Organisms and Populations — BIOLOGY STD 12 Science — Question

Read the following text carefully and answer the questions that follow:
The reproductive cycle in female primates (e.g. monkeys, apes and human beings) is called the menstrual cycle. In human females, menstruation is repeated at an average interval of about 28/29 days, and the cycle of events starting from one menstruation till the next one is called the menstrual cycle Anita has show Diagrammatic presentation of various events during a menstrual cycle.

i. What role do pituitary gonadotropins play during the follicular and ovulatory phases of the menstrual cycle? (1)
ii. The first half of the menstrual cycle is called the proliferative phase as well as the follicular phase. Give reason.(2)
iii. Why does corpus luteum stay active throughout pregnancy and in the absence of fertilization, is active only for 10-12 days?
OR
What happens to corpus luteum in human female if the ovum is (2)
a. fertilised,
b. not fertilised?

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

Over population causes number of family problems. Strategies like birth control methods help to control population explosion. Natural methods of birth control do not involve medications or devices to prevent pregnancy, but rather rely on behavioural practices and/ or making observations about menstrual cycle.

1. Which method helps in contraception by temporary absence of sex?

1. Coitus interruptus.
2. Withdrawal method.
3. Rhythm method.
4. Lactational amenorrhea method.

2. Assertion: The effectiveness of coitus interruptus method is limited.

Reason: Some sperms may pass into vagina before ejaculation.

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.

3. Why is lactational amenorrhea effective for about 4-5 months after parturition?

1. Ovulation occurs on about the 14^th day of menstruation.
2. Ovulation does not occur during intense lactation.
3. This method inhibits mobility of sperms.
4. Both (b) and (c).

4. Which fact is not the basis of periodic absence method of birth control?

1. Ovum remains alive for about 1-2 days.
2. Ovulation occurs on about 14^th day of menstruation.
3. Sperms survive for about 3 days.
4. Alteration in uterine endometrium.

5. On which days of menstrual cycle should coitus be avoided to prevent fertilisation?

1. 10-17
2. 6-13
3. 1-5
4. 15-28

Explain the inheritance of one gene by Punnett Square ?

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

A typical angiospermic ovule is a small structure attached to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is formed. Mature ovules are classified on the basis of funiculus. It can be orthotropous, anadromous, hernitropous, campylotropous, etc.

1. The body of the ovule consists of a mass of parenchymatous cells called:

1. Integuments.
2. Nucellus.
3. Hilum.
4. Funiculus.

2. Refer to the given figure and select the correct statement regarding it.

1. This type of ovule is found in cactus.
2. The micropyle comes to lie close to the funiculus due to unilateral growth of ovule.
3. It is most common type of ovule found in the members of Chenopodiaceae.
4. It is half inverted ovule.

3. Identify the parts labelled as A, B, C and D in the given figure and select the correct option.

S. No	A	B	C	D
(a)	Chalaza	Female gametophyte	Embryo sac	Micropyle
(b)	Chalaza	NuceIIus	Embryo sac	Micropyle
(c)	Micropyle	Egg	Embryo sac	Chalaza
(d)	Micropyle	Nucellus	Embryo sac	Chalaza

4. Mature ovules are classified on the basis of funiculus. If micropyle lie close to the funiculus, the ovule is termed as:

1. Orthotropous.
2. Anatropous.
3. Hemitropous.
4. Campylotropous.

5. In Asphodel us, ovule is:

1. Unitegmic.
2. Tritegmic.
3. Bitegmic.
4. Ategmic.

What is sewage? Describe secondary treatment (biological treatment) in Sewage Treatment plant.

Read the following text carefully and answer the questions that follow:
A lymphocyte isa type of white blood cell. Enlarge. Blood cells. Blood contains many types of cells: white blood cells (monocytes, lymphocytes, neutrophils, eosinophils, basophils, and macrophages), red blood cells (erythrocytes), and platelets. Blood circulates through the body in the arteries and veins.

i. Why are the antigens called antibody-generating chemicals? (1)
ii. Which two types of lymphocytes are involved in immunity? (1)
iii. Give the common site of formation of two types of lymphocytes. (2)
OR
What is the site of differentiation of two types of lymphocytes? (2)

Read the following and answer any four questions from (i) to (v) given below:
In angiosperms, the pollen grains are being transferred from the anther to the stigma and is termed pollination. This phenomenon was first discovered by Camerarius (1694) in the end of seventeenth century. Pollen grains are immobile. They cannot reach the stigma by themselves. An external agent is required for this. The pollination is mainly of two types-self pollination and cross pollination. The diagram given below shows two plants of the same species showing different types of pollination.

1. What is transferred between the plants in the process indicated by arrow P?

1. Ova.
2. Pollen.
3. Nutrients.
4. Seeds.

2. Which of the following statements is correct regarding processes P, Q and R?

1. Processes P, Q and R introduce genetic variability in the offspring of sexually reproducing plants X and Y.
2. Wind serves as agent for process Q if plants X and Y belong to Genus Salvia.
3. Flowers of plants X and Y need to produce odour and nectar for completion of processes P and Q if they are entomophilous.
4. If plants X and Y belong to Genus Cannabis, then their flowers need to produce sticky and heavy pollens in very small amount for accomplishment of process Q.

3. Identify the processes P, Q and R.

S. No	P	Q	R
(a)	Geitonogamy	Xenogamy	Autogamy
(b)	Allogamy	Chasmogamy	Cleistogamy
(c)	Autogamy	Geitonogamy	Xenogamy
(d)	Geitonogamy	Allogamy	Autogamy

4. In Catliarantl1us, the growth of style brings the stigma in contact of ripe anthers present on the mouth of corolla tube. This is an example of:

1. Homogamy.
2. Cleistogamy.
3. Geitonogamy.
4. Xenogamy.

5. Which of the given processes represents a type of pollination that would result in greater adaptability of the particular species to potential environmental changes?

1. P.
2. Q.
3. R.
4. All of these.

Explain structure and working of biogas plant with diagram.

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

A young couple married for 5 years is unable to bear a child in spite of not practicing any birth control method. Upon consultation, doctor advised them an assisted reproductive technology involving transfer of gametes into oviducts.

1. Identify the technique adopted by the couple.

1. ZIFT
2. JUI
3. GIFT
4. ICSI

2. What is the pre-requisite of this technique?

1. Gamete formation should be normal.
2. Fallopian tubes should be normal.
3. Female should have thick endometrial lining.
4. Male should be able to copulate the female.

3. Assertion: GIFT is an in-vitro fertilisation technique.

Reason: In GIFT, gametes are fertilised outside the female body.

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.

4. The procedure advised to couple involves the transfer of:

1. Fertilised ovum.
2. Embryo with 8 blastomeres.
3. Sperms and unfertilised ovum.
4. Embryo with 16 blastomeres.

5. What is the success rate of this procedure?

1. 30-50%
2. < 20%
3. 80-85%
4. 27-30%