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Biology > 6.3.1 Ecosystems > Flashcards

6.3.1 Ecosystems Flashcards

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1
Q

Define ecosystem

A

all the living organisms found in an area and the non-living aspects of their environment

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2
Q

Define community

A

all the populations of living organisms in a particular habitat

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3
Q

Define population

A

a group of organims of the same species that live in the same place at the same time

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4
Q

Define habitat

A

the natural home or environment of an animal,plant or other organism

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5
Q

Define species

A
  • the smallest and most specific taxonomic group.
  • Can breed to produce fertile offspring
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6
Q

Define ecology

A

the study of the relationships between organisms and their environment

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7
Q

What is meant by ‘ecosystems are dynamic’?

A

dynamic ecosystems are constantly changing

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8
Q

Define biotic factor

A

living components of an ecosystem
e.g. species prescence, population size, competition for food source

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9
Q

Define abiotic factor

A

non-living factors of an ecosystem
e.g. rainfall vol, temp range, light intensity, wind speed

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10
Q

Define edaphic factor

A

factors to do with soil

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11
Q

What are the 3 main soil types?

A

1- clay - fine particles, easily waterlogged, forms clumps when wet
2- loam - different sized particles, retains water but doesnt become waterlogged
3- sandy - coarse, well-separated particles allowing free draining, doesnt retain water and easily erodes

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12
Q

Define food web

A

many interconnected possible routes of energy and biomass through an ecosystem

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13
Q

Define food chain

A

a single possible route of energy and biomass through an ecosystem

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14
Q

Define trophic level

A

each stage in a food chain - a feeding level

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15
Q

What do the arrows represent in a food web?

A

the direction of energy flow

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16
Q

Define heterotroph

A

another name for a consumer (eats plants + animals)

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17
Q

Define consumer

A

organisms that their and energy by feeding on other organisms

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18
Q

Define producer

A

an organism that converts light energy into chemical energy by photosynthesis
- producers are plants

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19
Q

Define primary consumer

A

animals that eat producers in a food chain

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20
Q

Define secondary consumer

A

an animal that eats primary consumers in a food chain

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21
Q

Define tertiary consumer

A

animals that eat secondary consumers in a food chain

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22
Q

Define herbivore

A

animals that eat plants - primary consumers

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23
Q

Define carnivore

A

animals that eat other animals - secondary consumer or higher

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24
Q

Define omnivore

A

animals that eat both plants and other animals

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25
Q

Define detritivore and give 2 examples

A

detrivore - animals that feed on decaying and dead material
e.g. woodlice and earthworms

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26
Q

Define decomposer

A

an organism that feeds on dead organic matter, turning the organic molecules into inorganic ones
e.g. fungi and bacteria

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27
Q

What is the role of detrivores in food webs?

A

detrivores speed up decay by breaking down detritus into smaller pieces
- increasing SA for decomposers to work on

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28
Q

What is the role of decomposers in food webs?

A

decomposers break down dead organisms releasing nutrients back into the ecosystem

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29
Q

Define biomass

A

the mass of living material present in a particular place or in particular organisms

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30
Q

Define dry mass

A

the mass of living material remaining once all the water has been removed

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31
Q

Why is dry mass a better indicator of biomass than fresh mass?

A

dry mass is a more reliable measure of mass as it excludes fluctuating water concentrations

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32
Q

Explain how to calculate the dry mass of each trophic level in a food chain

A

1 - organisms are killed and placed in an oven at 80 degrees c until all the water has evaporated
- this point is indicated by at least 2 identical mass readings

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33
Q

Explain how to experimentally measure the energy content of organic matter?

A

use a calorimeter - burn matter and measure the temperature rise of water

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34
Q

Which units are used for biomass in an ecosystem? - (land and aquatic)

A

land: gm^(-2) grams per metre squared
aquatic: gm^(-3) grams per metre cubed

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35
Q

Explain how pyramids of numbers, biomass and energy - represent data about an ecosystem and the negatives/positives of each when drawing a pyramid

A
  • pyramids of numbers - show number of each organism in a food chain
  • pyramid of biomass - shows mass at each trophic level in a food chain
    - food chain almost always pyramid shaped
  • pyramid of energy - shows energy available frokm each level
    - always pyramid
  • numbers - +easy to count - hard to draw due to variation
  • biomass - +easy to draw
  • energy - -hard to calculate
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36
Q

Which units are used for the energy at each trophic level in a food chain and explain why these units are appropriate?

A
  • kJm^(-2)yr^(-1) Kilojoules per metre squared per year

appropriate -
per year to account for fluctuations in photosynthetic production and feeding patterns

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37
Q

How is energy transferred from one trophic level to the next?

biomass and the energy contain within its carbon compounds is transferred as…..

A

….. organisms feed on eachother.
- when animals eat, only a small proportion of the food is converted into new tissue (biomass)
- therefore only a small proportion of the energy is available for the next level to eat

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38
Q

Define ecological efficiency

A

the efficiency in which biomass/energy is transfered from one trophic level to the next

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39
Q

Write an equation on how to calculate ecological efficiency

A

calculated by:
- dividing energy/biomass available after the transfer BY the energy/biomass available before the transfer x 100 = %

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40
Q

What are 3 reasons why producers only convert 1-3% of of the sunlight they recieve into chemical energy and hence biomass (tissue)?

A

1- factors may limit photosynthesis like water avaliability
2- a proportion of the energy is lost bc its used for photosynthetic reactions
3- not all of the light energy available is used for photosynthesis
- approx 90% reflected - some transmitted through the leaf
- some unusable wavelength

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41
Q

Define gross production

A

the total solar energy that plants convert to organic matter

42
Q

Define net production

A

the amount of energy available to the next trophic level

43
Q

Define respiratory losses

A

the energy used in respiration so therefore not available to the next trophic level

44
Q

Write an equation to link net production, gross production and respiratiory losses

A

net production = gross production - respiratory losses

45
Q

Define primary production

A

generation of biomass in a producer

46
Q

Define secondary production

A

generation of biomass in a consumer

47
Q

Explain 4 reasons why consumers at each trophic level convert only a small amount of the biomass in the tropic level below (their food) to their own organic tissue

A

1- not all of the biomass of an organism is eaten e.g plant roots not consumed
2- some energy is transferred to the environment as metabolic heat
- bc of movement and respiration
3- some parts of an organism are eaten but are indigestable -
- parts (and their energy) egested as faeces
4- some energy is lost from the animal in excretory materials such as urine

48
Q

Draw, label and annotate, a diagram showing the flow of energy through trophic levels and out of the food chain.

A
  • energy lost at every level as heat from respiration
  • all dead matter through decomposers and detrivores who also produce heat
49
Q

Why does biomass decrease at each trophic level in a food chain?

A
  • each level recieves less energy than the level before due to energy losses such as in respiration
50
Q

Why are food chains with more than 4 trophic levels rare?

A

there is not enough energy available as biomass to sustain another tier of organisms

51
Q

How have humans manipulated energy transfer through trophic levels in the farming of plants and animals to our advantage?

A

Plants+Animals
1 -provide with abiotic conditions needed to thrive
e.g. watering+warmth+nutrients (greenhouses+stables)
2 - Remove competition from other species
e.g. using pesticides
3 - remove threat of predators
e.g. barriers like fences
4 - minimise trophic levels so least amount of energy is lost in transfer as possible
e.g. agriculture -
–farming animals (3 trophic levels)
- producers (animal feed) -primary consumers (livestock) - secondary cons(humans)
— human plant consumption (2 trophic levels)
- producers (crops) - primary consumers (humans)

52
Q

What is the equation for calculating ecological efficiency?

A

ecological efficiency =
biomass available after transfer/ biomass available before the transfer X100

53
Q

Compare the movement of energy through an ecosystem, with the movement of nutrients like nitrogen and carbon

A
  • energy moves through ecosytsmes in a linear way + is always replenished at the start by the sun
  • nutrients like nitrogen and carbon are recycled round the ecosystem
  • bc there is no large external source constantly replenishing them
54
Q

Draw, label and annotate a diagram of the nitrogen cycle.

A

snaprevise flashcard

55
Q

What is the nitrogen cycle? What are the 4 processes called?

A
  • the movement of nitrogen by various processes
    (happens as organisms need it but cannot take it up in its natural form)
    1- Nitrogen fixation
    2- Nitrification
    3- Denitrification
    4- Ammonification
56
Q

What is the 1st step of the nitrogen cycle called?

A

Nitrogen fixation

57
Q

Explain the first step of the nitrogen cycle?

A

NITROGEN FIXATION:
1 - nitrogen fixating bacteria AZTOBACTER and RHIZOBIUM contain enzyme nitrogenase which does:
2 - atmospheric nitrogen N2 combines with H2 to produce ammonia (NH3)
2 - ammonia (NH3) can be absorbed + used by plants

58
Q

What are the 2 nitrogen-fixing bacteria called? where are they found? and which enzyme do they contain?

A
  • Azotobacter - in the soil
  • Rhizobium - in root nodules -(grow on roots of legume plants)
  • contain enzyme nitrogenase
59
Q

What is the 2nd step of the nitrogen cycle called?

A

Nitrification

60
Q

Explain the 2nd step of the nitrogen cycle?

A

NITRIFICATION:
- conversion of ammonium compounds in the soil into nitrates and nitrites using nitrifying bacteria
1- nitrifying bacteria like Nitrosomonas oxidise ammonium compounds into nitrites (NO2-)
2- nitrobacter oxidise nitrites into nitrates (NO3-)

61
Q

In which form does nitrogen enter the plant the most and why?

A

As nitrate ions e.g. NO2- and NO3- bc they are highly soluble

62
Q

What is an example of nitrifying bacteria used in nitrification?

A

Nitrosomonas

63
Q

What is the 3rd step of the nitrogen cycle called?

A

Denitrification

64
Q

Explain the 3rd step of the nitrogen cycle?

A

DENITRIFICATION:
- if there is absence of oxygen e.g. waterlogged soils
1- denitrifying bacteria covert nitrates in the soil back to nitrogen gas
NO3 –> N2

65
Q

Under only which state does denitrification happen?

A

only in anaerobic conditions

66
Q

How do denitrifying bacteria convert nitrates into nitrogen gas?

A

by using nitrates as a source of energy for respiration – and nitrogen gas is released

67
Q

What is the 4th step of the nitrogen cycle called?

A

Ammonification

68
Q

Explain the 4th step of the nitrogen cycle?

A

AMMONIFICATION:
1 - decomposers convert nitrogen-containing molecules (in dead organisms, faeces+urine) into ammonium compounds

69
Q

What is the importance of decomposers in the recycling of matter in ecosytems ?

A
  • decomposers break down the organic matter into small inorganic molecules - that are then used by producers
    C + N elements cant be used directly
70
Q

What is the importance of detritivores in the recycling of matter in ecosytems ?

A
  • detritvores speed up the decay process by breaking down organic material into smaller pieces (larger SA) for decomposers to work on
71
Q

Define nitrogen fixation

A

conversion of nitrogen gas into ammonium compounds

72
Q

Define nitrification

A

conversion of ammonium compounds into nitrites and nitrates

73
Q

Define denitrification

A

conversion of nitrates into nitrogen gas

74
Q

Define ammonification

A

conversion of nitrogen compounds in dead organic matter/waste into ammonium compounds by decomposers

75
Q

Name the micro-organisms involved in the nitrogen cycle and state the nitrogen-containing molecule they use and the nitrogen-containing molecule they produce.

A

Nitrogen fixing bacteria (Nitrogen to ammonia) :
- Rhizobium in root nodules
- Azotobacter in the soil
Nitrifying bacteria :
- Nitrosomonas - ammonia to nitrites
- Nitrobacter from nitrites to nitrates
Denitrification
- Pseudomonas denitrificans - nitrates to nitrogen

76
Q

Draw and label and annotate a diagram of the carbon cycle

A

snap revise flashcard

76
Q

What is the carbon cycle?

A

when carbon is recylced through biotic and abiotic factors of the ecosytem, in the form of CO2/fixed in organic molecules

77
Q

Why do CO2 levels in the atmosphere vary throughout a 24hr period, seasonally and over many years

A
  • light intensity effects - rate of photosynthesis and therefore rate of use of CO2 varies
  • at night CO2 levels higher as respiration continues, photosynthesis doesnt
  • CO2 levels lower in summer bc more light more photosynthesis
78
Q

What are 2 reasons why CO2 levels in the atmosphere have increased significantly over the last 200 years?

A

1- Industry - increased burning of fossil fuels -more CO2 released
2- Deforestation - fewer large areas of trees - less photosyntheis - less CO2 removed from atmosphere - cleared forest burnt = CO2

79
Q

How do scientists gather data about the atmospheric carbon dioxide levels and temperature 1000s of years ago?

A
  • look at ice poles formed 1000s yrs ago and never melted
  • air bubbles trapped in ice tested
80
Q

In the carbon cycle what happens to the dead organic matter and where does its carbon end up?

A

dead organic matter broken down by dcomposers and carbon end up in soil + atmosphere

81
Q

Define succession

A

the directional change in communities over time due to habitat changes

82
Q

Define primary succession

A

formation of a community on new bare land/no soil/no organic matter

83
Q

Define secondary succession

A

formation of a community on land with soul but no plant or animal species

84
Q

Define deflected succession

A

when the direction of succession is affected by farming or other human activities
e.g. grazing, mowing, burning crops

85
Q

Define pioneer species

A

the first organisms to colonise bare land
e.g. lichen, algae

86
Q

Define climax community

A
  • the final stage in succession, the community is said to be in stable state
87
Q

Define plagioclimax

A

stage in succession where artificial/natural factors prevent the natural climax community from forming

88
Q

What are 5 adaptations of pioneer species that enable them to colonise bare land?

A

1- ability to produce lots of speeds/spores - are blown by the wind into the ‘new land’
2- seeds that germinate quickly
3- ability to photosynthesise to produce own energy
4- tolerant to extreme environments
5- ability to fix nitrogen from the atmosphere - adding to mineral content of the soil

88
Q

What effect do pioneer species have on the environment?

A

as they die:
their organic matter makes the environment more able to support other species - creates humus for soil (nutrients etc)

89
Q

How does the conditions of the soil change as succession occurs and why?

A
  • weathering of bare rock produces particles that form basis of soil
  • organisms of pioneer species die and decompose releasing small organmic products into the soil - humus
90
Q

Explain why succession occurs

A

as a result of changes to the Environment (abiotic factors)
- causes plant and animal species to change

91
Q

Define dominant species

A

the most abundant species in an ecosystem

92
Q

Describe and explain the change in niche number and number of species (and so biodiversity) present as succession progresses

A

-niche number and biodiversity increase as succession continues
- as succession continues more organisms are available to eat and be eaten
- biodiversity can dip as climax community forms if a dominant species outcompetes others

93
Q

What does niche mean?

A

the particular role a species has in its habitat is its niche

94
Q

Why is secondary succession more likely to occur more quickly than primary succession

A

soil already present so there is no time spent eroding rock to form any soil

95
Q

What are 3 reasons why deflected succession may occur?

A
  • grazing + trampling of vegetation by domesticated animals
  • removing existing vegetation to plant crops - crop becomes climax /final community
  • burning to clear forests - often leads to increase in biodiversity as provides space+nutrient rich ash for other species to grow
96
Q

How can the abundance of plants be estimated? and how can the population size be calculated from this?

A

1- sample with quadrats
2- multiply up to the size of the whole area

97
Q

Describe how the caputre-mark-release-recapture technique can be used to estimate the population size of an animal species

A
  • capture as many possible and mark them
  • release and recapture as many as possible
  • proportion marked will be same for entire population
98
Q

What is the equation for the lincoln index to estimate the population size of an animal species

A

estimate of population size =
(number marked x number recaptured)/number of recaptured marked

99
Q

What are the assumptions made when using the lincoln index to estimate population size?

A
  • population is closed - no immigration/emmigration
  • time between samples must be small compared to life span (no deaths)
  • marked organisms must mix completely with the rest of the population between sampling

Biology (32 decks)

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