Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Read the following and answer any four questions from (i) to (v) given below:

Unlike animals, plants cannot runaway for their defence, therefore, they have evolved an astonishing variety of morphological and chemical defences against herbivores. Thorns are the most common morphological means of defence. Many plants produce and store chemicals that make the herbivore sick when they are eaten, inhibit feeding or digestion, disrupt its reproduction or even kill it. Some plants produce highly poisonous chemicals and that is why no cattle or goats browse on those plants. A wide variety of chemical substances that we extract from plants on a conunercial scale are produced by them actually as defence against grazers and browsers.

1. Why you never see cattle or goats browsing on weed Calotropisl?

1. It produces highly poisonous tannins.
2. It produces quinine which is bitter in taste.
3. It produces poisonous cardiac glycosides.
4. It bears prickles.

 

2. What could be the possible reason for invasive growth of the prickly pear cactus introduced in Australia?

1. Absence of predators.
2. New mycorrhizal association.
3. Abundant water availability.
4. All of these.

3. Which of the following is most likely to sick by consuming chemicals produced by plants?

1. Frog
2. Goat
3. Human
4. Pigeon

4. Plant evolve variety of morphological and chemical defences against.

1. Prey
2. Predator
3. Commenal
4. Mutualist

5. Assertion: Some plant functions as predator in nature.

Reason: Phytoph ago us insects feed on plant sap.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Read the following text carefully and answer the questions that follow:
The pathogen of a disease depends on RBCs of human for growth and reproduction. The person with this
pathogen suffers with chill and high fever.

i. Identify the disease. (1)
ii. Name the pathogen. (1)
iii. What is the cause of fever? (2)
OR
Represent the life cycle of the pathogen diagrammatically. (2)

What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.

Explain parasitism as population interaction with examples.

Read the following and answer any four questions from (i) to (v) given below:

In prokaryotes, DNA is circular and present in the cytoplasm but in eukaryotes, DNA is linear and mainly confined to the nucleus. DNA or deoxyribonucleic acid is a long polymer of nucleotides. In 1953, the first correct double-helical structure of DNA was worked out by Watson and Crick. Based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin. It is composed of three components, i.e., A phosphate group, a deoxyribose sugar and a nitrogenous base. Different forms of DNA are B-DNA, Z-DNA, A-DNA, C-DNA and D-DNA.

1. Name the linkage present between the nitrogen base and pentose sugar in DNA.

1. Phosphodiester bond
2. Phosphodiester bond
3. Hydrogen bond
4. None of these

2. The double helix structure of DNA was proposed by.

1. James Watson and Francis Crick.
2. Earwin Chargaff
3. Federick Griffith
4. Hershey and Chase.

3. The double chain of B-DNA is coiled in a helical fashion. The spiral twisting of B-DNA duplex produces.

1. Right and left part.
2. Major and minor grooves.
3. Upper and lower side.
4. Linear and circular part.

4. Assertion: The two strands of DNA helix have uniform distance between them.

Reason: A large sized purine always paired opposite to a small sized pyrimidine.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

5. Which of the following describes the structure of B-DNA?

S.no	Polynudeotide chains	Polynudeotide chains
(a)	Parallel	5
(b)	Anti-parallel	10
(c)	Parallel	15
(d)	Anti-parallel	20

The bacterium Bacillus thuringiensis is widely used in contemporary biology as:

1. Agent for production of dairy products.
2. Source of industrial enzyme.
3. Indicator of water pollution.
4. Insecticide.

What is chromosomal disorder? Explain any two aneuploidy with characters in humans.###Mention any two autosomal genetic disorders with their symptoms.

Explain in situ approach for conservation of biodiversity.

Read the following text carefully and answer the questions that follow:
When a microorganism invades a host, a definite sequence of events usually occur leading to infection and disease, causing suffering to the host. This process is called pathogenesis. Once a microorganism overcomes the defense system of the host, development of the disease follows a certain sequence of events as shown in the graph. Study the graph given below for the sequence of events leading to appearance of a disease and answer the questions that follow:

i. In which period, according to the graph there are maximum chances of a person transmitting a disease/infection and why? (1)
ii. Study the graph and write what is an incubation period. Name a sexually transmitted disease that can be easily transmitted during this period. Name the specific type of lymphocytes that are attacked by the pathogen of this disease. (1)
iii. Draw a schematic labelled diagram of an antibody. (2)
OR
In which period, the number of immune cells forming antibodies will be the highest in a person suffering from pneumonia?
Name the immune cells that produce antibodies. (2)