Organisms and Populations — BIOLOGY STD 12 Science — Question

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

Pollen-pistil interaction is the group of events that occur from the time of pollen deposition over the stigma to the time of pollen tube entry into ovule. It is a dynamic process which has checks at several places for promotion or inhibition of pollen growth. Pollen-pistil interaction is a safety measure to ensure that illegitimate crossings do not occur. Compatibility and incompatibility of the pollen-pistil is determined by special proteins. The compatible pollens are able to absorb water and nutrients from the surface of the stigma. They germinate and produce pollen tubes. Pollen tubes grow into the style. Their growth and path through the style are also determined by specific chemicals.

1. Which of the following parts of gynoecium determines the compatible nature of pollen?

1. Stigma.
2. Style.
3. Ovary.
4. Thalamus.

2. In Triforium, which type of self-incompatibility is found?

1. Gametophytic self-incompatibility (GSI).
2. Sporophytic self-incompatibility (SSI).
3.  Both GSI and SSI.
4. None of these.

3. Select the incorrect statement.

1. In Asteraceae, incompatibility is due to the genotype of the sporophytic stigmatic tissues.
2. In members of Brassicaceae, incompatibility is due to the genotype of the pollen.
3. Nature has imposed self-incompatibility to avoid highly homozygous individuals, which have a very low survival value.
4. None of these.

4. Which of the following are examples of self incompatibility?

1. Tobacco.
2. Potato.
3. Crucifers.
4. All of these.

5. Given figures show the pollen-stigma interaction, where pollen wall proteins are released onto the pellicle of stigmatic papillae, where a recognition reaction occurs.

Which of the following statements drawn from given figures is incorrect?

1. P indicates compatible reaction in which the pollen tube penetrates the cuticle and grows down the papilla.
2. Development of callose plug between the plasma membrane and pectocellulosic layer of stigmatic papillae results in the incompatibility reaction in Q.
3. A callose plug, which appears at the tip of pollen in Q, is dissolved by callase enzyme secreted by stigma resulting in compatibility reaction.
4. Deposition of callose can be employed as a reliable bioassay to detect compatibility or incompatibility reactions of pollen and stigma.

Describe pregnancy and embryonic development.

Write a short note on transcription unit.### Explain : Transcription unit

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

Rajesh, Ravi, and Rohit are roommates. 'They are doing their graduation. Few months back Ravi fell ill. it took him around 3 weeks to recover. Both his friends were absolutely healthy at that time. After sometime, Rajesh also fell ill from some other disease. This time Ravi and Rohit both contracted the same illness. Based on the above information, answer the following questions.

1. Which of the following holds true for Ravi's illness?

1. Ravi was suffering from a communicable disease that is transmitted through vector.
2. Ravi was suffering from a communicable disease that is transmitted through faecal oral route.
3. Ravi was suffering from a non-communicable disease like anaemia.
4. Ravi was suffering from a non-communicable disease like Down's syndrome.

2. Select the correct statement.

1. Ravi contracted a disease caused by air borne microbes.
2. Ravi could have suffered a nutritional disorder.
3. Ravi suffered a non-contagious disease.
4. Both (b) and (c)

3. Which could be correctly said for Rajesh's illness?

1. Rajesh's illness was due to a microbial infection.
2. Rajesh's illness could be contagious or non-contagious.
3. Rajesh's illness could be cured by antibiotics.
4. All of these

4. Which of the following may depicts Ravi's and Rajesh's illness?

S.no	Ravi	Rajesh
(a)	Which of the following may depicts Ravi's and Rajesh's illness?	Myocardial infection
(b)	Whooping cough	Tetanus
(c)	Gastritis	Rhinitis
(d)	Hypertensio	Thyroid

5. Assertion: Diabetes mellitus is a non-communicable disease which can be completely cured.

Reason: Diabetes mellitus is caused by deficiency of aldosterone hormone.

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.

Explain Predation as population interaction with different example.

Explain pBR322 with its cloning sites, enzymes with well labeled diagram.###Explain: cloning sites. (Diagram is not necessary)

Give an account of energy flow in an ecosystem.

With labeled diagrams describe the mechanism of Pollen-pistil Interaction.

Define decomposition and describe the processes and products of decomposition.###Describe factor affecting decomposition.

Explain Competition as a population Interaction with suitable examples.