A Level Biology OCR > Ecosystems > Flashcards

Ecosystems Flashcards

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1
Q

What is an ecosystem

A

Is made up of all the living organisms that interact with one another in a defined area, and also the physical factors present in that region

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2
Q

What are biotic and abiotic factors

A

Biotic - the living factors in an ecosystem
Abiotic - the non-living or physical factors in an ecosystem

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3
Q

What is a community

A

When species interact with other species they form communities

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4
Q

What are features of ecosystems (1)

A

There is a flow of energy within an ecosystem and nutrients within it are recycles
There are both biotic and abiotic components within an ecosystem
Ecosystems vary greatly in size and scale

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5
Q

What are features of ecosystems (2)

A

Ecosystems also vary in complexity

No ecosystems is completely self-contained as organisms from one ecosystem are often linked to organisms from another

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6
Q

What is a biotic factor

A

Anything that influences the populations within na community that is a result of another organism’s activity

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7
Q

Examples of biotic factors

A

Predation
Competition
Cooperation
Parasitism
Disease (pathogen disease caused by microorganisms)
Camouflage
Mimicry

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8
Q

What is an abiotic factor

A

Is any physical or chemical factor that influences the populations within a community

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9
Q

What are examples of abiotic factors?

A

Availability of water
Light
Radiation
Temperature
Turbidity
Humidity
Atmospheric composition
PH
Salinity
Soil composition

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10
Q

What are edaphic factors

A

They are abiotic factors that affect the soil

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11
Q

What are the three main soil types and features of each

A

Clay - fine particles, easily waterlogged, forms clumps when wet

Loam - this has different sized particles, it retains water but does not become waterlogged

Sandy - this has coarse well separated particles that allow free draining and is easily eroded

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12
Q

What is dry mass

A

The mass of the organism or tissue after all the water has been removed

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13
Q

What is each stage in a food chain called

A

A tropic level

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14
Q

What is the first tropic level

A

A producer

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15
Q

What is a producer

A

An organism that converts light energy into chemical energy by the process of photosynthesis

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16
Q

What are tropic levels other than 1

A

Consumers which are organisms that gain their energy by feeding on other organisms

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17
Q

Why do food chains only have a few trophies levels

A

As there is not sufficient biomass and stored energy left to support any further organisms

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18
Q

What are decomposers

A

They break down dead organisms releasing nutrients back into the ecosystem

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19
Q

What can food chains be represented as

A

Diagrammatically as a pyramid of number or pyramid of biomass

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20
Q

How do you calculate biomass

A

Multiply the biomass present in an organism by the total number of organisms at the trophic level

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21
Q

What does a pyramid of biomass show

A

It represents the biomass present at a specific moment in time and does not account seasonal changes

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22
Q

How is dry mass prepared

A

The organism is killed and then placed in an oven at 80*C until all the water has evaporated

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23
Q

What is biomass measured in

A

g/m^2 or g/m^3

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24
Q

What is ecological efficiency

A

The efficiency with which biomass or energy is transferred from one trophic level to the next

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25
What is the efficiency at the producer level
producers only convert 1-3% of the sunlight they receive into chemical energy and biomass
26
Why is the efficiency so low at the producer level
Not all of the solar energy available is used for photosynthesis Other factors may limit photosynthesis, such as water loss A proportion of the energy is lost as it is used from photosynthetic reactions
27
What is gross production
The total solar energy that plants convert to organic matter is called gross production
28
How much of the gross production is used in respiration and what is the rest used for
Around 20-50% of this energy is used in respiration, and the remaining is converted into biomass
29
How can the energy available at the next trophic level be calculated
Net production = gross production - respiratory losses
30
What is secondary production and primary production
The generation of biomass in a consumer is called secondary production, and the generation of biomass in a producer is called primary production
31
What is the efficiency of consumers
Consumers at each trophic level convert around 10% of the biomass into their own organic tissue
32
Why is the efficiency of consumers so low (1)
Not all the biomass of an organism is eater, for example plant roots or animal bones may not be consumed Some energy is transferred to the environment as metabolic heat, as a result of movement and respiration
33
Why is the efficiency of consumers so low (2)
Some parts of an organism are eaten but indigestible - these parts are digested as faeces Some energy is lost from the animal in excretory materials such as urine
34
What is ecological efficiencies formula
Energy or biomass available after transfer/ energy of biomass available before transfer x100
35
What does agriculture include
The manipulation of the environment to favour plant species that we can eat (crops) and to rear animals
36
What are examples of agricultural practices
Plants and animals are provided with the abiotic conditions they need to survive Reducing competition from other species (herbicides) Removal of predators using fences or pesticides
37
What is a feature of agricultural practices
They create very simple food chains, minimising energy loss as there are fewer trophic levels present than in the natural ecosystem, ensuring as much energy as possible is transferred into biomass that can be eaten by humans.
38
What is decomposition
It is a chemical process by which a compound is broken down into smaller molecules or its constituent elements
39
What is a decomposer
Is an organism that feeds on and breaks down plant or animal matter, thus turning organic compounds into inorganic ones
40
What is a feature of decomposers
They are saprotrophs as they obtain their energy from dead waste organic material. And they are usually fungi or microorganisms.
41
What is the process of decomposition
They digest their food externally by secreting enzymes onto dead organisms or organic waste matter. These enzymes break down complex organic molecules into simple soluble ones, the decomposer then absorbs these molecules.
42
What is released into the environment through decomposition
Inorganic compounds and elements
43
What are dertritivores
They are organisms that speed up the decay process by feeding on dead and decaying material breaking it down into smaller pieces of organic material, increasing the surface area for decomposers to work on.
44
Where is nitrogen found and what is a feature of it
Nitrogen is abundant in the atmosphere (78%) however this form of nitrogen can;t be taken up by plants. And to be used by living organisms it must be combined with other elements
45
What is nitrogen fixation and what carries it out
Nitrogen-fixing bacteria such as Azotobacter and Rhizobium contain the enzyme nitrogenase, which combines atmospheric nitrogen with hydrogen to produce ammonia, which can be absorbed and used by plants.
46
Where do nitrogen fixing bacteria live
In root nodules, which are growths on the roots of leguminous plants and they have a mutualistic relationship with them.
47
Which is the relationship between nitrogen fixing bacteria and root nodules mutualistic
The plant gains amino acids from Rhizobium, which are produced by fixing nitrogen gas in the air into ammonia The bacteria gain carbohydrates produced by the plant during photosynthesis which they use as an energy source
48
What is nitrification
The process by which ammonium compounds in the soils are converted into nitrogen-containing molecules that can be used by plants
49
What is a feature of nitrification
This is an oxidation reaction so can only occur in well aerated soil and occurs in two steps
50
What are the two steps of nitrification
1. Nitrifying bacteria (nitrosomonas) oxidise ammonium compounds into nitrites 2. Nitrobacter oxidise nitrites into nitrates or nitrosomes The nitrate ions are highly soluble and therefore the form in which most nitrogen enters a plant
51
What occurs in the absence of oxygen in the nitrogen cycle
Denitrifying bacteria convert nitrates in the soils back into nitrogen gas - denitrification
52
What is the benefit for the bacteria in denitrification
They use the nitrates as a source of energy for respiration and nitrogen gas is released
53
What is ammonification
The process by which decomposers convert nitrogen-containing molecules in dead organisms into ammonium compounds.
54
Draw the nitrogen cycle
55
Draw the carbon cycle
56
Why do CO2 levels fluctuate throughout the day
Photosynthesis only takes place in the light, and so CO2 levels are lower during the day However respiration is carried out by all living organisms through the day and night, so therefore the CO2 levels are higher at night than during the day
57
Why do CO2 levels fluctuate seasonally
They are lower in summer than winter as the photosynthesis levels are higher
58
Why have CO2 levels increased significantly
The combustion of fossil fuels, which has released CO2 back into the atmosphere which has been trapped for millions of years below the earth’s surface. Deforestation which has removed lots of photosynthesising biomass from the earth, reducing how much CO2is removed from the atmosphere
59
What is the impact of increased CO2 levels
There is more thermal energy trapped in the atmosphere The amount of CO2 dissolved in seas is affected by the temperature of the water, so higher temperatures reduce the carbon banks in oceans and releases more CO2 into the atmosphere
60
What is an example of a free living soil bacterium
Azotobacter
61
What are the non living nitrogen fixation processes
Lightning and the hater process
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