6.3.1 Ecosystems Flashcards
(121 cards)
1
Q
what is ecology
A
the study of relationships between organisms and their environment
2
Q
what is a habitat
A
the place where an organism lives, e.g. rocky shore or a field
3
Q
what is a population
A
all the organisms of one species in a habitat
4
Q
what is a producer
A
an organism that produces organic molecules using sunlight energy
5
Q
what is a consumer
A
an organism that eats other organisms, e.g. animals and birds
6
Q
what is a decomposer
A
an organism that breaks down dead or undigested organic material, e.g. bacteria and fungi
7
Q
what is a trophic level
A
a stage in the food chain occupied by a particular group of organisms
8
Q
what is an ecosystem
A
the living organisms that interact with each other in a defined area, and also the physical factors present in that region, so abiotic and biotic factors
9
Q
what is it meant by ecosystems being dynamic
A
they are constantly changing all the time
10
Q
what are the 2 factors that affect an ecosystem
A
biotic and abiotic factors
11
Q
what are biotic factors
A
the living factors of an ecosystem
12
Q
what are abiotic factors
A
the non-living factors of an ecosystem
13
Q
examples of biotic factors
A
- presence of predators and food
- breeding partners
- competition of space (territory)
14
Q
examples of abiotic factors
A
- light intensity: plants need it to photosynthesis
- temperature: affects the enzymes controlling metabolic reactions (mainly plants and ectothermic animals)
- rainfall/water availability
- topology (the shape of the land)
- soil nutrient availability, and different types of soil as some can become waterlogged
- oxygen availability (which decreases with waterlogged soil)
- pH and salinity (salt content) in aquatic ecosystems
15
Q
what are the biotic factors of a rock pool
A
- seaweed can be a food source for consumers here like limpets that graze on this producer
- intense competition for food can limit the number of organisms in this small rock pool ecosystem
16
Q
what are the abiotic factors in a rock pool
A
- rock pools are heavily influenced by the tides
- at high tide, completely submerged by the ocean, so experience similar abiotic factors to the ocean ecosystem
- e.g. pH, salinity and temperature
- at low tide, experience more extreme abiotic conditions
- like higher salinity and temperature
- only certain organisms can tolerate these conditions
17
Q
what are the biotic factors of a playing field
A
- producers include grass, daisies, clovers and dandelions
- large amounts of these plants might attract a large number of organisms
- which use them as a food source
- e.g. rabbits and caterpillars
18
Q
what are the abiotic factors of a playing field
A
- rainfall and sunlight may affect the growth of the producers in the ecosystem
- in a very wet year, soil may become waterlogged
- makes it difficult for plants to grow
- poor plant growth may decrease the number of consumers the ecosystem is able to support
19
Q
what are the biotic factors of a large tree
A
- insects, such as caterpillars, can use the leaves of the tree as a source of food
- they may consume all the leaves on the tree (defoliation)
- can slow down tree growth
- even lead to its death
20
Q
what are the abiotic factors of a large tree
A
- drought conditions (with prolonged periods of very low rainfall) can negatively impact the growth of the tree
- in severe cause parts of the tree or the whole thing in dying
21
Q
what do all organisms in an ecosystem require, and where does this originate from for almost all ecosystems
A
- energy to function and survive
- light energy from the sun converted to chemical energy in plants and photosynthetic organisms, and this energy can be used by other organisms
- the plants that do this are called producers
- store the energy as biomass
- (some energy enters sea ecosystems when bacteria uses chemicals from deep sea vents as an energy source)
22
Q
what is biomass
A
the mass of living material
- e.g. mass of plant material
23
Q
what is biomass transfer
A
the following energy transfers through an ecosystem, starting from the producer
24
Q
when is energy transferred through living organisms in an ecosystem
A
- transferred through living organisms
- when the organisms eat eachother
- e.g. producers eaten by primary consumers, which are eaten by secondary consumers which are eaten by tertiary consumers
25
what do food chains and webs show
both show the transfer of biomass and therefore energy through organisms in an ecosystem
- so how energy is transferred through an ecosystem
26
what is the difference between a food chain and food web
FOOD CHAIN: show simple lines of energy transfer
FOOD WEB: show lots of food chains in an ecosystem and how they overlap
27
what happens to the energy locked up in things that cannot be eaten in an ecosystem
- e.g. bones and faeces
- gets recycled back into the ecosystem
- through decomposers
28
what is each stage of a food chain called
trophic level
29
what is the first trophic level always
a producer:
- organism that converts light energy into chemical energy via photosynthesis
30
what are all trophic levels except for the first one
consumers:
- organisms that obtain their energy from feeding on other organisms
31
does all of the energy get transferred to the next trophic level
- NO
- not all the energy (either from sunlight or food) that is available to the organism in a trophic level is transferred to the next trophic level
- around 90% of the total available energy is lost in various ways
32
why does an organism not take in all the energy available to it in the first place
- plants can't use all of the light energy that reaches their leaves, as some is the wrong wavelength, some is reflected and some passes straight through their leaves
- some sunlight can't be used as it hits parts of the plant that can't photosynthesis (e.g. the bark of a tree)
- some parts of food aren't eaten by organisms (e.g. the roots or bones), so the energy isn't taken in and these parts pass to decomposers
- some parts are indigestible, so pass through an organism and come out as waste, e.g. faeces, and this once again passes to decomposers
- around 60% of the available energy is never taken in
33
what is gross productivity
all the available energy that is taken in (absorbed) by organisms
34
why is all the energy taken in by an organism (gross productivity) not available for the next trophic level
- 30% of the total energy available (75% of the gross productivity) is lost to the environment when organisms use energy produced from respiration for movement or body heat = called respiratory loss
- 10% of the total energy available (25% of the gross productivity) becomes biomass (and is stored or used for growth), called net productivity
35
what is net productivity (or net biomass)
the amount of energy that is available for the next trophic level
36
what is the sequence of steps of energy loss through trophic levels
- ALL AVAILABLE ENERGY
- 60% of available energy is not taken in
- 40% is, called gross productivity
- of this energy actually taken in, 75% of it is lost via respiratory loss
- only 25% of it is kept as biomass and net productivity, and is available to the next trophic level
- so only about 10% of the energy from the start is actually available for the next trophic level
- cycle continues again for this next trophic level
37
how is net productivity calculated
net productivity = gross productivity - respiratory loss
38
what units is biomass measured in
kJm-2yr-1
39
how do you calculate percentage efficiency of energy transfer
energy transferred / energy intake x100
- where energy transferred is the net productivity
- a measure of how efficient organisms are at converting what they eat into energy for the next trophic level
40
how do you measure the energy transfer between trophic levels
calculate the difference in the amount of energy in each level (so the net productivity of each level)
41
how do you calculate the amount of energy in a trophic level
- measure the dry mass of organisms
- i.e. their biomass
- as energy is stored in biomass, so it acts as an indicator of how much energy an organism contains
42
how do you calculate the biomass of a whole trophic level
- calculate the amount of biomass in a sample of organisms
- e.g. 1m2 area of wheat or a single mouse that feeds on wheat
- multiply the results from the sample by the size of the total population (e.g. the whole field or the total number of mice in the population)
- this gives the total amount of energy in the organisms in that trophic level
- the difference in energy between trophic levels is the amount of energy being transferred
43
what are the problems with using samples to calculate the total amount of energy in a trophic level and the amount of energy being transferred
- the consumers may have taken in energy from other sources than the producer being measured
- means that the difference between the biomass of the 2 figures wouldn't be an accurate estimate of the energy transferred between just those 2 organisms
- for an accurate estimate, you would have to include all of the individual organisms at each trophic level
44
how do humans impact the transfer of energy between trophic levels
by implementing farming methods that increase the transfer of energy through an ecosystem, and therefore increase productivity
45
what are examples of human activities that increase the transfer of energy in an ecosystem, focussed on plants
1) HERBICIDES: kill weeds that compete with the agricultural crop for energy, reducing competition and meaning that the crop receives more energy (so grows faster and becomes larger, increasing productivity)
2) FUNGICIDES: kill fungal infections that could damage the crop, so crops use more energy for growth rather than fighting infection, (so grow faster and larger and increase productivity)
3) INSECTICIDES: kill pests that eat and damage crops, so less biomass is lost from the crops (so grow larger, and increase productivity)
4) NATURAL PREDATORS: introduced to the ecosystem that eat the pest species (e.g. ladybirds eating greenflies), so crops lose less energy and biomass (increases productivity)
5) FERTILISERS: chemicals that provide the crops with minerals needed for growth, e.g. nitrates, as usually, crops use up the minerals in the soil when they grow, limiting growth when there aren't enough minerals, but adding fertiliser replaces the lost minerals, so more energy from the ecosystem can be used for growth, increasing the efficiency of energy conversion
46
what are examples of human activities that increase the transfer of energy in an ecosystem, focussed on livestock
- rear livestock intensely by controlling the conditions that they live in
- so more energy is used for growth rather than other activities
- means that the efficiency of energy conversion is increased
- more biomass is produced
- and productivity is increased
47
what are 2 examples of rearing livestock intensively
- animals kept in warm, indoor pens
- where their movement is restricted
- so less energy is wasted keeping warm and moving around
- animals may be given feed that is higher in energy than their natural food
- this increases the energy input
- so more energy is available for growth
48
what are the benefits of human activity manipulating the transfer of biomass in ecosystems
- more food is produced in a shorter space of time
- at lower cost too
49
what are the ethical issues behind human activities manipulating the transfer of biomass through ecosystems
- raises ethical issues
- some people believe that the conditions that intensively reared animals are kept in
- cause the animals pain, distress or restrict their natural behaviour
- so should not be done
50
what type of processes are present in the carbon cycle
- those involving organisms, like photosynthesis, respiration, decomposition
- chemical and physical processes too, like combustion and weathering
51
what is the carbon cycle
how carbon moves through living organisms and the non-living environment
52
why do organisms need carbon
- to make essential compounds
- e.g. plants using CO2 in photosynthesis to make glucose
53
what is decomposition
a chemical process in which a compound is broken down into smaller molecules, or its constituent elements
54
why is the carbon cycle important
- shows that carbon is recycled and can be reused by organisms
- recycling within the environment helps maintain balance in ecosystems
55
carbon cycle: explain how carbon from the air enters an ecosystem
- carbon in forms of CO2 in the air and water is absorbed by plants
- when they carry out photosynthesis
- and becomes a carbon compound in plant tissues
56
carbon cycle: what happens to the carbon that has been absorbed by plants and turned into plant tissue
- primary consumers eat the plants, and this carbon is passed onto them
- also passed to secondary and tertiary consumers when they eat other consumers
57
carbon cycle: what happens to the carbon when an organism dies
- all living organisms die
- and the carbon compounds in the dead organisms are digested by microorganisms called decomposers, e.g. bacteria and fungi
- feeding on dead organic matter = saprobiontic nutrition
58
carbon cycle: how does carbon return to the air
- air and water
- all living organisms (even decomposers) carry out respiration
- which produces CO2 gas
59
carbon cycle: what happens to the carbon in dead organic matter when there are no decomposers nearby
- e.g. deep ocean or bogs
- their carbon compounds are turned into fossil fuels over millions of years by heat and pressure
- the carbon in the fossil fuels (oil and coal) is released when they are burnt
- called combustion
60
carbon cycle: other than combustion, how else can carbon be released from rocks
- as well as coal, other rocks can also be formed from dead organic matter deposited on the sea floor
- e.g. rocks like limestone and chalk are mainly composed of CaCO3
- this comes from marine organisms like crabs, muscles, sea urchins and coral that utilise this compound in their development, e.g. to form shells
- carbon can also return to the atmosphere from these rocks by being drawn down deep into the earth's crust by the movement of tectonic plates
- here they undergo chemical changes and release CO2
- which is returned to the atmosphere by volcanoes
61
carbon cycle: explain chemical weathering
- rocks containing carbon can also eventually become land
- which is then weathered (broken down by the exposure to the atmosphere)
- this can occur chemically by rainwater (which is slightly acidic due to the CO2 dissolved in it)
- or physically (e.g. by plant roots and animals)
- chemical weathering causes mineral ions and bicarbonate HCO3- ions to be released from rocks into solution or enter groundwater
- here they are transported into rivers and oceans, where they combine with carbon containing compounds such as CaCO3
62
carbon cycle: explain how carbon can directly enter the ocean
- CO2 can dissolve directly into the ocean from the atmosphere
- is transported in the ocean by deep underwater currents (physical process)
- CO2 can remain in these slow-moving currents for hundreds of years
- before eventually returning to the surface and being released back into the atmosphere
63
why do plants and animals need nitrogen
to make proteins and nucleic acids (DNA and RNA)
64
what is the only way animals and plants can use nitrogen
- the atmosphere itself is made up of about 78% nitrogen
- but plants and animals cannot use it in that form
- need bacteria to convert it into nitrogen compounds first
65
what does the nitrogen cycle show
how nitrogen is converted into a useable form and then passed on between different living organisms and the non-living environment
66
what does the nitrogen cycle contain
- food chains (as nitrogen is passed on when organisms are eaten)
- 4 different processes involving bacteria:
- nitrogen fixation
- ammonification
- nitrification
- denitrification
67
what is a decomposer
an organisms that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones available to photosynthetic producers in the ecosystem
68
why can decomposers be called saprotrophs
they obtain their energy from dead or waste organic material, called saprotrophic nutrition
69
how do decomposers digest their food
- digest their food externally
- secrete enzymes onto dead organisms or organic waste matter
- enzymes break down complex organic molecules into simpler soluble molecules
- decomposers can absorb these molecules
- through this process, they can also released stored inorganic compounds and elements back into the environment
70
what are detritivores
- another class of organisms involved in decomposition
71
how do detritivores help with decomposition
- speed up decay by feeding on on detritus (dead and decaying material)
- they break it down into smaller pieces of organic material
- this increases the surface area for decomposers to work on
- e.g. woodlice breaking down wood and earthworms breaking down dead leaves
72
what type of digestion do detritivores perform
internal digestion
73
explain the process of nitrogen fixation
- when nitrogen gas from the atmosphere is tuned into ammonia by bacteria
- such as Rhizobium and Azotobacter
- this ammonia can then be used by plants
74
where are Rhizobium found
- inside root nodules (growths on the roots)
- of leguminous plants
- e.g. peas, beans, and clover
75
explain the symbiotic/mutualistic relationship between Rhizobium and plants
- the bacteria provide the plant with nitrogen compounds
- plants provide them with carbohydrates
76
where is Azotobacter found
- found living in the soil
- do NOT have a mutualistic relationship with plants
77
explain the process of ammonification
- nitrogen compounds from dead organisms are turned into ammonia
- by decomposers
- which go on to form ammonium ions
- animal waste (urine and faeces) also contain nitrogen compounds
- these are also turned into ammonia by decomposers
- and go on to form ammonium ions
78
what is the process of nitrification
- when ammonium ions in the soil are changed into nitrogen compounds that can be used by plants
- called nitrates
- 2 step process:
- first, nitrifying bacteria called Nitrosomonas changes ammonium ions into nitrites
- then, other nitrifying bacteria called Nitrobacter change nitrites into nitrates
79
what is the process of denitrification
- when nitrates in the soil are converted into nitrogen gas
- by denitrifying bacteria
- which use the nitrates in the soil to carry out respiration
- and produce nitrogen gas
- happens under anaerobic conditions
- where there is no oxygen, like waterlogged soils
80
what are other ways, other than bacteria and food chains, that nitrogen can enter an ecosystem
- by lightning (which fixes atmospheric nitrogen)
- by artificial fertilisers (produced from atmospheric nitrogen on an industrial scale in the Haber process)
81
what is succession
the process by which an ecosystem changes overtime
- the biotic conditions (plant and animal communities) change as the abiotic conditions (water availability) change
82
what are the 2 types of succession
primary and secondary
83
what is primary succession
- occurs on land that has been newly formed or exposed
- e.g. where a volcano has erupted to form a new rock surface
- e.g. where the sea level has dropped exposing a new area of land
- NO SOIL OR ORGANIC MATERIAL TO START WITH (just bare rock)
84
what is secondary succession
- occurs on land that has been cleared of all plants
- but where the SOIL REMAINS
- e.g. after a forest fire
- e.g. where a forest has been cut down by humans
85
when does primary succession start
- when a species colonises a new land surface
- seeds and spores are blown in by the wind
- and begin to grow
86
what is the pioneer species
the first species to colonise the area
- make up the first stage of succession
87
what occurs during the first stage of succession
- the abiotic conditions are hostile (harsh)
- e.g. as there is no soil to retain water
- only the pioneer species can grow
- as they are specialised to cope with the harsh conditions
- e.g. marram grass is able to grow in sand dunes near the sea because it has deep roots to get water, and can tolerate the salty environment
88
what happens after the first stage of succession, where it was just the pioneer species present
- the pioneer species change the abiotic conditions
- they die and microorganisms decompose the dead organic material (humus)
- this forms basic soil
89
what happens in succession once soil has been formed
- the conditions become less hostile
- e.g. the basic soil helps to retain water, which means new organisms can move in and grow
- these then die and decompose, adding more organic material
- this makes the soil even deeper and richer in minerals
- so larger plants like shrubs can start to grow in this deeper soil, which retain even more water
- as more plants move in, they create more habitats, so more animals move in
90
what is the difference in the steps between primary and secondary succession
- primary and secondary occur in the same way
- but in secondary succession, there is already a soil layer
- so succession just begins at a later stage
- the pioneer species here would be larger plants
- like shrubs
91
what occurs in every stage of succession once plants and animals are already present at a basic level
- at each stage
- different plants and animals which are better adapted for the improved conditions move in
- outcompete the plants and animals that are already there
- and become the dominant species in the ecosystem
92
explain what happens to the complexity of an ecosystem at each stage of succession
- the ecosystem becomes more complex at each stage
- new species move in alongside existing species
- so the species diversity (the number of different species and the abundance of each species) increases
93
what happens to biomass at each stage of succession
- amount of biomass also increases
- as plants at later stages are larger and more dense, e.g. woody trees
94
what is the final stage of succession
- called the climax community
- the ecosystem is supporting the largest and most complex community of plants and animals it can
- it will not change much more
= in a steady state
95
explain the primary succession that would take place from bare rock to woodland
1) PIONEER SPECIES colonise the rocks, e.g. lichens grow on and break down rocks, releasing minerals
2) the lichens DIE and DECOMPOSE, helping to form a thin soil, which thickens as more organic material is formed, so other species like mosses can grow
3) larger plants that need more water can move in as SOIL DEEPENS, like grassses and small flowering plants, and the soil will continue to deepen as the larger plants die and decompose
4) shrubs, ferns and small trees begin to grow, OUT-COMPETING the grasses and smaller plants to become the DOMINANT species, and diversity increases
5) finally, soil is deep and rich enough in nutrients to support large trees, which become the dominant species and the CLIMAX COMMUNITY is formed
96
other than bare rock, where else can succession begin
- sand dunes
- salt marshes
- lakes
97
what does the species making up the climax community of an ecosystem depend on
- depend on the climate of that ecosystem
- the climax community for a particular climate is called the climatic climax
98
what is likely to be the climatic climax of a temperate climate
- plenty of water available
- mild temperatures
- not much change between season
- large trees, as they can grow in these conditions once deep soils have developed
99
what is likely to be the climatic climax of a polar climate
- not much water available
- temperatures are low
- and massive changes between the seasons
- large trees can never grow in these conditions
- climatic climax likely to contain only herbs and shrubs
- but still the climax community
100
why may biodiversity decrease slightly as succession reaches the climax community
- decreases towards the end of succession
- as the dominant species out-compete the other species
- resulting in their elimination (e.g. pioneer species)
- more successful the dominant species, the less biodiverse and ecosystem is
101
what is a plagioclimax
the climax community that develops when succession is stopped artificially
- e.g. via human activities which prevent succession, stopping the normal climax community from developing
102
what is deflected succession
when succession is prevented by human activity, but the plagioclimax that develops is one that is different to any of the natural stages of the ecosystem
- so the path of succession has been deflected from its natural course
103
what are examples of deflected succession
- a regularly mown grassy field wont develop woody plants,even if the climate of the ecosystem could support them
- the growing points of the woody plants are cut off by the lawnmower, so the larger plants cannot establish themselves
- only the grasses can survive being mowed
- so the climax community is the grassy field
- grassy field is not a natural stage, as there should still be other things like small flowering plants present
- so succession has been deflected
104
other than mowing, what other things can be used to deflect succession
grazing and mowing grassy fields
105
what 2 factors are you looking at when investigating populations of an ecosystem
abundance and distribution of species in a particular area
106
what is species abundance, and what are ways of determining it
the number of individuals of one species in a particular area
- the abundance of mobile organisms (that can move) and plants can be estimated by counting the number of individuals in the sample taken #
- percentage cover can also be used to measure the abundance of plants, where you are concerned with how much of the area you are covering is covered by a species
107
what is species distribution
where a particular species is within the area you are investigating
108
why would you take a sample from the area you are investigating
measuring the number and distribution of every species in an entire area you are investigating would be too time-consuming
109
how do you take samples
- choose an area to sample (small area within the area being investigated)
- make sure the area is random, to avoid bias
- use an appropriate technique to take a sample of the population
- repeat the process, taking as many samples as possible [more precise estimate for the total area]
- estimate the number of individuals in the whole area by taking the average of the data collected in each sample, and multiplying it by the size of the whole area
- percentage cover can also be estimated through taking averages of the samples
110
what is important to consider when taking samples of a specific species
- you need to identify them correctly
- use an identification key to help
111
what is a frame quadrat, and how is it used
- a square frame divided into a grid of 100 smaller squares through strings attached through frames
- placed on the ground at random points within the area you are investigating
- can be done through selecting random coordinates
- the number of individuals of each species is recorded for each quadrat
112
how can you measure percentage cover using a frame quadrat
- counting how much of the quadrat is covered by a species
- you count the squares that are more than half-covered
- is a quick way to investigate populations as you don't need to count all the individual plants
113
explain use of frame quadrats for small and large species
- useful for quickly investigating areas with species that fit within a small quadrat
- usually 1m by 1m
- areas with larger plants and trees need very large quadrats
- large quadrats aren't always in a frame
- can be marked out by a tape measure
114
what is a point quadrat and how is it used
- a horizontal bar on two legs with a series of holes at set intervals along its length
- placed on the ground at random points within the area you are investigating
- pins are dropped through the holes in the frame and every plant that each pin touches is recorded
- if a pin touches several overlapping plants, all of them are recorded
- the number of individuals of each species are recorded
115
how can a point quadrat be used for percentage cover
by calculating the number of times a pin has touched a species as a percentage of the total number of pins dropped
116
where are point quadrats especially useful
in areas with a lot of dense vegetation close to the ground
117
what are line transects used to find
the distribution of plant populations across an area
- e.g. from a hedge towards the middle of the field
118
what are the 3 different types of transects
- line transect
- belt transect
- interrupted transect
119
what is a line transect
- a tape measure is placed along the transect and the species that touch the tape measure are recorded
120
what is a belt transect
- data is collected along a transect using fram quadrats placed next to eachother
121
what is an interrupted transect
- instead of investigating the whole transect (like in line and belt)
- measurements are recorded at intervals
- e.g. by placing point quadrats at right angles to the transect at set intervals along its length, e.g. every 2 metres
