Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology OCR A level > Ecosystems > Flashcards

Ecosystems Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

what is an ecosystem

A

all the interacting living organisms and non-living factors within an area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is a key characteristic of an ecosystem

A

it is dynamic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is a habitat

A

place where an organism lives

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is biomass

A

the mass of living material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

why is not all the energy transferred through trophic levels

A
  • plants don’t use all the light energy that reaches their leaves
  • some light is the wrong wavelength so is reflected or passes straight through the leaves
  • some light energy can’t be used as it hits parts of the plant that aren’t photosynthetic
  • not all parts are eaten/digested (plants contain lots of undigestible parts eg. cellulose cell walls)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the net productivity

A

the amount of energy that is available to the next trophic level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how can percentage efficiency of energy transfer be calculated

A

net productivity of trophic level / net productivity of previous trophic level

x100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how can you calculate how efficient organisms in one trophic level are at converting what they eat into energy for the next trophic level

A

energy transferred/energy intake x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Farmers try to reduce the amount of energy lost from the food chain in order to increase productivity, what do these methods include and why are they done?
(6 methods)

A
  • herbicides, kill weeds that compete reducing competition
  • fungicides, kill fungal infections that damage crops so more energy used for growing than fighting infection
  • insecticides, kill insects that eat crops, less biomass lost
  • introduce natural predators, these eat the pests so less biomass lost
  • fertilisers, chemicals provide crop with minerals
  • rearing livestock intensively, controls conditions so more energy used for growth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how might a farmer rear animals intensively

A

animals kept in thermostatically controlled room - less energy used maintaining body temp

given feed that is higher in energy

kept in small cages to reduce energy lost through movement

(these have ethical concerns)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how is carbon returned to the atmosphere ( 6 ways)

A
  • respiration
  • combustion, burning of fossil fuels
  • release from volcanoes, limestone and chalk drawn into earths crust undergo chemical changes that release CO2
  • weathering, rocks are broken down by chemicals in rainwater (Acid rain) this causes mineral ions and bicarbonate ions to be released from the rock into grounwater
  • release from and absorbtion into ocean - CO2 dissolves directly into oceans, transported by currents and later released.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why can plants not obtain nitrogen from the atmosphere

A

N2 is unreactive and is a stable compound as contains a triple bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the 2 types of bacteria that convert nitrogen gas to ammonia during nitrogen fixation, where are these 2 types found

A

Rhizobium - found inside root nodules of legumious plants (mutualistic relationship)

Azotobacter- found free living in the soil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

outline the process of ammonification

A

Nitrogen compounds from dead plants and animals are broken down by decomposers into ammonia which is returned to the soil.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

outline the process of nitrification, what are the 2 types of bacteria involved

A

ammonium ions (NH3) converted into nitrites (NO2 - ) by Nitrosomonas

nitrates are converted to nitrates by nitrobacter (NO3-)

nitrates are taken up by plants via assimilation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

outline the process of dentrification

A

nitrates (NO3-) are converted back into nitrogen gas via dentrifying bacteria that use nitrates to carry out respiration.

happens under ANAEROBIC CONDITIONS eg. waterlogged soil

17
Q

apart from bacteria, what 2 other ways nitrogen fixation can occur

A

naturally - lightning fixed atmospheric nitrogen

artificially - Haber process

18
Q

how much nitrogen and oxygen is there in the atmosphere

A

nitrogen - 78%
oxygen - 20%

19
Q

what is succession

A

process by which an ecosystem changes over time, occures in stages, at each stage a new species changes the environment so it is less suitable for the previous species therefore each existing species is outcompeted by the new species

20
Q

when does primary succession occur

A

occurs on land that has been newly formed or exposed resulting in no soil or organic material to start with

21
Q

outline the pioneer stage of succession

A
  • seeds and spored are blown in by the wind and begin to grow.
  • first species to colonise are called the pioneer species.
  • Abiotic conditions are hostile + recquire specialised species eg Marram grass

these species die and decompose to form a basic soil making conditions less hostile.

New organisms come in, which die and decompose adding more organic material to soil.

Nitrogen fixing bacteria makes ammonia which is used by plants

larger plants grow and retain water and nutrients

22
Q

outline the later stages of succession

A

plants and animals that are better adapted move in and create competition to become the dominant species. This changes the abiotic environment.

ecosystem becomes complex resulting in a climax community

23
Q

what is a climax community

A

the ecosystem is supporting the largest and most complex community of organisms - steady state.

24
Q

what is secondary succession

A

occurs on land that has been cleared of all plants but soil remains. This succession occurs at a later stage, the pioneer species are larger plants.

usually occurs as a result of natural disaster or drastic change to environment.

25
Q

what is prevention and what is the name of the climax communtiy that occurs as a result of it

A

human activity prevents succession preventing the normal climax community developing.

plagioclimax

26
Q

what is deflected succession

A

when succession is prevented by human activity, but the plagioclimax is different to any of the natural stages of the ecosystem.
eg - regularly mown grassy field wont develop woody plants even if climate could support

27
Q

what is meant by the term population

A

group of organisms of the same species living in the same area

28
Q

what is meant by the term community

A

all the populations of different species in the same area at the same time

29
Q

what is a niche

A

an organisms role within the ecosystem eg. position in food web

30
Q

what is gross primary production

A

the total energy entering a food chain as a result of photosynthesis

31
Q

what is net primary production

A

what energy is left over to. create new biomass in the plant, and so is the amount of biomass that can be passed on to next level

32
Q

what are the units for production

A

KJ H -1 year -1

33
Q

what are the biomass units for land mammals

A

g m -2

34
Q

what are the biomass units for marine animals

A

g m -3

Biology OCR A level (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions