Gujarat Board GSEB Textbook Solutions Class 10 Science Chapter 8 How do Organisms Reproduce Textbook Questions and Answers, Additional Important Questions, Notes Pdf.
Gujarat Board Textbook Solutions Class 10 Science Chapter 8 How do Organisms Reproduce
Gujarat Board Class 10 Science How do Organisms Reproduce InText Questions and Answers
What is the importance of DNA copying in reproduction?
DNA copying is an important phenomenon of reproduction through which the organisms pass on their characteristics to their offspring. It maintains the characteristics in different generations of the species. It also produces variations which are useful for the survival of species for long time.
Why is variation beneficial to the species but not necessary for the individual?
Accumulation of variations after several generations results in new set of traits required for survival. As they show results after many generations so they are not important for individual.
How does binary fission differ from multiple fission?
Binary Fission: An organism is divided into two individuals. Mitotic division takes place resulting in two identical individuals or daughter cell.
Example : Amoeba.
Multiple Fission: Mitotic division takes place. The nucleus divides repeatedly to form a number of equal sized and similar individuals.
Example : Plasmodium.
How will an organism be benefited if it reproduces through spores?
During adverse circumstances spore remain coated with protective layer. This helps an organism survive adverse conditions. Spores are means to tide over bad phases.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
More complex organisms cannot give rise to new individuals because:
- Their body design is highly complicated.
- There are specific organs to do specific functions.
- There is a labour division in the body of complex organisms.
- Exception is lizard, which can regenerate its tail.
Why is vegetative propagation practised for growing some types of plants?
The process by which some plants can reproduce asexually by their vegetative parts like roots, stems and leaves is called vegetative propagation. It has many advantages. Plants raised by this method can bear flowers and fruits earlier than those produced from seeds. Plants that have lost capability to produce seeds like banana, orange, rose and jasmine can be propagated. All plants produced are genetically similar to the parent plant.
Why is DNA copying an essential part of the process of reproduction? (AI 2009)
DNA copying is needed because information stored in DNA is used to make protein. Synthesis of different proteins will lead to altered body design. Thus, reproduction at its most basic level involves making copies of the blueprints of body design.
How is the process of pollination different from fertilization?
Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. These are transferred by agents such as insects, birds, wind or water. Fertilization is defined as the fusion of a male gamete (sperm) with a female gamete (ovary) to form a zygote by sexual reproduction.
What is the role of seminal vesicles and prostate gland?
Seminal vesicles – are a pair of thin-walled muscular and elongated sacs which secrete a fluid for nourishment of sperms.
Prostate glands – also produce a fluid which is released in the urethra along with secretion of seminal vesicle. It affects the vaginal pH so that sperms move smoothly inside the vagina.
What are the changes seen in girls at the time of puberty?
At the time of puberty, breast size begins to increase, with darkening of the skin of the nipples. Also, girls begin to menstruate at around this time.
How does the embryo get nourished inside the mother’s body?
The embryo grows inside the mother’s womb and gets nourishment from its mother’s blood through placenta. Placenta contains villi which connects the embryo with the mother’s blood. These villi provides a large surface area for glucose and oxygen to pass from mother to the embryo.
If a woman is using copper-T, will it help in protecting her from sexually transmitted diseases?
No, it will not protect the woman from sexually transmitted diseases as fluid to fluid contact occurs in the vagina.
In-Text Activities Solved
Aim : to demonstrate asexual reproduction by budding.
Material required : Sugar, water, test tube, yeast granules, cotton, slide, coverslip.
Procedure : Dissolve about 10 gm of sugar in 100 ml of water. Take 20 ml of this solution in a test tube and add a pinch of yeast granules to it. Put a cotton plug on the mouth of the test tube and keep it in a warm place.
After 1 or 2 hours. Put a small drop of yeast culture from the test tube on a slide and cover it with a coverslip
Observation : You will observe that the yeast shows asexual reproduction by budding.
Wet a slice of bread, and keep it in a cool, moist and dark place. Observe the surface of the slice with a magnifying glass. Record your observations for a week.
Observation : On bread grows fungi called bread mould, initially it is white in colour then it becomes brown to black on maturity.
Observe a permanent slide of Amoeba under a microscope. Similarly, observe another permanent slide of Amoeba showing binary fission. Compare the observations of both the slides.
Observation: The slide of Amoeba shows single Amoeba and the one with binary fission appears to be a big sized Amoeba with a constriction in the centre.
Collect water from a lake or pond that appears dark green and contains filamentors structures. Put one or two filaments on a slide. Put a drop of glycerine on these filaments and cover it with a coverslip Observe the slide under a microscope.
Observation : It appears as shown Spirogyra filament.
Take a potato and observe its surface. See the notches (Eyes of potato).
Cut the potato into small pieces such that some pieces contain a notch or bud and some do not. Spread same cotton on a tray and wet it. Place the potato pieces on this cotton. Note where the pieces with buds are placed. Observe the change taking place in these potato pieces over the next few days. Make sure that the cotton is kept moistened.
Observation : Potato with notches or buds show the growth of a new plantation whereas the other pieces of potato do not show such growth.
Select a money plant. Cut some pieces such that they contain at least one leaf. Cut out some other portions between two leaves. Dip one end of all the pieces in water and observe over the next few days. Observe which ones grow and give rise to fresh leaves.
Observation : The stems of money plant with leaves showed the growth while the other parts between two leaves did not show any growth
Soak a few seeds of Bengal gram (chana) and keep them overnight. Drain the excess water and cover the seeds with a wet cloth and leave them for a day. Make sure that the seeds do not become dry. Cut open the seeds carefully and observe . the different parts. Identify different parts.
Observation : The seed consists of two cotyledons (dicotyledon) when it starts growing it shows the growth of future shoot called plumule and root called radicle.
Gujarat Board Class 10 Science How do Organisms Reproduce? Textbook Questions and Answers
Asexual reproduction takes place through budding in –
Which of the following is not a part of the female reproductive system in human beings?
(c) Vas deferens
(d) Fallopian tube
(c) Vas deferens
The anther contains –
(d) pollen grains
(d) pollen grains
What are the advantages of sexual reproduction over asexual reproduction?
In asexual reproduction, the offspring is almost identical to the parent because they have the same gene as their parent. Thus, variation is not present.
Sexual reproduction involves fusion of male and female gametes. The offspring exhibits diversity of characters because they receive some genes from the mother and some from the father. The mixing of genes in different combinations; results . in genetic variations. This variation leads to the continuous evolution of various species to produce various organisms.
What are the functions performed by testis in human beings?
The function of testis is to produce sperms and male sex hormone called testosterone.
Why does menstruation occur?
Menstruation occurs in females when the egg produced by ovary is not fertilized. Since the egg does not fuse with the male gamete, so the thick and soft lining of uterus having a lot of blood capillaries in it are not required. This unfertilized egg dies within a day and the lining breaks down shedding blood along with other tissues. This comes out of the vagina in the form of bleeding.
Draw a labelled diagram of the longitudinal section of a flower.
What are the different methods of contraception?
Contraception is the method to avoid pregnancy. Various methods of contraception are as follows:
Physical Barrier Methods – Use of condoms, diaphragms, cervical caps can be used. These prevent the entry of sperms into the female genital tract by acting as a barrier between them.
Chemical Methods – Oral pills can be used which change the hormonal balance and stop release of egg. Vaginal pills kill the sperms.
Surgical Methods – This includes vasectomy (sperm duct is removed) in males and tubectomy (removal of small portion of fallopian tube) in females.
How are modes of reproduction different in unicellular and multicellular organisms?
Unicellular organisms have only one cell. There is no separate tissue for reproduction. So, they can reproduce by the process of fission or budding. Multicellular organisms contain various cells and have separate system for reproduction. So, they can reproduce by both sexual and asexual methods.
How does reproduction help in providing stability to the population of species?
Stability is provided by equalizing the birth and death ratio. Thus, the rate of birth should approximately be equal to the rate of death.
What could be the reasons for adopting contraceptive methods?
The reasons for adopting contraceptive methods could be:
- Protection from sexually transmitted diseases such as HIV-AIDS, gonorrhoea, syphilis, warts etc.
- Restricting the number of children.
- Sufficient gap between successive births.
- Enjoying a good reproductive health.
- Controlling population.
Gujarat Board Class 10 Science How do Organisms Reproduce? Additional Important Questions and Answers
Very Short Answer Type Questions
Why do organisms reproduce?
Organisms reproduce to perpetuate their race and maintain their species.
flow do we Know that two different individual belong to the same species?
Members of same species are capable of interbreeding the same species by the similarity in their body design and other physical features.
Name the nucleic acids.
DNA and UNA are the two nucleic acids present in the living cells.
Give the full form of DNA.
Deoxyribo Nucleic Acid.
What happens during copying of DNA?
Copies of DNA are’ formed and hereditary information is passed on from one generation to the next.
When does copying of DNA occur?
Copying of DNA occurs during cell division.
The mode of reproduction depends on which feature of the organism.
The mode of reproduction depends on the body design of the organism.
Name two plants whose flowers are unisexual.
Name two plants whose flowers are bisexual.
Mustard, china rose.
What is fertilization?
Fertilization is the process of fusion of the male and the female gametes.
What is pollination?
The process of transfer of pollen grains from the stamen to the stigma of a flower is called pollination.
What is the importance of DNA copying in reproduction?
DNA copying during reproduction is important for the transfer of parental characters to the offsprings.
How does the developing embryo get nourishment inside the mother’s body?
The embryo gets nourishment from the mother’s blood with the help of a special tissue called placenta.
What are the structural changes observed in the flower after fertilization?
The calyx and corolla wither and fall off and so do the stamens. The ovary turns into the fruit. The embryo turns into seed. Once the seed becomes mature, fruit dries up . so that dispersal of seeds can take place.
What do you mean by Sexual Dimorphism?
The physical dissimilarities in the male and female of a species which give them different appearances is called sexual dimorphism.
Short Answer Type Questions
Differentiate between asexual and sexual reproduction.
- Asexual reproduction involves a single parent.
- No gametes are formed during asexual reproduction.
- No or little variations occur during asexual reproduction.
- Sexual reproduction involves two parents (male and female).
- Gamete formation takes place in sexual reproduction.
- Many variations occur during sexual reproduction.
Enumerate the various methods of asexual reproduction in living organisms.
The various methods of asexual reproduction are fission (binary and multiple), fragmentation, regeneration, budding, vegetative propagation, spore formation and tissue culture.
What is binary and multiple fission? Name the organisms in which they occur.
Binary fission is the division of one parent cell into two identical daughter cells. It takes place in Amoeba, Paramecium, Euglena and other protozoa. In multiple fission one single celled organism divides into many daughter cells within a cyst. These are released when the cyst breaks. This takes place in Plasmodium (malarial parasite).
What is fragmentation?
Fragmentation is the method of breaking up of an organism into smaller pieces or fragments which grow into new organisms as in algae Spirogyra.
What is regeneration? Name two organisms that can reproduce by regeneration.
Many fully differentiated organisms have the ability to give rise to new organisms from their body parts by being cut or broken into many pieces. This is known as regeneration. All organisms do not have the capacity to reproduce by regeneration. Hydra and Planaria can reproduce by the process of regeneration.
What is budding? Name two organisms that reproduce asexually by budding.
In budding a small part of the parents body grows out as a bud which then detaches and becomes a new organism. Hydra and yeast reproduce by budding.
What is vegetative propagation? What are its advantages?
The process by which some plants can reproduce asexually by their vegetative parts like roots, stem and leaves is called vegetative propagation. It has many advantages. Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Plants that have lost the capacity to produce seeds like banana, rose and jasmine can be propagated by this method. All plants produced by this method are genetically similar to the parent plant.
How do potato and Bryophyllum plants reproduce vegetatively?
Potato tuber has depressions called “eyes” on its surface. These eyes have vegetative buds in them which germinate to produce a new potato plant. Similarly the fleshy leaves of Bryophyllum bear vegetative buds in the notches along the leaf margin. These buds germinate to form small plantlets which form new plants on being detached.
Name two plants that can reproduce asexually by formation of spores.
Bread mould (Rhizopus) and ferns reproduce asexually by formation of spores.
What are the limitations of asexual mode of reproduction?
In asexual mode of reproduction there are no genetic variation so there is less adaptability in the offspring.
What is the significance of sexual reproduction?
- A sexual reproduction results in new combination of characters and increases genetic variations.
- It promotes diversity of characters in the offspring.
- It speeds up the process of making variations in the population.
How is the amount of DNA maintained in each generation?
The amount of DNA is maintained in each generation by a specialized mode of cell division called meiosis which produces specialized male and female germ cells called gametes which are haploid. One male and female gamete fertilize to give rise to a diploid zygote which has the same chromosome number as the parent. This process maintains the chromosome number and the amount of DNA in each generation.
State the advantages of seed formation in plants.
The seed contains the future plant or embryo which can develop into a seedling under appropriate conditions. The seed is in a state of dormancy and can be kept in secure state for long period of time.
What is germination of seed?
When the seed gets the right conditions the embryo within it starts growing to form the shoot and the root. When the embryo emerges out of the seed to form a new seedling it is called the germination of seed.
What is puberty?
Puberty is the age at which the gametes start forming in the male and female human beings. At this age boys and girls become sexually mature.
What changes occur in the flower after fertilisation?
After fertilisation the flower withers. The sepals and the petals dry up, the ovary converts into fruit, the ovule forms the seed and the zygote forms the embryo which is enclosed in the seed.
Name the agents of pollination.
The agents that bring about pollination are wind, water, birds and insects.
State the functions of the human male and female sex hormones.
The human male sex hormone testosterone regulates the formation of the male gamete, the sperms and brings about changes in appearance seen in boys at the time of puberty. The human female sex hormone estrogen brings about the changes occurring in girls at puberty and progesterone controls the uterus changes occurring during the menstrual cycle and also helps in maintaining the pregnancy.
What happens when the egg is fertilised?
When the egg is fertilised zygote is formed, it starts dividing and gets implanted in the lining of the uterus.
What is menstruation? Why does it occur?
Menstruation is the process of breakdown and removal of the inner lining of the uterus along with the blood vessels in the form of vaginal bleeding. This happens after every 28 days if the egg is not fertilised. This takes place in human females and in some primates.
What is STD? Name two STDs.
STD is Sexually Transmitted Disease. Two STDs are syphilis and gonorrhoea.
What is the role of seminal vesicles and prostate gland?
These are the accessory glands associated with the male reproductive system. Seminal vesicles and prostrate gland secrete a fluid which makes the transport of sperms easier and also provides nourishment to the sperms. This fluid together with the sperms is called the semen.
Draw a well labelled diagram of a dicot seed (gram seed).
Device an experiment to show germination of gram seed.
- Soak a few seeds of Bengal gram (chana) and keep them overnight.
- Drain the excess water and cover the seeds with a wet cloth and leave them for a day. Make sure that the seeds do not become dry.
- Cut open the seeds carefully and observe the different parts.
- Compare your observations with the figure above that shows the germination of gram seed and see if you can identify all the parts.
Draw a well labelled diagram of a bisexual flower.
State the changes that occur in human males and females at puberty.
Puberty is the state of sexual maturiy in humAnswer: The changes that take place in males during puberty are growth of hair on the body, appearance of beard and moustache and the voice becomes hoarse. Females show development of breasts, and beginning of menstruation.
What is self and cross pollination?
Self Pollination – It is the transfer of pollen grains from the anther of a flower to the stigma of the same or another flower on the same plant.
Cross Pollination – It is the transfer of the pollen grains from the anther of a flower to the stigma of another flower on a different plant of the same species.
(a) Name the parts labelled A, B, C, D, and E
(b) Where do the following functions occurs?
(i) Production of an egg
(iii) Implantation of zygote
(c) What happens to the lining of uterus
(i) before release of fertilised egg.
(ii) if no fertilisation occurs.
- A → Fallopian tube
- B → Ovary
- C → Uterus
- D → Cervix
- E → Vagina
- Production of an egg – ovary
- Fertilisation – fallopian tubes
- Implantation of zygote – lining of the uterus
- Before release of fertilized egg – the uterus wall becomes thick.
- If no fertilisation occurs – the lining of uterus slowly breaks down and comes out in the form of bleeding.
What is the role of following in reproduction?
- Egg production
- Zygote formation
- Attainment of sexual maturity
- Birth control
Explain the process of sexual reproduction in plants.
After the pollen lands on a suitable stigma it germinates to form the pollen tube. The pollen tube grows through the style and carries the male germ cells in it. The pollen tube enters the ovule and the male germ cells fuse with the egg cell to form the zygote. This process is called fertilisation.
What is the mode of reproduction in amoeba when the condition is unfavourable?
When conditions become unfavourable, i.e. food, moisture, proper temperature, etc. are not available then amoeba show mitotic cell division. The organism develops a thick coating around itself called cyst. The cyst helps the organism to protect in this condition. The nucleus divides into several nuclei and each daughter nucleus is surrounded by a membrane.
All metabolic activities stop in the organism, after cyst formation. When favourable conditions return, the cyst breaks down releasing the daughter nuclei. The daughter nuclei in turn grow into new individuals. Plasmodium and amoeba undergo cyst stage, when they are not in the body of their prime host, i.e. humans.
Explain the structure of seed.
A seed contains an embryo, some reserve food and is enclosed by a protective covering called seed coat. The reserve food is stored in the cotyledons. The embryo has two pointed parts. The upper part is called plumule which gives rise to the shoot system. The lower part is called radicle which gives rise to the root system. Cotyledons supply food when the embryo needs it during germination. Seed germination is the process by which the embryo in the seed starts a new life.
Name the following:
- Name two plants that cannot produce seeds.
- An organism that reproduces by budding and regeneration.
- An organism that grows by multiple fission
- One unisexual flower.
- Bryophyllum, Banana
- Maize flower
What does the male and female reproductive system consists of?
The male reproductive system in human beings consists of testes which produce sperms, vas deferens, seminal vesicles, prostrate gland, urethra and penis. The female reproductive system consists of a pair of ovaries, fallopian tube, uterus and vagina.
Give one term for the following:
- Beginning of menstrual cycle
- Release of ovum from the ovary
- Fusion of male and female eggs
- Prevention of unwanted pregnancy
- Time for development of offspring in female human.
- Nine months
Long Answer Type Questions
Draw a well labelled diagram of the female reproductive system in humans.
With the help of diagrams explain the process of budding in Hydra and fission in Amoeba.
State the functions of the following:
(c) vas deferens
(a) Testis – Form the male gametes the sperms and secrete the male sex hormone testosterone.
(b) Ovaries – Form the female gamete ovum or the egg cell and secrete the female sex hormones estrogen and progesterone.
(c) Vas deferens – Transport the sperms from the testis to the exterior.
(d) Stamen – Form the pollen grains in flowers. The pollen grains bear the male gametes.
(e) Pistil -The ovary forms the egg and the stigma helps in attracting the pollen grains for fertilisation.
What are the various artificial methods of vegetative propagation in plants?
The various artificial methods of vegetative propagation in plants are:
(a) Cutting – In this, any part of the plant like the stem root or leaf is cut and buried in the soil which gives rise to a new plant as in rose, guava, grapes etc.,
(b) Layering – In plants like jasmine and strawberry a branch from the plant is brought down to the ground and covered with damp soil. After few days new roots are formed and the branch is cut from the main plant.
(c) Grafting – In this, the stem of a plant is given a cut and the other plant is fixed (with its stem) in it e.g., sugarcane, roses, grapes are grown for agricultural purposes.
(d) By Roots – Plants like sweet potato show the growth of more plants from a root.
(e) Stem – Plants like potato, ginger, onion, they show growth from their stems.
(f) By Buds – Plant like Bryophyllum and potato grow small buds on them and a growth of new plant takes place.
(a) Name the human male reproductive organ that produces sperms and also secretes a hormone. Write the functions of the secreted hormone.
(b) Name the parts of the human female reproductive system where (i) fertilisation takes place, and (ii) implantation of the fertilised egg occurs.
Explain how the embryo gets nourishment inside the mother’s body.
(a) Testis – secrete male hormone – testosterone.
- Formation of sperms
- Development of secondary sexual characters.
- Fallopian tube / oviduct
Placenta is a special disc like tissue embedded in the mother’s uterine wall and connected to the foetus / embryo. Placenta provides a large surface area for glucose and oxygen / nutrients to pass from the mother’s blood to the embryo / foetus.
Practical Based Questions (Solved)
Name two organisms each which can reproduce asexually by (i) fission and (ii) by budding.
- By Fission: amoeba, paramecium
- By buddung: yeast and Hydra
During the asexual reproduction of amoeba the first stage is karyokinesis and second stage is cytokinesis. Explain the two stages.
Karyokinesis is the process of the division of the nucleus. It corresponds to the separation of the daughter chromosomes into two daughter nuclei. Karyokinesis is usually followed by Cytokinesis.
Cytokinesis is the process of the division of the cytoplasm. It corresponds to the separation of the daughter nuclei into two daughter ceils. Cytokinesis occurs immediately after mitosis.
List any four observations one can make while studying the yeast cell showing reproduction.
- One or more bulblike projections (buds) arise from the cell membrane.
- The nucleus of the parent cell divides and one of the daughter nuclei passes into the bud.
- The bud is finally separated from the parent body and grows into a new individual.
- The parent’s identity is maintained in budding.
List any four observations one can make while studying the amoeba slide showing reproduction.
- In this division, two similar individuals are formed from a single parent.
- A mature Amoeba cell is larger. Its nucleus elongates and gradually divides amitotically into two.
- The division of the nucleus is followed by the division of the cytoplasm.
- Thus two new amoebae are formed from a single parent and the parent’s identity is lost.
List the factors required for the seed to germinate.
Seeds need water, light, nutrients, a substrate to grow in, and often a suitable temperature.
Name any three substrate one can use for the germination of seed.
The seeds can be germinated on wet cotton, soil or cloth.