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A2 OCR Biology F215 > Ecosystems > Flashcards

Ecosystems Flashcards

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1
Q

Define ecosystem

A

A natural system in which biotic and abiotic factors interact with each other (and the environment)

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2
Q

Define biotic factor

A

The living components of an ecosystem that affect distribution and abundance of species

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3
Q

Give an example of biotic factors

A

feeding, predation, parasitism, mutualism and competition

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4
Q

Define abiotic factor

A

The non-living components of an ecosystem that affect distribution and abundance of species

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5
Q

Give an example of abiotics factors

A

temp, light intensity, O2 conc, CO2 conc, water supply, pH, humidity, wind speed

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6
Q

Define producer

A

Organisms that transfer light energy into organic or inorganic compunds e.g. plants

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7
Q

Define primary consumer

A

The first consumer in a food chain; a herbivore

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8
Q

Define secondary consumer

A

The second consumer in a food chain; carnivore that eats herbivores

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9
Q

Define tertiary consumer

A

The third consumer in a food chain; a carnivore that feeds on a secondary consumer

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10
Q

Define trophic levels

A

The levels in the food chain in which an organism feeds

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11
Q

Define food web

A

Many interconnection food chains which show sequence of organisms and how energy is passed

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12
Q

Define decomposer

A
  • An organism that breaks down organic remains of other organisms into the soil
  • Death of plants and animals means organic N moves into soil
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13
Q

Define detritus feeders

A

Remains of plants and animals e.g. dead leaves which are used as a nutrient source for by decomposers and detritivores

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14
Q

Define detritivores

A

An organism that feeds on detritus (remains of plants and animals) for nutrient sources

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15
Q

Why is some energy lost by plants

A
  • The plants convert less than 3% of sunlight into chemical energy
  • The sunlight misses leaves entirely so little photosynthesis
  • Sunlight reflected from surfaces of leaves
  • Only certain wavelengths of light being absorbed by chlorophyll
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16
Q

Why is some energy lost by animals

A
  • Movement
  • Excretion
  • Respiration
  • Lost as heat energy from digestive system
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17
Q

Define efficiency of a food chain

A

The total energy put into the system divided by the useful energy obtained

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18
Q

Define productivity of a food chain

A

Rate at which energy passes through each trophic level

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19
Q

Define primary productivity

A

The conversion of the sunlight energy into biomass/chemical energy by plants per unit of area, per unit of time measured in kJ

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20
Q

Define gross primary productivity

A

The total quantity of energy transferred by plants from sunlight into plant tissues

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21
Q

Define net primary productivity

A

The chemical energy left after plants have supplied needs for respiration (GPP-R)

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22
Q

How do you measure the energy transfer between trophic levels

A
  • Population size of each species is measured
  • Mean dry mass of a single organism is calculated
  • Energy content per gram of dry material calculated for each kind of organism by burning sample of known mass in a calorimeter and measuring heat produced
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23
Q

Define monoculture

A

When a single variety of crop is just grown in one area

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24
Q

Define photosynthetic efficiency

A

The amount of light energy onto a crop divided by the amount of light energy converted to carbohydrate

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25
Q

What is a pyramid of numbers

A
  • Measures number of organisms on a trophic level

- Doesn’t show the mass so not as accurate

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26
Q

What is a pyramid of biomass

A
  • The dry mass of each organism on a trophic level

- Usually a pyramid shape

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27
Q

What is a pyramid of energy

A
  • How much energy in a particular area at a particular time of the year
  • Changes throughout the year
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28
Q

Define succession

A

A directional change in a community of organisms over time

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29
Q

What is the role of pioneer plants in succession

A
  • They alter the soil as when they shed leaves, they provide nutrients for decomposers so numbers increase
  • Proper soil can form which helps hold water and mineral ions and so other species can live there
30
Q

Define pioneer plant

A

A plant that is adapted to grow on newly exposed ground and therefore are often found in very early stages of primary succession

31
Q

What is primary succession

A

Succession that occurs on a piece of ground that began with no soil

32
Q

Define secondary succession

A

Succession that occurs following the clearance of land that already has soil

33
Q

What is deflected succession

A
  • When human intervention stabilses/halts the plant communities and therefore succession, preventing ecosystems from developing further
  • Also known as a plagioclimax
34
Q

What is a climax community

A

The final stage at the end of the process of succession

35
Q

Define sere

A

A composition of a series of different plant communities that change with time. Communities are known as seral stages

36
Q

What are seral stages

A

One of the communities that exist during a succession

37
Q

What is a line transect

A

Taking samples along a line running across the area to be surveyed

38
Q

What is a belt transect

A

Taking samples from quadrats placed along a line running across the area to be surveyed

39
Q

What is a continuous transect

A

A line along which the organisms at every point on the line are recorded

40
Q

What are interrupted transects

A

Taking samples at intervals along the length of a line

41
Q

Describe the process of succession on sand dunes

A
  • FOREDUNE- Very few plants can survive mobile sand and sea water spray. Sea holly can survive
  • YELLOW DUNE- Dominated by a few grasses e.g. sea couch grass and marram grass
  • GREY DUNE- sand is fixed by roots and has accumulated humus. Nutrient levels are higher and water supply is so diverse range of species can live there e.g. restharrow. Temporary pools of water can form
42
Q

What is nitrogen fixation

A
  • The process where nitrogen gas is converted to nitrogen containing compounds.
  • Can be carried out industrially or naturally when lightning passes through the atmosphere.
  • Also carried out by two types of micro-organism:
  • Free living nitrogen fixing bacteria - Reduce gaseous nitrogen to ammonia, which they use to manufacture amino acids. Nitrogen rich compounds are released from them when they die.
  • Mutalistic nitrogen fixing bacteria - Are attached to nodules of roots of plants, plants provide them with carbohydrates and they provide plants with amino acids.
43
Q

What is nitrification

A
  • The production of nitrate and nitrite ions by oxidation of ammonium ions
  • Nitrosomonas bacteria; oxidation of ammonium ions intro nitrites in soil (NH4+ to NO2-)
  • Nitrobacteria bacteria; oxidation of nitrites into nitrates in soil (NO2- to NO3-)
44
Q

What is denitification

A
  • The process by which denitrifying bacteria convert nitrogen ions in the soil to gaseous nitrogen.
  • Takes place in waterlogged fields where there is not much oxygen.
  • As there is not much oxygen, few aerobic bacteria like nitrifying bacteria remain, this means that there are more anaerobic denitrifying bacteria.
  • So in order to keep nitrogen in the soil drainage and aerated fields are important.
45
Q

Define ammonification

A

The production of ammonia from nitrogen-containing compounds e.g. urea

46
Q

What is mutualism

A

A close relationship between 2 organisms in which both benefit

47
Q

What is rhizobium

A

Nitrogen fixing bacteria

48
Q

What are root nodules

A

Location for Rhizobium in legumes

49
Q

What is nitrosomonas

A

Bacteria which convert ammonium compounds –> nitrites

50
Q

What is nitrobacter

A

Bacteria which convert nitrites –> nitrates

51
Q

Describe the lag phase (populations)

A

No increase, the population grows slowly as the organisms are acclimatising to the conditions and the rate of reproduction is low

52
Q

Describe the exponential phase (populations)

A

If resources are plentiful the population will start to increase rapidly i.e birth rate > death rate

53
Q

What is environmental resistance

A

Prevents the population from increasing indefinitely due to environmental resistance

54
Q

What are limiting factors

A

The variable that limits a particular process- These can be both abiotic and biotic factors

55
Q

Define carrying capacity

A

The maximum population density of an organism that can be supported permanently in a habitat and is determined by one or more density dependant limiting factors.

56
Q

Why is a population not static

A

Population tends to fluctuate over time depending on the birth rate and death rate and migration.

57
Q

Define predation

A

Animals eating other organisms

58
Q

Describe the predator-prey relationship

A

As the prey population increases there is more food available for the predators so they are more likely to survive, successfully breed, their population will increase. As the predator population increases more prey are eaten, which brings about a decrease in the prey population. As the prey numbers fall there is less food for the predator so they do not survive and predator numbers also fall.

59
Q

Define intra-specific competition

A

Competition for a limited resource between members of the same species

60
Q

Define inter-specific competition

A

Competition between members of a different species.

61
Q

What is competitive exclusion

A

Due to competition two species cannot occupy the same niche in a habitat

62
Q

Describe sustainable forestry

A

Seeks to provide a regular supply of timber without adverse side effects to the environment and ensure that thee habitat is largely unaffected and the biodiversity maintained.

63
Q

What is coppicing

A

The tree is cut leaving a live stump from which new shoos grow.
It can be done rotationally to ensure a constant supply of wood for several years. This maintains biodiversity and ensures a range of different trees.

64
Q

What is pollarding

A

A pruning system in which the tree is cut back to promote a dense head of foliage

65
Q

Describe selective felling

A

Largest most valuable trees, diseased trees or unwanted trees are cut down and removed.

66
Q

Describe strip felling

A

Each year different small strips of forest are removed completely and replanted. This gives each area time to regrow, ensuring a range of ages of trees

67
Q

Describe clear felling

A

Not sustainable - removing all the trees leaves bare soil which is susceptible to erosion and leaching out of minerals. heavy rainfall can wash the soil into rivers causing silting and increased risk of flooding.

68
Q

Define conservation

A

The dynamic process of protecting, managing an retaining ecosystems with the purpose of maintaining increasing biodiversity between species, genetic diversity within species and the maintenance of a variety of habitats & ecosystems.

69
Q

Define preservation

A

Protection of ecosystems so that they are kept with purpose of maintaining biodiversity between species and genetic diversity within the species. Nothing is removed or added.

70
Q

Give 2 threats to species of the galapogos

A
  • Increase human population and tourisim meaning greater demands for water, sanitation and energy
  • Habitat disturbance for agriculture, infrastructure and buildings
  • Over exploitation of resources- fishing, tortoises for food
  • Deforestation - wood for building
  • Introduction of non-native species e.g Goats (out compete tortoises for food) & Red quinine tree (threatens scalesia tree)
71
Q

Describe conservation methods in the Galapagos

A
  • Wildlife sanctuary in 1959, national park in 1986, marine reserve
  • Quarantine system introduced to reduce the chance of exotic species arriving in the islands.
  • Culling of goats and pigs on some islands to prevent soil erosion
  • Fishing exclusion zone
  • Restrictions on the areas that tourists can visit

A2 OCR Biology F215 (9 decks)

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