
Ferns — Grasses — Shrubs — Small Trees

At each seral stage, the rock is eroded more, increased humus, increased water retention
Better adapted plants outcompete members at the previous seral stage, less specific adaptations

31
Q

What is the climax community?

A

A stable state with a few dominant species
Lower biodiversity than
End of primary succession

32
Q

What is the process of animal succession?

A

After plants arrive
Insect/Worms from neighbouring areas —- secondary —- tertiary
Slower than plants

33
Q

What is deflected succession and a plagioclimax?

A

Succession halted by humans/ artificially with the new community called a plagioclimax
e.g via trampling of vegetation by domesticated animals, or burning

34
Q

What is distribution? What is abundance?

A

Distribution- Locations of organisms within an ecosystem, likely to not be random
Abundance- The number of organisms

35
Q

What are two ways to measure distribution?

A

Line Transect- Line, sample at regular intervals
Belt- Two parallel lines, sample space in between at regular intervals

Useful for measuring how changes

36
Q

What factors affect abundance?

A

Immigration and births increase abundance
Emigration and deaths decrease abundance

37
Q

Evaluate random sampling

A

Cheap and quick to run
But unlikely to be representative if the sample size is small

38
Q

What is the calculation for an estimate of population? From 1 sample

A

(Number of individuals in a sample) / (sample area)
Organisms per m2

39
Q

How does capture-recapture work? Calculation?

Some disadvantages?

A

Sample- mark, release
Sample later, same area, same technique

Size= (first sample x second sample) / second which were marked

Doesn’t take into account emigration/immigration
Needs a large sample size to be accurate

40
Q

What is the formula for Simpson’s Index?

A

D = 1- sum of (n/N)^2

41
Q

Which process in the nitrogen cycle is anaerobic?

A

Nitrogen fixation
Denitrification

42
Q

How would you use a belt transect to investigate distribution?

A

Lay tape measures from the starting area
Place a quadrat between the tapes
Identify the species and count the number of them, record.
Repeat at regular intervals

43
Q

How would beavers increase habitat diversity?

A

Constructed dams- Reduce flow rate to make slow water a new habitat
Felled trees- gives sunlight to lower levels, prevent climax community
Lodges- sheltered habitats for insects

Also promotes ecotourism

44
Q

What are the downsides to introducing beavers to Scotland?

A

Fallen trees could cause damage to river beds, but areas likely to not be full of business
Dams could promote flooding so loss of farmland. Depends on severity of flooding.

45
Q

What are the units for primary production for woods vs oceans?

A

Woods KJ/M^-2Yr^-1
Ocean KJ/M^-3 Yr^-1

46
Q

How do you convert m^-2 to km^-2?

A

Ans/ (/1000/1000)
1/ 1x10^-6

47
Q

How do farmers maximise growth of animals?

A

Reduce space for movement so reduce energy for muscle contraction/respiration
Keep warm to reduce energy for thermoregulation
High protein/energy diets
Vaccinations
Use selective breeding/ genetic engineering to provide genes to maximise growth

48
Q

Why does decomposition not occur in peat bogs?

A

Acidic conditions mean decomposers cannot survive
Denatures enzymes and lack of oxygen
So decomposition does not take place

49
Q

How can you measure the ecological efficiency transfer between a producer and primary consumer?

A

Take a sample of the producers, either measure dry mass or use calorimetry (burn in oxygen) to measure energy change via temperature change of the water heated
Scale up to calculate energy change of the population
Repeat for a sample of the primary consumers and scale

Efficiency= (energy consumers / energy producers) x 100

50
Q

Why may net primary production of different ecosystems differ?

A

Different temperatures, light intensities- greater rate of photosynthesis in some places which can be transferred into more biomass
Less limiting for space
Other factors such as lower humidities, species produce less waste

51
Q

When comparing organisms to harvest for maximum efficiency, what is the most important thing to look at?

A

Position within the food chain
Primary consumers the best, they are herbivores

As they become carnivorous, even if more biomass at that stage is transferred, too much is lost between the stages to be efficient

Biology OCR A (42 decks)

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