How Do Organisms Reproduce - Class 10 Biology - Extra Questions

The presence of large number of chromosomes in an organism is not a hindrance to sexual reproduction because number of chromosomes has no role in deciding a particular mode of reproduction. For example; there are 8 chromosomes in a somatic cell of a fruit fly, while there are 380 chromosomes in a somatic cell of a butterfly but both of them reproduce sexually.

Explanation-

Answer-

1. Part that develops into a fruit-Ovary

2. Part that produces pollen grain-Anther

3. Part that transfers male gametes-Style

4.  Part that is sticky to trap-Stigma

Scrotum is a sac-like structure present outside the body cavity in human males. It keeps the temperature of testes $$1 - 3^{\circ}\ C$$ below the body temperature. This is important as a lower temperature is essential for the development of sperms.

• The term fission in biology refers to the division of an organism, or a cell into two or more parts and the regeneration of each part into a new organism or a new cell. The nucleus divides by the process of karyokinesis. The cytoplasm divides by the process of cytokinesis. Karyokinesis is followed by cytokinesis.
  
• For example, binary fission and multiple fission.

In amoeba, splitting of the cell into two during cell divison can take place in any plane. Leishmania has a whip like structure at one end of the cell, hence binary fission occurs in a definite orientation in relation to this structure.

Young people get acne and pimples on face due to the hormonal changes that take place in their body during the stage of puberty. More sebum is secreted in the skin and the oil glands get larger in this stage due to hormones. 

Fragmentation is the mode of asexual reproduction in which multicellular organism splits into two or more fragments, which survive as new individual e.g., Spirogyra.

The part marked 'D' is the ovule. After fertilization the ovules form seed and contain an embryo and endosperm.

Under favorable conditions, spores germinate to produce new organism, this type reproduction is called asexual reproduction and is seen in Rhizopus.

When the egg is not fertilized, it is shredded off from the body and the menstrual cycle takes place. 

• Reproduction is very necessary for a living organism. It is the process by which a new organism is produced. 
• Reproduction is necessary for the continuation of the generation of particular species rather than the species extinct from the earth. It is also a source of recombination.

Reproduction is important for living organisms to maintain the continuity of their species. 

• If an egg is not fertilized, it is expelled from the body during menstruation cycle. The lining of uterus wall breaks and it is released in the form of blood and mucus by the vagina.

Difference between fragmentation and regeneration is crucial in the field of advanced biology. Fragmentation refers to the process of splitting an organism into fragments, and each fragment grows into an organism. In contrast, regeneration is like a modified form of fragmentation and is the process of regrowth in organisms.

When a mature Spirogyra filament attains considerable length, then it breaks into two or more fragments. These fragments then grow into complete organisms.

After fertilization, the flower loses its shine. After fertilization four major changes that take places are development of endosperm and embryo, development or maturation of ovules into seeds and formation fruit from ovary.

Explanation:

• The shedding of the endometrium lining along with blood and mucus is called menstruation. It is often called “periods”.  It's a monthly cycle that acts as an indication that no fertilization has occurred.

• Every month the uterine wall undergoes cyclic changes.

• Starting from the first 5 days, this phase is considered menses.

• From the 7th day onward till the 14th day it is considered the proliferative phase. Here follicles development occurs.

• On ovulation, the egg is released, and LH surge is maximum.

• When the egg is not fertilized, the corpus luteum degenerates and becomes corpus albican. This phase is the secretory phase.

• After 14 days of ovulation, again the menses occurs and the cycle is repeated.

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Sexual reproduction involves two parents, whereas asexual reproduction involves only one parent. So, the offspring resulting from sexual reproduction will have mixed characteristics from both the parents and therefore, will be different from each parent. This will bring variations in the population. Variations are important for the survival of species over time. If a population of asexually reproducing organisms is suited to a particular environmental condition and the condition is drastically altered then the population would be wiped out. However, if some variations were to be present in a few individuals in this population, there would be some chance for them to survive in the new environmental condition.

Paramoecium, Euglena and Amoeba reproduce via binary fission; Whereas, Hydra reproduces by budding.

Answer:

• Contraceptive methods include any approach to prevent conception; for example, oral contraceptive pills, surgical methods (vasectomy, tubal ligation), contraceptive implants, diaphragm, cervical cap, condoms, intrauterine devices etc.
• These methods are adopted for protection against sexually transmitted diseases, to have a sufficient gap between two successive childbirth to ensure better health of mother and children, to restrict the number of kids, to enjoy reproductive health and to control exponential population growth. 

Explanation-

• Menstrual cycle refers to the female reproductive cycle characterized by regularly occurring changes in the uterine lining and the loss of blood and tissue during this cycle.
• The cycle includes egg maturation and preparation of the uterus for implantation by thickening of the endometrium under hormonal regulation. In absence of egg fertilization, egg rupture is followed by disintegration of the uterine lining (endometrium).
• Since the uterine wall is rich in blood capillaries and tissues, its shedding off results in the release of blood and tissues which come out through the vagina in menses. 

Four methods of contraception are

Answer:

All living organisms must reproduce to survive. It is a biological process in which living creatures generate offspring that are genetically identical to themselves.

The following reasons make reproduction necessary for organisms:

• The birth rate and death rate are kept in balance by reproduction.
• The aged and dying population is replaced by new people.
• It also aids in the expansion of the ecosystem's species.
• The genes are passed down from one generation to the next.
• Species evolve as a result of this.
• Reproduction is the cause of variation in species and their ability to thrive in varied situations.

The process of asexual reproduction in yeasts is called budding.

Multiple fission is found in Plasmodium in which the nucleus divides repeatedly forming huge number of nuclei. These nuclei will develop into new individuals and they come out of the parent cell by destroying it. Multiple fission is also called schizogony.

Image source- Ncert 10th CBSE science.

It is the necessity of the living organisms to increase their number in order to maintain the continuity of the species. Reproduction is the process through which one organism give rise to a similar organism of its own kind. It is one of the most important characteristics of the living organism.  This is the method which allows the survival of the species. If reproduction does not take place, no living being will survive on the earth and all the organisms will go extinct. 

Asexual type of reproduction is found only in lower organisms. Lower organisms produce same young ones by this method which are also exactly similar to parents. In amoeba, the nucleus in the cell elongates and divide into two parts from the centre. After nuclear division, the cell membrane divides into two parts by constriction and along with this the cytoplasm also divides due to which two offsprings are produced from the parent amoeba which develops individually.

• Budding is the asexual mode of reproduction. In budding, a genetically identical new organism grows attached to the body of parent Hydra and separates later on. 
• In the process of budding, a bud develops as an outgrowth due to repeated cell division at one specific site. This bud grows randomly and there is no specific order or direction they follow. 

There are different methods which can be used for preventing pregnancy. 

Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. 

Organisms such as Hydra use regenerative cells for reproduction in the process of budding. In Hydra, a bud develops as an outgrowth due to repeated cell division at one specific site. These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals.

The given statement is false because seed production is a result of sexual reproduction in plants whereas, vegetative propagation is a type of asexual reproduction.

Adolescence is a transitional stage in physical and psychological development that is generally confined to the period from puberty to adulthood. It is also a period of multiple transitions involving education, training, employment and unemployment, as well as transitions from one living circumstance to another. A thorough understanding of adolescence in a society depends on the availability of information and awareness about its various perspectives including psychological, historical, sociological, and cultural backgrounds. The ability of understanding, appreciating, and digesting the experience and knowledge of adults by adolescents varies from someone to another. Hence, conduction of well-planned studies and researches is crucial to understand the different disturbing issues of adolescence as a stage. The proper utilization of the outcomes and conclusions of such studies and researches is a cornerstone of success in raising our adolescents to be healthy adults both physically and mentally. Accordingly, adolescence is considered as a crucial stage in human life that needs utmost parental care, guidance, and empathy

Dizygotic twins are formed from two fertilized eggs. They are also called as Fraternal Twins.

Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy.

Papaya is dioecious because the staminate and pistillate flowers are born on two different plants. Self-fertilization is not found in papaya, thus in different plants, the flower may be developing at a different time and that is why few plants bear fruit.

Yeast is a unicellular organism that belongs to the kingdom Fungi.

Adolescence is a period marked by psychological and physical changes. The hormonal changes causes some parts of the body grows faster than the other making them look awkward or disproportionate.

Only one ovum is released each month in human females, around 14th day of menstrual cycle. If fertilization takes place, all the activities of menstrual cycle stop. Hence, fertilization can occur only once in a month in a human female.

The most important change marked by the puberty is the growth and development of the sex organs. They initiate the secretion of sex hormones and begin the formation of the gametes. In males the testes start the secretion of testosterone and spermatogenesis begins. In females, the ovaries start secretion of estrogen and the menstrual cycle starts resulting in oogenesis.

The main functions of the female reproductive system are to produce the egg cells necessary for reproduction and to produce the female sex hormones estrogen and progesterone. The system is also designed to allow the fertilisation of the egg and the sperm cells and the development of the embryo.

Copper-T is an intra-uterine device which does not allow fertilisation to take place. As it does not provide any barrier against mixing of body fluids from two individuals, therefore, it acts only as a contraceptive method but does provide protection against STDs.

Explanation:

• The shedding of the endometrium lining along with blood and mucus is called menstruation.

• It is often called “periods”.  It's a monthly cycle that acts as an indication that no fertilization has occurred.

• Every month the uterine wall undergoes cyclic changes.

• Starting from the first 5 days, this phase is considered menses.

• From the 7th day onward till the 14th day it is considered the proliferative phase. Here follicles development occurs.

• On ovulation, the egg is released, and LH surge is maximum.

• When the egg is not fertilized, the corpus luteum degenerates and becomes corpus albican. This phase is the secretory phase.

• After 14days of ovulation again the menses occurs and the cycle is repeated.

Asexual reproduction is a mode of reproduction in which a single parent produces the offspring. The offspring are both physically and genetically identical to each other. They are their parent's exact copies and hence called clones. Budding is a type asexual technique that creates  a new organism form the buds originating on the parent organism. The buds grow and mature and eventually detach from the parent organism and grow into new individuals. This a commonly observed in Hydra and yeasts.

The female reproductive system provides several functions. The ovaries produce the egg cells, called the ova or oocytes. The oocytes are then transported to the fallopian tube where fertilization by a sperm may occur. The fertilized egg then moves to the uterus, where the uterine lining has thickened in response to the normal hormones of the reproductive cycle. Once in the uterus, the fertilized egg can implant into thickened uterine lining and continue to develop. If implantation does not take place, the uterine lining is shed as menstrual flow. In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.

Hydra reproduces by two different methods namely, regeneration and budding.
Both the methods are asexual methods of reproduction.

Yes, we can because in unicellular animals there is only one cell, when it will divide form a new cell and hence new organisms. 

Explanation :

• Any approach used to prevent the conception of unwanted pregnancy refers to contraception. Major contraceptive methods are categorized as barrier methods, surgical and chemical methods. 
• Barrier methods are the physical devices that prevent conception by inhibiting the entry of sperms in the female genital tract. Example: condoms, diaphragms, cervical caps, etc. 
• Surgical methods include vasectomy (blocks vas deferens to prevent sperms from coming out) and tubectomy (blocks fallopian tubes to prevent the entry of eggs in it) in males and females respectively. 
• Chemical methods of contraception include any hormonal preparation that serves to alter the hormonal balance of the body to prevent egg maturation or fertilization. For example, oral and vaginal pills. 
• Other methods include intrauterine devices (inserted by a physician into the uterus to prevent implantation), medical termination of pregnancy, coitus interruptus, etc.

The changes that occur in a girl during adolescence:

• They become curvier and the overall fat content of the body increases

• Breasts start to develop.
• Hips widen---girls even during childhood have wider hips as compared to boys and this difference becomes more evident in adolescence.
• In response to rising levels of estrogen, the lower half of the pelvis widens. Fat deposition occurs in the hips, thighs, upper arms, etc. This produces the typical female body shape.
  
• Hair grows in the pubic area, underarm and leg.
• Menstruation starts. The first menstrual event is referred to as menarche. The average age of menarche in girls is about 12-13 years.
  
• Hair and skin may turn oily.
• A rapid increase in height or growth spurt (girls, in general, reach their adult height by about 16 years of age)

Puberty is the phenomenon of physical changes by which adolescents become capable of reproduction. Puberty talks about bodily changes, while adolescence is the period of psychological and social transition between childhood and adulthood.

Binary fission is a form of asexual reproduction that occurs in bacteria and some unicellular Eukaryotes. 

Leishmania reproduces by the process of binary fission. It has a greater degree of organisation in its body, having a whip-like structure called flagellum at its one end. In Leishmania, the splitting of parent cell takes place in a definite plane { longitudinally} with respect to flagellum at its end.

After adolescence sweat glands and sebaceous glands increase their secretion. Pimples on Salma's face were the result of the increase in secretion of the sweat and sebaceous glands. So, She was advised to wash her face regularly with clean water to get rid of pimples. 

According to the question
a) The part which contains pollen grains: Anther
b) The part where the female gamete is formed: Ovary
c) The female reproductive part where pollen grains germinate: Stigma
d) The colourful part of flower which attracts insects: Petals 

Style - It is the path for transferring of pollen from stigma to ovary. 

ROUCDPRENTOI - unscrambles as Reproduction: Because of this, we find organisms of the same kind.

Carpel/pistil is the female reproductive organ of the flower.

Reproduction is the process by which new individuals are produced by the parents. The process of reproduction ensures that a plant or animal species does not disappear from Earth. This process is very important in maintaining stability in the ecosystem and for the continuation of life on earth.

In the given figure the labels are: 

(a) Ovary is concerned with the production of eggs.

The different parts of a flower are:
1. Androecium (male reproductive organ) - The androecium consists of whorls of the stamen. The stamen consists of the filament (long and slender stalk) and anther (bilobed structure). A typical anther is bilobed, which contains the pollen grains. 
2. Gynoecium (female reproductive organ) - Gynoecium represents the female reproductive part made up of carpels. The carpel is made up of:
Style - It connects the stigma to the ovary.
Stigma - It acts as a receptacle for the pollen grains.
Ovary - It is the enlarged basal part on which style lies. Each ovary bears one or more ovules attached to the cushion-like placenta. After fertilisation, ovules develop into seeds and ovary into a fruit. 
3. Calyx (accessory organ bearing sepals) - Calyx refers to the sepals. They are green in colour. They protect the plant in the bud stage and also attract the insects for pollination. 
4.Corolla (accessory organ bearing petals) - Corolla refers to the brightly coloured whorl of a flower. The individual unit of the corolla is petals. Petals protect the inner essential organs (i.e., stamens and carpels) and attract pollinators since they are brightly coloured. 

Gamete	Zygote
Formed after meiosis	Formed after fusion of two gametes.
Has a haploid number of chromosomes.	Has a diploid number of chromosomes.
Produced by male and female parts.	Formation takes place In the female part
Role in sexual reproduction: A gamete is necessary for sexual reproduction to take place because zygote cannot be formed without gametes. Brings gene pool from two individuals.	Role in sexual reproduction: Zygote formation Is a precursor of embryo formation.

Male gametes or sperms are motile. The tail helps the sperm to swim through the reproductive tract of the female to reach the oviduct.

Boys	Girls
Broad Shoulders	Wider region below waist
Wilder Chest	Development of mammary glands
Growth of muscles	Acne and pimples on face
Growth of facial hair	Development of sex organs
Acne and pimples on face	High pitched voice
Development of sex organs	Development of pubic hair
Development of public hair

The process represented in the figure is fertilization.

 The primary reproductive organs in humans are the ovaries and testes.

Functions of the primary sex organ, the ovary, in women are as follows: 
Production of eggs. 
Production of hormones, estrogen and progesterone

The male reproductive organ in flower is called stamen Example, Hibiscus . The sterile stamen is called staminode. Example Canna 

(a) Ovary develops into fruit.
(b) Ovules develop into seeds.

The ovary develops into fruits and ovules develop into seeds.

(a) Fertilization: Zygote is formed by fusing sperm and eggs from the opposite partners. It is called fertilization.
(b) Implantation: The fertilised egg (zygote) soon starts developing and by the time it reaches the uterus, a small ball of numerous cells is already formed. This is a kind of embryo which forms a pit in the wall of the uterus and gets fixed in it. Thus implantation occurs, which is the natural way of fixing the embryo in the uterus wall. This produces the state of pregnancy.
(c) Puberty: Puberty is the period during which the reproductive systems of boys and girls mature. In girls, it starts at the age of about ten and the first sign of puberty is the development of breasts. In boys, it starts at about 11 years of age of the enlargement of the testes is its first sign. The sudden spurt in growth, the shoulder girdle grows more than a hip girdle.

The following table depicts the structure and function of the respective structures:

$$\textbf{Structure }$$	$$\textbf{Location }$$	$$\textbf{Function }$$
$$\text{a)}$$ Placenta	Swollen area or cushion in the ovary.	Renders origination to the ovules.
$$\text{b)}$$Thalamus	Tip of the stalk of the flower.	Bears all the floral parts.
$$\text{c)}$$ Anther	Section of the stamen	Production of pollen grains.
$$\text{d)}$$ Stigma	Knob-like structure at the terminal end of style.	During pollination, provides landing site for the pollen grains.

(a)Seed - Ovules 
(b)Fruit - Ovary 
(c) Fruit wall - Ovarian wall 

When maturation time of reproductive parts in a flower is different - Dichogamy 

Tapetum cells provide nutrition for developing pollen. Besides this, the tapetum cells deposit sporopollenin substance and help in the formation of the exine coat of pollen. The importance of tapetum can be understood by the fact that if the tapetum degenerates before the formation of pollen grains, the pollen grains remain sterile or abortive. 

1. Hilum - The point of attachment of the body of the ovule with its stalk is called hilum.

Arrangement of flowers on a twig/stem - Inflorescence 

2- (Fallopian tube) for fertilization
3 - (Uterus) for implantation 

Hormonal methods of contraception include pills, skin patches, vaginal rings and shots containing a combination of the hormones estrogen and progesterone or may only progesterone hormone. These hormones alter the levels of reproductive hormones in the body, resulting in alteration of the menstrual cycle and hence ovulation is either delayed or halted during the period when these contraceptives are administered.

Reproduction : Reproduction is the process of producing new young individuals of similar type by the mature individuals.

Importance of DNA Copying.
Types. Asexual reproduction and sexual reproduction.
New Characteristics: New characteristics appear only in sexual reproduction due to Chance separation of chromosomes during meiosis required for gamete formation, Crossing over during meiosis.
Chance coming together of chromosomes during fertilization, Mutations or mistakes during DNA replication.

$$1$$ - fallopian tube,
$$2$$ - ovary,
$$3$$ - Uterus,
$$4$$ - cervix,
$$5$$ - vagina.

Answer:

A) Coarse adjustment screw should move to focus the slides.

Parents' should keep friendly relationship with adolescence.
-should let them to do their own decision -should cooperate them to take any independent work etc.

The risk factors are motor vehicle crushes, violence, substance use and sexual behavior.

Major changes happens in adolescents are both physically and mentally. The physical changes are growing of hairs 
in public regions, appearance of beard and development of mammary glands.
Mentally changes such as they rejects some advices of their parents or elders.

Adolescents get safe and nurturing environment by the proper guidance of parents, teachers etc.

The growth of female secondary sex organs is stimulated in puberty by estrogens. This hormone is produced mostly by ovaries and occurs in three forms.

• Hydra use regenerative cells for reproduction in the process of budding.
• A bud develops as an outgrowth due to repeated cell division at one specific site. These buds develop into tiny individuals and, when fully mature, detach from the parent body and become new independent individuals.

The chromosome number of the zygote, embryonal cell and adult of a particular organism is always constant. Meiosis is the cell division which happens during gametogenesis. This results in a number of chromosomes getting halved in gametes. When fertilization happens, the number of chromosomes becomes equal to that in somatic cells. After that, mitosis takes place during the rest of the stages of life. 

So, the constancy of chromosomal number is maintained in all the three stages.

Bread mold grows profusely on a moist slice of bread rather than on a dry slice of bread because microorganisms need optimum temperature and moisture to grow and if there is no moisture they will not grow profusely.  We can see during rainy season microorganisms are highly active and grow profusely as compared to winters and dry season because during rainy season moisture is present in the air which helps microorganisms to grow profusely.

The given diagram represents the process of budding in yeast.

• Fertilization is the process of fusion of the female gamete (ovum or egg) and the male gamete produced in the pollen tube by the pollen grains.
  
• Post- fertiliztion changes in a flower include- 

1. The diploid zygote develops into an embryo that forms the future plant. 

2. The endosperm cells provides the required nutrition for the developing embryo.

3. The ovule forms the seed.

4. The ovary forms the fruit.

5. The outer and inner integuments of the ovule forms the testa or the seed coat of the seed. 

7. Petals and sepals fall off.

Zygote

Petals	Petaloid sepals
They are the non-essential parts of a flower that provides protection to the reproductive parts thereby making the flower attractive for cross. pollination.	The non-green perianth is called as petaloid. The perianth is a whorl of undifferentiated sepals and petals.

When calyx and corolla cannot be differentiated from each other, they are collectively known as perianth.

(a) The figure A represents stamen. Collectively, stamens form androecium. 
(b) The contents of the pollen sacs in B are male gametes. 
(c) The contents of the pollen sacs can come out by the following modes: 
$$*$$ Wind 
$$*$$ Insects 

(a) The labelings are as follows: 
1  - Style 
2 - Pollen tube 
3 - Polar nuclei 
4 - Embryo sac 
5 -  Antipodal cells 
6 -  Micropyle 

Gamete	Zygote
Gamete is unicellular	Zygote is unicellular
Formed by the meiosis of germ cells	Formed by the fusion of gametes
A gamete is haploid	A zygote is diploid
Gametes are formed in gonads	A zygote is formed in the fallopian tubes.