3. What is the effect of DNA copying, which is not perfectly accurate in the reproduction process?
Ans. If the DNA copying is not perfect during the process of copying the DNA, some variations will occur each time due to the creation of some error, and the DNA copies created will be similar, but may not be identified as the original. Some of these variations may be so strong that the new DNA copy cannot work with the cellular apparatus and newborn cells may die but many other variations in the DNA copies don't affect. Thus, the surviving cells are similar, but may not be identical. In a population, variations are useful for ensuring the long survival of the species. This tendency for variation in DNA copying during the process of reproduction is the cause of evolution.
4. How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
Ans. In multi-cellular organisms during cell division cells in specialized organs have only half the number of chromosomes and half the amount of DNA as compared to the parent cells or non-reproductive cells. When these germ-cells from two individuals combine during sexual reproduction to form new individual cells and each has the same number of chromosomes and DNA as the parent.
That is why the amount of DNA remains constant though each new generation is a combination of DNA copies of two individuals.
5. Draw the diagram to explain the regeneration that takes place in each of the body parts of planaria when its body is out into pieces.
Name any other organisms in which a similar process can be observed.
Ans.
Process of regeneration in planaria
It is a type of asexual reproduction in which one single parent is involved. It is dependent on the cut in an organism. In this process, each piece can grow into a separate complete organism.
Hydra is the other organism in which a similar process can be observed.
6. Write the name of the part of a flower that serves as the same function as the following do in the animals:
(i) testes (ii) sperm (iii) ovary (iv) egg.
State the functions of flower in the flowering plants.
Ans. (i) Testes - stamen of flower serves as the same function as the testes.
(ii) Sperms - pollen grains of a stamen of the flower serves as the same function as the sperms.
(iii) Ovary - Ovary bottom part of the pistil of the flower.
(iv) Egg - ova are tiny egg cells of the lower part of plants.
Functions of flower -
The different parts of a flower are– sepals, petals,
stamens, and carpels.
Sepals provide support and protection for the flowers bud. It also provides protection for the reproductive parts inside the flower
Petals help in pollination by attracting insects through beautiful colour and smells.
Stamen and carpels - Stamens and carpels are the reproductive parts of a flower which contain the germ-cells and helps in reproduction.
7. Define the following process of sexual reproduction:
(i) Spore formation (ii) Regeneration (iii) Multiple Fission.
Ans. (i) Spore formation- is a process of asexual reproduction in a nonflowering plant-like Rhizopus, bacteria, in which the parent plants produce a large number of spores and these spores can develop into new individuals. Example- Rhizopus.
(ii) Regeneration- is a process in which the individual is somehow cut into many pieces, most of these pieces grow into separate individuals. Example - Hydra and Planaria.
(iii) Multiple fission - When a unicellular organism divide into many daughter cells by fission is called multiple fission.
Example - Leishmania which causes kala-azar.
8. i. Describe in brief the function of various parts of the female reproductive part of a bisexual flower.
ii. Write two examples each of sexually transmitted disease caused by virus and bacteria.
Ans. The carpel is the female reproductive part and present in the center of a flower. It has three parts. The swollen bottom part is the ovary, the middle part which is elongated is the style and the top sticky part is the stigma. The ovary contains ovules and each ovule has an egg cell. Female gamete present in the ovule fuses with the male germ-cell produced by pollen grain and fertilized that gives us the
zygote which is capable of developing into a new plant.
ii. Gonorrhea and syphilis are caused by bacteria, and HIV-AIDS and warts are caused by a virus.
9. Explain how the transmission of AIDS disease is prevented.
Ans. The sexual activity is a very close and personal connection of bodies and due to this diseases can be sexually transmitted like bacterial infections such as syphilis, gonorrhea and viral infections such as HIV-AIDS. It can prevent transmission of these diseases by using a contraceptive method like covering, called a condom. create a mechanical barrier.
The sexual activity is a very close and personal connection of bodies and due to these diseases like viral infections such as HIV-AIDS can be transmitted sexually through semen or vaginal fluid. It also transmitted through blood, and breast milk. So to protect from these diseases use condoms every time you have sex and don't share needles with anyone.
10. Name the following
(i) Threadlike nonreproductive structures represent in Rhizopus.
(ii) Blobs that develop at the tips of the nonreproductive thread in Rhizopus.
(iii) Explain the structure and the function of the structure released from the Blobs in Rhizopus.
Ans. (i) Threadlike nonreproductive structures represent in Rhizopus are the hyphae.
(ii) Blobs that develop at the tips of the nonreproductive thread in Rhizopus are sporangia that contain spores.
(iii) The spores are covered by thick walls that protect them until they come into contact with another moist surface and spores can develop into new Rhizopus individuals.
11. Name three parts of the carpel and given one function of each.
Ans. Three parts of the carpel are:
I. The swollen bottom part is the ovary,
ii. The middle elongated part is the style,
iii. The terminal sticky part is the stigma.
Functions:
I. The ovary contains ovules and each ovule has an egg cell. After fertilization, the ovary grows rapidly and ripens to form a fruit.
II. After the pollen lands on a suitable stigma, a tube grows
out of the pollen grain and travels through the style to reach the
ovary.
III. Stigma helps to stick the pollen grains for the pollination.
12. Is copying a DNA formed during reproduction identical to the original cell? Give a reason for the support of your answer and explain how DNA copying is beneficial for the species.
Ans. See the answer to long Q 3.
13. Mention two secondary sexual characters in human males. Why testes in the male body are extra-abdominal. Write the dual purpose served by urethra in the male.
Ans. Two secondary sexual characters in human males are: new thick hair growth on the face and their voices begin to crack.
Testes are located outside the abdominal cavity in the scrotum or are external because sperm formation requires a lower temperature than the normal body temperature.
The dual-purpose served by urethra in the male are to forms a common passage for both the urine and sperms.
14. What is vegetative propagation? When it is used? List two uses.
Ans. Vegetative propagation is asexual reproduction in plants in which plant parts like the root, stem, and leaves develop into new plants under appropriate conditions.
This method is used in plants that have lost the capacity to produce seeds. Example rose, banana, orange, etc and to produce fruits and flowers earlier in the plant.
Two advantages of vegetative propagation are:
1. Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
2. The fruit can be grown without any seed.
15. Distinguish between self-pollination and cross-pollination. How does the fusion of male and female gametes take place in plants?
Ans. Self-pollination - If the transfer of pollen grains occurs in the same flower in the same plant, it is called self-pollination.
Cross-pollination - If the pollen grain is transferred from one flower to another, it is known as cross-pollination.
Each pollen grain contains two male gametes but only one male gamete fuses with the egg while the other fuses with the polar nuclei to form the endosperm
The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule which gives us the zygote which is capable of growing into a new plant.
16. Explain the following:
(i) Testes and Ovaries are considered as a primary sex organ.
(ii) Advantage of seed production in plants
(iii) Vas defense is long in human males.
Ans. (i) Ovaries produce oestrogen and progesterone while testes produce testosterone.
These hormones are responsible for control the whole reproduction process, due to these ovaries in females and testes in males are called primary sex organs.
(ii) Production of seeds can help in pollination of it and can grow in different areas, it can be pollinated by wind
animals, birds and water and it can be cross-pollinated to form new varieties.(iii) Vas difference is a thick-walled tube that conveys mature sperm from the epididymis to the ejaculatory duct and it is about 18 inches long, arising from the lower end of the epididymis.
17. (i) Name an organism that reproduces by regeneration. Name any two plants that reproduce by grafting.
(ii) List any two benefits to an organism that reproduce through spores.
Ans. (i) Hydra is an organism that has the ability to give rise to new individual organisms from their damaged or lost body parts. If the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. This is known as regeneration.
Sugarcane and rose plants are reproduced by grafting.
(ii)Two benefits are :
(a) These types of organisms do not need any reproductive organs that are male and female parts.
(b) spores do not need any medium to disperse and a large number of pores are produced in one organism.
18. With the help of a diagram showing a sexual reproduction in rhizopus. How this method is disadvantageous for rhizopus?
Ans.
The thread-like structures that developed on
the bread is the hyphae of the bread mould
(Rhizopus). The tiny blob is sporangia-on-a-stick structures that are involved in reproduction which contains spores and they are not reproductive parts. Spores develop into new Rhizopus. The spores
are covered by thick walls that protect them until they come into
contact with another moist surface and can begin to grow.
This method does not lead to genetic variation in a population, this species suited to one habitat and disease may affect all the individuals in a population.
19. Differentiate between binary and multiple fission. Name an organism that reproduces by binary and multiple fission. Vegetative propagation is beneficial to plants that are propagated asexually. Give two advantages.
Ans. Binary fission is the process of splitting of a cell into two cells during cell division. Amoeba simply split into two equal halves during cell division. After replicating its genetic material, the cell divides into two nearly equal-sized daughter cells. The genetic material is also equally split.
Multiple fission: is the process of splitting a cell into many cells during cell division. in which a large number of offsprings are produced at the same time. Example - Plasmodium.
Two advantages of Vegetative propagation are:
1. We can get more plants from one plant by the stem, root or leaf planted.
2. It is not very expensive and it is very faster to grow it than the seeds.
20. Give reasons:(i) Wind act as pollinating agents (ii) Variation is essential and beneficial to the species. (iii) The use of condoms prevents pregnancy.
Ans. (i) Wind act as a pollinating agent because pollen grains are very light and wind can carry them away easily, hence helps in pollination.
(ii) Variation is essential and beneficial to species because it provides the basis of evolution.
(iii) Condoms help in the creation of a mechanical barrier so that sperm does not
reach the egg and fertilization cannot occur.
21. Draw a neat labeled diagram for a germinated seed and level radicle plumule and cotyledon. Mention functions of each of these parts.
Or
Name the parts A, B, and C shown in the given diagram of seed germination and state one function of each part.
Ans.
Germination of Seed
The function of :
cotyledon - The cotyledons are the first part of the plant that emerges from the soil. They are the energy sources that contains the stored food reserves from the seed for the new baby plant and helps in the initial growth of the plant.
Plumule - Plumule is a part of the seed embryo that grows upwards and forms the shoot system and it is the first true leaves of a plant.
Radicle - Radicle is a part of the seed embryo that grows downwards and forms the root system. It emerged from the seed through the micropyle. It helps to stick the plant to the soil and absorbs water to send the leaves for photosynthesis.
22. What is the placenta explain its role in the development of a human embryo?
Ans. The embryo gets nutrition from the mother’s blood with the help of a special tissue called the placenta. This is a disc that is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta.
23. State, in brief, the function of following organs in the human male reproductive system :(i) Ovary (ii) Fallopian tubes, (iii) Uterus.
Ans. (i) The role of ovaries - Role of ovaries is the production of eggs for fertilization and production of reproductive hormones, estrogen, and progesterone.
(ii) Role of fallopian tube - It is the site of fertilization in a female. One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct called a fallopian tube. The sperms enter through the vaginal passage during sexual intercourse and travel upwards and reach the fallopian tube where they may encounter the egg and egg becomes fertilized.
(iii) Role of the uterus- The two oviducts unite into an elastic bag-like structure known as the uterus that opens into the vagina through the cervix. After fertilization of egg with sperm in the fallopian tube, the fertilized egg, the zygote forms and gets implanted in the lining of the uterus and starts dividing. The uterus opens into the vagina through the cervix.
24. How many eggs are produced every month by either of the ovaries in human females? Where does fertilization take place in the female reproductive system? What happens in the case of an egg released by the ovary is not fertilized.
Ans. One egg is produced every month by one of the ovaries in human females.
Fertilization takes place in the fallopian tube in the female reproductive system.
The egg which is released by the ovary is carried from the ovary to the womb through a fallopian tube where egg fertilized with sperms forming zygote.
If the egg is not fertilized it lives for about one day and so the lining of the ovary is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation.
25. Why is vegetative propagation practiced for going some type of plant? Name the different parts of a flower that has themselves. List any two agents of pollination.
Ans. Vegetative propagation is practiced for growing some type of plants because it is an easy way to get a vegetative part from the plant itself.
This method is used in plants that have lost the capacity to produce seeds. Example rose, banana.
Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
The fruit can be grown without any seed
The four main parts of a flower are the petals, sepals, stamen ( male part - anther and filament), and carpel( female part - stigma, style, ovary, and ovule).
Two agents of pollination are birds and insects.
26.State one function of each of the following parts of a human male reproductive system.
(i) Vas defense (ii) Testes (iii) Prostate gland.
Ans. (i) Vas defense -The sperms formed from the testes are delivered through the vas deferens which unites with a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine.
(ii) Roles of testes are the secretion of the hormone testosterone that is brought about changes in appearance seen in boys at the time of puberty, and to regulate the formation of sperms.
(iii) Role of the prostate gland - Prostate with seminal vesicles that are present along the path of vas deferens – secrete fluids to provide nutrition to the sperm and the sperms can transport with fluid easily.
27. Name the reproductive part of the human female reproductive system:
(i) that produces eggs
(ii) where the fusion of eggs and sperms takes place, and
(iii)where zygote gets implanted.
Ans. (i) The ovary is a reproductive part of the human female reproductive system that produces eggs.
(ii) The fusion of eggs and sperms takes place in the fallopian tubes which is the site of fertilization in a female. The sperms enter through the vaginal passage during sexual intercourse and travel upwards and reach the fallopian tube where they may encounter the egg and egg becomes fertilized and form zygote.
(iii) After fertilization of egg with sperm in the fallopian tube the fertilized egg, the zygote forms which are got implanted in the uterus, then it began to divide itself from a single cell to multiple cells.
28. Describe in brief what happens to the zygote after it gets implanted?
Ans. A zygote is got implanted in the uterus, then it began to divide itself from a single cell to multiple cells. After a fixed time period the zygote becomes an embryo, and then the embryo becomes a fetus after some more time, body parts began to develop. The embryo gets its nutrition through a tube connected with the mother called the placenta, is a disc that is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The development of the child from a fetus inside the mother’s
body takes approximately nine months. The child is born as a result of
rhythmic contractions of the muscles in the uterus.
29. Write the name of the male reproductive organ that produces sperm and secretes hormones. Name the hormone secreted and state its functions.
Ans. Testes are the male reproductive organ that produces sperm and secretes hormones.
The hormone that is secreted by testes is testosterone.
The hormone testosterone helps to bring about changes in appearance seen in boys at the time of puberty and it helps to regulate the formation of sperms.
It stimulates the development, maturation, and functioning of the male accessory sex organs like vas deferens and seminal vesicles Stimulates muscular growth, growth of facial hair, low pitch voice, sperm production.
30. Draw a diagram showing the germination of pollen on the stigma of a flower. Level pollen grains, male germs cell, pollen tube and female germ cells in the above diagram. Define fertilization in plants.
Ans.
When pollen grains lands on the stigma after pollination, it forms a pollen tube and travels through it to reach the ovary that contains ovules and ovules contain eggs. The pollen grain is the male part of the flower fuses with an egg which leads to fertilization.
31. What are the different methods of asexual reproduction? Explain budding and regeneration with diagrams.
Ans. The different methods of asexual reproduction are
binary fission, multiple fission, budding, fragmentation, spore formation, and regeneration.
Budding is a form of asexual reproduction seen in plants. Like Hydra, only a single plant is involved and the identical offspring are formed and become new independent individuals.
Regeneration Many organisms have the ability to give rise to new individual organisms from their damaged or lost body parts. If the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. This is known as regeneration. Example: Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism.
32. Name the following: Organism which reproduce by :
(i) Binary fission
(ii) Multiple fission
(iii) Budding
(iv) Fragmentation
(v) Spore formation.
Ans. (i) Binary fission - bacteria and protozoa
(ii) Multiple fission - malarial parasite, Plasmodium
(iii) Budding - hydra and yeast
(iv) Fragmentation - spirogyra and molds
(v) Spore formation - bread mould (Rhizopus)
33. Name to sexually transmitted disease. Why parental determination is prohibited by law? What are the different methods of contraception?
Ans. HIV and STDs are tow sexually transmitted diseases.
STDs are spread by sexual intercourse and HIV is spread by only certain body fluids like blood, breastmilk, semen and vaginal fluid from a person who has HIV.
Many ways or contraceptive methods to avoid pregnancy are – using condoms, changing the hormonal balance by using pills, by using a loop or the copper-T in female, blocked the male and female vas deferens and fallopian tubes respectively.
Prenatal sex determination has been prohibited by law because of indiscriminate female foeticide and declining female male sex ratio.
This is prohibited by law also for a healthy society in which the female-male sex ratio must be maintained.
34. Differentiate between the following:
(i) Pollen tube and style,
(ii) Fission in Amoeba and plasmodium.
(iii) Fragmentation and regeneration.
(iv) Bud of Hydra and bud of Bryophyllum
(v) Vegetative propagation and spore formation.
Ans. I. (i) Pollen tube and style - Pollen tube growing out of pollen grains and pollen grains travels through it to reach the ovary.
Style - Middle elongated part of the carpel and the attachment of the stigmas to the ovary.
(ii) Fission in Amoeba and plasmodium- Fission in amoeba is the binary fission in which parental body part divides into two daughter cells at a time whereas fission in plasmodium is multiple fission.
(iii) Fragmentation and regeneration - Fragmentation - In this method multicellular organisms divides into two or more smaller fragments whereas Regeneration Many organisms have the ability to give rise to new individual organisms from their damaged or lost body parts. If the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. This is known as regeneration.
(iii) Bud of Hydra and bud of Bryophyllum- bud of hydra develops as an outgrowth during cell division and develops into tiny individuals. When this bud fully mature, detach from the parent body and become new independent
individuals. Similarly, buds produced in the notches along the leaf
margin of Bryophyllum and when these buds fall on the soil and develop into
new plants.
(iv) Vegetative propagation and spore formation- In vegetative propagation new plants are develope from the different parts of the parent plants whereas in spore formation spores fall on land, germinate and form new fungal colonies under favorable condition.
35. II. List three distinguishing features between sexual and asexual types of reproduction.
Ans. Asexual reproduction -
i. Process of creating new individual using one parent organism.
ii. It does not involve the fusion of gametes,
iii. It produces offspring that are identical to the parent.
Sexual reproduction:
i. Process of creating new individuals using two individuals' parent organisms. In such cases, both sexes, males and females, are needed to produce new generations.
ii. It involves the fusion of two gametes,
iii. It Produces offspring that are not identical to either of the two parents
36. Explain why variation is observed in the offspring of sexually reproducing organisms?
Ans. During sexually reproducing organisms the DNA copying is not perfect during the process of copying the DNA, some variations will occur each time due to the creation of some error, and the DNA copies created will be similar, but may not be identified as the original. Some of these variations may be so strong that the new DNA copy cannot work with the cellular apparatus and newborn cells may die but many other variations in the DNA copies don't affect. Thus, the surviving cells are similar, but may not be identical.
37. What is pollination? How does it occur in plants? How does pollination lead to fertilization? Explain.
Ans. The transfer of pollen grains from one flower to another is called pollination.
When pollen grains lands on the stigma, it forms a pollen tube and travels through it to reach the ovary that contains ovules and ovules contain eggs. The pollen grain is the male part of the flower fuses with an egg which leads to fertilization.
38. (i) Draw a neat diagram of the human male reproductive system and label the parts performing the following functions. (a) Production of sperms (b) Gland which provides fluid. (c) provides low temperature for the production of sperm (d) common passage for sperm and urine.
(ii) Name a sexually transmitted disease and a method to avoid it.
Ans. (i) A neat diagram of the human male reproductive system.
The function of the main parts of the male reproductive system:
(a) Production of sperms - The testes are responsible for making the primary male sex hormone testosterone and for generating sperm.
(b) The gland which provides fluid - Prostate gland and seminal vesicles secrete fluids to provide nutrition to the sperm and the sperms can transport with fluid easily.
(c) provides low temperature for the production of sperm- The scrotum acts as a temperature control system for the testes.
(d) common passage for sperm and urine - Urethra is the tube that carries urine from the bladder to outside of the body and ejaculating semen during reproduction.
39. What is meant by vegetative reproduction? How will a plant be benefited if it reproduces by vegetative propagation?
Ans. In many plants in which parts like the root, stem, and leaves develop into new plants under appropriate conditions. This is known as vegetative propagation.
Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds.
Another advantage of vegetative propagation is that all plants produced are genetically similar enough to the parent plant to have all its characteristics.
40. In the diagram of the human male reproductive system given below: (i) Level the part A and B (ii) Name the hormones produced by organ X (iii) Mention the name of the substance that is transported by tubes (a) C and(b) D.
Ans. (i) A - Seminal vesicles
B - Posted gland
(ii) X is testes- Testosterone hormones are secreted by testes.
(iii) (a) C is vas deference transports mature sperm to the urethra, and
(b) D is Urethra a tube of common passage transport urine from the bladder to the outside of the body and ejaculating semen during reproduction.
41. In the diagram of the human female reproductive system name the parts A, B, C, D and E and state one function of each part.
Ans. Function of :
A - Fallopian tube
Function: It is the site of fertilization in a female through which egg is carried from the ovary to the womb.
B - Ovary
Function: The function of ovaries is the production of eggs for fertilization and production of reproductive hormones, estrogen, and progesterone.
C - Uterus,
Function: After fertilization of egg with sperm in the fallopian tube, the fertilized egg, the zygote forms and gets implanted in the lining of the uterus and starts dividing.
D - Cervix,
Function: Cervix is a physical barrier between the vaginal canal and the uterus. It helps to the flow of menstrual blood from the uterus into the vagina and directs the sperms into the uterus.
E - Vagina
Function: Vagina is an elastic muscular tube that provides a passageway for blood and mucosal tissue from the uterus during a woman’s monthly period and provides a passageway for childbirth.
41. Name the parts A, B, and C shown in the given diagram and state one function of each part.
Ans. A - Pollen grain
Function: Pollen grain is the male reproductive cell of plants. It contains tube cells that grow into the pollen tube and the generative cell which releases the sperm nuclei for fertilization.
B - Pollen tube
Function: Pollen tube helps to travels the male reproductive cell through the style to reach the
ovary.
C - Ovary
Function: The ovary contains ovules and each ovule has an egg cell. After fertilization, the ovary grows rapidly and ripens to form a fruit.
D - Female germ cell
Function: Female germ cell helps in pollination.
