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Biology Module 6 > ecosystems > Flashcards

ecosystems Flashcards

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1
Q

What is an ecosystem

A
  • Ecosystem is a community of animals, plants, and bacterial interrelated with the physical and chemical environment
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2
Q

what is an abiotic factor

A

non living components of an ecosystem than affect other living organisms

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3
Q

what is a biotic factor

A

environmental factors associated with living organisms in an ecosystem that affect each other

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4
Q

what is a habitat

A

a place where an organism lives

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5
Q

what is a population

A

– all the organisms of one species who live in the same place at the same time and who can breed together

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6
Q

what is a community

A

all the populations of different species who live in the same place at the same time and who can interact with each other

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7
Q

what is a niche

A

the role of each speices in an ecosystem is its niche

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8
Q

ecosystems can be on ….

A

on a large scale such as an African grassland, a medium scale such as a playing field or on a small scale like a rock pool

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9
Q

what are the components of an ecosystem

A
  • habitat
  • population
  • community
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10
Q

why is it almost impossible to define an organisms niche entirely

A
  • because each organism interacts with both living and non-living organisms
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11
Q

what things are used to describe a niche

A
  • how and what it feeds on
  • what it excretes
  • how it reproduced
  • it is impossible for two species to occupy the same niche in the same ecosystem
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12
Q

what are biotic factors

A
  • Producers – plants and some photosynthetic bacteria which supply chemical energy to all other organism
  • Consumers = primary consumers are herbivores which feed on plants and which are eaten by carnivorous secondary consumers and these are eaten by carnivorous tertiary consumers
  • Decomposers – decomposers feed on waste material or dead organisms
  • Because these components of the ecosystem require their own source of materials they can affect other organisms food supply and can be responsible for predation and disease
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13
Q

draw the graph for the effect of an abiotic factor on an organisms acitivty when the abiotic factor is lethal at both extremes

A

draw it

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14
Q

draw the graph for the effect of an abiotic factor when it is lethal at one one extreme

A

draw it

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15
Q

describe abiotic factors

A
  • These are the non living components of an ecosystem such as Ph, relative humidity, temperature and the concentration of pollutants these can vary in space and time and these factors can also include disturbance to the ecosystem by other factors such as turbulence and storms
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16
Q

abiotic can be…

A

influenced by biotic

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17
Q

why are ecosystems dynamic

A
  • Because ecosystems can change they are therefor dynamic
  • Non living elements change and the living elements grow and die, with populations of particular speices rising and failing
  • Living things in an ecosystem interact with each other and there physical environment
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18
Q

what are the three type of changes in ecosystems that affect population size

A
  • cyclic changes
  • directional changes
  • unpredictable and erratic changes
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19
Q

descirbe cyclic changes

A

these changes repeat themselves in rhythm, for example movement of tides and changes in day length are cyclic, for example movement of tides and changes in day length

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20
Q

describe directional changes

A

these changes are not cyclic, they go in one direct and tend to last longer than the lifetime of organisms within the ecosystem, within such change particular variables continue to increase or decrease

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21
Q

describe unpredictable and erratic changes

A

these have no rhythm and no constant direction for example changes may include the effects of lightning or hurricanes

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22
Q

each level of a food chain is a

A

trophic level

23
Q

what can tracking biomass changes in a food chain help us do

A
  • track the movement of materials and energy through the food chain
24
Q

what happens to materials within an ecosystem

A
  • Materials are constantly recycled within an ecosystem – nutrient cycles such as the nitrogen cycle and carbon cycle, energy is not recycled but it does flow through the ecosystem
25
Q

describe pyramids of biomass

A
  • When the organism are about the same size this means there will be fewer consumers at the higher levels, ecologists draw a pyramid of numbers to represent this idea, the area of each bar in the pyramid is proportional to the number of individuals as an approximation for the total biomass at that level, pyramids can be drawn for individual food chains or for an ecosystem as a whole
26
Q

how is biomass lost

A
  • At each trophic level organisms need energy to carry out life processes, respiration releases energy from organic molecules like glucose and some of this energy is converted to heat and materials are lost in carbon dioxide and water
  • Biomass is also lost from a food chain in dead organisms and waste material which is then only available to the decomposers such as fungi and bacteria, this waste material also includes parts of animals and plants that cannot be digested by consumers such as bone and hair therefore biomass is less at higher levels of the food chain
27
Q

How do you calculate the efficiency of biomass transfer

A
  • Counting the number of organsism does not always provide an accurate measure of how much biomass exists at each level
  • Better to draw a pyramid of biomass where the area of each bar is proportional to the dry mass of all the organisms at that trophic level
  • The ecologists collects all the organisms at puts them in an oven at 80 degrees until all water in them has been evaporated they then check this by periodically finding the mass of the organsims, once the mass stops reducing they can be certainm that all the water has been removed, this is rather destructive to the ecosystem beign studies so ecologists just measure the wet mass of the organisms and calculate the dry mass based on previsouly published data
  • Biomass at higher trophic level/biomass at lower trophic level x 100
28
Q

the rate at which energy passes through each trophic level in a food chain is a..

A

measure of its productivity

29
Q

what is gross primary productivity

A
  • Gross primary productivity is the rate at which plants convert light energy into chemical energy through photosynthesis,
30
Q

why is photosynthesis not energy efficient

A
  • plants cant use all the light energy that reaches their leaves, some is the wrong wavelength and some is reflected and some passes straight through
  • some parts of food are not eaten by organism
  • some parts of food is completely indiegstable
  • some is excreted

in optical conditions only 40% of light energy from the sun enters the light reaction of photosynthesis and only half of this is used in glucose production, only 2/3 of the glucose is then used for production of starch, cellulose, lipids and proteins which contribute to growth and the rest is respired

31
Q

what is net primary productivity

A

this is the amount of energy that is available to the next trophic level

  • gross productivity - respiratory loss
32
Q

how humans can improve primary productivity

A
  1. Light levels limit rate of photosynthesis and production of biomass, some crops are planted early to provide a longer growing season to harvest more light and others are grown under light banks
  2. As well as irrigating crops, drought resistant strains have been bred , water is a reactant in photosynthesis when glucose is produced
  3. Growing plants in greenhouses provides a warmer temperature and increases the rate of photosynthesis and increases the rate of production of biomass, planting field crops early to provide a longer growing season also helps to avoid the impact of temperature on the final yield
  4. Lack of available nutrietns slows the rate of production of biomass through photosynthesis, crop rotation can help growing a different crop in each filed on a rotational cycle, this stops the reduction in soil levels of inorganic materials such as nitrates or potassium, many crops have been bred to respond to high levels of fertiliser which provides ammonium, nitrate, potassium and phosphorus
  5. Pests like insects or nematodes eat crop plants, removing biomass from the food chain and lowering the yield, spraying with pesticides may help and some plants have also been bred to be pest resistant or have been genetically modified with a bactierla gene
  6. Fungal disease reduces biomass, fungal root rot, damage xylem vessels, damage foliage through wilt, blight or spotting, damage phloem tubes or damage flowers and fruit. Farmers spray crops with fungicides and many crops have been bred to resist fungal infections, potatoes have been genetically modified to resist potato blight
  7. Competition from weeds for light, water and nutrietns reduces a crops NPP, farmers use herbicides to kill weeds, the herbicide usually binds to an enzyme stopping it from working and leading to a toxic build up of the enzymes substrate
33
Q

how can humans improve secondary productivity

A
  1. Young animal invests a larger portion of its energy into growth than an adult so harvesting animals just before adulthood minimises loss of energy from a food chain
  2. Selective breeding been used to improve animal breeds with faster growth rates, increased egg production and increased milk production
  3. Animals may be treated with antibiotics to avoid unnecessary loss of energy to pathogens and parasites
  4. Mammals and birds waste a lot of energy finding food and keeping their body temperatures stable, zero grazing for pig and cattle farming maximises energy allocated to muscle by stopping the animals from moving about, by suppling food to them and keeping the environmental temperature constant
  5. Grain can be used to feed humans directly
34
Q

what is biomass transfer

A
  • transfer of biomass from one trophic level to another
35
Q

what is trophic level

A
  • the level at which an organism feeds in a food chain
36
Q

what is productivity

A
  • the rate of production of new biomass by producers
37
Q

describe saprotrophic decomposition

A
  1. Saprotrophs secrete enzymes onto dead and waste material
  2. Enzymes digest the material into small molecules which are then absorbed into the saprotrophs body
  3. Having been absorbed the molecules are stored or respired to release energy
38
Q

what happens if bacteria and fungi did not break down dead organisms

A
  • In bacteria and fungi did not break down dead organisms energy and valuable nutrients would remain trapped within dead organism, by digesting microorganism obtain a supply of energy to stay alive and the trapped nutrients are recycled
39
Q

what are the parts of the nitrogen cycle

A
  • nitrogen fixation
  • ammonification and nitrification
  • denitrification
  • recycling carbon
40
Q

describe nitrogen fixing

A
  • Nitrogen unreactive and even though it makes up most of the earths atmosphere it is impossible for plant to use it directly therefore plants need it from fixed nitrogen such as ammonium ions or nitrate ions
  • Nitrogen fixing can occur when lightning strikes or through the haber processes in making fertiliser
  • Nitrogen fixing bacteria – supply the rest of fixed nitrogen AXOTBACTER are bacteria that live freely in the soil and fix nitrogen gas that is in the air within soil using it to make amino acids
  • RHIZOBIUM live inside the root nodules of plants such as peas, beans and clover which are all members of the bean family, these nitrogen fixing bacteria have a mutualistic relationship with the plant, the bacteria provide the plant with fixed nitrogen and receive carbon compounds such as glucose in return
  • Proteins such as leghaemoglobin in the nodules absorb oxygen and keep the conditions anaerobic, under these conditions the bacteria use an enzyme nitrogen reductase to reduce nitrogen gas to ammonium ions that can be used by the host plants
41
Q

describe ammonification and nitirifcation

A
  • Ammonium ions are released through ammonification by bacteria involved in puterfaciton of proteins found in dead or waste organic matter rather than getting their energy from sunlight some chemoautrophic bacteria in the soil obtain it by oxidising nitrites to nitrates this is called nitrification
  • Oxidation requires oxygen so it can only happen in well aerated soils
  • Nitrates can be absorbed from the soil by plants and used to make nucleotide bases and amino acids
42
Q

describe denitirfication

A
  • Other bacteria convert nitrates back to nitrogen gas, when the bacteria involved in growing under anaerobic conditions such as waterlogged soil, they use nitrates as a source of oxygen for their respiration and produce nitrogen gas nitrous oxide
43
Q

describe recycling carbon

A
  • Carbon cycle is driven by process of respiration and photosynthesis
  • Animals plants and microorganism respire to release carbon dioxide
  • Terrestrial plants use gaseous carbon dioxide in photosynthesis, whereas aquatic plant use dissolved carbonates
  • Carbon is exchanged between the air and water when carbon dioxide dissolves in water and then reacts to form carbonic acid, carbon also enters rivers and lakes from weathering of limestone and chalk in the form of hydrogen carbonate
  • Combustion of fossil fuels has increased across the last century so that the balance of the carbon cycle has changed and atmospheric carbon dioxide levels are higher, this change is responsible for global warming
44
Q

what is succession

A

progressive change in a community of organism over time

45
Q

what is a climax community

A

the final stable community that exists after the process of succession has occured

46
Q

what is deflected succession

A

happens when succession is stopped or interfered with, such as by graxing or when a lawn is mowed

47
Q

what is a pioneer species

A

the species that begins the process of succession often colonising an area as the first living things there

48
Q

how does primary succession happen

A
  1. Alage and lichens begin to live on the bare rock this is called pioneer community
  2. Erosion of the rock and a build up of dead and rotting organic material produce enough soil for larger plants like mosses and ferns to grow, these replace or succeed the algae and lichens
  3. In a similar way larger plants succeed these small plants until a final stable community is reached this is called a climax community
49
Q

where does secondary succession take place

A
  • Secondary succession takes place on a previously colonised but disturbed or damaged habitat
50
Q

describe how sand dunes show succession

A
  • Sand dunes display all the stages of succession in the same place at the same time
  • Sea deposits sand on the beach and the sand nearest to the sea is deposited more recently than the sand further away this means that the sand just above the water mark is the strt of the process of succession whereas the sands further away already hosts its climax community
51
Q

describe the stages of sand dune succession

A
  1. Pioneer speices like sea rocket and prickly snadwart colonise the sand just above the high water mark, these can tolerate being sprayed with salty water, lack of fresh water and unstable sand
  2. Wind blown sands builds up around the base of these plants forming a mini sand dune, as plants die and decay nutrients accumulate in this mini dune, as the dune gets bigger plants like sea sandwort and sea couch grass colonise it because sea couch grass has underground stems it helps to stabilise the sand
  3. With more stability and accumulation of more nutrients plants like sea spurge and marram grass start to grow, marram grass is special, it shoots trap wind-blown sand and as the sand accumulates the shoots grow taller and to stay above the growing dune trapping more sand in the process
  4. As the sand dune and nutrients build up other plants colonise the sand, many are leguminous such as hares foot clover and birds foot refoil which convert nitrogen into nitrate, with nitrate available more species colonise the dunes like sand fescue and vipers bugloss which stabilise them further
52
Q

describe ways in which deflected succession can happen

A
  • grazing
  • burning
  • application of fertiliser
  • herbicide
  • exposure to excessive amount of wind
  • human activity
53
Q

what is a plagioclimax

A
  • this is the sub-climax community that results from succession being stopped or interfered with

Biology Module 6 (13 decks)

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