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WJEC A2 Biology (English) > 3.5 - Population Size and Ecosystems > Flashcards

3.5 - Population Size and Ecosystems Flashcards

1
Q

What are abiotic factors?

A

The non-living aspects of an ecosystem (e.g. light, temperature, water availability, oxygen availability and soil pH)

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2
Q

What is an abundance?

A

The number of individuals per species in a specific area at a given time

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3
Q

What is ammonification?

A

The production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules

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4
Q

What is Azotobacter?

A

A type of nitrogen-fixing bacteria that lives freely in the soil

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5
Q

Define belt transect

A

A line along a sampled area upon which quadrats are placed at intervals to determine the abundance and distribution of organisms in an ecosystem

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6
Q

What is biomass?

A

The total mass of organic material, measured in a specific area over a set time period

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7
Q

What are biotic factors?

A

The living components of an ecosystem (e.g. food availability, pathogens, predators and other species)

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8
Q

What is birth rate?

A

The number of offspring born per thousand of population per year

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9
Q

What is the carbon cycle?

A

The cycle through which carbon (in the form of CO2) moves between living organisms and the environment, involving respiration, photosynthesis and combustion

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10
Q

Define carrying capacity

A

The average size of a population that can be supported by an ecosystem over extended periods of time. This varies depending on biotic and abiotic factors.

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11
Q

What is climax community?

A

The stable community of organisms that exists at the final stage of ecological succession

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12
Q

Define colonisation

A

The occupation of a new species in a location

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13
Q

What is a community?

A

All of the populations of different species living together in a habitat

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14
Q

Explain the term competition

A

When different organisms compete for the same resources (e.g. light, water, mates, territory) in an ecosystem. This limits population sizes.

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15
Q

Define death rate

A

The number of deaths per thousand of population per year

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16
Q

What is deforestation?

A

The removal of trees from land which is subsequently used to grow crops or provide space for livestock or construction.

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17
Q

What is denitrification?

A

The conversion of of nitrate ions to nitrogen gas by denitrifying bacteria

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18
Q

What does denitrifying bacteria mean?

A

Anaerobic micro-organisms found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas

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19
Q

What are density-dependent factors?

A

Factors whose effects on population size differ with population density (e.g. competition, predation, disease)

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20
Q

What are density-independent factors?

A

Factors which effects on population size remain the same regardless of population density (e.g. climate)

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21
Q

What are detritivores?

A

Organisms that feed on dead organic matter

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22
Q

What does distribution mean?

A

The spread of living organisms in an ecosystem

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23
Q

Define ecology

A

The study of the relationships among organisms and their environment

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24
Q

Define ecosystem

A

The community of organisms (biotic) and non-living (abiotic) components of an area and their interactions

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25
Q

Define efficiency of energy transfer

A

The efficiency of energy transfer between trophic levels, calculated using:

Efficiency = energy available after transfer / x100
energy available before transfer

26
Q

What is Emigration?

A

The numbers of individuals leaving a region per thousand of population per year

27
Q

What is eutrophication?

A

The process by which pollution by nitrogen-containing fertilisers result in algal blooms and subsequent oxygen level reduction in bodies of water

28
Q

Define extinction

A

The death of all living members of a species

29
Q

What are fertilisers?

A

Natural or artificial materials that are added to soils to provide essential nutrients and improve plant growth

30
Q

Define global warming

A

The gradual rise in the average temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas

31
Q

What is the greenhouse effect?

A

The increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere

32
Q

Explain what gross primary productivity (GPP) means

A

The rate of chemical energy fixture during photosynthesis by all producers in an ecosystem, measured in KJ-2 year-1

33
Q

What does habitat mean?

A

The region where an organism normally lives

34
Q

Define immigration

A

The number of individuals entering a region per thousand of population per year

35
Q

What is lag phase?

A

A period of slow population growth

36
Q

What is line transect?

A

A line along a sampled area. The species touching the transect at regular intervals are recorded to determine the abundance and distribution of organisms in an ecosystem.

37
Q

Define log phase

A

A period of rapid population growth in which birth rate exceeds the death rate. Also known as the exponential phase.

38
Q

What is net primary production (NPP)?

A

The amount of chemical energy that is available to heterotrophs in an ecosystem. It is calculated by subtracting chemical energy generated in respiration (R) from gross primary production:

NPP = gross primary production (GPP) - respiartory losses (R)

39
Q

What does niche mean?

A

Describes how an organism ‘fits’ into an ecosystem and its role to that environment

40
Q

What is nitrification?

A

The conversion of ammonium ions to nitrate ions by nitrifying bacteria. This takes place in two stages: ammonium ions are oxidised to nitrite ions; nitrite ions are oxidised to nitrate ions.

41
Q

What are nitrifying bacteria?

A

Aerobic micro-organisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions

42
Q

What is Nitrobacter?

A

A genus of nitrifying bacteria that oxidises nitrites into nitrates

43
Q

What is the nitrogen cycle?

A

The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification

44
Q

What is nitrogen fixation?

A

The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes

45
Q

What are nitrogen-fixating bacteria?

A

Micro-organisms responsible for the conversion of atmospheric nitrogen gas into nitrogen-containing compounds. They can be free-living or mutualistic

46
Q

What is Nitrosomonas?

A

A genus of nitrifying bacteria that oxidises ammonium compounds into nitrates.

47
Q

What are pioneer species?

A

Species that can survive in hostile environments and colonise bare rock or sand (e.g. lichens)

48
Q

Explain what the term population means?

A

All organisms of the species living with one another in a habitat at the same time

49
Q

What is primary succession?

A

A type of succession in which pioneer species colonise a newly formed or exposed area of land

50
Q

What are producers?

A

Photosynthetic organisms at the start of the food chain that manufacture biomass for all living things

51
Q

What is a pyramid of biomass?

A

A table of the dry mass of living material at each trophic level of a food chain. This forms the shape of a pyramid.

52
Q

What is a quadrat?

A

A single square grid of known area used in sampling to determine the abundance of organisms in a habitat

53
Q

What is random sampling?

A

A sampling technique use to avoid bias (e.g. creating a square grid and generating random coordinates

54
Q

What is Rhizobium?

A

A type of nitrogen-fixing bacteria that lives inside the root nodules of leguminous plants

55
Q

What are saprotrophs?

A

Organisms that feed by extracellular digestion. They release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter

56
Q

Define secondary succession

A

A type of succession in an ecosystem progressing towards a climax community

57
Q

Explain what the term soil aeration means

A

The exchange of oxygen between the soil and atmosphere to produce the aerobic conditions required for nitrification. Human activities such as drainage an ploughing are used to improve aeration

58
Q

What is the stationary phase?

A

A period of stability in which population numbers remain constant

59
Q

What is succession?

A

Describes changes in the community of organisms occupying a certain area over time

60
Q

What is systematic sampling?

A

A sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals (e.g. along a belt transect). This is commonly used in ecosystems where some form of gradual change occurs.

61
Q

Define trophic level

A

The position that an organism holds in a food chain, food web, pyramid numbers or pyramid of biomass.

WJEC A2 Biology (English) (12 decks)

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