FEBRUARY 2021 END-OF-SEMESTER COMMON TEST
QUESTION 1 (20 marks)
1.1 Identify if the following organisms are made of prokaryotic or eukaryotic cells. (2 marks)
a) Nematode
- Nematode is a multicellular eukaryotic organism.
b) Bacteria
- Bacteria are unicellular prokaryotic organisms.
1.2 Name the THREE factors that must be present at the same time for disease to occur. (3 marks)
1. Host: A susceptible host must be present, which can be a human, animal or plant.
2. Pathogen: A pathogen, which can be a virus, bacteria, fungus or parasite, must be present.
3. Environment: The environment in which the host and pathogen interact must be conducive to
disease transmission. This can include factors such as temperature, humidity, and the
presence of other organisms that may facilitate disease transmission.
1.3 Describe any TWO characteristics that help to diagnose the causal factor of a disease/disorder to
be abiotic. (4 marks)
Abiotic factors are nonliving factors that can contribute to disease or disorder.
1. Widespread distribution: If the disease or disorder affects a large number of individuals in a
wide geographical area, it may suggest that the causal factor is abiotic. Abiotic factors such as
temperature, light, and pollution can affect large areas and may lead to widespread disease or
disorder.
2. Lack of infectious agents: If there is no evidence of an infectious agent causing the disease
or disorder, it may suggest that the causal factor is abiotic. For example, if laboratory tests rule
out the presence of a virus, bacteria, fungus or parasite, it may suggest that the disease or
disorder is not caused by an infectious agent but rather by an abiotic factor such as exposure
to toxins or chemicals.
,1.4 Choose ONE of the abiotic factors listed below and answer questions (a) to (c). • Compacted soil
• Waterlogging or Flooded soil ( Chosen )
a) Identify ONE causal factor and suggest ONE method to rectify the problem. (2 marks)
One causal factor of waterlogging or flooded soil is 1. poor drainage. To rectify the problem, farmers
can 2. install drainage systems to improve water flow away from the affected area.
b) Describe any TWO symptoms seen on plants caused by the chosen abiotic factor. (2 marks)
Two symptoms seen on plants caused by waterlogging or flooded soil are 1. yellowing leaves and 2.
stunted growth.
1. Yellowing leaves occur because waterlogged soil lacks oxygen, which is needed for the roots
to function properly.
2. Stunted growth occurs because waterlogged soil reduces the availability of nutrients to the
plants.
c) Give TWO explanations of how the chosen abiotic factor affects soil quality and plant growth. (4
marks)
1. Reduced oxygen availability: When soil is waterlogged, the air spaces in the soil become
filled with water, which reduces the amount of oxygen available to the plant roots. Oxygen is
needed for respiration and nutrient uptake, so reduced oxygen availability can lead to reduced
plant growth and health.
2. Increased susceptibility to root diseases: Waterlogged soil can create anaerobic conditions
that favor the growth of harmful microbes that can cause root diseases. As a result, plants
growing in waterlogged soil are more susceptible to root rot and other diseases. Additionally,
waterlogged soil can lead to nutrient deficiencies and toxicities, which can further weaken the
plant's immune system and increase susceptibility to disease.
,1.5 Figure 1.5 shows the entry of pathogens into the host. 1. Identify the method of pathogen entry
and 2. name TWO types of microorganisms that gain entry into the host by this method. (3 marks)
1. Penetration through natural openings: pathogens can enter the plant through natural
openings such as stomata, hydathodes, or lenticels. These openings are necessary for gas
exchange, transpiration, and water movement, but they can also provide an entry point for
pathogens.
2. Two types of microorganisms that can gain entry into the host by natural openings include:
A. Viruses
B. Bacteria
QUESTION 2 (20 marks)
2.1 Name the TWO types of asexual spores produced by fungi. (2 marks)
1. Conidia: Conidia are a type of asexual spore that is formed at the tips of specialized hyphae
called conidiophores. Conidia are usually unicellular, but may be multicellular, and can be
produced in large numbers. They are commonly produced by many types of fungi, including
Aspergillus, Penicillium, and Fusarium.
2. Sporangiospores: Sporangiospores are another type of asexual spore that is produced
inside a specialized structure called a sporangium. The sporangium may be enclosed or open,
and the sporangiospores may be released when the sporangium ruptures. Sporangiospores
are produced by a variety of fungi, including the common bread mold Rhizopus.
, 2.2 Differentiate between the sign of 1. powdery mildew and 2. downy mildew disease. (2 marks)
The main differences between the signs of powdery mildew and downy mildew are:
1. Appearance: 1. Powdery mildew appears as a white or grayish powdery substance on the
leaves, stems, and flowers of plants. The powdery substance is made up of fungal spores and
mycelium, which look like a powder or dust. 2. Downy mildew appears as yellow or pale green
spots on the upper surface of leaves, while the underside of the leaves may have a
grayish-white or purple fuzzy growth.
2. Tissue Affected: 1. Powdery mildew affects the upper surface of leaves and other plant parts,
while 2. downy mildew affects the lower surface of leaves more than the upper surface.
3. Mode of Spore Release: Powdery mildew spores are easily airborne and can spread rapidly,
even without water. Downy mildew spores, on the other hand, require water for movement and
infection to occur, and are not as easily dispersed by the wind.
4. Environmental Conditions: Powdery mildew prefers dry weather, while downy mildew thrives
in moist or humid conditions.
In summary, the signs of powdery mildew and downy mildew differ in appearance, tissue affected,
mode of spore release, and environmental conditions.
2.3 Describe the 1. structure of a virus particle and state 2. its function. (4 marks)
A virus particle, also known as a virion, is a non-living infectious particle that can only replicate inside
the host cell. The structure of a virus particle is relatively simple and consists of the following
components:
1. Genetic Material: The genetic material of a virus can be either DNA or RNA, which is
enclosed in a protein coat called a capsid.
2. Capsid: The capsid is made up of protein subunits called capsomeres, which are arranged in
a precise geometric pattern. The capsid provides protection to the genetic material and
helps in attaching to the host cell.
3. Envelope (optional): Some viruses have an additional outer layer called an envelope, which is
made up of a lipid bilayer and viral proteins. The envelope is derived from the host cell's
membrane during the process of viral replication and helps the virus in evading the host's
immune system.
4. Spikes (optional): Some viruses have spike-like projections on their envelope, which help the
virus attach to specific receptors on the host cell.
The function of a virus particle is to infect the host cell and replicate. Once the virus particle enters the
host cell, the genetic material is released, and the virus hijacks the host's cellular machinery to
replicate itself. The new virus particles are then assembled and released from the host cell, which can
infect other cells and continue the cycle of infection.
QUESTION 1 (20 marks)
1.1 Identify if the following organisms are made of prokaryotic or eukaryotic cells. (2 marks)
a) Nematode
- Nematode is a multicellular eukaryotic organism.
b) Bacteria
- Bacteria are unicellular prokaryotic organisms.
1.2 Name the THREE factors that must be present at the same time for disease to occur. (3 marks)
1. Host: A susceptible host must be present, which can be a human, animal or plant.
2. Pathogen: A pathogen, which can be a virus, bacteria, fungus or parasite, must be present.
3. Environment: The environment in which the host and pathogen interact must be conducive to
disease transmission. This can include factors such as temperature, humidity, and the
presence of other organisms that may facilitate disease transmission.
1.3 Describe any TWO characteristics that help to diagnose the causal factor of a disease/disorder to
be abiotic. (4 marks)
Abiotic factors are nonliving factors that can contribute to disease or disorder.
1. Widespread distribution: If the disease or disorder affects a large number of individuals in a
wide geographical area, it may suggest that the causal factor is abiotic. Abiotic factors such as
temperature, light, and pollution can affect large areas and may lead to widespread disease or
disorder.
2. Lack of infectious agents: If there is no evidence of an infectious agent causing the disease
or disorder, it may suggest that the causal factor is abiotic. For example, if laboratory tests rule
out the presence of a virus, bacteria, fungus or parasite, it may suggest that the disease or
disorder is not caused by an infectious agent but rather by an abiotic factor such as exposure
to toxins or chemicals.
,1.4 Choose ONE of the abiotic factors listed below and answer questions (a) to (c). • Compacted soil
• Waterlogging or Flooded soil ( Chosen )
a) Identify ONE causal factor and suggest ONE method to rectify the problem. (2 marks)
One causal factor of waterlogging or flooded soil is 1. poor drainage. To rectify the problem, farmers
can 2. install drainage systems to improve water flow away from the affected area.
b) Describe any TWO symptoms seen on plants caused by the chosen abiotic factor. (2 marks)
Two symptoms seen on plants caused by waterlogging or flooded soil are 1. yellowing leaves and 2.
stunted growth.
1. Yellowing leaves occur because waterlogged soil lacks oxygen, which is needed for the roots
to function properly.
2. Stunted growth occurs because waterlogged soil reduces the availability of nutrients to the
plants.
c) Give TWO explanations of how the chosen abiotic factor affects soil quality and plant growth. (4
marks)
1. Reduced oxygen availability: When soil is waterlogged, the air spaces in the soil become
filled with water, which reduces the amount of oxygen available to the plant roots. Oxygen is
needed for respiration and nutrient uptake, so reduced oxygen availability can lead to reduced
plant growth and health.
2. Increased susceptibility to root diseases: Waterlogged soil can create anaerobic conditions
that favor the growth of harmful microbes that can cause root diseases. As a result, plants
growing in waterlogged soil are more susceptible to root rot and other diseases. Additionally,
waterlogged soil can lead to nutrient deficiencies and toxicities, which can further weaken the
plant's immune system and increase susceptibility to disease.
,1.5 Figure 1.5 shows the entry of pathogens into the host. 1. Identify the method of pathogen entry
and 2. name TWO types of microorganisms that gain entry into the host by this method. (3 marks)
1. Penetration through natural openings: pathogens can enter the plant through natural
openings such as stomata, hydathodes, or lenticels. These openings are necessary for gas
exchange, transpiration, and water movement, but they can also provide an entry point for
pathogens.
2. Two types of microorganisms that can gain entry into the host by natural openings include:
A. Viruses
B. Bacteria
QUESTION 2 (20 marks)
2.1 Name the TWO types of asexual spores produced by fungi. (2 marks)
1. Conidia: Conidia are a type of asexual spore that is formed at the tips of specialized hyphae
called conidiophores. Conidia are usually unicellular, but may be multicellular, and can be
produced in large numbers. They are commonly produced by many types of fungi, including
Aspergillus, Penicillium, and Fusarium.
2. Sporangiospores: Sporangiospores are another type of asexual spore that is produced
inside a specialized structure called a sporangium. The sporangium may be enclosed or open,
and the sporangiospores may be released when the sporangium ruptures. Sporangiospores
are produced by a variety of fungi, including the common bread mold Rhizopus.
, 2.2 Differentiate between the sign of 1. powdery mildew and 2. downy mildew disease. (2 marks)
The main differences between the signs of powdery mildew and downy mildew are:
1. Appearance: 1. Powdery mildew appears as a white or grayish powdery substance on the
leaves, stems, and flowers of plants. The powdery substance is made up of fungal spores and
mycelium, which look like a powder or dust. 2. Downy mildew appears as yellow or pale green
spots on the upper surface of leaves, while the underside of the leaves may have a
grayish-white or purple fuzzy growth.
2. Tissue Affected: 1. Powdery mildew affects the upper surface of leaves and other plant parts,
while 2. downy mildew affects the lower surface of leaves more than the upper surface.
3. Mode of Spore Release: Powdery mildew spores are easily airborne and can spread rapidly,
even without water. Downy mildew spores, on the other hand, require water for movement and
infection to occur, and are not as easily dispersed by the wind.
4. Environmental Conditions: Powdery mildew prefers dry weather, while downy mildew thrives
in moist or humid conditions.
In summary, the signs of powdery mildew and downy mildew differ in appearance, tissue affected,
mode of spore release, and environmental conditions.
2.3 Describe the 1. structure of a virus particle and state 2. its function. (4 marks)
A virus particle, also known as a virion, is a non-living infectious particle that can only replicate inside
the host cell. The structure of a virus particle is relatively simple and consists of the following
components:
1. Genetic Material: The genetic material of a virus can be either DNA or RNA, which is
enclosed in a protein coat called a capsid.
2. Capsid: The capsid is made up of protein subunits called capsomeres, which are arranged in
a precise geometric pattern. The capsid provides protection to the genetic material and
helps in attaching to the host cell.
3. Envelope (optional): Some viruses have an additional outer layer called an envelope, which is
made up of a lipid bilayer and viral proteins. The envelope is derived from the host cell's
membrane during the process of viral replication and helps the virus in evading the host's
immune system.
4. Spikes (optional): Some viruses have spike-like projections on their envelope, which help the
virus attach to specific receptors on the host cell.
The function of a virus particle is to infect the host cell and replicate. Once the virus particle enters the
host cell, the genetic material is released, and the virus hijacks the host's cellular machinery to
replicate itself. The new virus particles are then assembled and released from the host cell, which can
infect other cells and continue the cycle of infection.
