1. Microorganisms are tiny organisms that can only be seen under a microscope and include bacteria, protozoa, algae, fungi and viruses. 2. Bacteria are unicellular organisms with cell walls made of peptidoglycan that can be spherical, rod-shaped, or spiral. Algae are photosynthetic eukaryotes with cell walls made of cellulose. Fungi are heterotrophic with cell walls made of chitin and feed by secreting enzymes. 3. The nitrogen cycle is mediated by microorganisms and involves nitrogen fixation by bacteria, ammonification of organic nitrogen by bacteria and fungi, nitrification of ammonia by Nitrosomonas and N

1. DYNAMIC ECOSYSTEM
PART 5

2. Microorganism
Microorganisms are tiny
organisms that can only
seen clearly under the
microscope

3. TYPES OFTYPES OF
MICROORGANISMSMICROORGANISMS
VirusesViruses BacteriaBacteriaProtozoaProtozoa
AlgaeAlgae FungiFungi
MICROORGANISMA

4. Bacteria
N : Bacteria
C : - unicellular organisms which have basic cell
structure that
includes a cell wall, plasma membrane and DNA
that is not
enclosed in a membrane
- have cell walls made of a polymer called
peptidoglycan
- certain bacteria form spores under unfavourable
conditions
- their shape may be spherical (coccus), rod shape,
(bacillus) or
spiral (spirilium)

5. Algae
N : Algae
C : - photosynthetic eukaryotic plant-like organisms in
the
kingdom protista
- have a chlorophyll and chloroplast
- cell walls are made of cellulose
- do not have leaves, stems or roots
E : phytoplankton and Spirogyra sp.

6. Fungi
N : Fungi
C : - heterotrophic multicellular or unicellular
- do not have chlorophyll
- have a cell wall made up of chitin
- fungi feed by secreting enzymes that break the
surrounding
organic material down into simple molecules before
they are
absorbed
E : Mucor sp. and yeast

7. Protozoa
N : Protozoa
C : - unicellular organism
- have nucleus, cytoplasm and plasma membrane
- capable carry out living processes such as respiration,
reproduction and excretion
- have flagella, cilia or pseudopodia to move
E : Euglena sp., Paramecium sp., Amoeba sp.

8. Viruses
N : Viruses
C : - is not a living cell because it cannot survive or
reproduce on
its own outside the host
- is composed of DNA and RNA, surrounded by a
protein coat
- can be crystallised
E : T4 bacteriophage and tobacco mosaic virus

9. e Effect of Abiotic Components on the Activity of Microorganis
1.Nutrient:
- all microorganisms except viruses need nutrient
and water for reproduction and growth.
- without nutrient and water, microorganisms will
die or form spores

10. e Effect of Abiotic Components on the Activity of Microorganis
2. pH
- most bacteria prefer slightly alkaline condition
(pH around 7.4)
- moulds, yeast and protozoa (pH between 4.5 and
5.0)

11. 3. Temperature
- most microorganisms are inactive at low temperatures
- optimum temperature for most microorganisms is
between 35 ⁰C and 40 ⁰C
- beyond 60 ⁰C, the growth of microorganisms is inhibited
- microorganisms and their spores can only be destroyed
when they are sterilized at a temperature of about 121 ⁰C
e Effect of Abiotic Components on the Activity of Microorganis

12. 12/18/14 1.1_Classificationofmicros

13. 4. Light intensity
- microorganisms prefer places which are dark or have a
low light intensity
- a high intensity of sunlight and ultraviolet rays can kill
microorganisms
- however, algae and photosynthetic bacteria need light to
photosynthesis
he Effect of Abiotic Components on the Activity of Microorgani

14. Impact Of Microorganism on Life
 Decomposition – Bacteria & fungi break down
complex organic matter into simple inorganic
matter
 Alimentary canal of termites- microbes produce
celulase enzyme to break down cellulose in wood
 Digestive system of humans – bacteria in
intestines produce Vit B12 & K
 Nitrogen cycle

15. 1. Decomposition:
- bacteria and saprophytic fungi
break down complex organic matter into
simple inorganic matter

16. The Role of Useful Microorganisms in the Ecosystem
2. Digestion:
Alimentary canal of termites - microbes Trichonympha
sp. (flagellated protozoan) produce celulase enzyme to
break down cellulose in wood

17.  Digestive system of humans – bacteria in
intestines produce Vit B12 & K
The Role of Useful Microorganisms in the Ecosystem

18. The Nitrogen Cycle
The Role of Useful Microorganisms in the Ecosystem

19. Where is the reservoir of nitrogen?
AirAir
SoilSoil

20. The Nitrogen Cycle
Nitrogen 78%
 Atmospheric Gases

21.  plants & animals need nitrogen to make:
proteins
Nitrogen
78%
 plants cannot use
atmospheric nitrogen
Gases in air.
From where do plants
get the nitrogen they
need?

23. Animal
Dead animal & plants
Ammonia / Ammonium
Nitrites
Nitrates
Nitrosomonas sp.
Nitrobacter sp.
Plants
Denitrifying
bacteria
Atmosphere
fixation
Nitrogen
fixing
bacteria
Fertiliser
Nostoc sp.,
Rhizobium sp.
Thiobacillus sp.
NITROGEN CYCLE

24. The Nitrogen Cycle Converts:
 N2 into a chemical form that living
organisms can use
NameName two formstwo forms in whichin which
plants can use nitrogen fromplants can use nitrogen from
the soil.the soil.

25. NOT Nitrites!!

26. Biological processes involved in the nitrogen
cycle:
1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. Denitrification

27. Nitrogen fixation
What does ‘fixation’ refer to?
Converting atmospheric nitrogen into
compounds such as nitrates which can
be used by plants

28. N2 must be fixed to be of any use to plants:
 This is done in two ways:
 mostly by nitrogen fixing bacteria
 lightning

29. Animal
Dead animal & plants
Ammonia / Ammonium
Nitrites
Nitrates
Nitrosomonas sp.
Nitrobacter sp.
Plants
Denitrifying
bacteria
Atmosphere
fixation
Nitrogen
fixing
bacteria
Fertiliser
Nostoc sp.,
Rhizobium sp.
Thiobacillus sp.
NITROGEN CYCLE

31. Lightning:
 is an electrical discharge through the air
can cause:
N2 & O2 molecules
to change into the
atomic form
Combine with water to
form weak nitric acid
(HNO3)

32. Atmospheric nitrogen
precipitates to the earth,
adding nitrogen to the soil
in a usable form (nitrate,
NO3)

33. Question:
Atmospheric nitrogen may give rise to nitrate
through a natural, non-biological process.
What is this process called? (1)
Lightning

34. NITROGEN-FIXING BACTERIA
absorb nitrogen gas from the air and ‘fix’ it into
a form which the plant can use to build protein
change nitrogen gas into ammonium
compounds
Root nodule
full of bacteria.

35. NITROGEN-FIXING BACTERIA live:
Root nodules
1) freely in the soil e.g. Clostridium
2) in the root nodules of leguminous plants (e.g.
peas, beans, clover) e.g. Rhizobium

36. Nitrogen fixation
 Carried out by:
 nitrogen fixing bacteria e.g.
Azotobacter and Clostridium
 the cyanobacterium Nostoc
 90% of the total nitrogen-
fixation:
 is carried out by free-living
micro-organisms
Nostoc
Cyanobacteria

37. Rhizobium
 aerobic nitrogen-fixing bacilli
Rhizobium in
ruptured nodule
 live in:
 root nodules of
leguminous plants

38. Leguminous plants:
LegumesLegumes:
probably the largest
source of fixed nitrogen
Clover
Beans
Peas

39. Mutualism:
is the relationship between nitrogen fixing
bacteria and leguminous plants
Plant gains:
Ammonium
compounds
Bacteria gain:
1.Food
2.Shelter
carbohydrate
N

40. When leguminous plants decay:
the nitrogen which the bacteria have fixed
goes into the soil where it can be used by
plants
Nitrogen-fixing bacteria are very useful
because they increase the amount of useful
nitrogen compounds in the soil.
Nitrogen-fixing bacteria are very useful
because they increase the amount of useful
nitrogen compounds in the soil.

41. Biological processes involved in the nitrogen
cycle:
1. Nitrogen fixation
2. Ammonification (decay)
3. Nitrification
4. Denitrification

42. ammonia
Organic nitrogen in dead
bodies or animal waste
Ammonification
Ammonification (Decay)
 Bacteria:
 Pseudomonas
 Bacillus
 Clostridium
 Fungi:
 Mucor

43. Ammonification (Decay)
 anaerobic decomposition of
proteins (putrefaction) releases
foul-smelling compounds like
hydrogen sulfide
 once ammonification has been
accomplished, nitrification, can
occur

44. Biological processes involved in the nitrogen
cycle:
1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. Denitrification

45. NITRIFYING BACTERIA
change ammonia into nitrites and then into
nitrates
this is called nitrification
ammonia is present in:
dead remains
animal waste

46. Nitrification involves two stages:
1. Nitrosomonas bacteria change:
2. Nitrobacter bacteria change:
NO2
-
nitrite
NH4
+
ammonium
O2
+ energy
NO2
-
nitrite
O2 NO3
-
nitrate
+ energy
Nitrobacte
r

47. Production of nitrates from organic nitrogen involves
ammonification and nitrification
nitrate
nitrite
ammonia
Organic nitrogen
in dead bodies or
animal waste
Ammonification
Nitrification
Nitrification
Nitrobacter
Nitrosomonas
Bacillus

48. Biological processes involved in the nitrogen
cycle:
1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. Denitrification

49. 3. Denitrification
 is the conversion of nitrate (NO3
-
) into
nitrogen gas (N2) under anaerobic conditions
Nitrogen gas
Nitrate

50. Animal
Dead animal & plants
Ammonia / Ammonium
Nitrites
Nitrates
Nitrosomonas sp.
Nitrobacter sp.
Plants
Denitrifying
bacteria
Atmosphere
fixation
Nitrogen
fixing
bacteria
Fertiliser
Nostoc sp.,
Rhizobium sp.
Thiobacillus sp.
NITROGEN CYCLE

51. Denitrification
 Denitrification is carried out by:
 denitrifying bacteria
 These bacteria utilise the nitrate as an oxygen source
Nitrogen gas
Nitrate

52. Denitrifying bacteria are:
 facultative aerobes [can live in the presence
or absence of oxygen]
Pseudomonas denitrificansThiobacillus denitrificans

53. Denitrification
 is more likely in waterlogged soil
Why do farmers dig up the
land?
To improve drainage and
aeration

54. Why can carnivorous plants live in nitrogen-poor
soils?

55. Animal
Dead animal & plants
Ammonia / Ammonium
Nitrites
Nitrates
Nitrosomonas sp.
Nitrobacter sp.
Plants
Denitrifying
bacteria
Atmosphere
fixation
Nitrogen
fixing
bacteria
Fertiliser
Nostoc sp.,
Rhizobium sp.
Thiobacillus sp.
NITROGEN CYCLE

56. Question:
This question is concerned with the role of nitrogen in the
biosphere:
1. Why is nitrogen essential for living organisms? (1)
To be a component of nitrogenous compounds like
nucleotides, coenzymes and proteins.
2. Why is nitrogen generally a significant limiting factor in
agriculture? (1)
Plants take up nitrogen in the form of nitrates and
ammonium in soil but is not recycled. Plants grow close
together and place a heavy demand on the soil.

57. 3. Briefly describe each of the following processes in the context
of the nitrogen cycle:
a) Nitrogen fixation
Nitrogen in air is converted into ammonium by nitrogen
fixing bacteria e.g. Rhizobium and cyanobacteria e.g. Nostoc.
b) Nitrification
Ammonium is oxidised to nitrites by nitrifying bacteria e.g.
Nitrosomonas and then to nitrates by for example
Nitrobacter.
c) Denitrification (6)
Nitrogen is released into the air by denitrifying bacteria from
nitrates e.g. by Pseudomonas.

58. 2. The diagram below shows some of the processes
involved in the cycling of nitrogen in an ecosystem.
a) Name the processes represented by the arrows X and Y.
X: ammonification/decay; Y: denitrification

59. b) State the genus of one organism represented by
the letter S and one organism represented by the
letter T in the diagram. (2)
Rhizobium;
AzotobacterPseudomonas;
Thiobacillus

60. Distinguish between nitrification and
denitrification. (5)
Nitrification is carried out under aerobic
conditions but denitrification under anaerobic
conditions.
In the process of nitrification, ammonia is
converted into nitrites and then into nitrates.
In denitrification, nitrates are converted into
nitrogen gas.

61. END OF SECTION
Dung beetles play a
remarkable role in agriculture.
By burying and consuming
dung, they improve nutrient
cycling and soil structure.

62. BAD MICROORGANISM

63. Pathogens, Vectors and Symptoms of Some Diseases
DiseaseDisease PathogensPathogens VectorVector SymptomsSymptoms Method of infectionMethod of infection
TBTB BacteriaBacteria -- -Feeling tiredFeeling tired
-Constant coughingConstant coughing
-Coughing out bloodCoughing out blood
Droplet infection, dust,Droplet infection, dust,
food and drinks that arefood and drinks that are
contaminatedcontaminated
CholeraCholera Bacteria (Bacteria (VibrioVibrio sp.)sp.) House flyHouse fly -VomitingVomiting
-Serious diarrheaSerious diarrhea
Water or food that isWater or food that is
contaminatedcontaminated
FoodFood
poisoninpoisonin
gg
Bacteria, fungiBacteria, fungi House flyHouse fly -VomitingVomiting
-DiarrhoeaDiarrhoea
-Abdominal painsAbdominal pains
-FeverFever
Water or food that isWater or food that is
contaminatedcontaminated
ColdCold VirusVirus -- - Fever, HeadacheFever, Headache
- Muscle painMuscle pain
Through the airThrough the air
RingworRingwor
mm
FungiFungi -- - Red spot on theRed spot on the
skinskin
- ItchinessItchiness
TouchTouch

64. Pathogens, Vectors and Symptoms of Some Diseases
DiseaseDisease PathogenPathogen
ss
VectorVector SymptomsSymptoms Method ofMethod of
infectioninfection
DengueDengue VirusVirus Mosquito,Mosquito, Aedes aegyptiAedes aegypti - High feverHigh fever
- HeadacheHeadache
-RashesRashes
- Pain at the jointPain at the joint
-Bleeding from the nose,Bleeding from the nose,
gums and tooth socketsgums and tooth sockets
Mosquito biteMosquito bite
MumpsMumps VirusVirus -- - FeverFever
- Painful feeling whenPainful feeling when
eatingeating
-Difficulty opening theDifficulty opening the
mouthmouth
-Soft swelling in front andSoft swelling in front and
below the earsbelow the ears
Through the airThrough the air

65. DiseaseDisease PathogensPathogens VectorVector SymptomsSymptoms Method of infectionMethod of infection
AIDSAIDS VirusVirus
(HIV 1 and(HIV 1 and
HIV 2)HIV 2)
-- - FeverFever
-Loss of body weightLoss of body weight
-TirednessTiredness
-Candidiasis around theCandidiasis around the
mouth and throatmouth and throat
-PneumoniaPneumonia
-Kaposis’s sarcomaKaposis’s sarcoma
-Through sexual contactThrough sexual contact
with a person infectedwith a person infected
with HIVwith HIV
- Transfusion of bloodTransfusion of blood
from a HIV victimfrom a HIV victim
-Sharing of injectionSharing of injection
needlesneedles
MalariaMalaria ProtozoaProtozoa
((PlasmodiumPlasmodium))
MosquitoMosquito - FeverFever
-HeadacheHeadache
- Muscle painMuscle pain
-ShiveringShivering
Mosquito biteMosquito bite
SARSSARS VirusVirus -- - High feverHigh fever
-Cry coughCry cough
-Shortness of breath orShortness of breath or
breathing difficultybreathing difficulty
-PneumoniaPneumonia
-Headache, muscularHeadache, muscular
stiffnessstiffness
-Loss of appetiteLoss of appetite
-Rash, diarrhoeaRash, diarrhoea
-Droplet infection touchDroplet infection touch
- Close contact withClose contact with
someone who has SARSsomeone who has SARS
-Body secretionBody secretion

66. Transmission of Microorganisms
1.Through five ways :
i) the air
ii) touch
iii) food
iv) vectors
v) water

67. Controlling Pathogens
Methods of controlling
pathogens
Antibiotics
Penicillin and streptomycin are
chemicals produced by
microorganisms which inhibit the
growth or kill other
microorganisms, especially bacteria
Vaccines
Are modified or weakened forms of
bacteria or viruses. Is a suspension of
dead bacteria or viruses which is
inoculated into our body to induce
the production of antibodies.
Examples of vaccine are Sabine
vaccine and BCG
Antiseptics
Are used on cuts and wounds
to kill and inhibit the growth
of microorganisms. Examples
of antiseptics are acriflavin
and iodine solution
Disinfectants
Use to kill microorganisms on
the floor, buildings or furniture
and sterilise surgical equipment.
Example : phenol, formaldehyde
and carbolic acid

69. The Role of Useful Microorganisms in the Ecosystem
1. Medicine
- fungi – produce antibiotic (prevent the growth of bacteria)
Examples: Penicillium notatum – gonorrhoea, syphilis, lung
infection, Streptomycine – tuberculosis (TB)
- dead bacteria or viruses – produce vaccine
Examples: BCG for TB

70. 2. Food Processing
- production of alcohol –
using yeast through the
fermentation process of
sugar, starch or grains
- production of vinegar –
the bacterium,
Acetobacter, acts on
alcohol to produce vinegar

71. 2. Food Processing
- Making bread – using yeast and sodium bicarbonate to
produce carbon dioxide to rises the bread dough
- Production of butter – cream is made sour by the action
of bacteria. Bacteria split protein from the fat of the cream.
This will enable the fat molecules to stick together when the
mixture is stirred strongly

72. 2. Food Processing
- production of fermented milk – tairu and yogurt
- bacteria, Lactobacillus sp. and Streptococcus sp.
and yeast - the milk will become sour and has
the smell of alcohol
- production of vitamins – Vitamin B2 – yeast
- Vitamin D – yeast and bacterium
- textile industry – bacteria are use to decompose
the soft plant tissues leaving the plant fibres