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Module 6- Genetics and Ecosystems > 6.5- ecosystems > Flashcards

6.5- ecosystems Flashcards

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1
Q

Define ecosystems

A

A community of animals, plants and bacteria, and ow they interrelate with the physical and chemical environment (interaction between biotic and abiotic factors)

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2
Q

Define habitat

A

The place where organisms live

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3
Q

Define population

A

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

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4
Q

Define 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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5
Q

Describe niche’s

A
  • the role of a species in an ecosystem
  • impossible to define an organisms niche specifically because each one interacts with living and non-living things
  • impossible for 2 species to occupy exactly the same niche in the same ecosystem
  • allows species to coexist
  • can be how and what it feeds on, what it excretes and how it reproduces
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6
Q

What are 2 types of factors that affect ecosystems

A
  • abiotic- effects of the non-living components of an ecosystem
  • biotic- living elements
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7
Q

Name biotic factors that affect organisms

A

Main:
- competition
- disease
- predators

Others:
- Parasitism
- Levels of producers-plants/ consumers (primary (herbivores, secondary, tertiary)/ decomposers (bacteria, fungi, some animals)

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8
Q

Describe abiotic factors

A
  • pH
  • relative humidity
  • temperature
  • concentration of pollutants
  • wind speed
  • light levels
  • amount of rainfall
  • may also include disturbance to ecosystems e.g. by storms and turbulence
  • can also be influenced by biotic factors- e.g. canopy of trees in a rainforest affects rainfall and sunlight
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9
Q

Describe species performance in relation to extremes of abiotic factors

A
  • may be lethal levels at each end- has an optimum- generalised curve- e.g. pH and temperature
  • alternatively, may not be a lethal level at either end- e.g. pollutant level- not standard curve
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10
Q

Name a quality of ecosytsems

A

dynamic

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11
Q

Describe why ecosystems are dynamic, name 3 types

A
  • they change
  • abiotic elements vary and change
  • living elements are born/die- population sizes rise/fall
  • as living things interact with each other and their physical environment, any small change to 1 can affect the other e.g. predator-prey relationships, levels of nitrogen
  • 3 types of changes (that affect population size)- cyclic, directional, erratic/unpredictable
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12
Q

Describe cyclic changes to ecosystems

A
  • changes that repeat themselves in rhythm
  • e.g. movement of tides, time of day
  • fluctuations of predator/prey
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13
Q

Describe directional changes to ecosystems

A
  • go in 1 direction
  • tend to last longer than the lifetime of organisms in the ecosystem
  • particular variables continue to increase/decrease
  • e.g. deposition of slit in an esturary erosion on a coastline
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14
Q

Describe unpredictable/ erratic changes to ecosystems

A
  • no rhythm or constant direction
  • e.g. effects of lightning or hurricanes
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15
Q

Describe how living things accommodate for the dynamic nature of organisms

A
  • e.g. small mammals hibernate on a cyclical basis to avoid the cold temperatures of winter
  • deciduous trees shed leaves
  • a mammal may change the thickness/colour of its fur between summer/winter
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16
Q

Describe energy and materials in an ecosystem

A
  • materials are constantly recycled within an ecosystem-e.g. nutrient cycles- carbon and hydrogen
  • energy is not recycled- flows through the ecosystem
  • all living things needs energy and materials
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17
Q

Describe energy/materials in producers

A
  • energy is captured by plants in photosynthesis to produce organic molecules like glucose from water and carbon dioxide
  • such energy is released from glucose during respiration
  • the products of photosynthesis are not only used immediately for respiration, but incorporated into tissues and organs such as cellulose (made up of large numbers of glucose molecules)
  • mineral ions are also absorbed through plant roots
  • together, the organic components [such as glucose molecules] and inorganic components [such as mineral ions, but excluding water] of the plant make up its biomass
  • So when a plant is eaten, its biomass is consumed by a primary consumer- biomass flows through food chain
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18
Q

What levels of the food chain called

A

Trophic levels

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19
Q

Name the trophic levels

A

Producer- Primary consumer- secondary consumer- tertiary consumer

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20
Q

What helps us to track the movement of materials and energy through the food chain

A

Tracking how biomass changes in a food chain- can do this for one feed chain or for a whole food web in an ecosystem

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21
Q

Describe food webs

A
  • arrows represent direction of flow of biomass
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22
Q

What happens to biomass at each trophic level

A

Some biomasses lost from a food chain and is therefore unavailable to the Organism at the next trophic level

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23
Q

Describe how biomass is lozt at each trophic level

A
  • living organisms needs energy to carry out life processes such as movement, reproduction, sensitivity, growth, excretion and nutrition
  • respiration releases energy from organic molecules like glucose- some of this energy is eventually converted to heat, and materials are lost in carbon dioxide and water
  • also lost in dead organisms and waste material, which is then only available to decomposers such as fungi and bacteria
  • this waste material also includes parts of animals and plants that cannot be digested by consumers, such as bones and hair
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24
Q

Describe how biomass is lost in producers

A

biomass is lost due to refection of sunlight and certain wavelengths not being used in photosynthesis

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25
Q

What is biomass

A

Living mass derived from energy consumed

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26
Q

Describe the consequence of loss of biomass

A
  • biomass is less at higher levels of the food chain
  • when the organisms in food chain are about the same size, this means there will be fewer consumers at the higher levels
  • also means there can’t be unlimited trophic levels as not enough biomass is conserved to provide energy
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27
Q

Name two types of pyramids used by ecologists

A
  • pyramids of number
  • pyramids of biomass
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28
Q

Describe pyramids of number

A
  • if organisms are roughly the same size, there will be fewer consumers at the higher levels (due to there being less biomass available at the higher levels)- use pyramid of numbers to represent this
  • if not pyramid shaped comma if not pyramid shaped, likely that individuals involved have very different masses
  • area of each bar is proportional to the number of individuals, as an approximation for the total biomass at that level
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29
Q

What are issues with pyramids of numbers, what is used to resolve this

A
  • counting the number of organisms does not always provide an accurate picture of how much biomass exists at each level
  • better approaches to draw a pyramid of biomass
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30
Q

Describe pyramids of biomass

A
  • the area of each bar is proportional to the dry mass of all the organisms at that trophic level
  • to do this properly, an ecologist collects all the organisms an puts them into an oven at 80oC until all the water in them has been evaporated
  • they cheque this by periodically finding the mass of the organisms
  • once the mass stops reducing, they can be certain that all the water has been removed
  • however, this can be destructive to the ecosystem being studied so ecologists often just measure the wet mass of the Organism and calculate the dry mass on the basis of previously published data
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31
Q

What is the equation for the efficiency of biomass transfer

A

Around 10% of biomass from previous trophic level is transferred

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32
Q

Name 2 categories of productivity

A
  • primary/secondary
  • gross/mass
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33
Q

Describe primary vs secondary productivity

A
  • primary- the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances- gross primary productivity is the rate at which plants convert light energy into chemical energy through photosynthesis
  • secondary- The rate at which consumers convert the chemical energy of their food into their own biomass
34
Q

Describe net vs gross productivity

A
  • gross- the overall rate of energy capture
  • net- lower, adjusted for energy used by organisms in respiration/metabolism
35
Q

describe why net primary productivity is low

A
  • Because photosynthesis produces glucose, entry of biomass into the food chain is also inefficient
  • in optimal conditions, only 40% off light energy from the sun enters the light reaction of photosynthesis
  • only half of this is involved in glucose production
  • only 2/3 of the glucose is then used for the production of starch, cellulose, lipid’s and proteins contributing to growth- rest is respired
  • hence, only a small proportion [between one and 8%] of the energy from the sun remains to enter the food chain- net primary productivity is 8%
36
Q

Name factors humans can manipulate to increase primary productivity- the entry of biomass into a food chain

A
  • light levels
  • water availability
  • temperature
  • nutrient availability
  • effect of pests
  • effect of fungi
  • competition
37
Q

describe how humans can manipulate light levels to increase primary productivity

A
  • light levels limit the rate of photosynthesis and hence production of biomass
  • some crops are planted early to provide a longer growing season to harvest more light
  • others are grown under light banks
38
Q

describe how humans can manipulate water levels to increase primary productivity

A
  • water is a reactant in photosynthesis when glucose is produced
  • irrigation
  • drought resistant strains have been bred- e.g. drought-resistance barley in North America, Wheat in Australia, sugar beet in the UK
39
Q

describe how humans can manipulate temperature to increase primary productivity

A
  • growing plants in greenhouse is provides a warmer temperature, 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 final yields- e.g. Winter wheat has a longer growing season than spring wheat
40
Q

describe how humans can manipulate nutrient levels to increase primary productivity

A
  • lack of available nutrients slows the rate of production of biomass through photosynthesis
  • crop rotation can help- growing a different crop in each fields on a rotational cycle
  • this stops the reduction in soil levels of inorganic materials such as nitrate or potassium
  • including a nitrogen fixing crop like peas or beans in that cycle replenishes nitrogen levels
  • many crops have been bred to respond to high levels of fertiliser which provides ammonium, nitrates, potassium and phosphorus
41
Q

describe how humans can manipulate effects of pests to increase primary productivity

A
  • pests like insects or nematodes eat crop plants, removing biomass from the food chain and lowering yields
  • spraying with pesticides may help
  • some plants have also been bred to be pest resistant or have been genetically modified with a bacterial gene (Bt) gene from Bacillus thuringiensis
  • in Bt cotton in the USA, this confers resistance against bollworm. and in maize against corn-borers
42
Q

describe how humans can manipulate effects of fungi to increase primary productivity

A
  • fungal disease reduces biomass- fungi cause:
  • root rot- reducing water absorption
  • damage Xylem vessels- interfering with water transport
  • damage foliage through wilt, blight or spotting- interfering with photosynthesis directly
  • damage phloem tubes- interfering with translocation of sugars
  • damage flowers and fruit- interfering with reproduction
  • farmers spray crops with fungicides
  • many crops have been bred to resist fungal infections- e.g. rhizomania resistance in sugar beet
  • potatoes have been genetically modified to resist potato blight
43
Q

describe how humans can manipulate competition to increase primary productivity

A
  • competition from weeds for night, water and nutrients reduces a crops net primary productivity
  • farmers use herbicides to kill weeds
  • the herbicide’s usually binds to an enzyme, stopping it from working, frequently leading to a toxic buildup of the enzymes substrate
44
Q

Describe why secondary productivity is low

A
  • transfer of biomass between trophic levels is inefficient
  • primary consumers do not make full use of plants biomass
  • some plants die, consumers do not eat every parts of the plants, are they do not digest everything they eat such as cellulose, adjusting a lot in their faeces
  • even when food is digested and absorbed, much of it is respired, with only a small amount contributing to an increase and biomass and being available to the next consumer in the food chain
45
Q

Describe how humans can improve secondary productivity (manipulating biomass transfer)

A
  • young animals invest a larger proportion of its energy into growth than in adults- harvesting animals just before adulthood minimises loss of energy from the food chain
  • selective breeding- used to produce improved animal breeds with faster growth rates, increased egg production and increased milk production
  • animals may be treated with antibiotics to avoid unnecessary loss of energy to pathogens and parasites
  • mammals and birds waste a lot of energy finding foods and keeping that body temperature stable- zero-grazing for pig and cattle farming maximises energy allocated to muscle [meat] by stopping the animals from moving about, by supplying food to them, and by keeping the environmental temperature constant
46
Q

Debates surrounding manipulating transfer of biomass

A
  • although transfer of energy from producers to consumers is inefficient, and grain could be used to feed humans directly as opposed to feeding cattle or pigs first, in some infertile areas grain cannot be grown but animals can survive- e.g. sheep often live on mountainsides- producing food for humans
  • many people have serious concerns about modern farming practises and animal welfare- it decided where the balance lies between welfare and efficient food production is a contentious topic that is constantly kept under review and should include informed public debate
47
Q

How do bacteria and fungi involved in decomposition feed, what does this make them

A
  • sapotrophically
  • sapotrophs
48
Q

Steps of sapotrophic decomposition

A

1) sapotrophs secrete enzymes onto dead and waste material
2) Enzymes digest the material into small molecules, which are then absorbed into the sapotrophs body
3) Having been absorbed, the molecules are stored or respired to release energy

49
Q

Advantage of bacteria/fungi breaking down dead organisms

A
  • if they didn’t, energy and valuable nutrients would remain trapped within the dead organisms
  • by digesting dead and waste material, microorganisms obtain a supply of energy to stay alive, and the trapped nutrients are recycled
50
Q

Name two examples of recycling within ecosystems

A

Carbon and nitrogen cycling

51
Q

Name 4 processes involved in the nitrogen cycle

A
  • ammonification
  • nitrogen fixation
  • nitrification
  • denitrification
52
Q

Nitrogen cycle diagram

A
53
Q

Describe why nitrogen fixation is necessary

A
  • other nitrogen gas makes up 79% of the earths atmosphere, it is very unreactive
  • means it is impossible for plants to use it directly even though it is so abundant
  • plants need a supply of fixed nitrogen such as ammonium ions (NH4+) or nitrates ions (NO3-)
54
Q

Describe different ways in which nitrogen fixation can occur

A
  • lightning strikes
  • Harber process making fertiliser
  • 90% from nitrogen fixating bacteria
55
Q

Name 2 nitrogen-fixating bacteria

A
  • Azotobacter
  • Rhizobium
56
Q

Describe Azotobacter

A

bacteria that live freely in the soil and fix nitrogen gas, which is in the air within soil, using it to manufacture amino acids

57
Q

Describe Rhizobium

A
  • also live inside the root nodules of plants e.g. peas, beans, clover (all part of bean family)
58
Q

Describe the relationship between nitrogen-fixing bacteria and plants

A

Mutualistic- the bacteria provides the plant with fixed nitrogen until receive carbon compounds such as glucose in return

59
Q

Describe the relationship between nitrogen-fixing bacteria and plants

A

Mutualistic- the bacteria provides the plant with fixed nitrogen until receive carbon compounds such as glucose in return

60
Q

Describe how nitrogen fixation occurs

A
  • proteins such as leghaemoglobin in the no and keep the conditions anaerobic
  • under these conditions, the bacteria use nitrogen reductase (enzyme) to reduce nitrogen gas to ammonium ions that can be used by the host plants
61
Q

Name a type of plant that contains organic nitrogen

A

Leguminous

62
Q

Describe ammonification

A
  • ammonium ions are released through ammonification by bacteria involved in putrefaction of proteins found in dead or waste organic matter
  • e.g. urea or organic nitrogen in soil from dead plants
63
Q

Describe the process of nitrification

A
  • chemoautotrophic bacteria don’t obtain energy from sunlight (like photoautotrophic bacteria, algae and plants do)
  • Instead, (Nitrosomonas bacteria) obtain it by oxidating ammonium ions to nitrites- NH4+ –> NO2-
  • others (nicobacter bacteria) obtain it by oxidising nitrites to nitrates - NO2- –> NO3-
  • oxidation requires oxygen- therefore will only happen in well aerated soils
64
Q

Describe the use of nitrates

A

nitrates can be absorbed from the soil plants and used to make nucleotide bases (for nucleic acids) and amino acids (for proteins)

65
Q

Describe denitrification

A
  • other bacteria can convert nitrates back to nitrogen gas
  • when the bacteria involved are growing under anaerobic conditions, such as waterlogged soil, they use nitrates as a source of oxygen for their respiration and produce nitrogen gas (N2) and Nitrous oxide (N2O)
66
Q

Describe the carbon cycle

A
  • cycled between biotic and abiotic components of an ecosystem
  • driven by the processes of respiration and photosynthesis
  • carbon dioxide is the main vehicle for the cycling of carbon between biotic and abiotic components of the cycle
  • animals, plants and microorganisms respire to release carbon dioxide
  • microorganisms are particularly important in the decomposition of dead organisms and waste
  • terrestrial plants use gaseous carbon dioxide in photosynthesis, whereas aquatic plants use dissolved carbonates
67
Q

Describe exchange between air and water in the carbon cycle

A
  • 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
68
Q

Describe a factor which has changed the carbon dioxide levels in the air

A
  • combustion of fossil fuels increased across the last century
  • balance of the carbon cycle has changed- atmospheric carbon dioxide levels are higher
  • this change is responsible for global warming
69
Q

Carbon cycle diagram

A
70
Q

Describe changing ecosystems

A
  • any change in a community of organisms can cause a change in the habitat
  • any change in a habitat can also cause a change in the make-up of the community
  • this helps to explain why gradual directional progressive changes happen in a community of organisms over time- succession
71
Q

Describe changing ecosystems

A
  • any change in a community of organisms can cause a change in the habitat
  • any change in a habitat can also cause a change in the make-up of the community
  • this helps to explain why gradual directional progressive changes happen in a community of organisms over time- succession
72
Q

What is the term for development of a community from bare ground

A

Primary succession

73
Q

Breifly outline primary succession

A

1) Pioneer community live on bare rock- e.g. algae and lichens
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 succeed the algae and lichens
3) In a similar way, larger plants succeed these small plants, until a final, stable community is reached- climax community- in UK, often woodland communities

74
Q

Describe a different type of succession, how this happens

A
  • secondary succession
  • not from bare ground- instead, on a previously colonised but disturbed/damaged habitat
75
Q

Name an example of succession, outline this briefly

A
  • Succession on sand dunes
  • sea deposits sand on the beach- sand nearest to sea is deposited more recently than sand further away
  • means the sand just above the high water mark is at the start of the process of succession, whereas sand much further away already hosts its climax community
76
Q

Succession on sand dunes diagram

A
77
Q

Describe the stages of succession on sand dunes

A

1:
- pioneer species (like sea rocket and prickly sandwort) 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 sand 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 (Ammophila arenaria) start to grow
- marram grass is special- shoots trap wind-blown sand, and as the sand accumulates the shoots grow taller 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 the hares foot clover and birds-foot trefoil, which convert nitrogen into nitrate
- with nitrate available, more species colonise the dunes, like sand fescue and vipers bugloss, which stabilise them further

78
Q

What happens when succession is stopped or interferred with

A

Deflected succession

79
Q

Describe deflected succession

A
  • landscape in UK heavily influences by agriculture- can be hard to work out whether a particular location has reached its climax community
  • e.g. cutting grass keeps it at that stage of succession- could reach climax community of woodland but this is being prevented
  • sub-climax community that results is called a plagioclimax
  • can also be deflected by grazing, burning, application of fertiliser and herbicide, and exposure to excessive amounts of wind
  • succession often deflected by human activities- has been for centuries- can make it hard for preservationists and conservationists to decide which habitats warrant preservation or conservation
80
Q

Calculation of population size (quadrats)

A

mean number of individuals of the species in each quadrat/ fraction of the total habitat area covered by a single habitat

81
Q

Describe how results from using transects can be plotted

A

Kite diagrams:
- can plot distance on X axis and number of individuals on the Y axis
- can also plot graph with abiotic factor on same scale, with factor on the Y axis and distance on X- line up this graph with kite diagram- see how abiotic factor affects distribution and abundance

82
Q

Kite diagram picture

A

Module 6- Genetics and Ecosystems (6 decks)

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