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Biology > ecosystems - MODULE 6 > Flashcards

ecosystems - MODULE 6 Flashcards

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1
Q

Nitrogen fixation

what happens
what bacteria

A

Nitrogen (N2) and 3Hydrogen (3H2) react together to form Ammonia (2NH3). Can be carried out by nirogen fixing bacteria (Rhizobium and Azotobacter(Using enzyme Nitrogenase)), lightning and the Haber process

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2
Q

Ammonification

A

Nitrogen compounds (NO3-) from dead organisms and nitrogenous waste (urine) are turned into ammonium (NH4+) by decomposers (mainly fungi and bacteria). The ammonium can then converted into ammonia

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3
Q

Nitrification

opposite of Ammonification

A

The oxidation of ammonium ions (NH4+)into Nitrites(NO2+) and then Nitrates(NO3-). Carried out by Nitrosomonas and* Nitrobacter*)

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4
Q

Denitrification

A

Denitrifying bacteria convert nitrates (NO3-) back into nitrogen gas (N2) under anaerobic conditions by Pseudomonas

bacteria use nitrates as a source of energy for respiration. Nitrogen is released

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5
Q

what is an ecosystem

A

all the organisms living in a certain area and all the non living conditions found there. both biotic and Abiotic factors

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6
Q

what is a biotic factor

A

living features of an ecosystem e.g: predators and food

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7
Q

what is an abiotic factor

A

non living features of an ecosystem

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8
Q

habitat

A

place where organism lives within a ecosystem

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9
Q

what is the main route that energy enters an ecosystem

A

photosynthesis

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10
Q

what are producers

A

plants

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11
Q

what is biomass

A

the mass of living material

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12
Q

order of consumers

A

PRoducer eaten by primary - > secondary - >tertiary consumer

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13
Q

what is a trophic level

A

a stage in a food chain that’s occupied by a particular group of organisms e.g: producers are the first trophic level

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14
Q

what is gross productivity

A

the rest of the available energy (40%) that is taken after rest is lost by previous trophic level q

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14
Q

what is respiratory loss

A

30% of total energy availiable is lost to environment when organisms use energy produced from respiration for movement or body heat

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15
Q

what is net productivity

A

only 10% of total energy becomes biomass.

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

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16
Q

how to work out net productivity

A

= gross productivity - respiratory loss

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17
Q

Efficiency of energy transfer

A

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

x100

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18
Q

Methods of controlling energy flow thru ecosystems

A

Herbicides

Fungicides

Insecticides

Natural predators

Fertilisers

Rearing livestock intensively (limit activity)

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19
Q

components to carbon cycle

A

Photosynthesis

Decomposition

Respiration

Combustion

Release from volcanoes

Weathering

Release from and absorption into the ocean

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20
Q

what is weathering in the carbon cycle

A

Rocks containing CArbon can eventually become land. THis is then weathered (broken down by exposure to the atmosphere). This can happen chemically by rain water. and physically by animals and plant roots etc.

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21
Q

what is Release from and absorption into the ocean in the carbon cycle

A

CO2 can also dissolve directly into oceans from the atmosphere. and be transported in the ocean by deep underwater currents. CO2 can remain in these slow-moving currents for hundreds of years before returning to the surface and being released back into the atmosphere

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22
Q

Azotobacter

A

free-living soil bacterium nitrogen fixating bacteria

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23
Q

Rhizobium

A

live inside root Nodules of leguminous plans such as peas ..

Nitrogen fixating bacteria

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24
Q

Nitrifying bacteria do

e.g

A

(e.g: nitrosomonas + nitrobacter) oxidise ammonium compounds into nitrites

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25
Q

Nitrobacter do

A

oxidise nitrites into nitrates

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26
Q

what processes are involved in the Nitrogen cycle

A

-Nitrogen fixation (N2 into Ammonia, mutualistic + free living)

-Nitrification (ammonium into nitrites)

-absorption (of ammonium and nitrates into plants)

-Feeding (tertiary consumers eat producers)

-Ammonification (decomposition of dead plants producing Ammonium ions by saprobionts)

-Denitrification (Nitrate into N2 in air)

27
Q

what are the two types of successtion

A

-primary

secondary

28
Q

what is secondary succession

A

occours on areas of land where soil is present, but it contains no plant or animal species
e.g: bare earth that appears affter a forest fire

29
Q

what is primary succession

A

occurs on an area of land that has been newly formed or exposed such as bare rock . no soil or organic material to begin with

30
Q

what are the stages of succession called

A

seral stage

31
Q

summary of a pioneer community

A

colonisers e.g: lichen + algae

32
Q

components of a Intermediate community

e.g:

A

secondary colonisers e.g: mosses

tertiary colonisers e.g: grasses

Scrubland e.g: shrubs and small trees

33
Q

summary of a climax community

A

Dominant species e.g: woodland

34
Q

what is humus

A

the organic component of soil from dead decomposed pioneer species

35
Q

when is biodiversity usually the highest during succesion

A

mid-succession due to later more dominant species wiping out others in later stages as they put compete them

36
Q

Deflected succession

A

Human activities can halt the natural flow of succession and prevent the ecosystem from reaching its climax community

37
Q

plagioclimax

A

when succession is stopped artifically, the final stage is plagioclimax

38
Q
  • The nitrogen cycle shares many similarities with the carbon cycle.
    Describe the similarities between the nitrogen cycle and the carbon cycle
A
  • inorganic gases
    o CO2 and N2
  • in atmosphere
  • elements fixed to organic compounds
    o C and N both form proteins /
    nucleic acids
  • incorporated into plants (producers) then
    animals (consumers)
  • animals obtain element by feeding on
    plants
  • decomposing microorganisms
  • break down organic macromolecules in
    living things
  • release inorganic molecules
    o carbon dioxide and ammonium
    ions
  • microorganisms return element to
    atmosphere
    o CO2 released during
    decomposition
    o N2 released by denitrifying bacteria
39
Q

decomposer

A

organisms that breaks down and feeds on dead animal or plant matter, turning organic compounds into inorganic ones (nutrients) available to photosynthetic producers in the ecosystem

40
Q

How is distribution of organisms within an ecosystem usually measured

plants

A

line or belt transect

41
Q

how is a line transect used

A

laying a line or surveyor’s tape along the ground and taking samples at regular intervals

42
Q

how is a belt transect used

A

Two parallel lines marked, samples taken of area between these specified points.

43
Q

what type of sampling are belt and line transects

A

systematic sampling, a form of non-random sampling

44
Q

Distribution of organisms refers to

A

where individual organisms are found within an ecosystem

45
Q

Abundance of organisms refers to

A

number of individuals of a species present in an area at any given time

46
Q

how is plant abundance measured

A

quadrats placed randomly in an area

count number of individual plants contained within the quadrat

Number of individuals in sample / Area of sample (m^2)

47
Q

name how animal abundance is measured

A

capture-mark-release-recapture method

48
Q

technique of capture-mark-release-recapture method

A

1)capture as many individuals as possible in a sample area
2)Mark or tag each individual
3)Release marked animals back into sample area and allow time for them to redistribute themselves throughout the habitat
4) Recapture as many individuals as possible in original sample area
5)Record number of marked and unmarked individuals present in the sample (release all individuals back into their habitat
6) use Lincoln index to estimate population size

49
Q

Lincoln Index

when is it used

what is it

A

population size =

(no. of indivs in first sample x no. indiv in 2nd sample ) / number of recaptured marked individuals

used when doing capture-mark-release-recapture method

50
Q

How to increase accuracy of a sample

A
  • use large sample size as possible
    the greater the number of individuals studies , the lower the probability that chance will influence the results

-use random sampling to reduce effects of sampling bias

51
Q

why can populations rarely be counted accurately

A

-some animals elude recapture
-may be too time consuming to count entire population
-counting process could damage population

so sampling techniques are used*

52
Q

chemical formula for nitrogen gas

A

N2 gas

53
Q

chemical formula for ammonia

A

NH3

54
Q

chemical formula for nitrates

A

NO3-

55
Q

chemical formula for nitrites

A

NO2−

56
Q

How does harvesting crops affect the Nitrogen cycle

A

death of plants and therefore ammonification and nitrification and absorption into plants.
Therefore, nitrate fertilisers need to be used
can result in eutrophication

57
Q

where does denitrification occour

A

only in areas of flooding/lack of aeration

as nitrifying bacteria are anaerobic

58
Q

what is nitrogen used for in plants and animals

A

-proteins
-DNA/RNA
-ATP
-NAD + NADP

59
Q

how to calculate biomass of organisms

A

use calorimeter

-collect sample
-kill organism
-plance in oven at 80 C

60
Q

units used for biomass of land animals vs marine animals

A

gm^-2

vs

gm^-3

61
Q

biotic limiting factors affecting ecosystem

A

Disease
predation
Competition (intra + interspecific)

62
Q

abiotic limiting factors affecting ecosystem

A

-light
-O2 availability
-H2O availability
-Temperature
-Edaphic (soil) factors (type of soil(ability to retain water) + PH)

63
Q

Density independant factors limiting a population e.g:

A

Natural disaster

64
Q

Density independant factors limiting a population e.g:

A

Natural disaster

Biology (45 decks)

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