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Reproduction is the natural mechanism by which new types of "posterity" of singular life are formed from their "parents." It is a crucial element of all living species. There are two forms of reproduction: asexual and sexual that we will cover in our article.
The topic of reproduction in NEET covers human reproduction and reproduction in other organisms.
It carries a total weightage of around 6 to 7% in the NEET Biology section.
Around 4 to 5 questions can be asked from this chapter in NEET.
Although there are other more important topics in the syllabus, students are required to have to pay more attention to them. However, the chapter on Reproduction is perhaps the most important in the biology portion of NEET 2020 and must be studied and explored in detail.
Humans are involved in sexual reproduction. They are viviparous, that is, those who give birth to young ones.
Human reproduction involves a number of sequential phases.
Gametogenesis: the development of male (sperm) and female (ovum) gametes.
Insemination: transfer of male gametes to female genital tract.
Fertilization: a fusion of gametes to form a zygote.
Blastocyst development: an ongoing mitotic division in the zygote.
Implantation: clinging of the blastocyst to the uterine wall endometrium.
Gestation: embryonic development (9 months in humans).
Parturition: a childbirth.
Male and female reproductive organs vary in their structure, function and development.
Testes: A pair of testes are found in the scrotum outside the body, helping to maintain an ideal temperature for sperm production. ~250 testicular lobules are active. The sperms are contained in seminiferous tubules. Every lobe contains 1-3 seminiferous tubules.
There are two groups of cells present in the inner lining of seminiferous tubules:
Spermatogonia is the germ cells of males that endure meiotic division to form sperms.
Sertoli cells supply the germ cells with nutrients.
Leydig cells (internal cells) are found in interstitial spaces outside of the seminiferous tubules. It produces and secretes androgens which are the male reproductive hormones.
Accessory ducts: Vasa efferentia, rete testis, epididymis, and vas deferens are the male accessory ducts. These ducts hold and transfer sperm from the testis to the urethra. Vas deferens, with a seminal vesicle duct, forms an ejaculatory duct and opens into the urethra.
Glands: There are three glands namely, a prostate gland, a pair of seminal vesicles, and a bulbourethral gland. These glands are involved in secreting the seminal plasma. This is rich in some enzymes, calcium, fructose and also lubricates the penis. Semen contains semen plasma and sperms.
Question: What is the hormone which is released by the testes known as?
None of the above
Spermatogenesis begins at puberty. The secretion of GnRH (gonadotropin-releasing hormone) from the hypothalamus is improved. GnRH stimulates the pituitary to let out both LH (luteinizing hormone) and FSH (follicle-stimulating hormone). LH activates the cells of Leydig to release androgens. The primary androgens are testosterone and androstenedione. These are the hormones that stimulate the spermatogenesis process. FSH stimulates the cells of Sertoli to secrete factors that aid in the process of spermiogenesis.
Spermatogonia get diploid (2n=46) and are divided by mitotic division into numerous cells known as primary spermatocytes.
Every primary spermatocyte cell then divides meiotically to the first two haploid (n=23) secondary spermatocytes of the same size.
Secondary spermatocytes further split in the 2nd meiotic division into haploid spermatids of the same size.
Every diploid primary spermatocyte cell is produced by four haploid spermatids.
Spermiogenesis is the mechanism of sperm formation from spermatids.
Spermiation is the method by which sperms get discharged from seminiferous tubules.
Question: A human primary spermatocyte contains ____ autosomes?
Approximately 200-300 million sperms get ejaculated in one go.
The head contains acrosome apically that includes enzymes which make it easier for the sperm to enter the ovum. This is accompanied by an elongated nucleus (haploid).
The middle part has multiple mitochondria which provide energy for sperm movement.
The tail is a flagellum that comes out of the cell body and is essential for the robust motility of the sperm. The tail allows the sperm to swim so that it can reach the ovum.
Question: Name the lytic enzyme that is released by the sperm.
None of the above
Ovaries: Two ovaries are present. Ovaries create ova and female reproductive hormones. The peripheral cortex is located in the boundary of the ovarian stroma and the inner medullary area.
Fallopian tubes: Two fallopian tubes or oviducts that attach the ovaries to the uterus are present. Infundibulum is a funnel-shaped portion of the fallopian tube near the ovaries. The infundibulum ends in finger-like projections called fimbriae which contain the ovum. Infundibulum leads by ampulla and isthmus to the uterus.
Uterus or womb: It is pear-shaped and inverted. The development of the embryo happens within the uterus. The uterine wall is divided into three layers:
It is the outer layer and it is membrane-like.
This is the middle part with smooth muscles. Powerful contractions during delivery is because of the myometrium.
It is glandular and undergoes cyclical changes during the menstrual cycle. Blastocyst is inserted for development in the endometrium.
The narrow cervix binds the uterus to the vagina. The vagina and the cervical canal make up the birth canal.
External genitalia: Mons pubis (fatty tissue), labia majora and labia minora (tissue folds) and clitoris are external female genitalia. The hymen membrane acts as a cover for the opening of the vagina.
Mammary glands: A pair of breasts is present in females. They have fat and mammary glands. Alveolar cells are involved in secreting milk.
Question: The ovary’s stroma comprises nerves, blood vessels, muscle fibers, and a kind of protein named ___.
Oogenesis is the development of a mature female gamete known as the ovum.
Oogenesis varies from spermatogenesis. The cycle of oogenesis begins during embryonic development. This is in contrast with spermatogenesis, which begins only at puberty.
Approximately two million oogonia are formed in the ovaries of the foetus, and no oogonia get formed afterwards.
Oogonia then mitotically divides and enters the prophase-1 of the meiotic division. At this point, the division temporarily stops and the cells are known as primary oocytes.
Primary oocytes are surrounded by granulosa cells to make primary follicles.
Several primary follicles degenerate and only 60,000 to 80,000 remain in puberty.
Primary follicles grow into secondary follicles. Then, they develop into tertiary follicles that comprise a fluid-filled cavity called the antrum.
The first meiotic division of primary oocytes happens within the tertiary follicle. It is an unequal division that leads to the development of a haploid secondary oocyte that is wide and a small polar body.
The tertiary follicle transitions to the Graafian follicle (mature follicle). The membrane of the zona pellucida forms around the secondary oocyte.
Ovulation is the process through which the ovum (secondary oocyte) gets released after the bursting of the Graafian follicle.
Question: Where is the Graafian follicle typically found?
ovary of frog
testis of mammal
thyroid of mammal
ovary of mammal
Menarche: It is the first menstruation that occurs at puberty.
The menstrual cycle is 28/29 days long on an average and the ovum is released in the middle of every cycle (~14th day).
A lack of menstrual cycle is a symptom of pregnancy or could be due to ill health or stress.
Menopause is the phase at which the menstrual cycle ends (~45-50 years). The reproductive phase of a female will be between menarche and menopause, while males keep producing sperms throughout their lifetime.
The menstrual cycle is split into three stages:
Menstrual phase: This happens when the ovum is not fertilized. The menstrual flow results from the disintegration of the endometrial lining.
Follicular phase: This phase is also called the proliferative phase. The main follicle grows into a Graafian follicle and then to an ovulation. The endometrium is also involved in regenerating. Gonadotropins (LH and FSH) get released from the pituitary. Gradually, there is a rise in their level, stimulating follicular development. The level reaches its peak in the middle of the cycle and the LH induces the rupture of the Graafian follicle. The growing follicle emits estrogen, and the level of estrogen rises at the midpoint as well.
Luteal phase: It is also called the secretory phase. The corpus luteum is produced by the remaining portion of the Graafian follicle. It releases a hormone called progesterone that is necessary for the maintenance of the endometrium and for the implantation of the fertilized ovum. When fertilization does not happen, the corpus luteum degenerates. It is followed by the menstrual process and a new cycle begins.
Question: Corpus Luteum secretes ___.
Fertilization occurs in the ampullary portion of the fallopian tube.
If one of the sperms comes into contact with the ovum's zona pellucida, more sperms cannot enter because of changes in the membrane.
The second meiotic division of the secondary oocyte is induced by the entry of the sperm. It forms a broad ootid (haploid) and a secondary polar body.
The sperm and the ovum join together to form the diploid zygote.
At this point, the sex of the child is determined. There are two forms of male gametes produced in spermatogenesis, one with the X chromosome and the other with the Y chromosome. Once the sperm with the X chromosome fuses with the ovum, the zygote develops into a female and when the sperm with the Y chromosome fuses with the ovum, the zygote develops into a male child.
The zygote divides the mitotic formation of blastomeres and moves through the oviduct towards the uterus.
Question: The ovum receives the sperm through which of the following?
None of the above
Morula is the phase with 8-16 blastomeres in the embryo.
The blastocyst is created by continuous division after the morula phase. At this point, the blastomeres are organized in the outer layer known as the trophoblast and the inner cells creating the inner cell mass.
The trophoblast is connected to the endometrium lining of the uterus and the inner cell mass is separated into the embryo.
The blastocyst is found in the endometrium because it is completely protected by the dividing uterine cells. This phase is referred to as implantation. It is the beginning of pregnancy.
Question: When do the fertilized eggs in human females get implanted in the uterus?
post one month of fertilization
post two months of fertilization
post about 7 days of fertilization
post 3 weeks of fertilization
After implantation, embryo cells begin to divide into the outer ectoderm, the inner endoderm, and then the middle mesoderm. These are known as primary germinal layers, and all adult tissues are created from these three layers.
Stem cells are found in the inner mass of the cells. They have the capacity to develop into all kinds of tissues and are named pluripotent. Stem cells are also being used and studied to treat numerous life-threatening diseases such as cancer.
Placenta is the connection between the growing fetus and the mother. It is produced by the interdigitation of uterine cells and chorionic villi (finger-like projections), which protrude from trophoblasts.
Placenta offers nutrients and oxygen to the developing foetus, and also helps eliminate excretory materials.
Umbilical cord binds the placenta to the fetus and holds nutrients.
Placenta contains several hormones that are essential for the maintenance of pregnancy, for fetal growth and at the time of delivery.
Human chorionic gonadotropin (hCG) and human placental lactogen (hPL) are produced only during birth. HCG levels of urine during pregnancy are a marker for the identification of pregnancy by test strips.
The level of relaxin rises at the later stages of pregnancy. The level of relaxin also increases at the time of ovulation, but the level decreases and menstruation begins in the absence of pregnancy.
Progesterone, prolactin, estrogen, cortisol and thyroxine levels also rise to assist the fetal growth.
Question: Which of the following is the temporary organ that connects a mother to her fetus?
None of the above
Humans: 9 months
Cats and dogs: 60-65 days
Elephants: 22 months
1st month: The heart has been formed.
2nd month: Limbs and numbers are created.
3rd month (first trimester): All vital organs are created, and the foetus can be recognized as an individual. External genitalia are beginning to differentiate and the sex of the foetus can be ascertained.
5th month: Foetus begins to move and hair appears on the head.
Second trimester: Developing eyelashes and eyelids, the body becomes covered with fine hair.
Third trimester: The foetus is completely developed by the end of the third trimester, and the body readies for the infant's birth (parturition).
Question: The nerve cells, brain, and spinal cord or the central nervous system develops from the embryonic ____.
both b and c
The childbirth process is called parturition. Parturition is initiated with signals from the neuroendocrines. When the foetus is fully grown, mild uterine contractions begin. Thereafter, oxytocin is secreted from the pituitary gland. When more oxytocin gets secreted, contractions become stronger and stronger, likely to result in childbirth. The placenta also gets delivered after the infant. Nowadays, the umbilical cord is cut and also retained because it contains stem cells, which can be used in the future to cure diseases not just of the patient but also of the immediate family.
Doctors inject an oxytocin injection to facilitate delivery.
Lactation: Increased prolactin secretion from the pituitary gland causes milk production in mammary glands.
Colostrum: This is what is formed first. It is the yellowish milk. It has a high content of antibodies and proteins, and is vital for the infant's immunity.
Question: When does lactation begin?
when the pregnancy ends
when the first trimester ends
Reproduction is the process through which an organism multiplies and gives birth to another similar organism. Reproduction is necessary to preserve a race's diversity and perpetuation, because each human has a limited span of life.
Reproduction is needed for the gene pool's continuity and also to obtain genetic variations that are inherited to the offspring.
Asexual reproduction is the mechanism by which a single parent produces offspring.
Sexual reproduction is the mechanism in which opposite sexes are involved, and offspring are formed by the fusion of male and female gametes.
Every individual can multiply.
The progeny produced is morphologically and genetically similar or is a parent's clone.
Asexual reproduction causes no genetic variations.
It is normal in microorganisms, single-cell plants and simple animals
Asexual reproduction methods are diverse:
Binary Fission: This is a common form of unicellular replication (Monera, Protista). The cell splits into two parts and then multiplies. The nucleus separates first and then the cytoplasm follows. After mitotic division, the daughter cells are genetically identical when they develop. Occasionally, the nucleus divides amitotically, resulting in multiple nuclei without cytoplasmic separation. Later, the cytoplasm accumulates around each nucleus, giving rise to several descendants. It is called multiple fission.
Examples: Simple binary fission: Amoeba, Binary longitudinal fission: Euglena, Binary transverse fission: Paramecium
Budding: Buds are created because of unequal division and stay attached to the parent. They split upon maturation.
Examples: Hydra, yeast
Fragmentation: This reproductive method is popular in many algae and fungi. The body breaks into fragments, and each fragment grows into a living body.
Examples: Ulothrix, Spirogyra
Spore formation: Asexual spore formation occurs in different algae and fungi under unfavorable circumstances, in special structures. These spores are potentially motile or non-motile. When the favourable conditions return, they develop into a new individual.
Examples: Amoeba develops a three-layered cyst (encystation) in order to avoid adverse conditions. It undergoes several fissions when conditions are favourable, and forms several pseudopodiospores. The cyst wall breaks open (sporulation), the spores are released. Then, many amoebae develop.
Conidia is non-motile in Penicillium.
Vegetative propagation in plants: Several plants are propagated from vegetative bits. These are called vegetative propagules. They mostly comprise nodes which grow roots and form a new plantlet upon contact with the soil and nutrients.
Examples: Runner-lawn grass, Suckers- mint
Question: What is budding in hydra a form of?
None of the above
Sexual reproduction is common in plants and animals of the higher order. Simple algae and fungi also shift towards sexual reproduction when adverse conditions commence. A unicellular protozoan, a conjugation in Paramecium, is a primitive sexual reproduction.
Male and female gametes combine in sexual reproduction to form a zygote following fertilization. The zygote grows into a new being that is not identical but similar to the parents.
To start reproducing sexually, all the species must achieve a certain stage of growth and maturity.
Plants demonstrate a distinct reproductive process. They are annual, biennial, or perennial.
Bamboo: Flowering happens once
Neelakurunji (Strobilus kunthiana): Flowering happens once in 12 years
Animals also sexually reproduce in several stages. Seasonally, many birds lay eggs. During reproductive processes, the placental animals undergo cyclical changes.
Example: Oestrous cycle in cows, dogs, sheep, tigers, etc. Menstruation cycle in primates.
There may be male and female reproductive systems in the same plant or animal (Bisexual) or on separate plants or animals (Unisexual)
In many species of fungi, plants and animals, bisexual is the same as homothallic or monoecious and unisexual is also called heterothallic or dioecious.
Monoecious plants: Coconut, chara, cucurbit
Dioecious plants: Papaya, marchantia, date palm
Bisexual flower: Sweet potato, sweet pea, lily, hibiscus, rose
Unisexual flower: Papaya, maize, bitter gourd, watermelon, coconut
Monoecious or hermaphrodite animals: Earthworm, leeches, sponges, flatworms
Dioecious: Cockroaches and various other higher animals
A few of the species are haploid, that is, their body contains only one set of chromosomes.
Example: Algae, bryophytes, fungi
Many of the animals and pteridophytes, gymnosperms and angiosperms are diploid, that is, 2 sets of chromosomes are present. They create haploid gametes by division of meiosis or reduction.
Sexual reproduction can be broken down into stages of pre-fertilization, fertilization, and post-fertilization.
Gametogenesis (gamete formation): Haploid gametes.
Isogametes or homogametes: The male and female gametes look identical.
Example: Alga, Cladophora
Heterogametes: In most organisms, morphologically distinct male and female gametes are produced. Male gametes are antherozoids or sperm. Female gamete is the egg or ovum.
Example: Alga, fucus, human beings
Gamete transfer (pollination): Male gamete is motile in most species and moves towards the female gamete. Algae, fungi, and plants (bryophytes, pteridophytes) need water as a means for gametes movement.
The pollen grains are moved to stigma in higher plants through the process of pollination. As stigma, bisexual flowers are self-fertilized, and anther is present nearby. Cross-pollinating flowers require a pollinating agent, like wind, bee, etc.
Dioecious animals possess special mechanisms to enable the transfer of gametes.
Fertilisation is also referred to as syngamy. Upon the fusion of male and female gametes, a diploid zygote is produced.
External fertilization: This is If additional gametes combine. The offspring produced through external fertilization is vulnerable to predators
Example: Algae, fish, amphibians
Internal fertilisation: Fertilisation happens naturally in the female body in higher plants and animals.
Diploid zygote is formed after fertilization. The zygote grows into a new organism and undergoes further division.
The zygote forms a thick wall around itself in algae and fungi to resist desiccation and damage, and only germinates after a resting period when favorable conditions return.
The zygote undergoes meiosis in organisms with a haplontic life cycle (haploid dominant phase) to form haploid spores. Then, a new haploid organism is formed.
Embryogenesis (Embryo Development): It is the cycle of a zygote's growth into an embryo. The zygote undergoes differentiation and cell division.
Cell division: Increases are seen in cell number and mass.
Cell differentiation: Cells get modified to form particular organs and tissues.
Animals that lay eggs.
A fertilized egg that is covered by a hard, calcareous shell is laid out outside.
After a time of incubation, the young one hatches out.
Example: Birds, reptiles
Animals that give birth to the young.
Embryogenesis happens within the female body, and the young ones are born. Different species have different periods of gestation.
The zygote grows within the ovule in angiosperms, and evolves into the embryo.
Seeds grow a protective covering named pericarp and then disperse. Once they get an acceptable medium and conditions, they germinate into a new plant.
In humans, the zygote goes through cleavages to form blastula and then three primary germ layers namely, ectoderm, endoderm, and mesoderm. These are formed after gastrulation. They differentiate all the tissues and organs in question.
Creation of a new organism without fertilization.
Example: Sterile drones are haploid (n=16) in honeybees, and develop from female gametes. Other examples are rotifers, lizards, and turkey.
In certain plants, parthenocarpy is induced artificially to bear seedless fruit.
Question: What is the fusion of unrelated gametes known as?
None of the above
Some sub-topics under Reproduction carry more importance than others in NEET 2020. Although it is recommended that a student studies all subtopics, more time can be dedicated to the more important topics given below.
Human male Reproductive System
Human female Reproductive System
Fertilization in Human Females
Development of Embryo in Human Females
Gestation in Human Females
Asexual Reproduction in Organisms
Sexual Reproduction in Organisms
Which of the following is the most remarkable quality of Planaria?
Survive without air
2. Root and shoot development in the tissue culture is influenced by ____.
Auxin and cytokinin ratio
None of the above
3. Bryophyllum daigremontianum undergoes reproduction through ___.
4. Which organelle assists the sperm in penetrating the ovum?
None of the above
5. Which of the following is an ovoviviparous animal?
None of the above
First, try to answer the simple questions
Simple questions must be answered as soon as possible. Do not ignore them just because they are easy. It can happen that you are wasting your time on difficult questions and there will be no time left to answer the simple ones.
Focus on Scoring Positive Marks
If you do not know the solution and are certain that you will not be able to remember it, do not solve it. This is to ensure that you do not get any negative marking. Getting a zero is better than getting a negative marking in view of your total score.
Keep your mind steady
Panicking does not take you anywhere. Just keep yourself calm and attempt the paper. You will note how important it is to be calm during such an important test. Doing so will certainly fetch you a good score.
An effective study plan goes a long way particularly when it comes to preparing for NEET Biology to keep the whole syllabus in perspective. The time available for NEET's syllabus and each of its topics must be allocated according to the topic's importance. It is also essential that one adheres to the schedule of study and incorporates changes as one advances. Since Reproduction is a vital section in Biology, follow the pointers below to create an effective plan for the topic and the subject.
Make tables and charts: Outline your study in the form of graphs and charts, which will serve as a quick summary technique prior to the days of the test. The use of personal keywords that require remembering will prove to be the most useful. Attempt to provide important examples to understand implementations in these maps.
Practice regularly: Aspirants studying NEET 2020 Biology need to cultivate the habit of rigorous practice. Comprehension of concepts in theory can only be understood by practice. A number of NEET sample papers and question papers from the previous year must be answered to get an idea of the pattern of questions that can be asked.
Take up mock tests: The National Testing Agency is setting up practice centers across the country in different places so aspirants can practice online testing. Therefore, one should take as many mock tests as possible to improve preparation in NEET Biology. Know More NEET Mock Test
Revise often: One must keep revising at regular intervals to reap the proper benefits of learning and training. It means that everything learned remains fresh in the mind. Aspirants must make it a point to revise the entire syllabus many times before the actual exam, so that each concept included in every topic is thorough.
Choose the best books: The standard of books one uses to study will be shown in the score. The NCERT should form, in the view of many toppers and experts, the basis of one's understanding of concepts. However, in order to refine the preparation, aspirants do need to try to include the books listed below in their preparation for NEET Biology. Read More
|Complete NEET Guide: Biology||MTG Editorial Board|
|A Textbook of CBSE Biology for Class 12||Sarita Aggarwal|
|Elementary Biology Volume 1 & 2||Trueman|
|NEET 2020 Biology Guide- 5th Edition||Disha Publications|
|Question Bank for Biology||Dr Ali|