Respiration and Circulation — BIOLOGY STD 12 Science — Question

Read the following and answer any four questions from (i) to (v) given below: The mature ovum or a female gamete is spherical in shape. The human ovum is almost free of yolk and is said to be alecithal. Human ovum loses its ability to be fertilised about 24 hours after ovulation. Refer to the given structure of ovum and answer the following questions.

1. Thick cellular layer formed of radially elongated follicular cells is:

1. Zona pellucida.
2. Plasma membrane.
3. Perivitelline membrane.
4. Corona radiata.

2. In humans, at which stage does ovum get released from ovary?

1. Secondary oocyte.
2. Oogonium.
3. Primary oocyte.
4. First polar body.

3. Cytoplasm of an ovum is enveloped by _____.

1. Zona pellucida.
2. Corona radiata.
3. Cell membrane.
4. Perivitelline space.

4. Select the correct option:

S. No	V	W	X
(a)	Cytoplasm	Zona pellucida	Plasma membrane
(b)	Cortical granules	Corona radiata	Zona pellucida
(c)	Cortical granules	Plasma membrane	Corona radiata
(d)	Cytoplasm	Corona radiata	Zona pellucida

5. Which of the following is not a characteristic of an ovum?

1. Nucleus of an ovum has prominent nucleolus.
2. Only one ovum formed from one oogonium.
3. It lacks centrioles.
4. It has very small amount of ooplasm.

Distinguish between: Asexual reproduction and Sexual reproduction.

Distinguish between : Glucocorticoids and mineralcorticoids

Read the following and answer any four questions from (i) to (v) given below:
Cleavage is the series of rapid mitotic divisions in zygote and forms blastula. The 2, 4, 8, 16 daughter cells are called blastomeres. Embryo with 64 blastomeres is known as blastocyst and has blastocoel cavity. Blastocyst gets implanted in uterine wall and leads to pregnancy.

1. Solid mass of cells with 16 blastomeres is called:

1. Morula.
2. Blastula.
3. Gastrula.
4. Zygote.

2. At which stage of embryonic development, trophoectoderm develops?

1. Zygote.
2. Morula.
3. Blastula.
4. Gastrula.

3. Site of implantation is:

1. Endometrium of uterus.
2. Cervix.
3. Uterine fundus.
4. Infundibulum of oviduct.

4. Correct sequence of various structures formed during embryonic development is:

1. Morula → Embryo → Gastrula → Blastula.
2. Zygote → Embryo → Morula → Blastula.
3. Blastula → Morula → Gastrula → Embryo.
4. Zygote → Morula → Blastula → Gastrula.

5. Assertion: Side of blastocyst with inner cell mass is called animal pole.

Reason: Inner cell mass gives rise to embryo.

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 and answer any four questions from (i) to (v) given below:
During copulation, semen is released by the penis into the vagina. 'The motile sperms swim rapidly, fuse with ovum in the ampullary region, resulting in fertilisation. Haploid nucleus of sperm fuse with that of ovum to form diploid zygote.

1. In female genital tract, sperms are made capable of fertilising the egg. This phenomenon of sperm activation is called:

1. Amphimixis.
2. Cortical reaction.
3. Capacitation.
4. Acrosomal reaction.

2. Select the correct sequence of various physical and chemical events that take place during fertilisation.

16. Fusion of cortical granules with plasma membrane of secondary oocyte.
17. Formation of fertilisation cone to receive sperm.
18. Release of sperm lysin from acrosome.
19. Mixing up of chromosomes of a sperm and an ovum.

1. R → Q → P → S
2. Q → S → R → P
3. Q → R → S → P
4. R → P → Q → S

3. Assertion: Only one sperm can fertilise an ovum.

Reason: The secretion of acrosome help the sperm to enter into cytoplasm of ovum through zona pellucida and plasma membrane.

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. What is the significance of fertilisation?

1. It restores haploid number of chromosomes.
2. It produces offspring genetically identical to parents.
3. It initiates cleavage.
4. Both (b) and (c).

5. Site of fertilisation in humans is:

1. Endometrium of uterine cavity.
2. Ampullary isthmic junction of oviduct.
3. Cervix of uterus.
4. Infundibulum of fallopian tube.

Read the following and answer any four questions from (i) to (v) given below:
Wetlands are called Ramsar sites because the first international convention on their conservation was held in Ramsar in Iran in 1971. Wetlands or Ramsar sites are low lying marshy areas which get filled up during rains due to runoff and overflow from other water bodies. They are often considered to be waste lands which are used as dumping areas and filled up to recover land for various constructions activities. As a result, a large number of wetlands have disappeared.

1. Select the incorrect match of wetland and its location.

	Wetland	Location
(a)	Harike	Punjab
(b)	Chandra Tai	H.P.
(c)	Bhoj	M.P.
(d)	Ashtamudi	Odisha

2. Migratory bird flamingo breeds in which of the following wetlands?

1. Bhitarkanika Mangroves.
2. Rann of Kutch.
3. Harike.
4. Chandra Tal.

3. Which of the following is not an importance of wetlands?

1. They are an important source of recharging groundwater.
2. They provide protection from floods.
3. They are good source of siltation and purification of water.
4. None of these.

4. Which of the following wetland ecosystem is highly acidic and has a accumulation of decomposed plants known as peat?

1. Bog
2. Mangrove
3. Estuary
4. Watershed

5. The mangroves of Bhitarkanika are famous for:

1. Rare migratory waterbirds.
2. Nesting sites for endangered olive ridley turtles.
3. Prawn cultivation.
4. All of these.

Distinguish between : Adenohypophysis and neurohypophysis.

Active absorption and Passive absorption.