Download Bio 1.3 Questions 11

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You are advised to spend 50 minutes answering the questions in this booklet.
QUESTION ONE
Read the following information and use it to answer the question that follows:
Kiwifruit vines in New Zealand have become infected by a bacterium called Psa.
Controlling this pathogen is essential because the kiwifruit industry is worth more than
$1.5 billion to New Zealand.
Plants are infected with the bacterium by insects (such as bees or sucking insects such as
aphids), or when plants are damaged by birds, rain wind and hailstorms. It spreads
quickly during cool, wet weather. The bacteria become dormant over the winter
months, remaining in the plant tissue to reinfect it in spring.
Once inside the plant, the bacterium feeds on plant sugars and other substances,
reproducing rapidly. The bacterium produces a toxin that causes leaves on the kiwifruit
vine to die, and can eventually wipe out an entire orchard.
There are few ways in which the bacterium can be controlled. Infected parts of a plant
can be carefully cut off during still, dry weather and burnt. The tools used must be
sterilized with alcohol or bleach, and the cut surfaces on the plants must be sealed with
a special paint.
When many vines are involved, the entire orchard can be treated with sprays containing
copper or an antibiotic. However, the Psa bacterium is becoming increasingly resistant
to these sprays, and kiwifruit growers are encouraged to use them only as a last resort.
(a) Describe what is meant by each of the highlighted words in the text above.
Pathogen: _______________________________________________________________
Dormant: _______________________________________________________________
Toxin: __________________________________________________________________
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(b) Explain:
(i) How the Psa bacteria feed.
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(ii) Why the Psa bacteria reproduce rapidly once they are in the plant.
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(c) Using the information above, discuss the control methods used for Psa (those in italics
in the text). In your discussion:
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Explain how the control methods affect the life processes of the bacterium.
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Explain how the bacterium is becoming increasingly resistant to the copper and
antibiotic control sprays.
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QUESTION TWO
Bacterial food poisoning affects hundreds of people each day, sometimes very seriously. Food
usually becomes contaminated with bacteria during its preparation or storage.
There are several methods in which foods can be preserved so they remain free from bacterial
contamination. If successful, foods can be preserved for periods of time that can range from a
few days to a few years (depending on the type of food).
Compare and contrast TWO food preservation methods used to minimize the amounts of
bacteria in the food. In your discussion:
 Describe how foods can become contaminated with bacteria.
 Explain how the bacteria cause food poisoning.
 Explain how each food preservation method minimizes the amounts of bacteria in
food. You need to consider the similarities and differences between each food
preservation method.
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QUESTION THREE
Some viruses can contaminate food, but they can’t be cultured on food.
(a)
Draw a clearly labelled diagram in the space below that shows the main structural
features of a virus.
(b)
Explain why it is not possible to culture viruses on substances such as bread or agar.
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Most children worldwide under the age of 5 can expect to be infected by a rotavirus. Rotaviruses
cause severe diarrhea and vomiting by damaging the cells that line the gut. Symptoms usually take
around 2 days to appear after infection and last up to 10 days.
There are two vaccines available in New Zealand for young children that offer protection against
the virus. However, some children who have been vaccinated against rotavirus still become ill.
(c) Discuss how a rotavirus causes the symptoms described above and how the rotavirus
vaccine works. Include an explanation of why some children can still become ill despite
having had the vaccination.
In your answer consider:
 How a virus reproduces.
 The length of time between infection with the virus and the appearance of
symptoms.
 The effects of mutations in the virus.
You may use accurate, clearly labelled diagrams to help you with your answer.
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QUESTION FOUR
Ecosystems contain fixed amounts of substances called nutrients that all living organisms
need. Therefore, nutrients must be recycled within ecosystems. Certain micro-organisms
are essential to the process of nutrient recycling.
Carbon (C) is one of the most important nutrients that is recycled. Carbon is recycled
through the life processes of aerobic and anaerobic decomposers in soil and water. This is
called the carbon cycle.
Discuss the role of micro-organisms in the carbon cycle. In your discussion:
 Describe the carbon cycle.
 Explain how decomposers enable carbon to be recycled.
 Explain how the life processes of these decomposers can be affected by
environmental factors.
 Explain the importance of the carbon cycle to ecosystems.
You may use accurate, clearly labelled diagrams to help you with your answer.
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Additional space if required. Clearly number each answer.
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