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Biology A-Level -James > Chapter 6.5-Ecosystems > Flashcards

Chapter 6.5-Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

A community of animals,plants and bacteria interrelated with the physical and chemical environment

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2
Q

What’s an example of a large scale ecosystem?

A

African grassland

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3
Q

What is an example of a medium scale ecosystem?

A

Playing field

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4
Q

What is an example of a small scale ecosystem?

A

Rock pool or large tree

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5
Q

What is a habitat?

A

The place where an organism lives

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6
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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7
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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8
Q

What is an organism niche?

A

The role the species plays in an ecosystem

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9
Q

What are biotic factors affecting an ecosystem?

A

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

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10
Q

What are two examples of biotic factors affecting an ecosystem?

A

Predation

Disease

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11
Q

What are abiotic factors affecting an ecosystem?

A

Non-living components of an ecosystem that affect other living organisms.

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12
Q

What are some examples of abiotic factors that affect an ecosystem?

A
  • pH
  • humidity
  • temperature
  • concentration of pollutants
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13
Q

Why are ecosystems described as being dynamic?

A

Ecosystems change a lot

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14
Q

What are the three types of changes in an ecosystem that affect population size?

A
  • Cyclic changes: These changes repeat themselves in a rhythm.
  • Directional changes: These changes are not cyclic. They go in one direction, and tend to last longer than the lifetime of organisms within the ecosystem. Within such change, particular variables continues to increase or decrease.
  • Unpredictable/erratic changes: These have no rhythm and no constant direction.
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15
Q

What is an example of a cyclic change?

A

-the way in which predator and prey species fluctuate

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16
Q

What is an example of a directional change?

A
  • The deposition of silt in an estuary

- erosion of coastline

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17
Q

What is an example of an unpredictable/ erratic change?

A

-effects of lightning or hurricanes

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18
Q

What is meant by biomass transfer?

A

transfer of biomass from one trophic level to another

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19
Q

What is meant by biomass?

A

the total quantity or weight of organisms in a given area or volume.

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20
Q

What are trophic levels?

A

the level at which an organism feeds in a food chain

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21
Q

How is biomass lost at each trophic level?

A
  • living organisms need energy to carry out life processes. Respiration releases energy from organic molecules like glucose. Some of this energy is eventually converted to heat, and materials are lost in CO2 and H20.
  • a lot is egested in their faeces
  • dead organisms and waste material, only available to decomposers such as fungi and bacteria. Waste material included parts of the animal that cant be digested by consumers, such as bones and hair
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22
Q

What is a pyramid of numbers?

A
  • area of each bar is proportional to the number of individuals
  • pyramids of numbers can be drawn for individual food chains or for an ecosystem as a whole
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23
Q

Starting from the bottom up, what type of organisms are in a pyramid of numbers?

A
  • producer
  • primary consumer
  • secondary consumer
  • tertiary consumer
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24
Q

What is a better approach then a pyramid of numbers?

A

-pyramid of biomass (area of each bar is proportional to the dry mass of all the organisms at that trophic level)

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25
Q

How does an ecologist work out an organisms dry mass?

A
  • ecologist collects all the organisms and puts them into an oven at 80 degrees until all the water has been evaporated
  • once the mass of the organism stops reducing, they can be certain that all the water has been removed
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26
Q

What doe ecologists measure instead of organisms dry mass?`

A

wet mass

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27
Q

How do you calculate the efficiency of biomass transfer between trophic levels?

A

Ecological efficiency=(Biomass at the higher trophic level/ Biomass at the lower trophic level) X 100

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28
Q

What does productivity mean?

A

the rate of production of new biomass by producers

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29
Q

What is meant by gross primary productivity?

A

rate at which plants convert light energy into chemical energy through photosynthesis

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30
Q

What is the net primary productivity(NPP)?

A

Gross primary product -respiratory losses

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31
Q

How can light levels and water availability when monitored by humans increase NPP?

A

-light levels:
crops planted earlier to provide a longer growing season
crops grown under light banks
-Water availability:
irrigation of crops
drought-resistant strains have been bred, for example drought-resistant barley in North Africa.

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32
Q

How can temperature and nutrient availability controlled by humans increase NPP?

A

-temperature:
growing plants in greenhouses provides a warmer temperature, increases the rate of photosynthesis, and increases the rate of production of biomass
-nutrient availability:
crop rotation (growing a different crop in each field on a rotational cycle) stops the reduction in soil levels of inorganic materials such as nitrate or potassium
lots of crops have been bred to respond to high levels of fertiliser which provides ammonium, nitrate, potassium and phosphorus.

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33
Q

What are some biotic factors that humans use to increase NPP?

A
  • protection from pests (spraying with pesticides)
  • protection from disease
  • spray plants with fungicides to top fungal growth
  • reduce competition from weeds by using herbicides
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34
Q

What are some ways that humans can manipulate energy transfer and improve secondary productivity?

A
  • harvest animals before adulthood
  • selective breeding, e.g. improved animal breeds with faster growth rates
  • protection against diseases and pests by treatment with antibiotics
  • reduce the distance needed to travel for food by supplying food to the animals
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35
Q

How does energy flow through an ecosystem?

A

materials in an ecosystem are recycled

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36
Q

What is a Saprotrophs?

A

decomposers

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37
Q

What are the steps in 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

Why are saprotrophs important?

A
  • energy and valuable nutrients would remain trapped within the dead organisms.
  • supply of energy is kept alive, and the trapped nutrients are recycled
39
Q

What are the two nitrogen fixating bacteria in the nitrogen cycle?

A
  • Rhizobium bacteria

- Azobacter

40
Q

Why does nitrogen gas have to be fixed?

A

it is very unreactive and impossible for plants to use it directly

41
Q

Where are Rhizobium bacteria found?

A

-found inside the root nodules of plants such as peas, beans and clover

42
Q

What type of relationship does Rhizobium bacteria have plant?

A

mutualistic relationship

43
Q

What is a mutaulistic relationship?

A

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

44
Q

Where are Azotobacter bacteria found?

A

they live freely in the soil

45
Q

Apart from nitrogen fixing bacteria, what are the two other ways in which nitrogen is fixed?

A
  • when lighting strikes

- Haber process in making fertiliser

46
Q

What are the two chemoautotrophic bacteria in the soil?

A

Nitrosomonas

Nitrobacter

47
Q

What do nitrosomonas bacteria do?

A

oxidise ammonium ions (NH4) into nitrites (NO2^-)

48
Q

What do Nitrobacter bacteria do?

A

oxidise nitrites into nitrates (NO3^-)

49
Q

What is the name of the process that converts ammonium ions into nitrites and then into nitrates?

A
  • nitrification

- oxidation of ammonium to nitrite and nitrite to nitrate

50
Q

What are nitrates used for in the soils?

A

absorbed from the soil by plants and used to make nucleotide bases (for nuclei acids) and amino acids (for proteins)

51
Q

What is denitrification?

A

conversion of nitrates back to nitrogen gas by bacteria

52
Q

What is the process in which urea(CO(NH2)2 from excretion is converted into ammonium ions (NH4^+)?

A

ammonification

53
Q

What are the two processes which drive the carbon cycle?

A
  • respiration

- photosynthesis

54
Q

What does nitrogen fixation by the Haber process convert N2(g) into?

A
  • nitrates (NO3^-)

- ammonium ions (NH4^+)

55
Q

What are the roles of decomposers in the carbon cycle?

A

detritus, humus and wastes are decomposed and turned back into carbon dioxide in the air and water

56
Q

What is the role of respiration in the carbon cycle?

A

plants and animals repsire and release carbon dioxide inot the atmosphere

57
Q

What is the role of photosynthesis in the carbon cycle?

A

plants photosynthesis and take in carbon dioxide

58
Q

What are the other ways in which carbon dioxide enters the atmosphere?

A

-combustion of fossil fuels

59
Q

How does carbon enter lakes?

A

weathering of limestone and chalk in the form of hydrogen carbonate

60
Q

How is carbon exchanged between the air and the water?

A

-CO2 dissolves in water and then reacts to form carbonic acid.

61
Q

What is succession?

A

progressive change in a community of organisms over time

62
Q

What are the steps in primary succession?

A
  1. Algae and lichens begin to live on the bare rock (pioneer species).
  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. Larger plants succeed these small plants, until a final, stable community is reached (climax community)
63
Q

What is secondary succession?

A

succession that takes place on a previously colonised but disturbed or damaged habitat (as a result of forest fires, flooding, urbanisation)

64
Q

What is a pioneer species?

A

the species that begin the process of succession, often colonising an area as the first living things there.

65
Q

What is a climax community?

A

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

66
Q

What is primary succession?

A

succession that starts from bare ground

67
Q

What is an example of where primary succession has taken place?

A

island of Surtsey in Iceland

68
Q

As succession takes place what are the changes to the ecosystem?

A
  • more habitats and niches are formed
  • biodiversity increases
  • complex food webs develop and increased biomass
69
Q

Outline the basic stages of succession from sand dunes into grassland and then woodland?

A
  1. Pioneer species colonise colonise the sand just above the high water mark
  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 sand dune As the dune gets bigger, plants like sea sandwort and sea couch grass colonise it. Sea couch grass has stems so helps to stabilise the sand.
  3. Stability increases and accumulation of more nutrients, plants like sea splurge and Marram grass start to grow.
  4. As the sand dune and nutrients build up, other plants colonise the sand.
70
Q

Why is Mariam grass special?

A

its 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.

71
Q

What is deflected succession?

A

happens when succession is stopped or interfered with

72
Q

What are two examples of deflected succession?

A
  • grazing

- burning

73
Q

What is the name of the sub-climax community that results from deflected succession?

A

plagioclimax community

74
Q

In the UK what is the typical climax community?

A

woodland communities

75
Q

What some of the characteristics of pioneer species?

A
  • reproduce asexually
  • tolerate extreme conditions
  • photosynthesise
  • produce spores or seeds that may be dispersed widely
76
Q

What is meant by abundance?

A

the total number of individuals in a species in a given area

77
Q

What is meant by sampling?

A

studying a small, representative area of habitat

78
Q

What is a quadrat?

A

usually a 1 m square, and can have strings across every 10cm, separating it into 100 smaller squares

79
Q

What is a point frame?

A

device with needles that can placed over a quadrat and the number of plants touching the needles can be measured.

80
Q

How do you carry out random sampling?

A
  • lay out two tape measures on two edges of the study site, so that they look like axes on a graph
  • using a random number generator, generate random co-ordinates and use these numbers to place your quadrat
  • lay the bottom left hand corner of the quadrat at the coordinate
81
Q

What is the formula for working out the total population size of a species?

A

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

82
Q

What is systematic sampling?

A

take samples at regular distances across the habitat, so you sample every part of the habitat to the same extent

83
Q

What are the two methods used to carry out systematic sampling?

A
  • belt transect

- line transect

84
Q

What is a transect?

A

line taken across a habitat

85
Q

What are the two type of belt transects that can be carried out?

A
  • interrupted belt transect: regular intervals, make a note of which species is touching the tape
  • continuous belt transect: place a quadrat next to the line, moving it along the line after looking at each quadrat
86
Q

What is a line transect?

A

at regular intervals, make a note of which species is touching the tape measure

87
Q

What are the three ways in which you can measure abundance?

A
  • count number of individuals of a species (but this may be difficult and take a long time)
  • work out the frequency (presence/absence)
  • calculate the percentage% cover by using quadrats
88
Q

What is a method to measure the abundance of animals?

A
  • mark- release- capture method
  • capture some animals, mark them, and then release them back into the habitat
  • later, catch more of the same species and inspect them for the marks that were put on the first catch to see how many you have caught twice
89
Q

What is the formula for working out the abundance of a species using the mark-release-capture method?

A

estimated population size=total number of individuals in 1st sample X total number of individuals in 2nd sample/number of marked individuals recaptured

90
Q

What are chemoautotrophic bacteria?

A

organisms that derive their energy from the oxidation of subtances

Biology A-Level -James (18 decks)

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