Key Definitions - Ecology and the environment

Question 1

define abiotic factors.

Answer 1

non-living parts of an ecosystem, e.g. temperature, light intensity, moisture, wind speed, soil pH, mineral concentration, carbon dioxide and oxygen levels

Question 2

define biodiversity.

Answer 2

variety of living organisms in an ecosystem. It takes into account the number of different species and the population of each

Question 3

define biotic factors.

Answer 3

living components of an ecosystem, e.g. food availability, pathogens, predation and competition (interspecific competition – competition between members of different species and intraspecific competition – competition between members of the same species)

Question 4

define community.

Answer 4

all the populations of different species living together in a particular place at a particular time

Question 5

define distribution.

Answer 5

spread of living organisms in an ecosystem, affected by environment changes

Question 6

define ecosystem.

Answer 6

the community of organisms (biotic) and non-living components (abiotic) of a particular area and how they interact with one another

Question 7

define habitat.

Answer 7

the place in an ecosystem when an organism lives

Question 8

define population

Answer 8

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

Question 9

define decomposers.

Answer 9

organisms that release enzymes which speed up the breakdown of dead plant and animal material, e.g. bacteria and fungi

Question 10

define decomposition.

Answer 10

the breakdown of dead materials into simpler organic matter that can eventually be absorbed by plants. The rate at which it occurs is affected by temperature, water and oxygen content

Question 11

define energy transfers.

Answer 11

the flow of energy from one trophic level to the next. Is never 100% and decreases the further you move up the food chain due to not all of the organism being eaten, not all of it being digested, some of the energy being used in respiration/movement of the organism and some energy being lost in the excretory products

Question 12

define food chain.

Answer 12

shows the feeding relationships between organisms and the stages of biomass transfer. The arrows represent the flow of energy between organisms

Question 13

define food web.

Answer 13

network of food chains that shows how energy can flow in different ways and that animals can feed on more than one organism

Question 14

define primary consumer.

Answer 14

herbivores that consume producers in a food chain

Question 15

define producers.

Answer 15

photosynthetic organisms at the start of the food chain that provide biomass for all the organisms in the food chain

Question 16

define pyramid of biomass.

Answer 16

a pyramid, with each layer of the pyramid representing the amount of mass of living material at each trophic level of a food chain. When asked to draw one in exams, they often start off bigger at the bottom and get smaller at each level above

Question 17

define pyramid of number.

Answer 17

a pyramid showing the numbers of each organisms at each trophic level, often looking similar to the pyramid above but if the producer is large and small in number, like a tree, can look quite different

Question 18

define quadrat.

Answer 18

a square grid used to sample populations and to determine abundance and distribution of organisms in an ecosystem

Question 19

define quaternary consumers.

Answer 19

carnivores that consume tertiary consumers

Question 20

define secondary consumers.

Answer 20

carnivores that consume primary consumers

Question 21

define tertiary consumers.

Answer 21

carnivores that consume secondary consumers

Question 22

define apex predator.

Answer 22

an organism in a food chain/web that is not consumed by another

Question 23

define trophic level.

Answer 23

the position of an organism in a food chain. Only around 10% of the energy is transferred from one level to the next

Question 24

define carbon cycle.

Answer 24

the cycle where carbon moves between organisms and the environment, namely in the form of carbon dioxide and involving respiration, photosynthesis, fossilisation and combustion

Question 25

define decomposers in the nitrogen cycle.

Answer 25

organisms that release enzymes that catalyse the breakdown of dead plant and animal material releasing nitrogen containing compounds such as ammonia into the soil.

Question 26

define denitrifying bacteria.

Answer 26

bacteria that convert nitrates in the soil into nitrogen gas. Occurs when conditions are anaerobic and can be prevented by ploughing the soil to aerate the soil and having good drainage to prevent the air spaces from filling with water, both ensuring there is adequate amounts of oxygen to prevent the growth of these organisms

Question 27

define nitrifying bacteria.

Answer 27

aerobic organisms that convert ammonia to nitrites and then nitrates which can be absorbed by plants using active transport in the roots

Question 28

define nitrogen cycle.

Answer 28

the cycle through which nitrogen moves between living organisms and the environment

Question 29

define nitrogen fixing bacteria.

Answer 29

bacteria that convert nitrogen gas into nitrogen containing compounds that plants can use. Can be free living in the soil or found in root nodules of leguminous plants (clover, peas) where they have a mutualistic relationship and convert nitrogen gas to nitrogen containing compounds which the plant receives and in return get sugars from the plant that have been produced via photosynthesis

Question 30

define deforestation.

Answer 30

removal of trees to use the resources on the tree for fuel or for space that the trees occupy

Question 31

define eutrophication.

Answer 31

pollution of water by fertilisers being added in nearby land and nutrients leaching into the water causing excessive growth of algae at the surface of the water (algal bloom), which prevents light reaching photosynthetic plants at the bottom of the water, causing them to die, reducing the oxygen levels in the water and eventually resulting in the death of all aerobic organisms in the water

Question 32

define global warming.

Answer 32

rise in average temperatures on earth due to increased levels of greenhouse gases like carbon dioxide, causing the enhanced greenhouse effect where more heat is trapped in the atmosphere and once reflected off the surface is reflected back to the surface rather than escaping

Question 33

define greenhouse gases.

Answer 33

gases in the earth’s atmosphere that trap heat and cause the greenhouse effect, examples being water vapour, carbon dioxide, methane, nitrous oxide and CFCs

Question 34

define leaching.

Answer 34

movement of nutrients e.g nitrates in the soil into lakes and rivers due to rain and can lead to eutrophication

Question 35

define pollution.

Answer 35

contamination or destruction of the environment due to human impacts