Biodiversity, Conservation and Environmental Issues — BIOLOGY STD 12 Science — Question

Read the following and answer any four questions from (i) to (v) given below:
RNA or ribonucleic acid is a single chain polyribonucleotide which functions as carrier of coded genetic or hereditary information from DNA to cytoplasm for taking part in protein and enzyme synthesis. Six types of RNAs are ribosomal, transfer, messenger, genomic, small nuclear and small cytoplasmic RNA. Out of these, rRNA, mRNA and tRNA are major classes of RNAs that are involved in gene expression.

1. Which one is referred to a soluble RNA?

1. mRNA
2. tRNA
3. rRNA
4. hnRNA

2. The RNA that picks up specific amino acid from amino acid pool in the cytoplasm to ribosome during protein synthesis is?

1. rRNA
2. hnRNA
3. mRNA
4. tRNA

3. Which of the following is found in both DNA and messenger RNA?

1. Double helix structure
2. Ribose
3. Sugar-phosphate chain
4. Thymine

4. Which of the following statements regarding RNA is correct?

1. Messenger RN As carries coded information for synthesis of polypeptide.
2. Ribosomal RNAs bind with tRNA to catalyse the formation of phosphodiester bonds.
3. Genomic RNA is always single stranded.
4. Synthesis of rRNA occurs in cytoplasm by RNA polymerase III

5. In studying a virus, you find the following proportions of nitrogenous bases present: adenine 23%, guanine 37%, cytosine 23% uracil 17%. Which of the following statement(s) regarding this virus is/are correct?

1. It probably uses RNA as its genetic material.
2. The genetic material of this virus is probably single stranded.
3. Base pairing rules in virus in this virus include adenine: cytosine.

1. I only
2. I and II only
3. II and III only
4. All of these.

Read the following and answer any four questions from (i) to (v) given below:
The endosperm makes the main source of food for the embryo. Generally the endosperm nucleus divides after the division of the oospore, but in several cases the endosperm is formed to a great extent even before the first division of the oospore. There are three general types of endosperm formation: (a) nuclear type, (b) cellular type and (c) helobial type. The endosperm is usually triploid, but haploid endosperm is also found. Endosperm may either be completely consumed by the developing embryo before seed maturation, or it may persist in the mature seed.

1. Haploid endosperm is found in:

1. Pin us.
2. Cauliflower.
3. Sunflower.
4. Pea.

2. Persistent endosperm is found in:

P. Pea Q. Castor R. Bean S. Coconut T. Groundnut.

1. Q and S.
2. P and T.
3. R, S and T.
4. P, S and T.

3. Milk of tender coconut represents (A) and the surrounding white coconut meal represents (B).

S. No	A	B
(a)	Cellular endosperm	Free- nuclear endosperm
(b)	Free-nuclear endosperm	Cellular endosperm
(c)	Helobial endosperm	Cellular endosperm
(d)	Free-nuclear endosperm	Helobial endosperm

4. If an endosperm cell of a gymnosperm contains 12 chromosomes, the number of chromosomes in each cell of the root will be:

1. 4
2. 24
3. 16
4. 6

5. In angiosperms, normally after fertilization:

1. The zygote divides earlier than the primary endosperm nucleus.
2. The primary endosperm nucleus divides earlier than the zygote.
3. Both the zygote and primary endosperm nucleus divide simultaneously.
4. Both the zygote and primary endosperm nucleus undergo a resting period.

Read the following and answer any four questions from (i) to (v) given below:
The first menstruation is called menarche, that usually occurs between 12 and 15 years. In human females, menstruation is repeated at an average interval of about 28/29 days and is called menstrual cycle. It is regulated by certain hormones, as pituitary gland is stimulated by releasing factors produced in the hypothalamus. The hormones produced by pituitary gland influence the ovaries. The hormones secreted by the ovaries affect the walls of the uterus.

1. The breakdown of endometrium is characteristic of:

1. Proliferative phase.
2. Luteal phase.
3. Ovulatory phase.
4. Menstrual phase.

2. Which days of the menstrual cycle marks the proliferative phase?

1. 1-5
2. 15-28
3. 6-13
4. 10-14

3. Which of the following occurs during secretory phase?

1. Empty Graafian follicle changes into corpus luteum.
2. Primary follicle changes into Graafian follicle.
3. Endometrium rebuilds and estrogen secretion increases.
4. LH surge, inducing release of an ovum.

4. Identify the hormones that attain peak level during ovulatory phase.

1. FSH.
2. Progesterone.
3. LH.
4. Both (a) and (c).

5. Withdrawal of which hormone causes degeneration of corpus luteum?

1. FSH.
2. LH.
3. Progesterone.
4. Estrogen.

1. What are the three options that can be thought of, to increase food production?
2. Mention the reasons for the success of Green Revolution in increasing food production.
3. Why do we still search for other alternatives to increase food production?

Natality and Mortality.

Distinguish between : Erythrocytes and Leucocytes.

Read the following and answer any four questions from (i) to (v) given below:
The pollen grains or microspores are the male reproductive bodies of a flower and are contained in the pollen sac or microsporangia. Each pollen grain consists of a single microscopic cell, possessing two coats: the exine and the in tine. The exine of a pollen grain is made of chemically stable material. Because of this, pollen grains are often very well preserved for thousands of years in soil and sediments.

1. One of the most resistant biological material present in the exine of pollen grain is:

1. Pectocellulose.
2. Sporopollenin.
3. Suberin.
4. Cellulose.

2. The exine possesses one or more thin places known as:

1. Raphe.
2. Germ pores.
3. Hilum.
4. Endothecium.

3. What is the function of germ pore?

1. Emergence of radicle.
2. Absorption of water for seed germination.
3. Initiation of pollen tube.
4. All of these.

4. What is the key advantage to the plant for having such strong pollen grain walls?

1. It protects the vital genetic material in the pollen grain.
2. It allows pollen to serve as a valuable fossil record for the study of ancient plants.
3. It prevents the pollen tube from growing out before the pollen grain reaches the stigma of a compatible species.
4. It gives weight to the pollen grain, allowing it to cling better to the body surfaces of insect pollinators.

5. The number of germ pores in dicots and monocots respectively are:

1. One and three.
2. Three and two.
3. Two and three.
4. Three and one.

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.