CBSE Class 12 Biology Revision Notes Chapter 2 Human Reproduction
CBSE Class 12 Biology Revision Notes Chapter 2 explain Human Reproduction through reproductive systems, gametogenesis, menstrual cycle and fertilisation. For CBSE 2026 Biology, Human Reproduction connects puberty, gamete formation, pregnancy, parturition and lactation with NCERT terms.
Human reproduction in Class 12 Biology begins with one central idea: humans reproduce sexually and are viviparous. The NCERT Class 12 Biology chapter Human Reproduction explains how male and female gametes form, how fertilisation produces a zygote, and how the embryo develops inside the uterus. The chapter also studies the male and female reproductive systems because each structure supports a specific event.
These class 12 biology chapter 2 human reproduction notes follow the NCERT 2026 sequence from reproductive organs to gametogenesis, menstrual cycle, fertilisation, implantation, pregnancy, parturition and lactation. The chapter is important for diagram-based questions, hormone-based answers and process-sequence questions in CBSE exams.
Key Takeaways
- Testicular lobules: Each testis has about 250 compartments called testicular lobules.
- Sperm count: A human male ejaculates about 200 to 300 million sperms during coitus.
- Menstrual cycle: Menstruation repeats at an average interval of about 28/29 days.
- Pregnancy duration: Human pregnancy lasts about 9 months before parturition.
CBSE Class 12 Biology Revision Notes Chapter 2 Structure 2026
| Question Type | What to Focus On | Answer Angle |
| Diagram-based | Male system, female system, sperm, ovary and follicle | Label parts with functions |
| Process-based | Spermatogenesis, oogenesis, fertilisation and implantation | Write sequence in correct order |
| Hormone-based | GnRH, LH, FSH, progesterone, oxytocin and hCG | Link hormone with event |
Human Reproduction and Major Events
Humans reproduce sexually and give birth to young ones. The major events include gametogenesis, insemination, fertilisation, implantation, gestation and parturition.
In CBSE Class 12 Biology Chapter 2 Human Reproduction, these events occur after puberty. The chapter also compares male and female reproductive events.
Main reproductive events
Human reproduction begins with formation of gametes. Sperms form in males, and ovum forms in females.
Sperms enter the female genital tract through insemination. Fusion of sperm and ovum forms the zygote.
The zygote develops into blastocyst and gets attached to the uterine wall. This process is called implantation.
Male and female differences
Sperm formation can continue even in old men. Ovum formation stops in women around the age of fifty years.
This is one key difference between male and female reproductive events. Menopause marks the end of the normal reproductive phase in females.
Male Reproductive System
The male reproductive system lies in the pelvic region. It includes a pair of testes, accessory ducts, accessory glands and external genitalia.
Male reproductive system class 12 biology questions usually test labelled diagrams, duct sequence and cell functions. NCERT places testes and seminiferous tubules at the centre of sperm formation.
Testes and scrotum
The testes lie outside the abdominal cavity in a pouch called the scrotum. The scrotum maintains a temperature 2 to 2.5°C lower than normal internal body temperature.
This lower temperature is necessary for spermatogenesis. Each adult testis is about 4 to 5 cm long and 2 to 3 cm wide.
Testicular lobules and seminiferous tubules
Each testis has about 250 testicular lobules. Each lobule contains one to three highly coiled seminiferous tubules.
Sperms are produced inside seminiferous tubules. Their inner lining has male germ cells and Sertoli cells.
Sertoli cells and Leydig cells
Sertoli cells provide nutrition to male germ cells. Male germ cells undergo meiosis and form sperms.
Leydig cells are present in interstitial spaces outside seminiferous tubules. They secrete androgens, which support spermatogenesis.
Male accessory ducts
Male accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. These ducts store and transport sperms.
The seminiferous tubules open into vasa efferentia through rete testis. Epididymis leads to vas deferens, which joins the ejaculatory duct.
Male accessory glands
Male accessory glands include paired seminal vesicles, a prostate gland and paired bulbourethral glands. Their secretions form seminal plasma.
Seminal plasma is rich in fructose, calcium and certain enzymes. Bulbourethral gland secretions help lubricate the penis.
Female Reproductive System
The female reproductive system lies in the pelvic region. It includes ovaries, oviducts, uterus, cervix, vagina, external genitalia and mammary glands.
Female reproductive system class 12 biology questions usually ask functions, diagrams and duct parts. The system supports ovulation, fertilisation, pregnancy, birth and child care.
Ovaries
Ovaries are the primary female sex organs. They produce the female gamete, ovum, and ovarian hormones.
Each ovary is about 2 to 4 cm long. It is connected to the pelvic wall and uterus by ligaments.
Oviducts
Oviducts are also called fallopian tubes. Each fallopian tube is about 10 to 12 cm long.
The part closer to the ovary is the funnel-shaped infundibulum. Its fimbriae help collect the ovum after ovulation.
The infundibulum leads to ampulla. The isthmus joins the uterus and has a narrow lumen.
Uterus and cervix
The uterus is also called the womb. It has the shape of an inverted pear.
The uterus opens into the vagina through the cervix. The cervical canal and vagina together form the birth canal.
The uterine wall has perimetrium, myometrium and endometrium. The endometrium changes during the menstrual cycle.
External genitalia
Female external genitalia include mons pubis, labia majora, labia minora, hymen and clitoris. These structures surround and protect the vaginal opening.
NCERT clearly states that presence or absence of hymen is not a reliable indicator of virginity or sexual experience. Hymen can break due to activities other than coitus.
Mammary glands
Mammary glands are paired structures present in females. They contain glandular tissue and variable fat.
Each breast has 15 to 20 mammary lobes. Alveoli secrete milk, which passes through mammary ducts and lactiferous ducts to the nipple.
Gametogenesis in Humans
Gametogenesis is the formation of gametes in primary sex organs. Testes produce sperms, while ovaries produce ovum.
Human reproduction class 12 notes often test spermatogenesis and oogenesis together. The two processes differ in timing, cell division and number of functional gametes.
Spermatogenesis
Spermatogenesis is the process of sperm formation from spermatogonia. It begins at puberty.
Spermatogonia are diploid and contain 46 chromosomes. They divide mitotically and increase in number.
Some spermatogonia become primary spermatocytes. Each primary spermatocyte undergoes meiosis and produces four haploid spermatids.
Spermiogenesis and spermiation
Spermiogenesis is the transformation of spermatids into spermatozoa. During this process, spermatids develop sperm structure.
After spermiogenesis, sperm heads become embedded in Sertoli cells. Their release from seminiferous tubules is called spermiation.
Hormonal control of spermatogenesis
Spermatogenesis begins at puberty due to increased GnRH secretion. GnRH acts on the anterior pituitary gland.
The pituitary releases LH and FSH. LH stimulates Leydig cells to secrete androgens.
FSH acts on Sertoli cells. Sertoli cells secrete factors that help spermiogenesis.
Structure of sperm
A sperm has head, neck, middle piece and tail. A plasma membrane covers the whole sperm body.
The head contains a haploid nucleus. The acrosome has enzymes that help fertilisation.
The middle piece has many mitochondria. These produce energy for tail movement and sperm motility.
Oogenesis and Follicle Development
Oogenesis is the formation of a mature female gamete. It begins during embryonic development, before birth.
The process is different from spermatogenesis because no new oogonia are added after birth. Oogenesis produces one large ovum and polar bodies.
Oogonia and primary oocytes
During foetal development, millions of oogonia form in each ovary. These cells start division and enter prophase-I of meiosis.
They get arrested at this stage as primary oocytes. Each primary oocyte gets surrounded by granulosa cells to form a primary follicle.
Primary to Graafian follicle
Many follicles degenerate from birth to puberty. At puberty, only 60,000 to 80,000 primary follicles remain in each ovary.
Primary follicles become secondary follicles. Secondary follicles develop into tertiary follicles with a fluid-filled cavity called antrum.
The tertiary follicle becomes a mature Graafian follicle. The Graafian follicle releases the secondary oocyte during ovulation.
Secondary oocyte
The primary oocyte completes its first meiotic division in the tertiary follicle. This division is unequal.
It forms a large haploid secondary oocyte and a small first polar body. The secondary oocyte keeps most of the nutrient-rich cytoplasm.
Menstrual Cycle
The menstrual cycle is the reproductive cycle in female primates such as monkeys, apes and humans. It begins at puberty with menarche.
Menstrual cycle class 12 biology questions often ask phases, hormones and ovulation. The average cycle repeats every 28/29 days in human females.
Menstrual phase
The menstrual cycle begins with the menstrual phase. Menstrual flow lasts for 3 to 5 days.
The flow occurs due to breakdown of the endometrial lining and blood vessels. Menstruation occurs only if the released ovum is not fertilised.
Follicular phase
During the follicular phase, primary follicles grow into a mature Graafian follicle. The uterine endometrium also regenerates.
FSH and LH levels gradually increase during this phase. Growing follicles secrete estrogens.
Ovulatory phase
LH and FSH reach peak levels around the middle of the cycle. A rapid rise in LH is called LH surge.
LH surge induces rupture of the Graafian follicle. This causes release of the ovum, called ovulation.
Luteal phase
After ovulation, the remaining Graafian follicle becomes corpus luteum. The corpus luteum secretes large amounts of progesterone.
Progesterone maintains the endometrium for implantation. If fertilisation does not occur, corpus luteum degenerates.
Fertilisation and Implantation
Fertilisation occurs in the ampullary region of the fallopian tube. It can happen only when ovum and sperms reach this region at the same time.
Fertilisation and implantation class 12 biology questions need correct sequence. The order is insemination, sperm movement, fertilisation, cleavage, blastocyst formation and implantation.
Insemination and sperm transport
During coitus, semen is released into the vagina. This process is called insemination.
Motile sperms pass through the cervix and uterus. They finally reach the ampullary region of the fallopian tube.
Fertilisation
Fertilisation is the fusion of sperm with ovum. A sperm contacts the zona pellucida layer of the ovum.
This contact induces membrane changes that block entry of additional sperms. It ensures that only one sperm fertilises the ovum.
The acrosome helps sperm enter the ovum. The haploid nuclei of sperm and ovum fuse to form a diploid zygote.
Sex determination
The sex of the baby is decided at fertilisation. Human females produce ova carrying only X chromosome.
Males produce sperms carrying either X or Y chromosome. An XX zygote develops into a female baby, while an XY zygote develops into a male baby.
So, scientifically, the sex of the baby is determined by the father. The mother is not responsible for determining the child’s sex.
Cleavage and blastocyst
The zygote undergoes mitotic divisions as it moves through the oviduct. These divisions are called cleavage.
The embryo forms 2, 4, 8 and 16 blastomeres. The embryo with 8 to 16 blastomeres is called morula.
The morula transforms into blastocyst in the uterus. The blastocyst has trophoblast and inner cell mass.
Implantation
Implantation is the embedding of the blastocyst in the endometrium. The trophoblast attaches to the uterine lining first.
The inner cell mass differentiates into the embryo. Implantation leads to pregnancy.
Pregnancy and Embryonic Development
Pregnancy begins after implantation. The developing embryo gets support from the placenta and maternal body.
In CBSE Class 12 Biology Chapter 2 Human Reproduction, pregnancy is studied through placenta, hormones and month-wise development. These points are important for short answers.
Placenta
After implantation, chorionic villi appear on the trophoblast. These villi interact with uterine tissue and maternal blood.
Together they form the placenta. Placenta is the structural and functional connection between the developing foetus and mother.
Functions of placenta
Placenta supplies oxygen and nutrients to the embryo. It also removes carbon dioxide and waste materials.
The placenta connects to the embryo through the umbilical cord. This cord transports substances to and from the embryo.
Placental hormones
Placenta acts as an endocrine tissue. It produces hCG, hPL, estrogens and progestogens.
In later pregnancy, the ovary secretes relaxin. hCG, hPL and relaxin are produced in women only during pregnancy.
Embryonic layers
The inner cell mass differentiates into ectoderm and endoderm. Mesoderm appears between them later.
These three germ layers give rise to all adult tissues and organs. Inner cell mass also contains stem cells.
Month-wise development
After one month, the embryo’s heart forms. By the end of the second month, limbs and digits develop.
By the end of 12 weeks, most major organ systems form. By the fifth month, foetal movements and head hair are usually seen.
By about 24 weeks, the body has fine hair, eyelids separate and eyelashes form. By nine months, the foetus is fully developed and ready for delivery.
Parturition and Lactation
Parturition is the process of childbirth. It occurs after about 9 months of gestation in humans.
The NCERT chapter explains parturition as a neuroendocrine mechanism. Lactation begins near the end of pregnancy and supports the newborn.
Foetal ejection reflex
Signals for parturition come from the fully developed foetus and placenta. These signals induce mild uterine contractions.
This is called the foetal ejection reflex. It triggers oxytocin release from the maternal pituitary.
Role of oxytocin
Oxytocin acts on uterine muscles and causes stronger contractions. Strong contractions stimulate more oxytocin release.
This positive feedback continues until the baby is expelled through the birth canal. Soon after delivery, the placenta is also expelled.
Lactation
Lactation is the production of milk by mammary glands. Mammary glands differentiate during pregnancy and start producing milk near the end of pregnancy.
Milk produced in the first few days is called colostrum. It contains antibodies essential for newborn resistance.
Important Terms in Human Reproduction
Human Reproduction uses fixed terms from anatomy, gamete formation, cycles and pregnancy. These terms help answer one-mark and short-answer questions in CBSE Class 12 Biology Chapter 2.
Gametogenesis
Gametogenesis is the formation of male and female gametes.
Spermatogenesis
Spermatogenesis is the formation of sperms from spermatogonia.
Oogenesis
Oogenesis is the formation of a mature female gamete.
Ovulation
Ovulation is the release of secondary oocyte from the Graafian follicle.
Menarche
Menarche is the first menstruation at puberty.
Menopause
Menopause is the stopping of menstrual cycles around 50 years of age.
Fertilisation
Fertilisation is the fusion of sperm and ovum.
Implantation
Implantation is the embedding of blastocyst in the uterine endometrium.
Parturition
Parturition is the process of childbirth.
Lactation
Lactation is milk production by mammary glands.
NCERT-Style Questions from Human Reproduction
In CBSE Class 12 Biology Chapter 2 Human Reproduction, NCERT-style questions usually test diagrams, gametogenesis, menstrual cycle, fertilisation, pregnancy and hormones. Strong answers should use correct sequence and NCERT terms.
Q1. What are the two major functions of testes?
Testes produce sperms and secrete androgens.
Explanation:
Seminiferous tubules produce sperms through spermatogenesis. Leydig cells in interstitial spaces secrete androgens.
Fact:
Androgens support male reproductive functions.
Q2. What is spermatogenesis?
Spermatogenesis is the process of sperm formation from spermatogonia.
Explanation:
Spermatogonia divide and form primary spermatocytes. Meiosis produces secondary spermatocytes and then spermatids.
Fact:
Spermatids transform into sperms through spermiogenesis.
Q3. What is the role of acrosome?
Acrosome helps the sperm enter the ovum during fertilisation.
Explanation:
It contains enzymes that help the sperm pass through the zona pellucida and plasma membrane of the ovum.
Fact:
Acrosome covers the anterior part of the sperm head.
Q4. What induces ovulation?
LH surge induces ovulation.
Explanation:
LH reaches a peak level around the middle of the menstrual cycle. This causes rupture of the Graafian follicle.
Fact:
Ovulation releases the secondary oocyte from the ovary.
Q5. Why are women not responsible for the sex of the baby?
Women are not responsible because the sperm determines whether the zygote becomes XX or XY.
Explanation:
All ova carry the X chromosome. Sperms carry either X or Y chromosome.
Fact:
X sperm forms XX female zygote, while Y sperm forms XY male zygote.
Useful Links for Class 12 Biology
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| NCERT Solutions | NCERT Solutions for Class 12 Biology |
| Revision Notes | CBSE Class 12 Biology Revision Notes |
| Syllabus | CBSE Class 12 Biology Syllabus |
| Sample Papers | CBSE Sample Papers for Class 12 Biology |
Q.1 Spermatophytes are characterized by the ability to produce seeds. Discuss the advantages of producing seeds.
Ans
1. Pollination and fertilization of seed plants are free from requirement of water, hence are more dependable.
2. Seeds are variously adapted to be dispersed through various agencies.
3. Hard seed coat and dormant embryo increases the chances of its survival in unfavorable conditions.
4. Presence of reserve food, ensures the development of embryo into seedling until it is capable of photosynthesizing.
5. Seeds are usually a product of sexual reproduction; hence generate new genetic combinations leading to variation.
Q.2 Enlist all the main steps in the development of female gametophyte with labeled diagrams of the different stages of the development.
Ans
1) A single MMC (megaspore mother cell) is differentiated from the nucellar tissue of the ovule.
(2) MMC undergoes meiosis to form four megaspores.
(3) Three megaspores degenerate, only a single megaspore develops into the functional megaspore.
(4) The nucleus of the functional megaspore undergoes three successive mitotic divisions (free nuclear) to form an eight nucleated embryo sac.
(5) At eight nucleated stage, cell walls are laid down. Three cells grouped together at micropylar end, constitute egg apparatus and three cells arranged at chalazal end are called antipodal cells, whereas two nuclei present in the center are called polar nuclei. Thus, typical angiospermic embryo sac (female gametopyte) at maturity is eight nucleated and seven celled.
Q.3 Draw a labelled diagram of longitudinal section of an embryo of grass showing its various parts.
Ans
Q.4 Define inbreeding depression. Mention any four natural mechanisms in the plants to avoid inbreeding depression.
Ans
Loss of vigor due to continuous self-pollination is called inbreeding depression.
Four natural mechanisms that avoid self-pollination and favour cross-pollination are :-
(a) Anthers and carpels are matured at different times. When pollen grains are released, stigma is not receptive or when stigma is receptive, pollen grains are immature.
(b) Anthers and stigma are placed at different position, so that they do not come in contact with each other.
(c) By some genetic mechanism, pollen germination or pollen tube growth is inhibited (self incompatibility).
(d) Plants are dioecious, plants bear either female flowers or male flowers.
Q.5 Define anemophily. Give any four characteristics of anemophilous flowers.
Ans
Pollination by wind is termed as anemophily.
a) Pollen grains are light and non-sticky.
b) Well exposed stamens and stigma.
c) Feathery stigma to trap pollen grains.
d) Numerous flowers are packed into an inflorescence.
Q.6 Mention the significance of following structures in the megasporangium of the plant
a) Funicle
b) Micropyle
c) Integuments.
Ans
a) Funicle: The megasporangium is attached to the placenta through a stalk called funicle.
b) Micropyle: Integuments are present all over the ovule leaving a small opening called micropyle, through which pollen tube enters into the ovule for fertilization.
c) Integuments: Megasporangium is protected by two layers called integuments, which later forms two seed coats after fertilization.
Q.7 (i) What do you understand by double fertilisation?
(ii) Mention the ploidy of following structures:
a) Cells of endosperm
b) Synergids
Ans
(i) The characteristic fertilisation in angiosperms is called double fertilisation where two types of fusion take place, which are; syngamy and triple fusion.
Syngamy: Fusion of one male gamete with egg cell is called syngamy. This forms zygote, which develops into embryo.
Triple fusion: Fusion of one male gamete with two polar nuclei is called triple fusion; it results in primary endosperm cell, which develops into the endosperm.
(ii) a) Cells of endosperms are Triploid
b) Synergids are Haploid
Q.8 Differentiate among autogamy, geitonogamy and xenogamy.
Ans
Autogamy: The type of pollination, in which pollen grains are transferred from the anther to the stigma of the same flower of the same plant.
Geitonogamy: The type of pollination, in which pollen grains are transferred from the anther to the stigma of another flower of the same plant.
Xenogamy: The type of pollination, in which pollen grains are transferred from the anther of the one plant to the stigma of a other plant.
Q.9 Draw labelled enlarged view of transverse section of a mature anther showing different layers of tissues.
Ans
Q.10 Enlist the main steps in the development of a three-celled pollen grain.
Ans
i) Microspore mother cells (2n) undergoes meiosis to form four microspores (n).
(ii) Each microspore undergoes mitotic division with an unequal cytoplasmic division to form a bigger cell (vegetative cell) and a smaller cell (generative cell).
(iii) The generative cell divides mitotically to give rise to two male gametes.
Q.11 Differentiate between a false and a true fruit.
AnsTrue fruit: The fruit which develops only from ripened ovary, is called as true fruit.
False fruit: If some part of the flower other than ovary also contributes in the formation of fruit, it is called as false fruit, e.g., in apple, thalamus is also ripened along with the ovary.
Q.12 Define perisperm. Where is it found?
Ans
The residual, persistent nucellus within the seed is called perisperm, e.g., seed of black pepper and beet.
Q.13 What is the most common type of endosperm development? What is meant by non-endospermous seed?
Ans
Primary endosperm nucleus undergoes free nuclear division to form free nuclei; later cell wall is laid down around free nuclei. This is called as free nuclear endosperm development and it is the most common type.
Seeds in which endosperm is completely exhausted during the development of embryo, are called as non-endospermous seed.
Q.14 Mention the fate of the following structures of the ovule after fertilisation.
a) Integuments
b) Synergids
c) Polar nuclei
d) Egg cell
Ans
a) Two integuments develop into seed coats.
b) Synergids degenerate and provide nourishment to developing embryo.
c) Polar nuclei develop into endosperm.
c) Egg cell form zygote and later develop into embryo.
Q.15 Mention any two characteristics of pollen grains produced by hydrophillous flower.
Ans
a) Long, needle like or ribbon like pollen.
b) Covered by a mucilaginous covering to prevent wetting or decaying of pollen grain.
Q.16 Name any water pollinating plant and explain how pollination is accomplished in it?
Ans
Vallisneria, is fresh water, submerged, water-pollinating plant. The female flower reach the surface of water by the long stalk and the pollen grain from the male flowers are released on the surface of water, float with the water current and reach female flowers.
Q.17 Cleistogamous flowers are strictly self pollinating,” Explain. What is the disadvantage of this phenomenon?
Ans
Cleistogamous flowers remain closed until pollination is accomplished. i.e. anthers and stigma are not exposed to outside, therefore, they are invariable autogamous/self pollinating. The phenomenon does not bring genetic variations and leads to loss of vigour.
Q.18 Differentiate between exine and intine.
Ans
|
Exine
|
Intine
|
|
i) Thick, tough, cuticularized, outer layer of pollen grain.
ii) Made up of a substance called sporopollenin.
|
i) Thin and soft inner layer of pollen grain.
ii) Made up of cellulose and pectin.
|
Q.19 Define polyembryony. Give one example of it.
Ans
The phenomenon of the presence of more than one embryo in the ovule is called polyembryony. e.g. Citrus.
Q.20 Apomictic genes” are trying to be inserted in hybrid varieties, Explain.
Ans
Hybrid varieties of the crop usually show vigorous growth with advantageous characters, but the production of hybrid seeds is costly. These hybrids can be converted into apomicts (capable of producing seed without fertilization from the cells of the ovary ) by transferring apomictic genes. This will lead to production of new plants exactly similar to parents without any genetic variation.
Q.21 Dehydration of seed during its maturation increases its shelf life. Explain.
Ans
Dehydration leaves the seed with only 10-15% of moisture by mass. The metabolic activity of the embryo is slowed down and eventually stopped. In this dormant state, seed can be stored safely without decaying.
Q.22 What are the characteristics of insect pollinated flowers?
Ans
Such flowers are usually large, brightly coloured, scented and produce nectar.
Q.23 Name the term used when pollen tube enters through the micropyle?
Ans
Porogamy.
Q.24 Give the name of a plant which causes pollen allergy.
Ans
Parthenium.
Q.25 Name the substance which forms the exine of the pollen grain.
Ans
Sporopollenin.
Q.26 Can we preserve the pollen grains?
Ans
Yes, because of the presence of sporopollenin.
Q.27 Which condition does refer to apocarpy?
Ans
When pistils are free.
Q.28 In which part of the flower is embryo sac found?
Ans
Ovule.
Q.29 How will you define megasporogenesis?
Ans
The process of formation of megaspores from megaspore mother cell.
Q.30 At what stage of embryo sac does the fertilization take place in a flower?
Ans
8 nucleate and 7-celled.
Q.31 Give two examples of water-pollinated flowers.
Ans
Vallisneria and Hydrilla.
Q.32 What is the use of filiform apparatus of synergids?
Ans
It guides the pollen tubes to enter into the synergids.
Q.33 Define emasculation.
Ans
Removal of anthers from a bisexual flower bud by using a pair of forceps.
Q.34 What is Apomixis?
Ans
Production of seeds without fertilization.
Q.35 What are chasmogamous flowers?
Ans
Chasmogamous flowers open and exposes the stamens and style to the environment for cross pollination. These flowers are similar to flowers of the other species.
Q.36 Name the tissue located inside the ovarian cavity on which the ovule develops.
Ans
The name of the tissue is Placenta.
Q.37 It is the process of formation of megaspores from megaspore mother cell by meiotic division in anther. Name the process.
Ans
The name of the process is Megasporogenesis.
Q.38 Holding a flower, the teacher asked Heena to show the part of a flower which has four-sided (tetragonal) structure consisting of four sporangia, grouped as a pair in each lobe. What would be the part of the flower?
Ans
The part of the flower is anther.
Q.39 Pineapples and grapes are developed from an unfertilised ovary and further resulting in seedless fruit. Can you name the developmental process?
Ans
The developmental process is called Parthenocarpy.
Q.40 Vijaya started sneezing and developed some rashes on her hand after returning from her school garden. What causes such type of reaction?
Ans
The cause of such type of reaction is allergy to pollen grains.
Q.41 It is made of sporopollenin, which can withstand high temperature and action of strong acids or alkalis, no enzymes can degrade it and hence the pollen grains are well preserved as fossils. Name the layer.
Ans
The hard outer layer of the pollen grain is called Exine.
Q.42 If favorable conditions like adequate moisture, oxygen and suitable temperature are not available, then the embryo may enter a state of inactivity. Name this state of inactivity.
Ans
The embryo may enter a state of Dormancy. The general metabolic activity of the embryo slows down.
Q.43 A flower is large in size, colourful and rich in nectar. This type of adaptation corresponds to which pollination strategy?
Ans
The type of pollination corresponds to flowers that are pollinated by Insects.
Q.44 A general mechanism to prevent the self pollen from fertilising the ovules by inhibiting the pollen germination or pollen tube growth on the pistil. Name the mechanism.
Ans
Self incompatibility.
Q.45 Fruits are developed from the ovary but in few species such as apple, strawberry, cashew etc., other parts of the flower also contribute to fruit formation. Name the floral part and the name given to such fruits.
Ans
In plants such as apple, strawberry and cashew, the thalamus contributes to fruit formation. Such fruits are called False Fruits.
Q.46 What similarities do you find in seed bank and pollen bank? Write their importance.
Ans
Pollen grain of different species of plants can be stored for years in liquid nitrogen (-196ºC) like seeds. Such type of storage is called pollen bank that is similar to seed banks in crop breeding programme.
Q.47 Unisexual flowers have pollen grains which are small, dry and non-sticky. Stigma and style of such flowers are well exposed and hairy. Name the pollinating agent. How do such adaptations help in pollination?
Ans
Wind is the pollinating agent.
Wind pollination requires that the pollen grains are light and non-sticky so that they can be transported in wind currents. They also possess well exposed stamens so that the pollens are easily dispersed into the wind currents. Their stigma is large and feathery so as to easily trap air borne pollen grains.
Q.48 Name the following and give the function of any two:
a. Three cells present at the chalazal end in the embryo sac.
b. A small pore in the ovule through which the pollen tube enters.
c. Wall of fruit having mesocarp, endocarp and epicarp.
d. Two cells present on either side of the egg cell in an embryo sac.
e. Mass of parental cells enclosed within the integument.
Ans
a. Antipodals
b. Micropyle
c. Pericarp
d. Synergids : Plays an important role in guiding the pollen tubes into the synergids.
e. Nucellus : Cells of nucellus have abundant reserve food materials.
Q.49 It is a major approach of crop improvement programme. In such crossing experiment, it is important to make sure that only the desired pollen grains are used for pollination and the stigma is protected from contamination. How can it be achieved?
Ans
It can be achieved through Artificial Hybridization involving emasculation and bagging. Removal of anthers from the flower bud before the anther dehisces is called as emasculation.
Emasculated flowers are covered with a bag of suitable size to prevent contamination of its stigma with unwanted pollen, this process is called bagging. When the stigma of the bagged flowers attains receptivity, mature pollen grains from the anthers of male parent are dusted on the stigma and the flowers are rebagged and the fruits are allowed to develop.
Q.50 How fruits help in seed dispersal?
Ans
Fruits help in the seed dispersal to a large extent. Fruits help in the dispersal of seeds to distant places as they get carried away by wind, birds or insects.
Q.51 Which type of seeds contain a hard fruit shell?
Ans
Soft seeds generally possess a hard fruit shell around them. For example, cashew fruit has a hard fruit shell.
FAQs (Frequently Asked Questions)
Spermatogenesis forms four functional sperms from one primary spermatocyte. Oogenesis forms one large ovum and polar bodies. Spermatogenesis starts at puberty, while oogenesis begins during embryonic development.
Fertilisation occurs in the ampullary region of the fallopian tube. It happens only when sperm and ovum reach the ampulla at the same time. This is why every coitus does not lead to pregnancy.
Corpus luteum secretes progesterone, which maintains the endometrium. A maintained endometrium is needed for implantation and pregnancy. If fertilisation does not occur, corpus luteum degenerates.
During implantation, the blastocyst attaches to and becomes embedded in the uterine endometrium. Trophoblast cells attach first. The inner cell mass then develops as the embryo.
Colostrum is important because it contains several antibodies. These antibodies help newborn babies develop resistance. Doctors recommend breastfeeding during the initial period of infant growth.