1
Q
What is an ecosystem?
A
It is all the organisms living and interacting in a certain area, and the non living components of their environment
2
Q
What system is an ecosystem?
A
A dynamic system. This means it is changing all the time
3
Q
What are biotic factors?
A
The living features of an ecosystem. E.g prey predator interactions, breeding partners, food.
4
Q
What are abiotic factors?
A
All the non living factors such as light levels, climate, season, soil type, temperature etc
5
Q
What is the place where an organism lives within an ecosystem called?
A
A habitat
6
Q
What can ecosystems be?
A
Different sizes
7
Q
What does density dependant mean?
A
This means the size of the effect changes as population increases
8
Q
Wjat does density independent mean?
A
The effect on the population remains the same regardless of the size of the population
9
Q
What is the main route energy enters an ecosystem?
A
Photosynthesis
10
Q
What do plants store energy as?
A
Biomass
11
Q
What is biomass?
A
The mass of living material
12
Q
What is primary productivity?
A
The rate producers convert light energy into chemical energy
13
Q
What is the gross productivity (Gross primary productivity)?
A
The amount of sunlight energy converted into organic molecules by photosynthesis. It is measured in kJm-2yr-1.
14
Q
What are Respiratory losses?
A
The energy used due to movement or body heat
15
Q
What is the net productivity?
A
The total energy available that becomes biomass. It is the energy available to the next trophic level.
16
Q
What is productivity?
A
It is a measure of the quantity of energy incorporated into the organism in a trophic level in an area over a certain time.o
17
Q
What is Ecological efficiency?
A
The efficiency with which biomass or energy is transfered between trophic levels
18
Q
Why is not all biomass available to the next trophic level?
A
-Some sunlight is the wrong wavelength so is not absorbed by chlorophyll
-Some sunlight hits paets of the planet that cannot photosynthesis
-Some parts of food emg bones are not eaten by consumers so the energy isn’t taken in
-Some parts of food are indigestable so come out as waste
19
Q
What is a food chain?
A
It shows how energy is transfered through an ecosystem. It shows simple lines of energy transfer
20
Q
What is a food Web?
A
It shows how energy is transfered through an ecosystem. They show lots of food chains in an ecosystem and how they overlap
21
Q
What is a trophic level?
A
It is a stage in a food chain occupied by a particular of organisms. E.g producers are the first trophic level.
22
Q
What are all primary consumers?
A
Herbivores
23
Q
How do you work out net productivity?
A
Gross productivity - Respiratory loss
24
Q
What is secondary production?
A
The amount of energy used in making consumer biomass
25
How do you work out Ecological efficiency?
Energy or biomass available after transfer ÷ energy or biomass available before transfer x 100
Or
Net productivity of trophic level ÷ net productivity of previous trophic level x 100
26
How do you estimate biomass?
Measure biomass of one individual and multiply it by the number of individuals in the species.
27
Why may estimating biomass be inaccurate?
Because that includes water and water content will differ in each individual
28
Hoe is biomass better measured?
By using dry mass. This is acheived when the dead organism is weighed then places in an 80ºc oven and reweighed periodically until there is not further mass change. This is measured as gm-2 in terrestrial ecosystems, and gm-3 in aquatic ecosystems. This is then shown in a pyramid of biomass
29
How can energy be measured?
By using a calorimetre. This takes into account variations in photosynthesis rate and is usually calculated over a whole year. In kjm-2yr-1for terrestrial ecosystems, and kjm-3yr-1 for aquatic ecosystems. This is then shown in a pyramid of energy
30
How do you calculate how efficient organisms are at converting wjat they eat into energy for the next trophic level?
Energy transfer ÷ energy intake x 100
31
What is the efficiency of energy transfer from producer to consumer?
Around 2%. This is because not all light energy that plants receive can be absorbed and some energy is lost during photosynthesis
32
What is the efficiency of energy transfer from producer to consumer?
Around 5-10%. Energy transfer is less efficient from producer to consumer than from consumer to consumer. This is because plants have a greater proportion of indigestable material.
33
What I'd the efficiency of energy transfer from consumer to consumer?
Around 15-20%
34
How can farmers reduce the energy lost from food chains and therefore increase productivity?
-Herbicides:
To kill weeds that conpete with agricultural crops for energy
-Fungicides:
Kill fungal infections that damage agricultural crops. They use more energy for growth and less for fighting infection
-Insecticides:
Kill insects that damage crops. This reduces biomass loss
-Natural predators:
Eat pest species and reduce biomass loss
-Fertilisers:
Replaces lost minerals so more energy from the ecosystem can be used
-Rearing livestock intensively:
More energy is used for growth and less for moving and keeping warm, increasing biomass
35
Explain photosynthesis in the carbon cycle
Atmospheric carbon enters the cycle during photosynthesis. This causes carbon compounds in plant tissues.
36
Explain respiration in the carbon cycle
When plants and animals respire they release CO2 beack into the atmosphere
37
Explain decomposition in the carbon cycle
Dead plants and animals are decomposed by decomposes. They do this by saprobiontic nutrition. These respire then release CO2 into the atmosphere
38
39
Explain combustion in the carbon cycle
Carbon compounds may be turned into fossil fuels in correct conditions e.g peat bogs. These can then be burned and releases CO2
40
Explain the release from volcanos in the carbon cycle.
Rocks can be formed by dead organic matter deposited on the sea floor. These may be drawn down deep into earths crust by the movement of tectonic plates where they undergo chemical changes and release carbon dioxide, which is returned by the atmosphere by volcanos
41
Explain weathering in the carbon cycle.
Carbon containing rock (as in volcanos) which eventually becomes land. This is broken down. This can also happen by chemical rainwater and physically due to plants growing etc. Chemical weathering causes mineral ions and sodium bicarbonate to be released and enter groundwater and then rivers and oceans. They then combine to form carbon containing compounds such as calcium carbonate
42
Explain ocean releases and absorption of CO2 in the carbon cycle
CO2 can dissolve directly I to oceans and be transported in currents. They can remain in slow moving ones for hundreds of years before being released. The ocean releases more CO2 when it is hotter
43
What percentage of the atmosphere is nitrogen?
78%
44
Explain nitrogen fixing in the nitrogen cycle
It is where nitrogen gas Is converted into ammonia by bacteria inside root nodules of leguminous plants (rhizobium) and free living (azotobacter). These form mutualistic relationships where they provide the plant nitrogen compounds and the plant provides them carbohydrates.
45
What is ammonification in the nitrogen cycle?
Where nitrogen compounds from dead organisms are turned into ammonia by decomposes which forms amonium ions.
46
What free living bacteria fixes nitrogen?
Azotobacter
47
What bacteria living in root nodules fix nitrogen?
Rhizobium
48
What are leguminous plants?
E.g peas, beans, clover
49
What is nitrification in the nitrogen cycle?
When ammonium ions in the soil are changed into nitrogen compounds. First, Nitrosomonas change ammonium ions into nitrites. Then nitrobacter change nitrites into nitrates which can then be used by plants.
50
What is dentrification in the nitrogen cycle?
When nitrates in the soil are converted into nitrogen gas by dentrifying bacteria. Bacteria ( pseudomonas denitrificans) in anaerobic conditions break down nitrates for respiration and produces nitrogen gas.
51
What are some other ways nitrogen can enter an ecosystem?
-Lightning fuses nitrogen gas and oxygen which fixes nitrates in the soil via rain
-Artificial fertilisers produced by the haber process
52
What is succession?
It is the process by which an ecosystem changes over time due to the environment changes due to the action of the plant or animal species. It begins with the absence of a species. It also occurs in stages
53
What are the two types of succession?
Primary and secondary
54
What is a pioneer community?
(Primary colonisers)
The group of organisms that are the first to colonise on newly formed land because they are adapted to growing in harsh environment. These are usually plants but poor competitors. As they grow and reproduce they make the environment less harsh and easier for them to be outcompeted.
55
What are secondary colonisers?
The organisms that outcompete the pioneer community. They are part of the intermediate community. These also change the environment and then are out competed by the next group of colonisers.
56
What is each stage of succession called?
A sere and is categorised by a specific group of organisms
57
What do early seres tend to show?
Small populations and low species diversity
58
What is the climax community?
The last sere in succession which shows a community that is sustainable. This usually doesn't show the highest diversity but often has the highest biomass. This community is usually dominated by woody species in temperate conditions
59
What is primary succession?
The process can take decades or centuries. It is when there is bare ground caused by volcanic eruption or deposition of rock particles formed by erosion.
-Pioneer plant seeds colonise and the pioneer community grows, eroding rock and depositing dead leaves which drcompose into organic matter (humus) forming soil.
-Pioneer plants make the co editions less harsh. Soil increases. Due to humus the soil shows better water retention and fertility
-Secondary colonisers develop and pioneers are outcompeted
-Secondary colonisers further develop the environment making it less harsh
-These are then out competed eventually leading to a stable and diverse group of species: the climax community
-As this succession continues, nitrogen fixing bacteria add more nitrogen into the soil. As pioneer species die, they will decompose and also add to the nitrogen in the ground allowing for more complex species
60
What is secondary succession?
It happens on land that has been cleared of all plants but where soil remains e.g after a forest fire. The established community of species is usually destroyed but without much disturbance to the soil. This can occur during any stage of primary succession. The pioneer community in secondary succession are larger plants e.g shrubs.
61
What is a climax community called got a particular climate?
It's climatic climax
62
What is deflected succession?
When succession is halted artificially and the climax community is prevented from being established by human activities such as agriculture. The final stage of this is called plagioclimax
63
What is abundance?
The number of individuals of one species in a particular area. The abundance of plants can be estimated by counting the number of individuals in samples.
64
What is percentage cover?
It is a way of measuring abundance of plants. This is how much of thr area investigated is covered by a species.
65
What is distribution?
Where a particular species is within the area you are investigating
66
How do you use frame quadrats and what are they?
It is a grid divided into 100 smaller squares by string. They are placed on the ground at different points randomly. The number of individuals can then be recorded. Percentage cover can also be estimated using these.
67
What are point quadrats and how are they used ?
It is a horizontal bar on two legs with a series of holes at set intervals along the length. They are places at random points. The pins are dripped and every plant that each pin touches is recorded. The percentage cover can also be measured using these by calculating the number of times a pin has touched a species as a percentage of the total number of pins dropped. This is very useful in dense vegetation.
68
What are transects?
They use point and frame quadrats that allow you to measure the change in distribution of a plant species across an area.
Line transect:
A tape measure placed along the transect and each species that touch thr tape measure is recorded
Belt transect:
Data is collected along the transect using frame quadrats placed next to each other
Interrupted transect:
You take measurements at intervals e.g every 2m
69
What methods do scientists use to measure and study ecosystems?
1) Measuring distribution:
Where an organism is found in an ecosystem. Systematic sampling is mainly used for this usually using a belt transect. The abundance of each plant is measured as density, frequency and percentage cover. This gives spatial data. Abiotic factors can also be measured to make a correlation. This is important when measuring succession.
70
How do you sample plants?
You must record then as direct counts. If you know the total amount of individuals and the total area sampled, you can express the abundance as density.
71
How do you estimate density?
Total individuals in the sample ÷ area of sample (m²)
72
How do you estimate animal abundance?
You can use systematic or random sampling for non mobile animals like barnacles. But for mobile animals methods like Sweep nets need to be paired with the capture, mark, release and recapture technique. You then need to work out the Lincoln index
73
How do you work out the licon index?
Estimate population size = no. Individuals sample 1 × no. Individuals sample 2 ÷ no. Of recaptured marked Individuals
74
Wjat do you do once the abundance of all organisms in a habitat has been determined?
Use simpsons index is biodiversity to calculate the biodiversity
75
What are Ecological pyramids?
Quantitative data of a food web
76
What is a pyramid of numbers?
It shows the number of organisms at each trophic level. The length of the bar is proportional to the number. You always start with the producers at the bottom.
77
What are the negatives of a pyramid of numbers?
-The range if numbers may be enormous and must be drawn to scale
-The pyramid may be inverted
-Doesn't take into account biomass
78
What is a pyramid of biomass?
You weigh the mass of all individuals at a trophic level. The length is proportional to the biomass. This is always the right way up.
79
What are the negatives of a pyramid of biomass?
-It must be dry weight which is destructive
-Usually taken as a small sample
-Not ethical
80
What is a pyramid of energy?
It shows the energy in each trophic level over a fixed period of time. It is measured in kjm²yr¹. It gives us the best picture of what is happening in a food Web. Information is only given by putting samples in a calorimetre
Biology OCR
flashcards
Decks in class (25)
# Cards
-
Cell Structure And Microscopy51
-
Biological Molecules97
-
Nucleotides And Nuclaic Acids32
-
Enzymes35
-
Biological Membranes36
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Cell Division And Organisation41
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Exchange And Transport55
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Transport In Animals66
-
Transport In Plants46
-
Disease And The Immune System71
-
Biodiversity59
-
Classification And Evolution77
-
Ecosystems80
-
Populations And Sustainability45
-
Neurology124
-
Homeostasis And Hormonal Control83
-
Plant Responses And Hormones79
-
Excretion133
-
Photosynthesis75
-
Respirstion56
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Cellular Contril53
-
Patterns Of Inheritance58
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Evolution ^31
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Manipulating Genomes97
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Cloning And Biotechnology57
