Population size and ecosystems terms

Question 1

Abiotic factors

Answer 1

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

Question 2

Abundance

Answer 2

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

Question 3

Ammonification

Answer 3

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

Question 4

Azotobacter

Answer 4

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

Question 5

Belt transect

Answer 5

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

Question 6

Biomass

Answer 6

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

Question 7

Biotic factors

Answer 7

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

Question 8

Birth rate

Answer 8

The number of offspring born per thousand of population per year.

Question 9

Carbon cycle

Answer 9

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

Question 10

Carrying capacity

Answer 10

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.

Question 11

Climax community

Answer 11

The stable community of organisms that exists at the finals stages of ecological succession.

Question 12

Colonisation

Answer 12

The occupation of a new area by a species.

Question 13

Community

Answer 13

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

Question 14

Competition

Answer 14

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

Question 15

Death rate

Answer 15

The number of deaths per thousand of population per year.

Question 16

Deforestation

Answer 16

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

Question 17

Denitrification

Answer 17

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

Question 18

Denitrifying bacteria

Answer 18

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

Question 19

Density-dependent factors

Answer 19

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

Question 20

Density-independent factors

Answer 20

Factors whose effects on population size remain the same regardless of population density e.g. climate

Question 21

Detritivores

Answer 21

Organisms that feed on dead organic matter.

Question 22

Distribution

Answer 22

The spread of living organisms in an ecosystem

Question 23

Ecology

Answer 23

The study of the relationships among organisms and their environment

Question 24

Ecosystem

Answer 24

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

Question 25

Efficiency of energy transfer

Answer 25

The efficiency of energy transfer between trophic levels is calculated using: Efficiency= energy available after transfer/ energy available before transfer x100

Question 26

Emigration

Answer 26

The number of individuals leaving a region per thousand of population per year.

Question 27

Eutrophication

Answer 27

The process by which pollution by nitrogen- containing fertilisers results in algae blooms and subsequent oxygen level reduction in bodies of water.

Question 28

Extinction

Answer 28

The death of all living members of a species.

Question 29

Fertilisers

Answer 29

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

Question 30

Global warming

Answer 30

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

Question 31

Greenhouse effect

Answer 31

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

Question 32

Gross primary productivity (GPP)

Answer 32

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

Question 33

Habitat

Answer 33

The region where an organism normally lives.

Question 34

Immigration

Answer 34

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

Question 35

Lag phase

Answer 35

A period of slow population growth

Question 36

Line transect

Answer 36

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.

Question 37

Log phase

Answer 37

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

Question 38

Net primary production (NPP)

Answer 38

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: Net primary production (NPP)= gross primary production (GPP)- respiratory losses (R)

Question 39

Niche

Answer 39

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

Question 40

Nitrification

Answer 40

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

Question 41

Nitrifying bacteria

Answer 41

Aerobic microorganisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions.

Question 42

Nitrobacter

Answer 42

A genus of nitrifying bacteria that oxidises nitrites into nitrates

Question 43

Nitrogen cycle

Answer 43

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

Question 44

Nitrogen fixation

Answer 44

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

Question 45

Nitrogen-fixing bacteria

Answer 45

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

Question 46

Nitrosomans

Answer 46

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

Question 47

Pioneer species

Answer 47

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

Question 48

Population

Answer 48

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

Question 49

Primary succession

Answer 49

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

Question 50

Producers

Answer 50

Photosynthesis organisms at the start of the food chain that manufacture biomass of all living things.

Question 51

Pyramid of biomass

Answer 51

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

Question 52

Quadrat

Answer 52

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

Question 53

Random Sampling

Answer 53

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

Question 54

Saprotrophs

Answer 54

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

Question 55

Secondary succession

Answer 55

A type of succession in which a habitat is re-colonised after a disturbance

Question 56

Seres

Answer 56

Various intermediate stages in succession in an ecosystem progressing towards a climax community.

Question 57

Soil aeration

Answer 57

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

Question 58

Stationary phase

Answer 58

A period of stability in which population numbers generally remain constant.

Question 59

Succession

Answer 59

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

Question 60

Systematic sampling

Answer 60

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.

Question 61

Trophic level

Answer 61

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